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  • Title: Ceramide promotes calpain-mediated proteolysis of protein kinase C beta in murine polymorphonuclear leukocytes.
    Author: Tanabe F, Cui SH, Ito M.
    Journal: Biochem Biophys Res Commun; 1998 Jan 06; 242(1):129-33. PubMed ID: 9439623.
    Abstract:
    Ceramide has been recognized as an important second messenger in intracellular signaling. We demonstrate here that ceramide promotes the down-regulation of protein kinase C (PKC) activity in phorbol ester-stimulated murine polymorphonuclear leukocytes (PMNs). As reported previously, treatment of PMNs with phorbol ester caused a translocation of PKC from the cytosolic to the membrane fractions. When PMNs were pretreated with cell-permeable ceramide analogue, C2-ceramide, the membrane-associated PKC activity was rapidly down-regulated by phorbol ester stimulation. E64-d, a potent inhibitor of calpain which proteolyzes PKC, eliminated the rapid down-regulation of PKC activity. By hydroxyapatite column chromatography and Western blotting, the predominant PKC isoform was PKC beta with a small amount of PKC alpha in murine PMNs. We found that ceramide strikingly promoted calpain-mediated proteolysis of PKC beta in vitro. Ceramide was also shown to inhibit [3H]phorbol 12,13-dibutyrate(PDBu) binding to PKC beta. Moreover, we show that ceramide stimulates PKC beta autophosphorylation. These results suggest that ceramide directly activates PKC beta and promotes calpain-mediated proteolysis in murine PMNs.
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