Loss-of-function of MYO5B induces epithelial cell scattering in enterocytes

A non-functional myosin Vb motor in duodenal enterocytes results in disruption of epithelial cell polarity characterized by complete loss of microvilli and mislocalization of apical brush border proteins in the cytoplasm which finally cause a devastating disease in neonates with severe malabsorption defects accompanied by protracted diarrhea during infancy, classified as microvillus inclusion disease (MVID). The exact mechanisms how loss-of-function of MYO5B induces polarity loss are not completely understood in MVID pathogenesis. Obtaining better insights in cell polarity defects caused by loss of MYO5B, we performed microarray- in combination with protein expression-analysis in an inducible CaCo2 MYO5B RNAi cell system. Surprisingly, in MYO5B-depleted CaCo2 cells, CDH1 coding for the cell adhesion protein E-Cadherin and important for cell adhesion and therefore maintenance of cell polarity, was significantly downregulated. Interestingly, mesenchymal cell markers, specifically Vimentin and N-Cadherin, physiologically not expressed in differentiated epithelium, were upregulated and accompanied by increased phospho-c-jun levels in the nucleus. Importantly phospho-c-jun was also found in nuclei of duodenal enterocytes in MVID patients, indicating loss of MYO5B induces epithelial cell scattering in enterocytes.

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Thoeni CE, Vogel GF, Tancevski I, Geley S, Lechner S, Pfaller K, Hess MW, Müller T, Janecke AR, Avitzur Y, Muise A, Cutz E, Huber LA