Calcium ion stimulated endogenous protein kinase catalyzed phosphorylation of peripheral nerve myelin proteins.
Myelin isolated from the rat peripheral nervous system (sciatic nerve and cauda equina) contained Mg2+-dependent protein kinase that phosphorylated myelin polypeptides. Ca2+, in micromolar concentrations, markedly stimulated phosphorylation (half-maximal stimulation at 5 microM (free) Ca2+) but at higher concentrations (greater than 100 microM Ca2+) it caused inhibition. In the presence of Triton X-100, phosphorylation (+/-Ca2+) of myelin was increased and Ca2+ caused up to a 10-fold increase in phosphorylation. Among the myelin polypeptides, P0 (Mr, 28 000), a major glycoprotein, accounted for nearly 60% of the total phosphate incorporated into the myelin and Ca2+ markedly promoted phosphorylation of P0. Phosphorylation of other myelin polypeptides, P2 (Mr, 16 000), Y (Mr, 26 000), and P1 (Mr, 20 000), and the Ca2+-stimulatory effect on phosphorylation of these were also evident. Cyclic AMP (or other cyclic nucleotides) failed to show any significant stimulatory effect on myelin phosphorylation.
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008970:Molecular Weight; D009185:Myelin Proteins / Q000378:metabolism*; D010525:Peripheral Nerves / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D051381:Rats; D012584:Sciatic Nerve / Q000378:metabolism; D013997:Time Factors
D009185:Myelin Proteins; D011494:Protein Kinases; D002118:Calcium