Publications by authors named "Zsuzsa Bartos"

6 Publications

  • Page 1 of 1

Identification of Specific Trafficking Defects of Naturally Occurring Variants of the Human ABCG2 Transporter.

Front Cell Dev Biol 2021 9;9:615729. Epub 2021 Feb 9.

Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences Centre of Excellence, Budapest, Hungary.

Proper targeting of the urate and xenobiotic transporter ATP-binding transporter subfamily G member 2 (ABCG2) to the plasma membrane (PM) is essential for its normal function. The naturally occurring Q141K and M71V polymorphisms in ABCG2, associated with gout and hyperuricemia, affect the cellular routing of the transporter, rather than its transport function. The cellular localization of ABCG2 variants was formerly studied by immunolabeling, which provides information only on the steady-state distribution of the protein, leaving the dynamics of its cellular routing unexplored. In the present study, we assessed in detail the trafficking of the wild-type, M71V-, and Q141K-ABCG2 variants from the endoplasmic reticulum (ER) to the cell surface using a dynamic approach, the so-called Retention Using Selective Hooks (RUSH) system. This method also allowed us to study the kinetics of glycosylation of these variants. We found that the fraction of Q141K- and M71V-ABCG2 that passes the ER quality control system is only partially targeted to the PM; a subfraction is immobile and retained in the ER. Surprisingly, the transit of these variants through the Golgi apparatus (either the appearance or the exit) was unaffected; however, their PM delivery beyond the Golgi was delayed. In addition to identifying the specific defects in the trafficking of these ABCG2 variants, our study provides a novel experimental tool for studying the effect of drugs that potentially promote the cell surface delivery of mutant or polymorphic ABCG2 variants with impaired trafficking.
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http://dx.doi.org/10.3389/fcell.2021.615729DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7900420PMC
February 2021

Syndecan-4 Modulates Cell Polarity and Migration by Influencing Centrosome Positioning and Intracellular Calcium Distribution.

Front Cell Dev Biol 2020 15;8:575227. Epub 2020 Oct 15.

Department of Biochemistry, Faculty of Medicine, University of Szeged, Szeged, Hungary.

Efficient cell migration requires cellular polarization, which is characterized by the formation of leading and trailing edges, appropriate positioning of the nucleus and reorientation of the Golgi apparatus and centrosomes toward the leading edge. Migration also requires the development of an asymmetrical front-to-rear calcium (Ca) gradient to regulate focal adhesion assembly and actomyosin contractility. Here we demonstrate that silencing of syndecan-4, a transmembrane heparan sulfate proteoglycan, interferes with the correct polarization of migrating mammalian myoblasts (i.e., activated satellite stem cells). In particular, syndecan-4 knockdown completely abolished the intracellular Ca gradient, abrogated centrosome reorientation and thus decreased cell motility, demonstrating the role of syndecan-4 in cell polarity. Additionally, syndecan-4 exhibited a polarized distribution during migration. Syndecan-4 knockdown cells exhibited decreases in the total movement distance during directional migration, maximum and vectorial distances from the starting point, as well as average and maximum cell speeds. Super-resolution direct stochastic optical reconstruction microscopy images of syndecan-4 knockdown cells revealed nanoscale changes in the actin cytoskeletal architecture, such as decreases in the numbers of branches and individual branch lengths in the lamellipodia of the migrating cells. Given the crucial importance of myoblast migration during embryonic development and postnatal muscle regeneration, we conclude that our results could facilitate an understanding of these processes and the general role of syndecan-4 during cell migration.
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http://dx.doi.org/10.3389/fcell.2020.575227DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7593626PMC
October 2020

Cellular Processing of the ABCG2 Transporter-Potential Effects on Gout and Drug Metabolism.

Cells 2019 10 8;8(10). Epub 2019 Oct 8.

Institute of Enzymology, Research Centre for Natural Sciences, Magyar Tudosok krt. 2, 1117 Budapest, Hungary.

The human ABCG2 is an important plasma membrane multidrug transporter, involved in uric acid secretion, modulation of absorption of drugs, and in drug resistance of cancer cells. Variants of the ABCG2 transporter, affecting cellular processing and trafficking, have been shown to cause gout and increased drug toxicity. In this paper, we overview the key cellular pathways involved in the processing and trafficking of large membrane proteins, focusing on ABC transporters. We discuss the information available for disease-causing polymorphic variants and selected mutations of ABCG2, causing increased degradation and impaired travelling of the transporter to the plasma membrane. In addition, we provide a detailed in silico analysis of an as yet unrecognized loop region of the ABCG2 protein, in which a recently discovered mutation may actually promote ABCG2 membrane expression. We suggest that post-translational modifications in this unstructured loop at the cytoplasmic surface of the protein may have special influence on ABCG2 processing and trafficking.
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http://dx.doi.org/10.3390/cells8101215DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6830335PMC
October 2019

Cellular expression and function of naturally occurring variants of the human ABCG2 multidrug transporter.

Cell Mol Life Sci 2020 Jan 28;77(2):365-378. Epub 2019 Jun 28.

Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar Tudosok krt. 2, Budapest, 1117, Hungary.

The human ABCG2 multidrug transporter plays a crucial role in the absorption and excretion of xeno- and endobiotics; thus the relatively frequent polymorphic and mutant ABCG2 variants in the population may significantly alter disease conditions and pharmacological effects. Low-level or non-functional ABCG2 expression may increase individual drug toxicity, reduce cancer drug resistance, and result in hyperuricemia and gout. In the present work we have studied the cellular expression, trafficking, and function of nine naturally occurring polymorphic and mutant variants of ABCG2. A comprehensive analysis of the membrane localization, transport, and ATPase activity, as well as retention and degradation in intracellular compartments was performed. Among the examined variants, R147W and R383C showed expression and/or protein folding defects, indicating that they could indeed contribute to ABCG2 functional deficiency. These studies and the applied methods should significantly promote the exploration of the medical effects of these personal variants, promote potential therapies, and help to elucidate the specific role of the affected regions in the folding and function of the ABCG2 protein.
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http://dx.doi.org/10.1007/s00018-019-03186-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6971004PMC
January 2020

Clinically relevant mutations in the ABCG2 transporter uncovered by genetic analysis linked to erythrocyte membrane protein expression.

Sci Rep 2018 05 10;8(1):7487. Epub 2018 May 10.

Institute of Enzymology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, Magyar Tudosok krt. 2, Budapest, 1117, Hungary.

The ABCG2 membrane protein is a key xeno- and endobiotic transporter, modulating the absorption and metabolism of pharmacological agents and causing multidrug resistance in cancer. ABCG2 is also involved in uric acid elimination and its impaired function is causative in gout. Analysis of ABCG2 expression in the erythrocyte membranes of healthy volunteers and gout patients showed an enrichment of lower expression levels in the patients. By genetic screening based on protein expression, we found a relatively frequent, novel ABCG2 mutation (ABCG2-M71V), which, according to cellular expression studies, causes reduced protein expression, although with preserved transporter capability. Molecular dynamics simulations indicated a stumbled dynamics of the mutant protein, while ABCG2-M71V expression in vitro could be corrected by therapeutically relevant small molecules. These results suggest that personalized medicine should consider this newly discovered ABCG2 mutation, and genetic analysis linked to protein expression provides a new tool to uncover clinically important mutations in membrane proteins.
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http://dx.doi.org/10.1038/s41598-018-25695-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5945641PMC
May 2018

Effects of 4-nonylphenol on the steroidogenesis of human adrenocarcinoma cell line (NCI-H295R).

J Environ Sci Health A Tox Hazard Subst Environ Eng 2017 Feb 11;52(3):221-227. Epub 2016 Nov 11.

a Department of Animal Physiology , Faculty of Biotechnology and Food Sciences, Slovak University of Agriculture , Nitra , Slovak Republic.

In this study, the human H295R adrenocarcinoma cell line was exposed to different concentrations (0.04, 0.2, 1.0, 2.5 or 5 µg/mL) of nonylphenol (NP) to investigate its impact on the inhibition or induction of the steroid hormones production during 48 h of in vitro culture. The hormone production was measured using ELISA kits. Results of this in vitro study suggest various effect of nonylphenol in relatively low concentrations on the selected steroid hormones production by the human H295R adrenocarcinoma cell line. The inhibiting impact on progesterone and androstenedione production was observed. The amount of progesterone was significantly decreased at 1.0, 2.5 and 5 µg/mL NP. Equally, the androstenedione production significantly decreased at 5 µg/mL NP. On the other hand, the amount of testosterone and 17β-estradiol was induced after nonylphenol exposition. The significant increase of testosterone level was found out at treatment with 5 µg/mL NP. 17β-estradiol production significantly increased at the doses of 2.5 and 5 µg/mL NP.
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http://dx.doi.org/10.1080/10934529.2016.1246936DOI Listing
February 2017