Diversity of vinculin/meta-vinculin in human tissues and cultivated cells. Expression of muscle specific variants of vinculin in human aorta smooth muscle cells

Abstract

Microheterogeneity of different vinculin and meta-vinculin isoforms in adult human tissues and cultured cells was studied by two-dimensional gel electrophoresis and immunoblotting technique. Four isoforms of vinculin (alpha, alpha', beta, and gamma) and two isoforms of meta-vinculin (alpha and beta) were resolved. alpha-, alpha'-, and beta-isoforms of vinculin were found in all cell types and tissue samples analyzed in the present study. gamma-Isoform of vinculin and both alpha- and beta-isoforms of meta-vinculin were found in smooth (aorta wall and myometrium) and cardiac muscle, rather than in skeletal muscle, liver, foreskin fibroblasts, and macrophages. In the primary culture of human aorta smooth muscle cells, the fractional content of gamma-isoform of vinculin and meta-vinculin was dramatically reduced, and, by the onset of intensive cell division, the proteins could hardly be detected. Subcultured human aorta smooth muscle cells did not contain gamma-vinculin and meta-vinculin. We analyzed the microheterogeneity of vinculin and meta-vinculin in three smooth muscle layers of human aorta wall--media, muscular-elastic (adjacent to media) intima, and subendothelial (juxtaluminal) intima. It was shown that in media the fractional content of gamma-isoform of vinculin was 45% and meta-vinculin, 42%; in muscular-elastic intima the fractional content of gamma-vinculin was 42% and meta-vinculin, 36%. However, in subendothelial intima, the share of these proteins was significantly lower than in adjacent muscular-elastic intima and media. Isoactin pattern that is characteristic of smooth muscle was identical in all aortic layers, thus proving the smooth muscle origin of subendothelial intima cells. These findings demonstrate that human aortic smooth muscle cells in vivo and in vitro undergo coordinated differential expression of smooth muscle specific variants of vinculin, i.e. gamma-vinculin and meta-vinculin.