Antipeptide antibodies directed against the C-terminus of protein kinase C zeta (PKC zeta) react with a Ca(2+)- and TPA-sensitive PKC in HT-29 human intestinal epithelial cells.
We have studied the PKC isoforms present in HT-29 M6 colon cancer cells, the differentiation of which to mucus-secreting cells is blocked by TPA. In addition to a major 72 kDa band, a 77 kDa PKC isoform was recognized by two different antibodies raised against a C-terminus-specific peptide for the TPA-insensitive isoform, PKC zeta. By different criteria (association to the membrane, down-regulation, PKC activity in immunoprecipitates) we conclude that, contrary to the 72 kDa band, the 77 kDa band corresponds to a Ca(2+)- and TPA-sensitive PKC. These results suggest that antipeptide antibodies directed against the C-terminus of PKC zeta react in human cells with a member of the conventional PKC subfamily besides PKC zeta. Therefore, the data indicating that PKC zeta is sensitive to different agents in various cell lines should be carefully re-evaluated.
Batlle
E
E
Department d'Immunologia, Institut Municipal d'Investigació Mèdica, Barcelona, Spain.
Fabre
M
M
García de Herreros
A
A
D000595:Amino Acid Sequence; D000906:Antibodies / Q000276:immunology*; D000918:Antibody Specificity; D002118:Calcium / Q000494:pharmacology*; D003110:Colonic Neoplasms / Q000201:enzymology*; D004533:Egtazic Acid / Q000494:pharmacology; D004848:Epithelium / Q000201:enzymology; D006801:Humans; D007527:Isoenzymes / Q000276:immunology; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000276:immunology*; D010718:Phosphatidylserines / Q000494:pharmacology; D011493:Protein Kinase C / Q000276:immunology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014407:Tumor Cells, Cultured
D000906:Antibodies; D007527:Isoenzymes; D010446:Peptide Fragments; D010718:Phosphatidylserines; D004533:Egtazic Acid; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium