| Literature References | 1. NOMURA, M., UETA, Y., SERINO, R., YAMAMOTO, Y., SHIBUYA, I. AND
YAMASHITA, H.
Upregulation of synapsin IIa and IIb mRNAs in the paraventricular and
supraoptic nuclei in chronic salt loaded and lactating rats.
NEUROSCI.RES. 37 201-210 (2000).
2. LLINAS, R., MCGUINNESS, T., LEONARD, C.S., SUGIMORI, M. AND GREENGARD, P.
Intraterminal injection of synapsin I or calcium/calmodulin-dependent
protein kinase II alters neurotransmitter release at the squid giant
synapse.
PROC.NATL.ACAD.SCI.U.S.A. 82 3035-3039 (1985).
3. ROSAHL, T.W., SPILLANE, D., MISSLER, M., HERZ, J., SELIG, D.K.,
WOLFF, J.R., HAMMER, R.E., MALENKA, R.C. AND SUDHOF, T.C.
Essential functions of synapsins I and II in synaptic vesicle regulation.
NATURE 375 488-497 (1995).
4. FERREIRA, A., KAO, H-T., FENG, J., RAPOPORT, M. AND GREENGARD, P.
Synapsin III: developmental expression, subcellular localization, and role
in axon formation.
J.NEUROSCIENCE 20 3736-3744 (2000).
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| Documentation | The synapsins are a family of neuron-specific phosphoproteins that coat
synaptic vesicles and are involved in the binding between these vesicles
and the cytoskeleton (including actin filaments). The family comprises 5
homologous proteins Ia, Ib, IIa, IIb and III. Synapsins I, II, and III are
encoded by 3 different genes. The a and b isoforms of synapsin I and II are
splice variants of the primary transcripts [1].
Synapsin I is mainly associated with regulation of neurotransmitter release
from presynaptic neuron terminals [2]. Synapsin II, as well as being
involved in neurotransmitter release, has a role in the synaptogenesis and
synaptic plasticity responsible for long term potentiation [3]. 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 [4].
Structurally, synapsins are multidomain proteins, of which 3 domains are
common to all the mammalian forms. The N-terminal `A' domain is ~30 residues
long and contains a serine residue that serves as an acceptor site for
protein kinase-mediated phosphorylation. This is followed by the `B' linker
domain, which is ~80 residues long and is relatively poorly conserved.
Domain `C' is the longest, spanning approximately 300 residues. This domain
is highly conserved across all the synapsins (including those from
Drosophila) and is possessed by all splice variants. The remaining six
domains, D-I, are not shared by all the synapsins and differ both between
the primary transcripts and the splice variants.
SYNAPSIN is a 6-element fingerprint that provides a signature for the
synapsins. The fingerprint was derived from an initial alignment of 7
sequences: the motifs were drawn from conserved regions spanning the `C'
domain, towards the central portion of the alignment. Two iterations on
SPTR37_10f were required to reach convergence, at which point a true set
comprising 10 sequences was identified.
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