CHARACTERIZATION OF THE INTERACTION BETWEEN SYNAPSIN-I AND CALSPECTIN(BRAIN SPECTRIN OR FODRIN)

We characterized the properties of the interaction between synapsin I and calspectin using purified proteins, The binding assay in the nativ e state using antibodies specific to the tail region of synapsin I rev ealed that the binding is a high affinity with K-d of 9 nM, which is a lmost comparable to that of synapsin I to synaptic vesicles and to F-a ctin, We demonstrated that the head-middle region of synapsin I binds the NH2-terminal domain of beta subunit of calspectin, which also cont ains an actin binding site. Furthermore, the interaction was significa ntly inhibited by phosphorylation of synapsin I by cAMP-dependent prot ein. kinase or by Ca2+, calmodulin-dependent protein kinase II, These properties of the interaction between synapsin I and calspectin may he lp understanding of its modulatory roles in neurotransmitter release. (C) 1997 Academic Press.