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Involvement of SASH1 in the Maintenance of Stable Cell–Cell Adhesion

A. S. Ilnitskaya1, I. Y. Zhitnyak1, and N. A. Gloushankova1,a*

1Blokhin National Medical Research Center of Oncology, Ministry of Health of the Russian Federation, 115478 Moscow, Russia

* To whom correspondence should be addressed.

Received April 1, 2020; Revised April 29, 2020; Accepted May 3, 2020
SASH1 is an adapter and signaling protein that contains SH3 and SAM domains responsible for protein–protein interactions. SASH1 downregulation has been observed in many tumors. We examined localization of SASH1 in cultures of normal IAR-20 epithelial cells and HT-29 colorectal cancer cells using immunofluorescence staining and confocal microscopy. IAR-20 normal epithelial cells and HT-29 cells with epithelial phenotype formed stable linear adherens junctions (AJs) associated with circumferential actin bundles. In both IAR-20 and HT-29 cells, SASH1 was co-localized with zones of circumferential actin bundles and linear AJs. SASH1 was not detected in lamellipodia. IAR-20 and HT-29 cells treated with Epidermal Growth Factor underwent epithelial-mesenchymal transition (EMT). We observed significant differences in the course of EMT between IAR-20 and HT-29 cultures. IAR-20 cells underwent partial EMT acquiring migratory phenotype but retaining E-cadherin in unstable radial AJs. SASH1 was present in these contacts. Disappearance of AJs was observed in HT-29 cell undergoing a complete EMT, which also resulted in disruption of stable cell–cell adhesion. SASH1 was lost from the zones of cell–cell interaction. SASH1 depletion by means of RNA interference in IAR-20 cells led to destruction of stable linear AJs and acquisition of mesenchymal phenotype by some of the cells. These data indicate involvement of SASH1 in the maintenance of stable cell–cell adhesion.
KEY WORDS: SASH1, cell–cell adhesion, E-cadherin, epithelial-mesenchymal transition

DOI: 10.1134/S0006297920060036