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 po rcine epithelial cell line LLC-PK1 (CL-4), human peripheral blood leuk ocytes, and human liver was analyzed. PCR amplification yielded 8-11 p utative myosins (depending on the cDNA source) representing six distin ct myosin classes. Analysis of clones obtained by hybridization screen ing demonstrated that the original PCR products correspond to bona fid e myosins, based on the presence of sequences highly conserved in othe r myosins. RNase protection analysis confirmed mRNA expression of 11 m yosins in Caco-2(BBe) cells. Immunoblot analysis showed that at least 6 myosin immuno gens are expressed in Caco-2(BBe) cells. The results r eveal the existence of at least 11 unconventional human myosin genes, most of which are expressed in an overlapping fashion in different cel l types. The abundance of myosins suggests that the myosin I vs. myosi n Il paradigm is inadequate to explain actin-based cellular motility.