Differential expression of an 80-kDa protein kinase C substrate in preneoplastic and neoplastic mouse JB6 cells.
An 80-kDa protein (p80), previously reported to be a major protein kinase C substrate in preneoplastic JB6 mouse epidermal cells, has been shown to be transiently phosphorylated by phorbol 12-O-tetradecanoate 13-acetate. Phosphorylation was maximal at 2 hr of phorbol 12-O-tetradecanoate 13-acetate treatment and returned to basal levels by 24 hr. In contrast, using a p80-specific antibody, we found that phorbol 12-O-tetradecanoate 13-acetate treatment produced no increase in p80 concentration. p80 showed a progressive decrease in JB6 cells during progression from a preneoplastic to neoplastic phenotype. The lack of p80 expression in neoplastic cells was not attributable to lack of protein kinase C; the protein kinase activity and protein concentration were similar in cells of all three phenotypes. When p80 mRNA was analyzed by hybridization to a putative p80 cDNA clone, its relative concentration paralleled that of p80 protein, with high levels present in preneoplastic JB6 cells, and little or no evidence for p80-hybridizing RNA in transformed cells. Thus, p80 appears to be regulated pretranslationally at the level of mRNA concentration during preneoplastic progression in mouse epidermal JB6 cells.
Simek
S L
SL
Cell Biology Section, National Cancer Institute-Frederick Cancer Research Facility, MD 21701-1013.
Kligman
D
D
Patel
J
J
Colburn
N H
NH
D000818:Animals; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D051379:Mice; D008807:Mice, Inbred BALB C; D009363:Neoplasm Proteins / Q000302:isolation & purification / Q000378:metabolism*; D009374:Neoplasms, Experimental / Q000378:metabolism*; D010766:Phosphorylation; D011230:Precancerous Conditions / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D013379:Substrate Specificity; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D009363:Neoplasm Proteins; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate