DOMAIN-SPECIFIC PHOSPHORYLATION OF VIMENTIN AND GLIAL FIBRILLARY ACIDIC PROTEIN BY PKN

PKN is a serine/threonine protein kinase with a catalytic domain homol ogous to the protein kinase C family and unique N-terminal leucine zip per-like sequences, Using analyses with the yeast two-hybrid system an d in vitro binding assay, we found that the regulatory domain of PKN i nteracted with vimentin. We then examined whether PKN would phosphoryl ate vimentin in vitro. Vimentin proved to be an excellent substrate fo r PKN, and the phosphorylation of vimentin by PKN occurred in the head domain with the result of a nearly complete inhibition of its filamen t formation in vitro. Similar results were also obtained with another type III intermediate filament protein, glial fibrillary acidic protei n (GFAP), These results raise the possibility that PKN may regulate fi lament structures of vimentin and GFAP by domain-specific phosphorylat ion. (C) 1997 Academic Press.