Divergent Impact of Actin Isoforms on Division of Epithelial Cells
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Divergent Impact of Actin Isoforms on Division of Epithelial Cells G. S. Shagieva1, I. B. Alieva1,2,a*, C. Chaponnier3, and V. B. Dugina1 1
Belozersky Institute of PhysicoChemical Biology, Lomonosov Moscow State University, 119992 Moscow, Russia 2 Federal Research and Clinical Center of PhysicalChemical Medicine of the Federal Medical Biological Agency, 119435 Moscow, Russia 3 Department of Pathology and Immunology, Faculty of Medicine, University of Geneva, 1205 Geneva, Switzerland a email: [email protected] Received June 23, 2020 Revised July 22, 2020 Accepted July 25, 2020 Abstract—We investigated distribution and functions of beta and gammacytoplasmic actins (CYAs) at different stages of nonneoplastic epithelial cell division using laser scanning microscopy (LSM). Here, we demonstrated that beta and gammaCYAs are spatially segregated in the early prophase, anaphase, telophase, and cytokinesis. Small interfering RNA (siRNA) experiments revealed that in both betaCYA and gammaCYAdepleted cells, the number of cells was significantly reduced compared with the siRNA controls. BetaCYA depletion resulted in an enlargement of the cell area in metaphase and high percentage of polynuclear cells compared with the siRNA control, indicating a potential failure of cytokinesis. GammaCYA depletion resulted in a reduced percentage of mitotic cells. We also observed the interdependence between the actin isoforms and the microtubule system in mitosis: (i) a decrease in the gammaCYA led to impaired mitotic spindle organization; (ii) suppression of tubulin polymerization caused impaired betaCYA reorganization, as incubation with col cemid blocked the transfer of short betaactin polymers from the basal to the cortical compartment. We conclude that both actin isoforms are essential for proper cell division, but each isoform has its own specific functional role in this process. DOI: 10.1134/S0006297920090072 Keywords: cytoplasmic actin, mitosis, microtubules, cell division
INTRODUCTION Actin and its regulatory proteins are critically impor tant in the cell division. The actin cytoskeleton of epithe lial cells consists of two cytoplasmic actin (CYA) isoforms and numerous actin binding proteins providing different cytoskeleton structures. Beta and gammaCYAs are expressed almost in all human cells in different propor tions and differ only by four amino acids located at posi tions 1, 2, 3, and 9 at the Nterminus [1]. We have previ ously shown that beta and gammaCYAs display distinct distribution and functions in the fibroblasts and epithelial cells. BetaCYA predominantly forms contractile stress fibers, whereas gammaCYA is organized in a fine apical meshwork of actin filaments throughout the cell [2, 3]. During transition to cell division, all cytoskeletal components undergo significant changes. Interaction of Abbreviations: CYA, cytoplasmic actin; LSM, laser scanning microscopy; siRNA, small interfering RNA. * To whom correspondence should be addressed.
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