A major myristylated substrate of protein kinase C and protein kinase C itself are differentially regulated during murine B- and T-lymphocyte development and activation.

Abstract

The regulation and expression of protein kinase C (PKC) and phosphomyristin C (PMC) (a principal substrate of PKC which is the major myristylated protein in lymphocyte and glioma lines that express it) in murine B and T lymphocytes were investigated. Both PMC and PKC are differentially regulated during T-cell development. The level of PMC expression is highest in CD4-8-, intermediate in CD4+8+, and lowest in Jlld-, CD4, or CD8 single-positive thymocytes. PKC is equally expressed by all three thymic populations. In striking contrast to thymocytes, resting peripheral lymph node T cells and T-cell clones express little if any PMC and reduced levels of PKC. Neither PKC nor PMC is signfficantly induced upon the activation of lymph node T cells: treatment with anti-CD3 antibodies or anti-CD3 and interleukin-2 fails to induce PKC, whereas PMC is not induced by anti-CD3 alone and is only slightly induced by anti-CD3 and interleukin-2. In contrast to the situation with T cells, PMC and PKC are constitutively expressed at moderate levels in mature B cells. PMC is greatly increased in B-cell blasts generated by cross-linking the antigen receptor with antiimmunoglobulin. These results demonstrate that PMC and PKC are differentially regulated during the development and activation of B and T cells, suggesting that cellular events that rely upon PKC and PMC may differ during ontogeny and activation of different lymphocyte subsets.

Glutamate-stimulated protein phosphorylation in cultured hippocampal pyramidal neurons

“…As shown here, a reversible acidic isoelectric shift of MARCKS occurs with glutamate-stimulated phosphorylation. A similar acidic shift has been reported in the presumptive MARCKS homologue in lymphocytes following phorbol ester treatment (Hombeck et al, 1989) and in fibroblasts following TPA or lysophosphatidate treatment (van Corven et al, 1989). In the present studies, tryptic and thermolytic digests of MARCKS produced three and four phosphorylated peptides, respectively, suggesting that four or fewer sites are phosphorylated in situ.…”

Phosphorylation of MARCKS (80‐KDA) protein, a major substrate for protein kinase C in oligodendroglial progenitors

“…The function of MARCKS in its phosphorylated or unphosphorylated form is largely unknown, although the close correlation of its phosphorylation with PKC activation has suggested a role for this protein as a potential transducer of PKC Bhat signals. Recent reports have correlated changes in MARCKS protein abundance and/or phopshorylation with neoplastic transformation (Simek et al, 1989;Wolfman et al, 1987;Yang and Pardee, 1987), lymphocyte development and activation (Hornbeck et al, 1989), inflammatory response in human neutrophills , and neurite outgrowth in neuroblastoma cells (Girard and Kuo, 1990), suggesting a role for this protein in cell growth and differentiation.…”

“…Unlike many other kinase substrates, the 80-kDa substrate appears to be an exclusive PKC substrate (Albert et a]., 1986;Blackshear et al, 1985;Rozengurt et al, 1983) and, as such, it has been widely used as a marker of PKC activation in vivo (Niedel and Blackshear, 1986). The protein is myristoylated (Aderem et al, 1988;James and Olson, 1989; McInhinney and McGlone, 1990) and, based on recently reported sequence data, it has an unusual amino acid composition [e.g., contains 20% glutamic acid and 25% alanine) and a true molecular mass of 32 kDa (Stumpo et al, 1989) (Simek et al, 1989;Wolfman et al, 1987;Yang and Pardee, 1987), lymphocyte development and activation (Hornbeck et al, 1989), inflammatory response in human neutrophills , and neurite outgrowth in neuroblastoma cells (Girard and Kuo, 1990), suggesting a role for this protein in cell growth and differentiation.We recently demonstrated a marked stimulation by PMA of DNA synthesis, cell proliferation (Bhat, 1989), and c-fos proto-oncogene induction (Bhat et al, in press) in cultured oligodendroglial (OL) progenitors. The effects of PMA seemed to be mediated by an activation of PKC, as suggested by a reversal of cell responses to PMA by inhibitors of PKC, The present report deals with protein phosphorylation in OL progenitors stimulated with PMA and the identification by immunochemical means of a major phosphoprotein as the specific PKC substrate, i.e., MARCKS protein.…”

Differential expression of an 80-kDa protein kinase C substrate in preneoplastic and neoplastic mouse JB6 cells.

“…Tryptic and chymotryptic peptides (J.P. and D.K., unpublished results) were isolated using reverse-phase HPLC. An oligopeptide derived from the p80 protein sequence, having the sequence NH2-Glu-Ala-Ala-Glu-ProGlu-Gln-Pro-Glu-Gln-Pro-Glu-Gln-Pro-Ala-Ala-COOH described in detail elsewhere (18) was synthesized by solidphase methods (19). The publication costs of this article were defrayed in part by page charge payment.…”