Ca2+ and phorbol ester effect on the mast cell phosphoprotein induced by cromolyn.
Several phosphoproteins are involved in stimulus-secretion coupling. The beta and gamma subunits of immunoglobulin E binding protein (FC epsilonRI) and three other protein bands get phosphorylated during stimulation of mast cell secretion. These additional proteins of 42, 59 and 68 kDa are also phosphorylated when secretion is stimulated by compound 48/80 (C48/80). A 78 kDa band, however, is phosphorylated as secretion wanes after stimulation with C48/80 and by the anti-allergic drug disodium cromoglycate (cromolyn). Phosphorylation was blocked by protein kinase C inhibitors. We investigated the isozyme involved by first showing that a cation ionophore prevented the phosphorylation of the 78 kDa protein, while a Ca2+ chelator did not affect phosphorylation even though it enhanced the inhibitory effect of cromolyn. This protein was identified as moesin by immunoprecipitation. Protein kinase C activators had no effect on 78 kDa protein phosphorylation either in the presence or absence of Ca2+ ions, but prevented its phosphorylation by cromolyn. Protein phosphatase inhibitors prolonged the duration, but not the amount of phosphate incorporated in the 78 kDa protein band while cromolyn had no effect on protein phosphatase action in vitro. The insensitivity of the 78 kDa protein phosphorylation to calcium and protein kinase C activators suggests that an atypical protein kinase C isozyme may be involved. Western blot analysis identified the presence of isozymes alpha, beta, delta and zeta, of which only the latter fits the profile suggested by the present findings.
Wang
L
L
Department of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, Boston, MA 02111, USA.
Correia
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I
Basu
S
S
Theoharides
T C
TC
D000818:Animals; D018927:Anti-Asthmatic Agents / Q000494:pharmacology; D015153:Blotting, Western; D002118:Calcium / Q000494:pharmacology*; D002614:Chelating Agents / Q000494:pharmacology; D004205:Cromolyn Sodium / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D066298:In Vitro Techniques; D007527:Isoenzymes; D008297:Male; D008407:Mast Cells / Q000201:enzymology / Q000378:metabolism*; D008840:Microfilament Proteins / Q000378:metabolism; D010703:Phorbol Esters / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014764:Viral Proteins / Q000378:metabolism
D018927:Anti-Asthmatic Agents; D002614:Chelating Agents; D004268:DNA-Binding Proteins; D007527:Isoenzymes; D008840:Microfilament Proteins; D010703:Phorbol Esters; D010750:Phosphoproteins; D014764:Viral Proteins; C068734:rep proteins, Adeno-associated virus 2; C071058:moesin; D011493:Protein Kinase C; D010749:Phosphoprotein Phosphatases; D004205:Cromolyn Sodium; D002118:Calcium