Modulation of B-50 phosphorylation and polyphosphoinositide metabolism in synaptic plasma membranes by protein kinase C, phorbol diesters and ACTH.
JOURNAL OF RECEPTOR RESEARCH(2008)
摘要
One of the major phosphoproteins in synaptic plasma membranes (SPM) is the neuron-specific protein B-50 (Mr 48 kDa, IEP 4.5). Addition of purified protein kinase C (PKC) to native SPM increases B-50 phosphorylation. Exogenous PKC also phosphorylates B-50 in heat-inactivated SPM. Endogenous phosphorylation of B-50 in SPM is enhanced in a concentration-dependent manner by the tumor-promoting phorbol diesters 4 beta-phorbol 12-myristate, 13-acetate, 4 beta-phorbol 12,13-dibutyrate (PDB) and 4 beta-phorbol 12,13-diacetate, with an EC50 of 7 x 10(-8) M, 3 x 10(-7) M and 10(-6) M, respectively. This increase in the B-50 phosphorylation can be inhibited by ACTH1-24. PDB (10(-6) M) also stimulates B-50 phosphorylation by exogenous PKC in native and heat-inactivated SPM (204 and 712%, respectively). The increase in B-50 phosphorylation induced by the addition of PKC to SPM is accompanied by a decrease in the [32P]-incorporation into phosphatidylinositol 4,5-bisphosphate (PIP2). These data support the hypothesis that in neuronal membranes the degree of B-50 phosphorylation exerts a negative control on receptor-mediated hydrolysis of PIP2 in receptor systems coupled to phospholipase C.
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关键词
phospholipase c,protein kinase c,negative control
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