Premium
Modulation by sphingosine of substrate phosphorylation by protein kinase C in bovine mammary gland
Author(s) -
Katoh Norio
Publication year - 1993
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02537492
Subject(s) - sphingosine , phosphorylation , protein kinase c , cytosol , lipid signaling , biochemistry , protein phosphorylation , marcks , biology , kinase , ceramide , signal transduction , protein kinase a , chemistry , microbiology and biotechnology , enzyme , receptor , apoptosis
The effect of sphingosine on the phosphorylation of endogenous proteins by protein kinase C (PKC) was investigated in bovine mammary gland. Several proteins were shown to be substrates for PKC in both cytosolic and total particulate fractions by phosphorylation in the absence or presence of 1‐oleoy‐2‐acetyl‐ sn ‐glycerol, phosphatidylserine (PS) and Ca 2+ . At concentrations of 83 μM or less, sphingosine inhibited phosphorylation of several substrates for PKC in both fractions. Phosphorylation of cytosolic 36 kDa, 21 kDa and particulate 36 kDa proteins was particularly sensitive to sphingosine. Cytosolic 97 kDa phosphorylation (which was enhanced by Ca 2+ alone) was also sensitive to sphingosine. The inhibition was reversed by excess addition of lipid cofactors, particularly PS, but not by Ca 2+ . At higher concentrations (167 and 417 μM), in addition to the inhibition seen at lower concentrations, sphingosine stimulated phosphorylation of several proteins, including cytosolic 19 kDa and particulate 53 kDa, which were not detected in the absence of sphingosine. The sphingosine‐induced phosphorylation disappeared with excess addition of PS, but not with addition of Ca 2+ . The results point toward the importance of the interaction of sphingosine with membrane phospholipids in the signal transduction pathway mediated by PKC‐dependent phosphorylation in bovine mammary gland.