Microheterogeneity of avian and mammalian vinculin distinctive subcellular distribution of different isovinculins.

Vinculin from chicken gizzard and from pig heart may be separated by twodimensional gel electrophoresis into several isoelectrophoretic forms. Peptide map analysis and immunochemical comparison of the different isovinculins indicated that all the isoforms are closely interrelated at the molecular level. Moreover, it was shown that avian and mammalian vinculins have similar molecular structures. Some differences were detected between the isovinculin pattern in intact chicken gizzard tissue and that found in cultured cells from the same organ. Various degrees of vinculin microheterogeneity were also detected in a variety of cultured cells. including primary cultures and several cell lines. Labelling of chicken gizzard cells with [32P]orthophosphate resulted in the incorporation of 32P in the minor acidic isoform of vinculin (y-vinculin) exclusively. Extraction of the cultured cells with detergent, under conditions that remove the cytoplasmic “soluble” vinculin without significantly affecting focal contact-associated protein, indicated that specific vinculin isoforms may differ in their cellular distribution. The soluble fraction cont,ained almost exclusively the basic form (fi-vinculin). while the “organized” protein contained all three major isovinculins but, was enriched with the acidic form (x) and the intermediate form (T’). The functional significance of isovinrulin diversity and the involvement of phosphorylation events in vinculin interactions are discussed.