Vo. Rybin et al., PKC-LAMBDA IS THE ATYPICAL PROTEIN-KINASE-C ISOFORM EXPRESSED BY IMMATURE VENTRICLE, American journal of physiology. Heart and circulatory physiology, 41(4), 1997, pp. 1636-1642
We recently identified a developmental decline in protein kinase C (PK
C) isoform expression, at the level of the protein, in rat ventricular
myocardium. To investigate mechanisms regulating PKC isoform expressi
on in cardiac tissue, this study uses Northern blot analysis to compar
e the abundance of PKC isoform mRNAs in neonatal and adult rat ventric
ular myocardium. PKC-epsilon protein and mRNA were detected in both ne
onatal and adult rat ventricular myocardial preparations. In contrast,
coordinate postnatal declines in the abundance of PKC-alpha and PKC-d
elta proteins and transcripts were identified. An antiserum raised aga
inst the COOH-terminal sequence of PKC-zeta detected abundant immunore
activity in neonatal, but not adult, ventricular myocytes. However, PK
C-zeta transcripts were not detectable in the heart either by Northern
blot analysis or a reverse transcriptase-polymerase chain reaction ap
proach, indicating that neither the myocytes nor the contaminating cel
lular elements in the heart express PKC-zeta. Rather, PKC-lambda, anot
her atypical PKC isoform that is structurally highly homologous to PKC
-zeta, was detected at the protein and mRNA level in neonatal, but not
adult, ventricular myocardium. Taken together, these results establis
h that developmental declines in calcium-sensitive, novel, and atypica
l PKC isoforms are paralleled by changes in the levels of the mRNAs en
coding these proteins, suggesting transcriptional regulation of PKC du
ring normal cardiac development. The results of this study further ide
ntify PKC-lambda as the atypical PKC isoform expressed by the immature
ventricle.