Publications by authors named "Ari Elson"

46 Publications

Sorting Nexin 10 as a Key Regulator of Membrane Trafficking in Bone-Resorbing Osteoclasts: Lessons Learned From Osteopetrosis.

Front Cell Dev Biol 2021 20;9:671210. Epub 2021 May 20.

Department of Immunology, The Weizmann Institute of Science, Rehovot, Israel.

Bone homeostasis is a complex, multi-step process, which is based primarily on a tightly orchestrated interplay between bone formation and bone resorption that is executed by osteoblasts and osteoclasts (OCLs), respectively. The essential physiological balance between these cells is maintained and controlled at multiple levels, ranging from regulated gene expression to endocrine signals, yet the underlying cellular and molecular mechanisms are still poorly understood. One approach for deciphering the mechanisms that regulate bone homeostasis is the characterization of relevant pathological states in which this balance is disturbed. In this article we describe one such "error of nature," namely the development of acute recessive osteopetrosis (ARO) in humans that is caused by mutations in sorting nexin 10 (SNX10) that affect OCL functioning. We hypothesize here that, by virtue of its specific roles in vesicular trafficking, SNX10 serves as a key selective regulator of the composition of diverse membrane compartments in OCLs, thereby affecting critical processes in the sequence of events that link the plasma membrane with formation of the ruffled border and with extracellular acidification. As a result, SNX10 determines multiple features of these cells either directly or, as in regulation of cell-cell fusion, indirectly. This hypothesis is further supported by the similarities between the cellular defects observed in OCLs form various models of ARO, induced by mutations in SNX10 and in other genes, which suggest that mutations in the known ARO-associated genes act by disrupting the same plasma membrane-to-ruffled border axis, albeit to different degrees. In this article, we describe the population genetics and spread of the original arginine-to-glutamine mutation at position 51 (R51Q) in SNX10 in the Palestinian community. We further review recent studies, conducted in animal and cellular model systems, that highlight the essential roles of SNX10 in critical membrane functions in OCLs, and discuss possible future research directions that are needed for challenging or substantiating our hypothesis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fcell.2021.671210DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8173195PMC
May 2021

An SNX10-dependent mechanism downregulates fusion between mature osteoclasts.

J Cell Sci 2021 May 11;134(9). Epub 2021 May 11.

Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot 76100, Israel.

Homozygosity for the R51Q mutation in sorting nexin 10 (SNX10) inactivates osteoclasts (OCLs) and induces autosomal recessive osteopetrosis in humans and in mice. We show here that the fusion of wild-type murine monocytes to form OCLs is highly regulated, and that its extent is limited by blocking fusion between mature OCLs. In contrast, monocytes from homozygous R51Q SNX10 mice fuse uncontrollably, forming giant dysfunctional OCLs that can become 10- to 100-fold larger than their wild-type counterparts. Furthermore, mutant OCLs display reduced endocytotic activity, suggesting that their deregulated fusion is due to alterations in membrane homeostasis caused by loss of SNX10 function. This is supported by the finding that the R51Q SNX10 protein is unstable and exhibits altered lipid-binding properties, and is consistent with a key role for SNX10 in vesicular trafficking. We propose that OCL size and functionality are regulated by a cell-autonomous SNX10-dependent mechanism that downregulates fusion between mature OCLs. The R51Q mutation abolishes this regulatory activity, leading to excessive fusion, loss of bone resorption capacity and, consequently, to an osteopetrotic phenotype in vivo. This article has an associated First Person interview with the joint first authors of the paper.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1242/jcs.254979DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8182410PMC
May 2021

Role of OSCAR Signaling in Osteoclastogenesis and Bone Disease.

Front Cell Dev Biol 2021 12;9:641162. Epub 2021 Apr 12.

Division of Cell Matrix Biology and Regenerative Medicine, Faculty of Biology, Medicine and Health, School of Biological Sciences, University of Manchester, Manchester, United Kingdom.

Formation of mature bone-resorbing cells through osteoclastogenesis is required for the continuous remodeling and repair of bone tissue. In aging and disease this process may become aberrant, resulting in excessive bone degradation and fragility fractures. Interaction of receptor-activator of nuclear factor-κB (RANK) with its ligand RANKL activates the main signaling pathway for osteoclastogenesis. However, compelling evidence indicates that this pathway may not be sufficient for the production of mature osteoclast cells and that co-stimulatory signals may be required for both the expression of osteoclast-specific genes and the activation of osteoclasts. Osteoclast-associated receptor (OSCAR), a regulator of osteoclast differentiation, provides one such co-stimulatory pathway. This review summarizes our present knowledge of osteoclastogenesis signaling and the role of OSCAR in the normal production of bone-resorbing cells and in bone disease. Understanding the signaling mechanism through this receptor and how it contributes to the production of mature osteoclasts may offer a more specific and targeted approach for pharmacological intervention against pathological bone resorption.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3389/fcell.2021.641162DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8072347PMC
April 2021

PTPRJ promotes osteoclast maturation and activity by inhibiting Cbl-mediated ubiquitination of NFATc1 in late osteoclastogenesis.

FEBS J 2021 Feb 19. Epub 2021 Feb 19.

Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot, Israel.

Bone-resorbing osteoclasts (OCLs) are multinucleated phagocytes, whose central roles in regulating bone formation and homeostasis are critical for normal health and development. OCLs are produced from precursor monocytes in a multistage process that includes initial differentiation, cell-cell fusion, and subsequent functional and morphological maturation; the molecular regulation of osteoclastogenesis is not fully understood. Here, we identify the receptor-type protein tyrosine phosphatase PTPRJ as an essential regulator specifically of OCL maturation. Monocytes from PTPRJ-deficient (JKO) mice differentiate and fuse normally, but their maturation into functional OCLs and their ability to degrade bone are severely inhibited. In agreement, mice lacking PTPRJ throughout their bodies or only in OCLs exhibit increased bone mass due to reduced OCL-mediated bone resorption. We further show that PTPRJ promotes OCL maturation by dephosphorylating the M-CSF receptor (M-CSFR) and Cbl, thus reducing the ubiquitination and degradation of the key osteoclastogenic transcription factor NFATc1. Loss of PTPRJ increases ubiquitination of NFATc1 and reduces its amounts at later stages of osteoclastogenesis, thereby inhibiting OCL maturation. PTPRJ thus fulfills an essential and cell-autonomous role in promoting OCL maturation by balancing between the pro- and anti-osteoclastogenic activities of the M-CSFR and maintaining NFATc1 expression during late osteoclastogenesis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/febs.15778DOI Listing
February 2021

Massive osteopetrosis caused by non-functional osteoclasts in R51Q SNX10 mutant mice.

Bone 2020 07 8;136:115360. Epub 2020 Apr 8.

Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot 76100, Israel. Electronic address:

The R51Q mutation in sorting nexin 10 (SNX10) was shown to cause a lethal genetic disease in humans, namely autosomal recessive osteopetrosis (ARO). We describe here the first R51Q SNX10 knock-in mouse model and show that mice homozygous for this mutation exhibit massive, early-onset, and widespread osteopetrosis. The mutant mice exhibit multiple additional characteristics of the corresponding human disease, including stunted growth, failure to thrive, missing or impacted teeth, occasional osteomyelitis, and a significantly-reduced lifespan. Osteopetrosis in this model is the result of osteoclast inactivity that, in turn, is caused by absence of ruffled borders in the mutant osteoclasts and by their inability to secrete protons. These results confirm that the R51Q mutation in SNX10 is a causative factor in ARO and provide a model system for studying this rare disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bone.2020.115360DOI Listing
July 2020

Kinetic Modeling of DUSP Regulation in Herceptin-Resistant HER2-Positive Breast Cancer.

Genes (Basel) 2019 07 26;10(8). Epub 2019 Jul 26.

School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester Academic Health Science Centre, Manchester M13 9PT, UK.

Background: HER2 (human epidermal growth factor 2)-positive breast cancer is an aggressive type of breast cancer characterized by the overexpression of the receptor-type protein tyrosine kinase HER2 or amplification of the gene. It is commonly treated by the drug trastuzumab (Herceptin), but resistance to its action frequently develops and limits its therapeutic benefit. Dual-specificity phosphatases (DUSPs) were previously highlighted as central regulators of HER2 signaling; therefore, understanding their role is crucial to designing new strategies to improve the efficacy of Herceptin treatment. We investigated whether inhibiting certain DUSPs re-sensitized Herceptin-resistant breast cancer cells to the drug. We built a series of kinetic models incorporating the key players of HER2 signaling pathways and simulating a range of inhibition intensities. The simulation results were compared to live tumor cells in culture, and showed good agreement with the experimental analyses. In particular, we observed that Herceptin-resistant DUSP16-silenced breast cancer cells became more responsive to the drug when treated for 72 h with Herceptin, showing a decrease in resistance, in agreement with the model predictions. Overall, we showed that the kinetic modeling of signaling pathways is able to generate predictions that assist experimental research in the identification of potential targets for cancer treatment.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.3390/genes10080568DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6723192PMC
July 2019

Modelling the role of dual specificity phosphatases in herceptin resistant breast cancer cell lines.

Comput Biol Chem 2019 Jun 25;80:138-146. Epub 2019 Mar 25.

School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK. Electronic address:

Background: Breast cancer remains the most lethal type of cancer for women. A significant proportion of breast cancer cases are characterised by overexpression of the human epidermal growth factor receptor 2 protein (HER2). These cancers are commonly treated by Herceptin (Trastuzumab), but resistance to drug treatment frequently develops in tumour cells. Dual-specificity phosphatases (DUSPs) are thought to play a role in the mechanism of resistance, since some of them were reported to be overexpressed in tumours resistant to Herceptin.

Results: We used a systems biology approach to investigate how DUSP overexpression could favour cell proliferation and to predict how this mechanism could be reversed by targeted inhibition of selected DUSPs. We measured the expression of 20 DUSP genes in two breast cancer cell lines following long-term (6 months) exposure to Herceptin, after confirming that these cells had become resistant to the drug. We constructed several Boolean models including specific substrates of each DUSP, and showed that our models correctly account for resistance when overexpressed DUSPs were kept activated. We then simulated inhibition of both individual and combinations of DUSPs, and determined conditions under which the resistance could be reversed.

Conclusions: These results show how a combination of experimental analysis and modelling help to understand cell survival mechanisms in breast cancer tumours, and crucially enable us to generate testable predictions potentially leading to new treatments of resistant tumours.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.compbiolchem.2019.03.018DOI Listing
June 2019

Phosphorylation of the phosphatase PTPROt at Tyr is a molecular switch that controls osteoclast activity and bone mass in vivo.

Sci Signal 2019 01 8;12(563). Epub 2019 Jan 8.

Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel.

Bone resorption by osteoclasts is essential for bone homeostasis. The kinase Src promotes osteoclast activity and is activated in osteoclasts by the receptor-type tyrosine phosphatase PTPROt. In other contexts, however, PTPROt can inhibit Src activity. Through in vivo and in vitro experiments, we show that PTPROt is bifunctional and can dephosphorylate Src both at its inhibitory residue Tyr and its activating residue Tyr Whereas wild-type and PTPROt knockout mice exhibited similar bone masses, mice in which a putative C-terminal phosphorylation site, Tyr, in endogenous PTPROt was replaced with phenylalanine had increased bone mass and reduced osteoclast activity. Osteoclasts from the knock-in mice also showed reduced Src activity. Experiments in cultured cells and in osteoclasts derived from both mouse strains demonstrated that the absence of phosphorylation at Tyr caused PTPROt to dephosphorylate Src at the activating site pTyr In contrast, phosphorylation of PTPROt at Tyr enabled PTPROt to recruit Src through Grb2 and to dephosphorylate Src at the inhibitory site Tyr, thus stimulating Src activity. We conclude that reversible phosphorylation of PTPROt at Tyr is a molecular switch that selects between its opposing activities toward Src and maintains a coherent signaling output, and that blocking this phosphorylation event can induce physiological effects in vivo. Because most receptor-type tyrosine phosphatases contain potential phosphorylation sites at their C termini, we propose that preventing phosphorylation at these sites or its consequences may offer an alternative to inhibiting their catalytic activity to achieve therapeutic benefit.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1126/scisignal.aau0240DOI Listing
January 2019

Protein tyrosine phosphatase alpha inhibits hypothalamic leptin receptor signaling and regulates body weight in vivo.

FASEB J 2019 04 7;33(4):5101-5111. Epub 2019 Jan 7.

Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.

Understanding how body weight is regulated at the molecular level is essential for treating obesity. We show that female mice genetically lacking protein tyrosine phosphatase (PTP) receptor type α (PTPRA) exhibit reduced weight and adiposity and increased energy expenditure, and are more resistant to diet-induced obesity than matched wild-type control mice. These mice also exhibit reduced levels of circulating leptin and are leptin hypersensitive, suggesting that PTPRA inhibits leptin signaling in the hypothalamus. Male and female PTPRA-deficient mice fed a high-fat diet were leaner and displayed increased metabolic rates and lower circulating leptin levels, indicating that the effects of loss of PTPRA persist in the obese state. Molecularly, PTPRA down-regulates leptin receptor signaling by dephosphorylating the receptor-associated kinase JAK2, with which the phosphatase associates constitutively. In contrast to the closely related tyrosine phosphatase ε, leptin induces only weak phosphorylation of PTPRA at its C-terminal regulatory site Y789, and this does not affect the activity of PTPRA toward JAK2. PTPRA is therefore an inhibitor of hypothalamic leptin signaling in vivo and may prevent premature activation of leptin signaling, as well as return signaling to baseline after exposure to leptin.-Cohen-Sharir, Y., Kuperman, Y., Apelblat, D., den Hertog, J., Spiegel, I., Knobler, H., Elson, A. Protein tyrosine phosphatase alpha inhibits hypothalamic leptin receptor signaling and regulates body weight in vivo.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1096/fj.201800860RRDOI Listing
April 2019

The roles of protein tyrosine phosphatases in bone-resorbing osteoclasts.

Biochim Biophys Acta Mol Cell Res 2019 01 17;1866(1):114-123. Epub 2018 Jul 17.

Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot 76100, Israel. Electronic address:

Maintaining the proper balance between osteoblast-mediated production of bone and its degradation by osteoclasts is essential for health. Osteoclasts are giant phagocytic cells that are formed by fusion of monocyte-macrophage precursor cells; mature osteoclasts adhere to bone tightly and secrete protons and proteases that degrade its matrix. Phosphorylation of tyrosine residues in proteins, which is regulated by the biochemically-antagonistic activities of protein tyrosine kinases and protein tyrosine phosphatases (PTPs), is central in regulating the production of osteoclasts and their bone-resorbing activity. Here we review the roles of individual PTPs of the classical and dual-specificity sub-families that are known to support these processes (SHP2, cyt-PTPe, PTPRO, PTP-PEST, CD45) or to inhibit them (SHP1, PTEN, MKP1). Characterizing the functions of PTPs in osteoclasts is essential for complete molecular level understanding of bone resorption and for designing novel therapeutic approaches for treating bone disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bbamcr.2018.07.005DOI Listing
January 2019

Regulation of dual specificity phosphatases in breast cancer during initial treatment with Herceptin: a Boolean model analysis.

BMC Syst Biol 2018 04 11;12(Suppl 1):11. Epub 2018 Apr 11.

School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK.

Background: 25% of breast cancer patients suffer from aggressive HER2-positive tumours that are characterised by overexpression of the HER2 protein or by its increased tyrosine kinase activity. Herceptin is a major drug used to treat HER2 positive breast cancer. Understanding the molecular events that occur when breast cancer cells are exposed to Herceptin is therefore of significant importance. Dual specificity phosphatases (DUSPs) are central regulators of cell signalling that function downstream of HER2, but their role in the cellular response to Herceptin is mostly unknown. This study aims to model the initial effects of Herceptin exposure on DUSPs in HER2-positive breast cancer cells using Boolean modelling.

Results: We experimentally measured expression time courses of 21 different DUSPs between 0 and 24 h following Herceptin treatment of human MDA-MB-453 HER2-positive breast cancer cells. We clustered these time courses into patterns of similar dynamics over time. In parallel, we built a series of Boolean models representing the known regulatory mechanisms of DUSPs and then demonstrated that the dynamics predicted by the models is in agreement with the experimental data. Furthermore, we used the models to predict regulatory mechanisms of DUSPs, where these mechanisms were partially known.

Conclusions: Boolean modelling is a powerful technique to investigate and understand signalling pathways. We obtained an understanding of different regulatory pathways in breast cancer and new insights on how these signalling pathways are activated. This method can be generalized to other drugs and longer time courses to better understand how resistance to drugs develops in cancer cells over time.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s12918-018-0534-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5907139PMC
April 2018

Stepping out of the shadows: Oncogenic and tumor-promoting protein tyrosine phosphatases.

Authors:
Ari Elson

Int J Biochem Cell Biol 2018 03 20;96:135-147. Epub 2017 Sep 20.

Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot, 76100, Israel. Electronic address:

Protein tyrosine phosphorylation is critical for proper function of cells and organisms. Phosphorylation is regulated by the concerted but generically opposing activities of tyrosine kinases (PTKs) and tyrosine phosphatases (PTPs), which ensure its proper regulation, reversibility, and ability to respond to changing physiological situations. Historically, PTKs have been associated mainly with oncogenic and pro-tumorigenic activities, leading to the generalization that protein dephosphorylation is anti-oncogenic and hence that PTPs are tumor-suppressors. In many cases PTPs do suppress tumorigenesis. However, a growing body of evidence indicates that PTPs act as dominant oncogenes and drive cell transformation in a number of contexts, while in others PTPs support transformation that is driven by other oncogenes. This review summarizes the known transforming and tumor-promoting activities of the classical, tyrosine specific PTPs and highlights their potential as drug targets for cancer therapy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.biocel.2017.09.013DOI Listing
March 2018

Regulation of receptor-type protein tyrosine phosphatases by their C-terminal tail domains.

Biochem Soc Trans 2016 10;44(5):1295-1303

Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot 76100, Israel.

Protein tyrosine phosphatases (PTPs) perform specific functions in vivo, despite being vastly outnumbered by their substrates. Because of this and due to the central roles PTPs play in regulating cellular function, PTP activity is regulated by a large variety of molecular mechanisms. We review evidence that indicates that the divergent C-terminal tail sequences (C-terminal domains, CTDs) of receptor-type PTPs (RPTPs) help regulate RPTP function by controlling intermolecular associations in a way that is itself subject to physiological regulation. We propose that the CTD of each RPTP defines an 'interaction code' that helps determine molecules it will interact with under various physiological conditions, thus helping to regulate and diversify PTP function.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1042/BST20160141DOI Listing
October 2016

Production of Osteoclasts for Studying Protein Tyrosine Phosphatase Signaling.

Methods Mol Biol 2016 ;1447:283-300

Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot, 76100, Israel.

Osteoclasts, specialized cells that degrade bone, are key components of the cellular system that regulates and maintains bone homeostasis. Aberrant function of osteoclasts can lead to pathological loss or gain of bone mass, such as in osteopetrosis, osteoporosis, and several types of cancer that metastasize to bone. Phosphorylation of osteoclast proteins on tyrosine residues is critical for formation of osteoclasts and for their proper function and responses to physiological signals. Here we describe preparation and growth of osteoclasts from bone marrow of mice, use of viral vectors to downregulate expression of endogenous proteins and to express exogenous proteins in osteoclasts, and analysis of signaling processes triggered by M-CSF, estrogen, and physical contact with matrix in these cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/978-1-4939-3746-2_16DOI Listing
January 2018

Receptor Protein Tyrosine Phosphatase α-Mediated Enhancement of Rheumatoid Synovial Fibroblast Signaling and Promotion of Arthritis in Mice.

Arthritis Rheumatol 2016 Feb;68(2):359-69

La Jolla Institute for Allergy and Immunology, La Jolla, California.

Objective: During rheumatoid arthritis (RA), fibroblast-like synoviocytes (FLS) critically promote disease pathogenesis by aggressively invading the extracellular matrix of the joint. The focal adhesion kinase (FAK) signaling pathway is emerging as a contributor to the anomalous behavior of RA FLS. The receptor protein tyrosine phosphatase α (RPTPα), which is encoded by the PTPRA gene, is a key promoter of FAK signaling. The aim of this study was to investigate whether RPTPα mediates FLS aggressiveness and RA pathogenesis.

Methods: Through RPTPα knockdown, we assessed FLS gene expression by quantitative polymerase chain reaction analysis and enzyme-linked immunosorbent assay, invasion and migration by Transwell assays, survival by annexin V and propidium iodide staining, adhesion and spreading by immunofluorescence microscopy, and activation of signaling pathways by Western blotting of FLS lysates. Arthritis development was examined in RPTPα-knockout (KO) mice using the K/BxN serum-transfer model. The contribution of radiosensitive and radioresistant cells to disease was evaluated by reciprocal bone marrow transplantation.

Results: RPTPα was enriched in the RA synovial lining. RPTPα knockdown impaired RA FLS survival, spreading, migration, invasiveness, and responsiveness to platelet-derived growth factor, tumor necrosis factor, and interleukin-1 stimulation. These phenotypes correlated with increased phosphorylation of Src on inhibitory Y(527) and decreased phosphorylation of FAK on stimulatory Y(397) . Treatment of RA FLS with an inhibitor of FAK phenocopied the knockdown of RPTPα. RPTPα-KO mice were protected from arthritis development, which was due to radioresistant cells.

Conclusion: By regulating the phosphorylation of Src and FAK, RPTPα mediates proinflammatory and proinvasive signaling in RA FLS, correlating with the promotion of disease in an FLS-dependent model of RA.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/art.39442DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4770259PMC
February 2016

Adaptor protein GRB2 promotes Src tyrosine kinase activation and podosomal organization by protein-tyrosine phosphatase ϵ in osteoclasts.

J Biol Chem 2014 Dec 7;289(52):36048-58. Epub 2014 Nov 7.

From the Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot 76100, Israel,

The non-receptor isoform of protein-tyrosine phosphatase ϵ (cyt-PTPe) supports adhesion of bone-resorbing osteoclasts by activating Src downstream of integrins. Loss of cyt-PTPe reduces Src activity in osteoclasts, reduces resorption of mineralized matrix both in vivo and in cell culture, and induces mild osteopetrosis in young female PTPe KO mice. Activation of Src by cyt-PTPe is dependent upon this phosphatase undergoing phosphorylation at its C-terminal Tyr-638 by partially active Src. To understand how cyt-PTPe activates Src, we screened 73 Src homology 2 (SH2) domains for binding to Tyr(P)-638 of cyt-PTPe. The SH2 domain of GRB2 bound Tyr(P)-638 of cyt-PTPe most prominently, whereas the Src SH2 domain did not bind at all, suggesting that GRB2 may link PTPe with downstream molecules. Further studies indicated that GRB2 is required for activation of Src by cyt-PTPe in osteoclast-like cells (OCLs) in culture. Overexpression of GRB2 in OCLs increased activating phosphorylation of Src at Tyr-416 and of cyt-PTPe at Tyr-638; opposite results were obtained when GRB2 expression was reduced by shRNA or by gene inactivation. Phosphorylation of cyt-PTPe at Tyr-683 and its association with GRB2 are integrin-driven processes in OCLs, and cyt-PTPe undergoes autodephosphorylation at Tyr-683, thus limiting Src activation by integrins. Reduced GRB2 expression also reduced the ability of bone marrow precursors to differentiate into OCLs and reduced the fraction of OCLs in which podosomal adhesion structures assume organization typical of active, resorbing cells. We conclude that GRB2 physically links cyt-PTPe with Src and enables cyt-PTPe to activate Src downstream of activated integrins in OCLs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.M114.603548DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4276870PMC
December 2014

Metabolic regulation by protein tyrosine phosphatases.

J Biomed Res 2014 May 28;28(3):157-68. Epub 2014 Feb 28.

Department of Molecular Genetics, the Weizmann Institute of Science, Rehovot 76100, Israel.

Obesity and the metabolic syndrome and their associated morbidities are major public health issues, whose prevalence will continue to increase in the foreseeable future. Aberrant signaling by the receptors for leptin and insulin plays a pivotal role in development of the metabolic syndrome. More complete molecular-level understanding of how both of these key signaling pathways are regulated is essential for full characterization of obesity, the metabolic syndrome, and type II diabetes, and for developing novel treatments for these diseases. Phosphorylation of proteins on tyrosine residues plays a key role in mediating the effects of leptin and insulin on their target cells. Here, we discuss the molecular methods by which protein tyrosine phosphatases, which are key physiological regulators of protein phosphorylation in vivo, affect signaling by the leptin and insulin receptors in their major target tissues.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.7555/JBR.28.20140012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4085553PMC
May 2014

Protein tyrosine phosphatases ε and α perform nonredundant roles in osteoclasts.

Mol Biol Cell 2014 Jun 2;25(11):1808-18. Epub 2014 Apr 2.

Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel

Female mice lacking protein tyrosine phosphatase ε (PTP ε) are mildly osteopetrotic. Osteoclasts from these mice resorb bone matrix poorly, and the structure, stability, and cellular organization of their podosomal adhesion structures are abnormal. Here we compare the role of PTP ε with that of the closely related PTP α in osteoclasts. We show that bone mass and bone production and resorption, as well as production, structure, function, and podosome organization of osteoclasts, are unchanged in mice lacking PTP α. The varying effects of either PTP on podosome organization in osteoclasts are caused by their distinct N-termini. Osteoclasts express the receptor-type PTP α (RPTPa), which is absent from podosomes, and the nonreceptor form of PTP ε (cyt-PTPe), which is present in these structures. The presence of the unique 12 N-terminal residues of cyt-PTPe is essential for podosome regulation; attaching this sequence to the catalytic domains of PTP α enables them to function in osteoclasts. Serine 2 within this sequence regulates cyt-PTPe activity and its effects on podosomes. We conclude that PTPs α and ε play distinct roles in osteoclasts and that the N-terminus of cyt-PTPe, in particular serine 2, is critical for its function in these cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1091/mbc.E14-03-0788DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4038506PMC
June 2014

Protein tyrosine phosphatases as novel targets in breast cancer therapy.

Biochim Biophys Acta 2013 Dec 10;1836(2):211-26. Epub 2013 Jun 10.

BioCruces Health Research Institute, Hospital de Cruces, Plaza Cruces s/n, 48903 Barakaldo, Spain.

Breast cancer is linked to hyperactivation of protein tyrosine kinases (PTKs), and recent studies have unveiled that selective tyrosine dephosphorylation by protein tyrosine phosphatases (PTPs) of specific substrates, including PTKs, may activate or inactivate oncogenic pathways in human breast cancer cell growth-related processes. Here, we review the current knowledge on the involvement of PTPs in breast cancer, as major regulators of breast cancer therapy-targeted PTKs, such as HER1/EGFR, HER2/Neu, and Src. The functional interplay between PTKs and PTK-activating or -inactivating PTPs, and its implications in novel breast cancer therapies based on targeting of specific PTPs, are discussed.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.bbcan.2013.06.001DOI Listing
December 2013

Protein tyrosine phosphatases in health and disease.

FEBS J 2013 Jan 1;280(2):708-30. Epub 2012 Oct 1.

Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.

Protein tyrosine phosphatases (PTPs) represent a super-family of enzymes that play essential roles in normal development and physiology. In this review, we will discuss the PTPs that have a causative role in hereditary diseases in humans. In addition, recent progress in the development and analysis of animal models expressing mutant PTPs will be presented. The impact of PTP signaling on health and disease will be exemplified for the fields of bone development, synaptogenesis and central nervous system diseases. Collectively, research on PTPs since the late 1980's yielded the cogent view that development of PTP-directed therapeutic tools is essential to further combat human disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/febs.12000DOI Listing
January 2013

Expression profiling during mammary epithelial cell three-dimensional morphogenesis identifies PTPRO as a novel regulator of morphogenesis and ErbB2-mediated transformation.

Mol Cell Biol 2012 Oct 30;32(19):3913-24. Epub 2012 Jul 30.

Cold Spring Harbor Laboratory, Cold Spring Harbor, NY, USA.

Identification of genes that are upregulated during mammary epithelial cell morphogenesis may reveal novel regulators of tumorigenesis. We have demonstrated that gene expression programs in mammary epithelial cells grown in monolayer cultures differ significantly from those in three-dimensional (3D) cultures. We identify a protein tyrosine phosphate, PTPRO, that was upregulated in mature MCF-10A mammary epithelial 3D structures but had low to undetectable levels in monolayer cultures. Downregulation of PTPRO by RNA interference inhibited proliferation arrest during morphogenesis. Low levels of PTPRO expression correlated with reduced survival for breast cancer patients, suggesting a tumor suppressor function. Furthermore, we showed that the receptor tyrosine kinase ErbB2/HER2 is a direct substrate of PTPRO and that loss of PTPRO increased ErbB2-induced cell proliferation and transformation, together with tyrosine phosphorylation of ErbB2. Moreover, in patients with ErbB2-positive breast tumors, low PTPRO expression correlated with poor clinical prognosis compared to ErbB2-positive patients with high levels of PTPRO. Thus, PTPRO is a novel regulator of ErbB2 signaling, a potential tumor suppressor, and a novel prognostic marker for patients with ErbB2-positive breast cancers. We have identified the protein tyrosine phosphatase PTPRO as a regulator of three-dimensional epithelial morphogenesis of mammary epithelial cells and as a regulator of ErbB2-mediated transformation. In addition, we demonstrated that ErbB2 is a direct substrate of PTPRO and that decreased expression of PTPRO predicts poor prognosis for ErbB2-positive breast cancer patients. Thus, our results identify PTPRO as a novel regulator of mammary epithelial transformation, a potential tumor suppressor, and a predictive biomarker for breast cancer.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1128/MCB.00068-12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3457532PMC
October 2012

Multifaceted modulation of K+ channels by protein-tyrosine phosphatase ε tunes neuronal excitability.

J Biol Chem 2012 Aug 21;287(33):27614-28. Epub 2012 Jun 21.

Department of Physiology and Pharmacology of the Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel 69978.

Non-receptor-tyrosine kinases (protein-tyrosine kinases) and non-receptor tyrosine phosphatases (PTPs) have been implicated in the regulation of ion channels, neuronal excitability, and synaptic plasticity. We previously showed that protein-tyrosine kinases such as Src kinase and PTPs such as PTPα and PTPε modulate the activity of delayed-rectifier K(+) channels (I(K)). Here we show cultured cortical neurons from PTPε knock-out (EKO) mice to exhibit increased excitability when compared with wild type (WT) mice, with larger spike discharge frequency, enhanced fast after-hyperpolarization, increased after-depolarization, and reduced spike width. A decrease in I(K) and a rise in large-conductance Ca(2+)-activated K(+) currents (mBK) were observed in EKO cortical neurons compared with WT. Parallel studies in transfected CHO cells indicate that Kv1.1, Kv1.2, Kv7.2/7.3, and mBK are plausible molecular correlates of this multifaceted modulation of K(+) channels by PTPε. In CHO cells, Kv1.1, Kv1.2, and Kv7.2/7.3 K(+) currents were up-regulated by PTPε, whereas mBK channel activity was reduced. The levels of tyrosine phosphorylation of Kv1.1, Kv1.2, Kv7.3, and mBK potassium channels were increased in the brain cortices of neonatal and adult EKO mice compared with WT, suggesting that PTPε in the brain modulates these channel proteins. Our data indicate that in EKO mice, the lack of PTPε-mediated dephosphorylation of Kv1.1, Kv1.2, and Kv7.3 leads to decreased I(K) density and enhanced after-depolarization. In addition, the deficient PTPε-mediated dephosphorylation of mBK channels likely contributes to enhanced mBK and fast after-hyperpolarization, spike shortening, and consequent increase in neuronal excitability observed in cortical neurons from EKO mice.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.M112.342519DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3431696PMC
August 2012

Epidermal growth factor receptor (EGFR)-mediated positive feedback of protein-tyrosine phosphatase epsilon (PTPepsilon) on ERK1/2 and AKT protein pathways is required for survival of human breast cancer cells.

J Biol Chem 2012 Jan 23;287(5):3433-44. Epub 2011 Nov 23.

Centro de Investigación Príncipe Felipe, Valencia 46013, Spain.

Increased tyrosine phosphorylation has been correlated with human cancer, including breast cancer. In general, the activation of tyrosine kinases (TKs) can be antagonized by the action of protein-tyrosine phosphatases (PTPs). However, in some cases PTPs can potentiate the activation of TKs. In this study, we have investigated the functional role of PTPε in human breast cancer cell lines. We found the up-regulation and activation of receptor PTPε (RPTPε) in MCF-7 cells and MDA-MB-231 upon PMA, FGF, and serum stimulation, which depended on EGFR and ERK1/2 activity. Diminishing the expression of PTPε in human breast cancer cells abolished ERK1/2 and AKT activation, and decreased the viability and anchorage-independent growth of the cells. Conversely, stable MCF-7 cell lines expressing inducible high levels of ectopic PTPε displayed higher activation of ERK1/2 and anchorage-independent growth. Our results demonstrate that expression of PTPε is up-regulated and activated in breast cancer cell lines, through EGFR, by sustained activation of the ERK1/2 pathway, generating a positive feedback regulatory loop required for survival of human breast cancer cells.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1074/jbc.M111.293928DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3270997PMC
January 2012

Protein tyrosine phosphatase epsilon affects body weight by downregulating leptin signaling in a phosphorylation-dependent manner.

Cell Metab 2011 May;13(5):562-72

Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot, Israel.

Molecular-level understanding of body weight control is essential for combating obesity. We show that female mice lacking tyrosine phosphatase epsilon (RPTPe) are protected from weight gain induced by high-fat food, ovariectomy, or old age and exhibit increased whole-body energy expenditure and decreased adiposity. RPTPe-deficient mice, in particular males, exhibit improved glucose homeostasis. Female nonobese RPTPe-deficient mice are leptin hypersensitive and exhibit reduced circulating leptin concentrations, suggesting that RPTPe inhibits hypothalamic leptin signaling in vivo. Leptin hypersensitivity persists in aged, ovariectomized, and high-fat-fed RPTPe-deficient mice, indicating that RPTPe helps establish obesity-associated leptin resistance. RPTPe associates with and dephosphorylates JAK2, thereby downregulating leptin receptor signaling. Leptin stimulation induces phosphorylation of hypothalamic RPTPe at its C-terminal Y695, which drives RPTPe to downregulate JAK2. RPTPe is therefore an inhibitor of hypothalamic leptin signaling in vivo, and provides controlled negative-feedback regulation of this pathway following its activation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.cmet.2011.02.017DOI Listing
May 2011

Protein tyrosine phosphatase epsilon regulates integrin-mediated podosome stability in osteoclasts by activating Src.

Mol Biol Cell 2009 Oct 19;20(20):4324-34. Epub 2009 Aug 19.

Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot 76100, Israel.

The nonreceptor isoform of tyrosine phosphatase epsilon (cyt-PTPe) supports osteoclast adhesion and activity in vivo, leading to increased bone mass in female mice lacking PTPe (EKO mice). The structure and organization of the podosomal adhesion structures of EKO osteoclasts are abnormal; the molecular mechanism behind this is unknown. We show here that EKO podosomes are disorganized, unusually stable, and reorganize poorly in response to physical contact. Phosphorylation and activities of Src, Pyk2, and Rac are decreased and Rho activity is increased in EKO osteoclasts, suggesting that integrin signaling is defective in these cells. Integrin activation regulates cyt-PTPe by inducing Src-dependent phosphorylation of cyt-PTPe at Y638. This phosphorylation event is crucial because wild-type-but not Y638F-cyt-PTPe binds and further activates Src and restores normal stability to podosomes in EKO osteoclasts. Increasing Src activity or inhibiting Rho or its downstream effector Rho kinase in EKO osteoclasts rescues their podosomal stability phenotype, indicating that cyt-PTPe affects podosome stability by functioning upstream of these molecules. We conclude that cyt-PTPe participates in a feedback loop that ensures proper Src activation downstream of integrins, thus linking integrin signaling with Src activation and accurate organization and stability of podosomes in osteoclasts.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1091/mbc.e08-11-1158DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2762143PMC
October 2009

PTPepsilon has a critical role in signaling transduction pathways and phosphoprotein network topology in red cells.

Proteomics 2008 Nov;8(22):4695-708

Department of Clinical and Experimental Medicine, Section of Internal Medicine, University of Verona, Verona, Italy.

Protein tyrosine phosphatases (PTPs) are crucial components of cellular signal transduction pathways. Here, we report that red blood cells (RBCs) from mice lacking PTPepsilon (Ptpre(-/-)) exhibit (i) abnormal morphology; (ii) increased Ca(2+)-activated-K(+) channel activity, which was partially blocked by the Src family kinases (SFKs) inhibitor PP1; and (iii) market perturbation of the RBC membrane tyrosine (Tyr-) phosphoproteome, indicating an alteration of RBC signal transduction pathways. Using the signaling network computational analysis of the Tyr-phosphoproteomic data, we identified seven topological clusters. We studied cluster 1 containing Fyn, SFK, and Syk another tyrosine kinase. In Ptpre(-/-)mouse RBCs, the activity of Fyn was increased while Syk kinase activity was decreased compared to wild-type RBCs, validating the network computational analysis, and indicating a novel signaling pathway, which involves Fyn and Syk in regulation of red cell morphology.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/pmic.200700596DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3008556PMC
November 2008

Protein tyrosine phosphatases in osteoclast differentiation, adhesion, and bone resorption.

Eur J Cell Biol 2008 Sep 14;87(8-9):479-90. Epub 2008 Mar 14.

Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot 76100, Israel.

Osteoclasts are large cells derived from the monocyte-macrophage hematopoietic cell lineage. Their primary function is to degrade bone in various physiological contexts. Osteoclasts adhere to bone via podosomes, specialized adhesion structures whose structure and subcellular organization are affected by mechanical contact of the cell with bone matrix. Ample evidence indicates that reversible tyrosine phosphorylation of podosomal proteins plays a major role in determining the organization and dynamics of podosomes. Although roles of several tyrosine kinases are known in detail in this respect, little is known concerning the roles of protein tyrosine phosphatases (PTPs) in regulating osteoclast adhesion. Here we summarize available information concerning the known and hypothesized roles of the best-researched PTPs in osteoclasts - PTPRO, PTP epsilon, SHP-1, and PTP-PEST. Of these, PTPRO, PTP epsilon, and PTP-PEST appear to support osteoclast activity while SHP-1 inhibits it. Additional studies are required to provide full molecular details of the roles of these PTPs in regulating osteoclast adhesion, and to uncover additional PTPs that participate in this process.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ejcb.2008.01.006DOI Listing
September 2008

Protein tyrosine phosphatases: functional inferences from mouse models and human diseases.

FEBS J 2008 Mar;275(5):816-30

Department of Cell Biology, Radboud University Nijmegen Medical Centre, The Netherlands.

Some 40-odd genes in mammals encode phosphotyrosine-specific, 'classical' protein tyrosine phosphatases. The generation of animal model systems and the study of various human disease states have begun to elucidate the important and diverse roles of protein tyrosine phosphatases in cellular signalling pathways, development and disease. Here, we provide an overview of those findings from mice and men, and indicate several novel approaches that are now being exploited to further our knowledge of this fascinating enzyme family.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/j.1742-4658.2008.06249.xDOI Listing
March 2008

Protein tyrosine phosphatase epsilon and Neu-induced mammary tumorigenesis.

Cancer Metastasis Rev 2008 Jun;27(2):193-203

Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot, Israel.

Aberrant regulation of the phosphorylation of proteins on tyrosine residues is a well-established cause of cancer. Protein tyrosine phosphatases (PTPs) share in the crucial function of maintaining appropriate levels of phosphorylation of cellular proteins, making them potentially key players in regulating the transformation process. The receptor-type tyrosine phosphatase Epsilon (RPTPepsilon) participates in supporting the transformed phenotype of mammary tumor cells induced in vivo by the Neu tyrosine kinase. The phosphatase is overexpressed in mammary tumors induced in mice by a Neu transgene and expression of RPTPepsilon in mouse mammary glands leads to massive hyperplasia and associated tumorigenesis. Furthermore, cells isolated from mammary tumors induced by Neu in mice genetically lacking RPTPepsilon appear less transformed and proliferate less well than corresponding mammary tumor cells isolated from mice expressing the phosphatase. At the molecular level, RPTPepsilon dephosphorylates and activates Src and the related kinases Yes and Fyn, and the activities of these kinases are significantly reduced in tumor cells lacking RPTPepsilon. Restoring the activities of these kinases reveals that it is only the reduced activity of Src that causes the aberrant morphology and proliferation rate of tumor cells lacking RPTPepsilon. RPTPepsilon is primed to activate Src, and presumably related kinases, following its phosphorylation by Neu at Y695 within its C-terminus. This event is crucial in enabling RPTPepsilon to activate Src, but appears not to affect the activity of RPTPepsilon towards unrelated substrates. We conclude that a Neu-RPTPepsilon-Src pathway exists in mouse mammary tumor cells, in which Neu phosphorylates RPTPepsilon thereby driving the phosphatase to specifically activate Src family kinases and to assist in maintaining the transformed phenotype.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10555-008-9124-0DOI Listing
June 2008