IDENTIFICATION AND OVERLAPPING EXPRESSION OF MULTIPLE UNCONVENTIONAL MYOSIN GENES IN VERTEBRATE CELL-TYPES

Myosin diversity in the human epithelial cell line Caco-2(BBe), the porcine epithelial cell line LLC-PK1 (CL-4), human peripheral blood leukocytes, and human liver was analyzed. PCR amplification yielded 8-11 putative myosins (depending on the cDNA source) representing six distinct myosin classes. Analysis of clones obtained by hybridization screening demonstrated that the original PCR products correspond to bona fide myosins, based on the presence of sequences highly conserved in other myosins. RNase protection analysis confirmed mRNA expression of 11 myosins in Caco-2(BBe) cells. Immunoblot analysis showed that at least 6 myosin immuno gens are expressed in Caco-2(BBe) cells. The results reveal the existence of at least 11 unconventional human myosin genes, most of which are expressed in an overlapping fashion in different cell types. The abundance of myosins suggests that the myosin I vs. myosin Il paradigm is inadequate to explain actin-based cellular motility.