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S‐100‐Mediated Inhibition of Brain Protein Phosphorylation
Author(s) -
Patel Jitendra,
Marangos Paul J.,
Heydorn William E.,
Chang Garrick,
Verma Ajay,
Jacobowitz David
Publication year - 1983
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1983.tb09048.x
Subject(s) - phosphorylation , calmodulin , phosphoprotein , protein phosphorylation , biology , calcium , biochemistry , medicine , endocrinology , protein kinase a , enzyme
The effects of the glial‐specific, calcium‐binding, S‐100 protein on brain membrane and supernatant protein phosphorylation were assessed. S‐100 concentrations as low as 5 μg/ml caused a marked inhibition of the phosphorylation of a soluble brain protein having a molecular weight of 73,000 daltons (73K). This protein was designated the S‐100 protein‐modulated phosphoprotein (SMP). Half‐maximal inhibition of the phosphorylation of SMP by S‐100 was obtained at concentrations of 12 μg/ml (0.57 (μ M ). The inhibition of SMP phosphorylation by S‐100 was calcium‐dependent, with a calculated calcium K a of 2.0 ± 0.3 μ M . SMP phosphorylation was also inhibited by calmodulin, but only partially and with a much lower potency. The inhibition of SMP phosphorylation by S‐100 was not inhibited by fluphenazine, whereas the effect of calmodulin was. SMP was found in many brain areas, with the highest levels seen in the corpus callosum. Various peripheral tissues, such as kidney; liver; and pineal, pituitary, and adrenal glands, did not contain detectable SMP levels. At higher S‐100 concentrations, >10μg/ml, the phosphorylation of several other soluble proteins was markedly inhibited. These proteins have molecular weights of 56K, 50K, and 47K. The phosphorylation of these proteins was enhanced by calmodulin. These data suggest that the S‐100 protein may function to modulate the phosphorylation of brain proteins in a manner analogous to (although in a reciprocal fashion) that of calmodulin.