Overexpression of the α-type protein kinase (PK) C in LLC-PK1 cells does not lead to a proportional increase in the induction of two 12-O-tetradecanoylphorbol-13-acetate-inducible genes

Markus Wartmann, David A. Jans, Peter J. Parker, Yoshikuni Nagamine, Brian A. Hemmings, Susan Jaken, Urs Eppenberger, Doriano Fabbro

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Abstract

Phorbol esters, by activating protein kinase C (PKC), induce the expression of the urokinase-type plasminogen activator (uPA) gene and the proto-oncogene c-fos in LLC-PK1 (PK1) porcine kidney epithelial cells. To investigate the role of PKC in the regulation of these two 12-O-tetradecanoylphorbol-13-acetate (TPA)-inducible genes, the α-type PKC, the predominant subtype present in the PK1 cells, was overexpressed in this cell line. Two clonal PK1 derivatives overexpressing the αPKC 15- and 20-fold, respectively, were established. Compared with the parental and control cells, only a modest but substantially sustained (2- to 3-fold) increase in the accumulation of uPA as well as c-fos mRNAs were observed by TPA in these cells. These results indicate that the extent of induction of these genes mediated by TPA was not proportional to the amounts of α-type PKC stably overexpressed in these cells, suggesting that factor(s) downstream of the activation of the αPKC appear to be rate limiting for the induction of both TPA-inducible genes in PK1 cells.

Original languageEnglish
Pages (from-to)491-502
Number of pages12
JournalMolecular Biology of the Cell
Volume2
Issue number6
DOIs
Publication statusPublished - 1 Jan 1991
Externally publishedYes

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