Reference work entry
Synapsins were the first proteins identified in presynaptic terminals: Paul Greengard and colleagues identified protein I (now synapsin I, Kuo and Greengard 1969) as a major neuronal substrate for the cyclic AMP-dependent protein kinase (PKA) in rat brain (Johnson et al. 1972; Ueda et al. 1973). Protein I was also the first identified substrate of the Ca 2+/calmodulin-dependent protein kinase (De Camilli et al. 1990), indicating that synapsins serve as a central hub of numerous protein kinase signaling pathways (see below). Early on, it was appreciated that there are multiple synapsins; two isoforms, protein Ia (86 kDa) and Ib (80 kDa), could be distinguished by their molecular weights (Forn and Greengard 1978). We now know that there are even more synapsin isoforms (see Fig. 1). Protein I was found to be enriched in presynaptic terminals and bound to synaptic vesicles within these terminals, causing it to be renamed synapsin I...
- De Camilli P, Cameron R, Greengard P. Synapsin I (protein I), a nerve terminal-specific phosphoprotein. I. Its general distribution in synapses of the central and peripheral nervous system demonstrated by immunofluorescence in frozen and plastic sections. J Cell Biol. 1983;96:1337–54.PubMedPubMedCentralCrossRefGoogle Scholar
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