AJP - Cell Physiology, Vol 261, Issue 4 C699-C707, Copyright © 1991 by American Physiological Society
Serum and growth factor induction of Na(+)-K(+)-ATPase subunit mRNAs in Clone 9 cells: role of protein kinase C
A. Bhutada and F. Ismail-Beigi
Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, New York 10032.
In a previous study, we found that addition of serum to confluent Clone 9
cells, a nontransformed rat liver cell line, increased the abundance of
mRNA alpha 1 and mRNA beta 1 at 3 h by 2- and 2.7-fold, respectively
[Bhutada et al. Am. J. Physiol. 258 (Cell Physiol. 27): C1044-C1050, 1990].
We now report that exposure of these cells to 160 nM
12-O-tetradecanoylphorbol 13-acetate (TPA) for 6 h increases mRNA alpha 1
and mRNA beta 1 by 1.7 +/- 0.2- and 2.1 +/- 0.3-fold, respectively.
Incubation in the presence of 160 nM TPA for 24 h reduced high-affinity
phorbol dibutyrate-binding sites [dissociation constant (Kd) = 5 nM;
maximum binding (Bmax) = 1.2 pmol/mg protein] to undetectable levels. In
such cells, exposure to 10% serum for 6 h still resulted in two- and
fourfold increment in mRNA alpha 1 and mRNA beta 1 abundances,
respectively, while further addition of TPA to these protein kinase C
(PKC)-depleted cells resulted in no change in the subunit mRNA abundances.
The increments in mRNA alpha 1 content in response to 10% serum and 160 nM
TPA at 6 h were additive, whereas the increments in mRNA beta 1 were not.
The following agents increased mRNA alpha 1 and mRNA beta 1 abundance in
both control and PKC-depleted cells: epidermal growth factor,
platelet-derived growth factor, basic fibroblast growth factor, insulin,
dexamethasone, and hypothyroid calf serum. In contrast,
N6,2'-O-dibutyryl-adenosine 3',5'-cyclic monophosphate and aldosterone had
no effect.(ABSTRACT TRUNCATED AT 250 WORDS)
