Heat stressing stimulates nuclear protein kinase C raising diacylglycerol levels. Nuclear protein kinase C activation precedes Hsp70 mRNA expression.

Abstract

Protein kinase C (pKC) activity has been studied in rat liver after subjecting animals to heat shocking. Nuclear pKC activity was stimulated owing to heat shocking without any change in the cytosolic enzyme activity. The nuclear diacylglycerol levels were raised owing to heat stress along with the stimulation of polarhead phospholipid hydrolysis. Kinetically, the Vmax of nuclear pKC was enhanced as a result of heat shocking, with no change in apparent Km and with concomitant phosphorylation of nuclear lamin B2. Western blot analysis as well as phorbol dibutyrate binding indicate that pKC protein levels did not change because of heat shocking. The stimulation of nuclear pKC under heat stress conditions represents an in vivo phenomenon and the enzymes stimulation precedes Hsp70 mRNA expression.