Publications by authors named "Silvia Brambillasca"

10 Publications

  • Page 1 of 1

Discovery of Reversible Inhibitors of KDM1A Efficacious in Acute Myeloid Leukemia Models.

ACS Med Chem Lett 2020 May 13;11(5):754-759. Epub 2020 Feb 13.

Department of Experimental Oncology, Academic Drug Discovery, European Institute of Oncology IRCCS, Via Adamello 16, 20139 Milan, Italy.

Lysine-specific demethylase 1 (LSD1 or KDM1A) is a FAD-dependent enzyme that acts as a transcription corepressor or coactivator by regulating the methylation status of histone H3 lysines K4 and K9, respectively. KDM1A represents an attractive target for cancer therapy. While, in the past, the main medicinal chemistry strategy toward KDM1A inhibition was based on the optimization of ligands that irreversibly bind the FAD cofactor within the enzyme catalytic site, we and others have also identified reversible inhibitors. Herein we reported the discovery of 5-imidazolylthieno[3,2-]pyrroles, a new series of KDM1A inhibitors endowed with picomolar inhibitory potency, active in cells and efficacious after oral administration in murine leukemia models.
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http://dx.doi.org/10.1021/acsmedchemlett.9b00604DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7236255PMC
May 2020

Pharmacological boost of DNA damage response and repair by enhanced biogenesis of DNA damage response RNAs.

Sci Rep 2019 04 23;9(1):6460. Epub 2019 Apr 23.

IFOM - the FIRC Institute of Molecular Oncology, Via Adamello 16, 20139, Milan, Italy.

A novel class of small non-coding RNAs called DNA damage response RNAs (DDRNAs) generated at DNA double-strand breaks (DSBs) in a DROSHA- and DICER-dependent manner has been shown to regulate the DNA damage response (DDR). Similar molecules were also reported to guide DNA repair. Here, we show that DDR activation and DNA repair can be pharmacologically boosted by acting on such non-coding RNAs. Cells treated with enoxacin, a compound previously demonstrated to augment DICER activity, show stronger DDR signalling and faster DNA repair upon exposure to ionizing radiations compared to vehicle-only treated cells. Enoxacin stimulates DDRNA production at chromosomal DSBs and at dysfunctional telomeres, which in turn promotes 53BP1 accumulation at damaged sites, therefore in a miRNA-independent manner. Increased 53BP1 occupancy at DNA lesions induced by enoxacin ultimately suppresses homologous recombination, channelling DNA repair towards faster and more accurate non-homologous end-joining, including in post-mitotic primary neurons. Notably, augmented DNA repair stimulated by enoxacin increases the survival also of cancer cells treated with chemotherapeutic agents.
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http://dx.doi.org/10.1038/s41598-019-42892-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6478851PMC
April 2019

Novel potent inhibitors of the histone demethylase KDM1A (LSD1), orally active in a murine promyelocitic leukemia model.

Future Med Chem 2017 07 19;9(11):1161-1174. Epub 2017 Jul 19.

Department of Experimental Oncology, Academic Drug Discovery, European Institute of Oncology, Ifom-IEO-Campus, via Adamello 16, 20139 Milan, Italy.

Background: Histone lysine demethylases (KDMs) are well-recognized targets in oncology drug discovery. They function at the post-translation level controlling chromatin conformation and gene transcription. KDM1A is a flavin adenine dinucleotide-dependent amine oxidase, overexpressed in several tumor types, including acute myeloid leukemia, neuroblastoma and non-small-cell lung cancer. Among the many known monoamine oxidase inhibitors screened for KDM1A inhibition, tranylcypromine emerged as a moderately active hit, which irreversibly binds to the flavin adenine dinucleotide cofactor.

Material & Methods: The KDM1A inhibitors 5a-w were synthesized and tested in vitro and in vivo. The biochemical potency was determined, modulation of target in cells was demonstrated on KDM1A-dependent genes and the anti-clonogenic activity was performed in murine acute promyelocytic Leukemia (APL) blasts. An in vivo efficacy experiment was conducted using an established murine promyelocytic leukemia model.

Results: We report a new series of tranylcypromine derivatives substituted on the cyclopropyl moiety, endowed with high potency in both biochemical and cellular assays.

Conclusion: The most interesting derivative (5a) significantly improved survival rate after oral administration in a murine model of promyelocitic leukemia.
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http://dx.doi.org/10.4155/fmc-2017-0003DOI Listing
July 2017

CDK5 regulatory subunit-associated protein 1-like 1 (CDKAL1) is a tail-anchored protein in the endoplasmic reticulum (ER) of insulinoma cells.

J Biol Chem 2012 Dec 9;287(50):41808-19. Epub 2012 Oct 9.

Molecular Diabetology, Paul Langerhans Institute Dresden, Uniklinikum Carl Gustav Carus, Dresden University of Technology, Fetscherstrasse 74, 01307 Dresden, Germany.

Genome-wide association studies have led to the identification of numerous susceptibility genes for type 2 diabetes. Among them is Cdkal1, which is associated with reduced β-cell function and insulin release. Recently, CDKAL1 has been shown to be a methylthiotransferase that modifies tRNA(Lys) to enhance translational fidelity of transcripts, including the one encoding proinsulin. Here, we report that out of several CDKAL1 isoforms deposited in public databases, only isoform 1, which migrates as a 61-kDa protein by SDS-PAGE, is expressed in human islets and pancreatic insulinoma INS-1 and MIN6 cells. We show that CDKAL1 is a novel member of the tail-anchored protein family and exploits the TCR40/Get3-assisted pathway for insertion of its C-terminal transmembrane domain into the endoplasmic reticulum. Using endo-β-N-acetylglucosaminidase H and peptide:N-glycosidase F sensitivity assays on CDKAL1 constructs carrying an N-glycosylation site within the luminal domain, we further established that CDKAL1 is an endoplasmic reticulum-resident protein. Moreover, we observed that silencing CDKAL1 in INS-1 cells reduces the expression of secretory granule proteins prochromogranin A and proICA512/ICA512-TMF, in addition to proinsulin and insulin. This correlated with reduced glucose-stimulated insulin secretion. Taken together, our findings provide new insight into the role of CDKAL1 in insulin-producing cells and help to understand its involvement in the pathogenesis of diabetes.
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http://dx.doi.org/10.1074/jbc.M112.376558DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3516729PMC
December 2012

A VAPB mutant linked to amyotrophic lateral sclerosis generates a novel form of organized smooth endoplasmic reticulum.

FASEB J 2010 May 14;24(5):1419-30. Epub 2009 Dec 14.

Consiglio Nazionale delle Ricerche Institute of Neuroscience, via Vanvitelli 32, 20129 Milano, Italy.

VAPB (vesicle-associated membrane protein-associated protein B) is an endoplasmic reticulum (ER)-resident tail-anchored adaptor protein involved in lipid transport. A dominantly inherited mutant, P56S-VAPB, causes a familial form of amyotrophic lateral sclerosis (ALS) and forms poorly characterized inclusion bodies in cultured cells. To provide a cell biological basis for the understanding of mutant VAPB pathogenicity, we investigated its biogenesis and the inclusions that it generates. Translocation assays in cell-free systems and in cultured mammalian cells were used to investigate P56S-VAPB membrane insertion, and the inclusions were characterized by confocal imaging and electron microscopy. We found that mutant VAPB inserts post-translationally into ER membranes in a manner indistinguishable from the wild-type protein but that it rapidly clusters to form inclusions that remain continuous with the rest of the ER. Inclusions were induced by the mutant also when it was expressed at levels comparable to the endogenous wild-type protein. Ultrastructural analysis revealed that the inclusions represent a novel form of organized smooth ER (OSER) consisting in a limited number of parallel cisternae (usually 2 or 3) interleaved by a approximately 30 nm-thick electron-dense cytosolic layer. Our results demonstrate that the ALS-linked VAPB mutant causes dramatic ER restructuring that may underlie its pathogenicity in motoneurons.
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http://dx.doi.org/10.1096/fj.09-147850DOI Listing
May 2010

How tails guide tail-anchored proteins to their destinations.

Curr Opin Cell Biol 2007 Aug 16;19(4):368-75. Epub 2007 Jul 16.

National Research Council Institute for Neuroscience and Department of Medical Pharmacology, University of Milan, via Vanvitelli 32, 20129 Milano, Italy.

A large group of diverse, functionally important, and differently localized transmembrane proteins shares a particular membrane topology, consisting of a cytosolic N-terminal region, followed by a transmembrane domain close to the C-terminus. Because of their structure, these C-tail-anchored (TA) proteins must insert into all their target membranes by post-translational pathways. Recent work, based on the development of stringent and sensitive biochemical assays, has demonstrated that novel unexplored mechanisms underlie these post-translational targeting and membrane insertion pathways. Unravelling these pathways will shed light on the biosynthesis and regulation of an important group of membrane proteins and is likely to lead to new concepts in the field of membrane biogenesis.
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http://dx.doi.org/10.1016/j.ceb.2007.04.019DOI Listing
August 2007

Unassisted translocation of large polypeptide domains across phospholipid bilayers.

J Cell Biol 2006 Dec 27;175(5):767-77. Epub 2006 Nov 27.

Cellular and Molecular Pharmacology Section, Consiglio Nazionale delle Ricerche Institute of Neuroscience, University of Milan, 20129 Milan, Italy.

Although transmembrane proteins generally require membrane-embedded machinery for integration, a few can insert spontaneously into liposomes. Previously, we established that the tail-anchored (TA) protein cytochrome b(5) (b5) can posttranslationally translocate 28 residues downstream to its transmembrane domain (TMD) across protein-free bilayers (Brambillasca, S., M. Yabal, P. Soffientini, S. Stefanovic, M. Makarow, R.S. Hegde, and N. Borgese. 2005. EMBO J. 24:2533-2542). In the present study, we investigated the limits of this unassisted translocation and report that surprisingly long (85 residues) domains of different sequence and charge placed downstream of b5's TMD can posttranslationally translocate into mammalian microsomes and liposomes at nanomolar nucleotide concentrations. Furthermore, integration of these constructs occurred in vivo in translocon-defective yeast strains. Unassisted translocation was not unique to b5 but was also observed for another TA protein (protein tyrosine phosphatase 1B) whose TMD, like the one of b5, is only moderately hydrophobic. In contrast, more hydrophobic TMDs, like synaptobrevin's, were incapable of supporting unassisted integration, possibly because of their tendency to aggregate in aqueous solution. Our data resolve long-standing discrepancies on TA protein insertion and are relevant to membrane evolution, biogenesis, and physiology.
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http://dx.doi.org/10.1083/jcb.200608101DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2064676PMC
December 2006

Effects of cholesterol manipulation on the signaling of the human oxytocin receptor.

Am J Physiol Regul Integr Comp Physiol 2006 Oct 1;291(4):R861-9. Epub 2006 Jun 1.

Consiglio Nazionale delle Ricerche Institute of Neuroscience, Cellular and Molecular Pharmacology, Milan, Italy.

We have recently shown that oxytocin inhibits cell growth when the vast majority of oxytocin receptors (OTRs) are excluded from detergent-resistant membranes (DRMs; the biochemical counterpart of lipid rafts), but has a strong mitogenic effect when the receptors are targeted to these plasma membrane domains upon fusion with caveolin-2, a resident raft protein. The aim of this study was to investigate whether the manipulation of total cell cholesterol can influence OTR localization and signaling. Our data indicate that cholesterol depletion in HEK-293 cells does not affect the signaling events mediated by the OTRs located outside DRMs. When treated with 2 mM methyl-beta-cyclodextrin (MbetaCD), the receptors remained outside and continued to inhibit cell growth. On the contrary, the MbetaCD treatment of cells expressing receptors fused to caveolin-2 led to their redistribution outside DRMs, and converted the receptor-mediated proliferative effect into cell growth inhibition. These data indicate that 1) once released from DRMs, the receptors fused to caveolin-2 signal exactly as wild-type OTRs and 2) their DRM location is responsible for the specific OTR signaling leading to cell proliferation. Finally, we evaluated whether cholesterol loading could force the OTRs into lipid rafts and change their signaling, but, after cell treatment with an MbetaCD/cholesterol complex, receptor stimulation continued to lead to cell growth inhibition, thus indicating that increasing cell cholesterol levels is not sufficient per se to affect OTR signaling.
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http://dx.doi.org/10.1152/ajpregu.00333.2006DOI Listing
October 2006

Transmembrane topogenesis of a tail-anchored protein is modulated by membrane lipid composition.

EMBO J 2005 Jul 23;24(14):2533-42. Epub 2005 Jun 23.

CNR Institute of Neuroscience - Cell Mol Pharmacology - and Department of Medical Pharmacology, University of Milan, Milan, Italy.

A large class of proteins with cytosolic functional domains is anchored to selected intracellular membranes by a single hydrophobic segment close to the C-terminus. Although such tail-anchored (TA) proteins are numerous, diverse, and functionally important, the mechanism of their transmembrane insertion and the basis of their membrane selectivity remain unclear. To address this problem, we have developed a highly specific, sensitive, and quantitative in vitro assay for the proper membrane-spanning topology of a model TA protein, cytochrome b5 (b5). Selective depletion from membranes of components involved in cotranslational protein translocation had no effect on either the efficiency or topology of b5 insertion. Indeed, the kinetics of transmembrane insertion into protein-free phospholipid vesicles was the same as for native ER microsomes. Remarkably, loading of either liposomes or microsomes with cholesterol to levels found in other membranes of the secretory pathway sharply and reversibly inhibited b5 transmembrane insertion. These results identify the minimal requirements for transmembrane topogenesis of a TA protein and suggest that selectivity among various intracellular compartments can be imparted by differences in their lipid composition.
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http://dx.doi.org/10.1038/sj.emboj.7600730DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1176458PMC
July 2005

Translocation of the C terminus of a tail-anchored protein across the endoplasmic reticulum membrane in yeast mutants defective in signal peptide-driven translocation.

J Biol Chem 2003 Jan 22;278(5):3489-96. Epub 2002 Nov 22.

Program of Cellular Biotechnology, Institute of Biotechnology, University of Helsinki, Viikinkaari 9, 00710 Helsinki, Finland.

C-tail-anchored proteins are defined by an N-terminal cytosolic domain followed by a transmembrane anchor close to the C terminus. Their extreme C-terminal polar residues are translocated across membranes by poorly understood post-translational mechanism(s). Here we have used the yeast system to study translocation of the C terminus of a tagged form of mammalian cytochrome b(5), carrying an N-glycosylation site in its C-terminal domain (b(5)-Nglyc). Utilization of this site was adopted as a rigorous criterion for translocation across the ER membrane of yeast wild-type and mutant cells. The C terminus of b(5)-Nglyc was rapidly glycosylated in mutants where Sec61p was defective and incapable of translocating carboxypeptidase Y, a well known substrate for post-translational translocation. Likewise, inactivation of several other components of the translocon machinery had no effect on b(5)-Nglyc translocation. The kinetics of translocation were faster for b(5)-Nglyc than for a signal peptide-containing reporter. Depletion of the cellular ATP pool to a level that retarded Sec61p-dependent post-translational translocation still allowed translocation of b(5)-Nglyc. Similarly, only low ATP concentrations (below 1 microm), in addition to cytosolic protein(s), were required for in vitro translocation of b(5)-Nglyc into mammalian microsomes. Thus, translocation of tail-anchored b(5)-Nglyc proceeds by a mechanism different from that of signal peptide-driven post-translational translocation.
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http://dx.doi.org/10.1074/jbc.M210253200DOI Listing
January 2003