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Increased expression of a high molecular weight (130 KD) protein kinase C isoform in a differentiation‐defective ras‐transfected keratinocyte line
Author(s) -
Rosales J. L.,
Isseroff R. R.
Publication year - 1995
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.1041640309
Subject(s) - hacat , protein kinase c , immunoprecipitation , microbiology and biotechnology , transfection , biology , extracellular , cell culture , kinase , protein kinase a , biochemistry , chemistry , in vitro , genetics
The role of ras on protein kinase C (PKC) signaling was examined in two keratinocyte cell lines. Increasing the level of extracellular calcium from 0.15 mM to 1.0 mM induces some features of differentiation in the spontaneously immortalized HaCaT line, but fails to do so in a c‐H‐ras‐transfected subline (ras‐HaCaT). Raising extracellular calcium also induced a transient increase in membrane‐associated PKC activity 5 min after calcium addition, in HaCaT, but not in the ras‐HaCaT cells. Partial purification of PKC from the membrane/particulate fraction revealed the major isoform expressed in HaCaT to be an 80 KD species recognized by the anti‐PKCα antibody. In ras‐HaCaT, the major expressed isoform is a 130 KD species recognized by the PKCb̃ antibody. The kinase activity of the partially purified high molecular weight PKC is phospholipid dependent but calcium independent. Further evaluation of PKC in the HaCaT and ras‐HaCaT membrane/particulate cell fraction by immunoblotting using affinity‐purified antibodies against PKCα, b̃, δ, ε and ζ revealed a 130 KD band reacting with the PKCδ antibody. Increased expression of this high molecular weight protein was observed in ras‐HaCaT. Immunoprecipitation of PKC in ras‐HaCaT using the PKCδ antibody also revealed a 130 KD species. Analysis of the PKCδ immunoprecipitate demonstrated a phospholipid, but not calcium‐dependent kinase which autophosphorylated. These results suggest that the 130 KD protein may be a novel (calcium‐independent) PKC (nPKC) isoform and increased expression in the rastransfected HaCaT may be a consequence of oncogenic ras expression. This 130 KD species may also play a role in the ras‐associated inhibition of differentiation in HaCaT. © 1995 Wiley‐Liss, Inc.