THE PRESENCE OF H2-CALPONIN IN HUMAN KERATINOCYTE

Calponin (h1 isoform) was characterized as a smooth muscle specific, a ctin-, tropomyosin-, calmodulin-binding protein and described as a fac tor which inhibits contraction. H2-calponin, encoded by a different ge ne from h1-calponin, was identified from the smooth muscles of mouse a nd pig. However, non-muscle calponin analogues have recently been repo rted in rat and pig brains. Here we show the presence of calponin expr essed in human skin tissue and in cultured human keratinocytes using p olyclonal antibodies to bovine aortic smooth muscle calponin. Western blot analysis demonstrated that calponin with a molecular weight aroun d 36000 existed in extracts of keratinocytes. Immunofluorescence micro scopy displayed the localization of calponin in the cytoplasm of the b asal cells in situ, and along the cell-to-cell borders in cultured hum an keratinocytes maintained in standard calcium medium. Furthermore, a ccording to RT-PCR analysis using human h1- and h2-carponin-specific p rimers, calponin expressed by cultured human keratinocytes was identif ied as the h2 isoform. We demonstrated the presence of h2-calponin in human keratinocytes, and it might play a role in the structural organi zation of actin cytoskeleton at the cytoplasmic region of cell-to-cell junctions of keratinocytes. Copyright (C) 1997 Elsevier Science Irela nd Ltd.