Y. Arava et al., DIFFERENTIAL EXPRESSION OF THE PROTEIN-KINASE-A REGULATORY SUBUNIT (RI-ALPHA) IN PANCREATIC ENDOCRINE-CELLS, FEBS letters, 425(1), 1998, pp. 24-28
A PCR-based subtractive cloning procedure was used to identify genes e
xpressed at higher levels in the pancreatic beta cell line beta TC1, a
s compared to the pancreatic alpha cell line alpha TC1. One of the clo
nes isolated by this procedure corresponded to the regulatory subunit
(RI alpha) of protein kinase A (PKA). Using antibodies directed agains
t RI alpha, we now demonstrate both by immunoblot and immunofluorescen
ce that RI alpha protein is present at higher levels in cultured beta
cells as compared to alpha cells. In vitro PICA assays revealed high b
asal PKA activity in alpha TC1 extracts, which changed little on addit
ion of exogenous cAMP. On the other hand, extracts from beta cells sho
wed very low basal activity of PICA, which was elevated upon addition
of cAMP. A similar trend was observed in vivo using transfected lucife
rase constructs bearing multiple copies of a CRE element: in alpha TC1
cells, no induction by forskolin was observed, whereas in beta TC1 ce
lls, forskolin produced a 9-fold increase in activity, Therefore, the
results indicate that RI alpha of PW is selectively ex-pressed in panc
reatic beta cells as compared to alpha cells: this selective expressio
n is associated with major differences in the properties of the PICA s
ignal transduction pathway, Differential expression of the regulatory
subunit may play a role in determining the patterns of gene expression
and signal transduction characteristic of alpha and beta cells. (C) 1
998 Federation of European Biochemical Societies.