Studies on the function of Rho A protein in cardiac myofibrillogenesis

✍ Scribed by Seu-Mei Wang; Yi-Jye Tsai; Meei-Jyh Jiang; Yung-Zu Tseng

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 744 KB
• Volume: 66
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/(sici)1097-4644(19970701)66:1<43::aid-jcb6>3.0.co;2-y

✦ Synopsis

The aim of this study was to provide morphological evidence for the presence of rho A protein in developing cardiomyocytes and to investigate its possible role in myofibrillogenesis. Immunostaining with a monoclonal anti-rho antibody gave a diffuse pattern in the cytosol of cultured cardiomyocytes. Introduction of C3 exoenzyme into the cells by electroporation was used to inactivate rho A protein by ADP-ribosylation. An immunostaining with anti-vinculin, anti-talin, and anti-integrin antibodies showed the focal adhesions in electroporation control cardiomyocytes to be evenly distributed in the ventral sarcolemma; the costameric structure was also detected using these antibodies. In contrast, in C3 exoenzyme treated cells, focal adhesions were disassembled and costamere were absent; in addition, b-actin-positive, non-striated fibrils were lost and assembly of M-protein, titin, and a-actinin into myofibrils was poor, as shown by diffuse and filamentous staining pattern. C3 exoenzyme treatment had a less marked effect on mature cardiomyocytes than on immature cells; in this case, cells became distorted and few myofibrils were seen. The intensity of anti-phosphotyrosine antibody staining of the focal adhesion was also decreased or diffuse in C3 exoenzyme-treated cardiomyocytes, suggesting dephosphorylation of focal adhesion components. We therefore conclude that small G protein rho A plays an important role in myofibril assembly in cardiomyocytes.