| Type: | Family | Name: | Synapsin |
| Description: | The synapsins are a family of neuron-specific phosphoproteins that coat synaptic vesicles and are involved in the binding between these vesiclesand the cytoskeleton (including actin filaments). The family comprises 5 homologous proteins Ia, Ib, IIa, IIb and III. Synapsins I, II, and III areencoded by 3 different genes. The a and b isoforms of synapsin I and II are splice variants of the primary transcripts [].Synapsin I is mainly associated with regulation of neurotransmitter release from presynaptic neuron terminals []. Synapsin II, as well as being involved in neurotransmitter release, has a role in the synaptogenesis and synaptic plasticity responsible for long term potentiation []. Recent studies implicate synapsin III with a developmental role in neurite elongation and synapse formation that is distinct from the functions of synapsins I and II [].Structurally, synapsins are multidomain proteins, of which 3 domains are common to all the mammalian forms. The N-terminal `A' domain is ~30 residueslong and contains a serine residue that serves as an acceptor site for protein kinase-mediated phosphorylation. This is followed by the `B' linkerdomain, which is ~80 residues long and is relatively poorly conserved. Domain `C' is the longest, spanning approximately 300 residues. This domainis highly conserved across all the synapsins (including those from Drosophila) and is possessed by all splice variants. The remaining sixdomains, D-I, are not shared by all the synapsins and differ both between the primary transcripts and the splice variants. | Short Name: | Synapsin |
