The proteolysis of membrane-associated protein kinase C as a possible component of the signalling pathway leading to c-myc induction in B lymphocytes

Karen E. Pollok, E. Charles Snow

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12 Scopus citations


Occupancy of surface immunoglobulin (sIg) receptor for antigen expressed on resting B cells initiates increased turnover of membrane-associated phosphotidylinositol (PI), which ultimately leads to the enhanced expression of c-myc mRNA. The mechanism which links these initial membrane biochemical changes to subsequent alterations in c-myc transcription is unclear. The present study examines the possible involvement of PKC and its calpain-generated proteolytic fragment, proteion kinase M (PKM), in conveying the membrane-associated signal to the nucleus. Utilizing an in vitro phosphorylation assay, we have shown that a calcium-dependent protesase, similar to calpain, in involed in the downregulation of membrane-associated PKC induced by anti-immunoglobulin or phorbol 12-myristate 13-acetate (PMA) and ionomycin stimulation of resting B cells. In addition, we have confirmed previous studies showing the PMA and ionomycin are both required for optimal expression of c-myc mRNA. The enhanced expression of c-myc mRNA is sensitive to inhibitors of PKC, such as H-7 and sangavimycin, providing evidence for a prominent role of PKC and/or PKM in the receptor-mediated up-regulation of c-myc message expression. Finally, a calpain inhibitor interferes with the transmission of the membrane-associated signal which induces the increase expression of c-myc mRNA. Our results are consistent with the hypothesis that the calpain-mediated proteolysis of membrane-associated PKC is involved in the sIg-mediated signal transduction pathway.

Original languageEnglish (US)
Pages (from-to)435-452
Number of pages18
JournalCellular Signalling
Issue number5
StatePublished - 1991



  • B Lymphocyte
  • c-myc induction
  • calpain
  • protein kinase C
  • protein kinase M
  • proteolysis
  • signal transduction

ASJC Scopus subject areas

  • Cell Biology

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