Evidence for the Presence of Substrates for cGMP Dependent Protein Phosphorylation in Human Synaptosomal Membranes
Substantial evidence exists that cyclic nucleotide effects are mediated by specific (intracellular) protein kinases. Since biological regulatory agents can affect intracellular levels of cyclic nucleotides, it has been proposed that protein phosphorylation is a central mech anism mediating their actions and thereby involved in many aspects of cellular function (see WALSH, 1978) . Relevance to studies on changes in protein phosphorylation with age arise from findings that neurotransmitters have age-related effects on levels of cyclic nucleotides (SCHMIDT & THORNBERRY, 1978; SCHMIDT et al., 1978) coupled with observations that there are changes in synaptic function and morphology during senescence (WALKER & WALKER, 1973; CRAGG, 1975; MCGEER & MCGEER, 1975). At the present time very few studies exist on alterations in protein phosphorylation in synaptic membranes—the major target sites of neurotransmitter action (DAVIS, 1977; TRUEX et al., 1978; BOEHME et al., 1978).
KeywordsCyclic Nucleotide Synaptic Membrane cGMP Dependent Protein Kinase SYNAPTOSOMAL Membrane Dent Protein Kinase
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