We have analyzed the effects of synaptic vesicles on actin polymerization by using a time-resolved spectrofluorometric assay, We have found that synaptic vesicles have complex effects on the kinetics of actin polymerization, which vary depending on whether the synaptic vesicle-specific phosphoprotein synapsin I is absent or present on their membrane, Synapsin I bound either to synaptic vesicles or to pure phospholipid vesicles exhibits phosphorylation-dependent actin-nucleating activity, Synaptic vesicles depleted of endogenous synapsin I decrease the rate and the final extent of actin polymerization, an effect ,which is not observed with pure phospholipid vesicles. Thus, the state of association of synapsin I with synaptic vesicles, which is modulated by its state of phosphorylation, may affect actin assembly and the physico-chemical characteristics of the synaptic vesicle microenvironment.
Effects of synaptic vesicles on actin polymerization
BENFENATI, FABIO;
1996-01-01
Abstract
We have analyzed the effects of synaptic vesicles on actin polymerization by using a time-resolved spectrofluorometric assay, We have found that synaptic vesicles have complex effects on the kinetics of actin polymerization, which vary depending on whether the synaptic vesicle-specific phosphoprotein synapsin I is absent or present on their membrane, Synapsin I bound either to synaptic vesicles or to pure phospholipid vesicles exhibits phosphorylation-dependent actin-nucleating activity, Synaptic vesicles depleted of endogenous synapsin I decrease the rate and the final extent of actin polymerization, an effect ,which is not observed with pure phospholipid vesicles. Thus, the state of association of synapsin I with synaptic vesicles, which is modulated by its state of phosphorylation, may affect actin assembly and the physico-chemical characteristics of the synaptic vesicle microenvironment.
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