The 28-kDa protein whose phosphorylation is induced by protein kinase C activators in MCF-7 cells belongs to the family of low molecular mass heat shock proteins and is the estrogen-regulated 24-kDa protein.

摘要: We have previously reported the presence of a 28-kDa protein in human mammary adenocarcinoma MCF-7 cells, whose phosphorylation by phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) and permeant diacylglycerol 1,2-dioctanoyl-sn-glycerol was correlated to growth arrest induced kinase C (PKC) activators. now investigate possible identity this with estrogen-regulated "24-kDa" shown as related mammalian heat shock 27 (Fuqua, S. A. W., Blum-Salingaros, M., McGuire, W. L. (1989) Cancer Res 49, 4126-4129). 32P-Labeled from TPA-treated cells immunoprecipitated 24-kDa-specific monoclonal antibody. Immunoblots cell extracts fractionated two-dimensional isoelectric focusing/SDS-polyacrylamide gel electrophoresis demonstrated that TPA conversion isoform "a" (pI 6.7) more acidic "b" 6.2). Two-dimensional analysis [3H]leucine-labeled conversely TPA, which only protein, both synthesis (increase a) (conversion isoforms b) protein. 32P labeling allowed demonstration an extra phosphoisoform "c" 5.9) upon well treatment. When were pretreated bisindolylmaleimide GF109203X, selective inhibitor PKC, shock-induced unchanged, while effect almost abolished, suggesting shock-activated very likely different PKC. However, peptide mapping phosphoprotein suggested identical sites stimulation. Partial amino acid sequencing revealed 24-kDa HSP27. The fact estrogens respectively, regulate expression 24/28-kDa strongly argues for its key role proliferation differentiation.