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Gene Review

SYN1  -  synapsin I

Bos taurus

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Disease relevance of SYN1

  • In order to investigate additional interactions of the synapsins with nerve terminal proteins, we have employed phage display library technology to select peptide sequences binding with high affinity to synapsin I [1].
  • Previous studies identified synapsin I as a potential substrate for a newly discovered growth factor-sensitive, proline-directed protein kinase originally isolated from rat pheochromocytoma [2].
  • Preincubation of botulinum neurotoxin serotype A, B, or E with ganglioside GT1b was previously found to enhance adherence of botulinum neurotoxin to synapsin I and an approximately 116-kDa bovine brain synaptosomal protein; in contrast, adherence to these two proteins by tetanus neurotoxin required preincubation with GT1b [3].
  • Partial cleavage of synapsin I by collagenase, 2-nitro-5-thiocyanobenzoic acid, and Staphylococcus aureus V8 protease suggests that at least three glycosylation sites exist along the molecule [4].
  • Cellular immune crossreactivity between myelin basic protein and synapsin in rats with experimental allergic encephalomyelitis [5].

High impact information on SYN1


Biological context of SYN1

  • The maximum stoichiometry of phosphorylation approached 1 mol of phosphate/mol of synapsin I protein [2].
  • Although synapsin I has been implicated in synaptic transmission, no activity has been previously ascribed to it [8].
  • In the present study, the interaction between synapsin I and phospholipid vesicles has been characterized, and the protein domains involved in these interactions have been identified [9].
  • Synapsin I enhances both the rate and the extent of Ca(2+)-dependent membrane fusion, although it has no detectable fusogenic activity per se [10].
  • The data indicate that synapsin I markedly affects synaptic vesicle traffic and cytoskeleton assembly in the nerve terminal and provide a molecular basis for the ability of synapsin I to regulate the availability of synaptic vesicles for exocytosis and thereby the efficiency of neurotransmitter release [11].

Anatomical context of SYN1

  • The results indicate that an interaction between synapsin I and Rab3A exists on synaptic vesicles that modulates the functional properties of both proteins [12].
  • However, despite its recent characterization as a spectrin-binding protein immunologically related to erythrocyte protein 4.1, other interactions of synapsin I with structural proteins remain unknown [7].
  • These observations may explain why synapsin I is found exclusively in neurons, since small synaptic vesicles are specific to neurons whereas large dense-core vesicles in neurons may be considered the equivalent of secretory organelles in endocrine cells [13].
  • No p38 was detectable on large dense-core vesicles (LDCVs). p38 and synapsin I were found to be present in similar concentrations throughout the brain [14].
  • Synapsin I appears to bind G-actin with a very high stoichiometry (1:2-4), and the complex behaves as an F-actin nucleus, producing actin filaments under conditions where spontaneous polymerization is negligible [15].

Associations of SYN1 with chemical compounds

  • Phosphorylation of synapsin I at a novel site by proline-directed protein kinase [2].
  • Digestion of phosphorylated synapsin I with trypsin followed by high performance liquid chromatography (HPLC) phosphopeptide analysis indicated that the tryptic peptide containing the major phosphorylation site eluted as a single peak at approximately 17% acetonitrile [2].
  • We further show that brain 4.1 is identical to the synaptic vesicle protein, synapsin I, one of the brain's major substrates for cyclic AMP and Ca2+-calmodulin-dependent kinases [8].
  • Characterization of synapsin I fragments produced by cysteine-specific cleavage: a study of their interactions with F-actin [16].
  • Synapsin I is composed of two distinct domains, a COOH terminal, collagenase-sensitive, hydrophilic, and strongly basic tail region, and an NH2 terminal, collagenase-resistant head region relatively rich in hydrophobic amino acids [16].

Physical interactions of SYN1


Other interactions of SYN1

  • We report partial amino acid analysis of ACAMP-81 and its interaction with synapsin I [17].
  • The kcat values were: G-substrate, 0.41 s-1; DARPP-32, 0.20 s-1; Protein K.-F., 0.7 s-1; synapsin I (site I), 0.053 s-1; synapsin I (site II), 0.040 s-1 [18].
  • The beta-elimination of galactosyltransferase radiolabeled synapsin I and subsequent analysis of released saccharide on high-voltage paper electrophoresis confirmed the presence of monosaccharidic GlcNAc moieties in O-linkage to the protein [4].
  • Similar behavior is observed when synapsin replaces MBP, while acetylated MBP and bovine serum albumin fail to induce any fluorescence change [19].
  • The kinase preparation was also able to phosphorylate exogenous synapsin, phospholamban, glycogen synthase, MAP-2, myelin basic proteins and kappa-casein, but not tubulin, pyruvate kinase, the regulatory subunit of cAMP protein kinase II, myosin light chain or phosphorylase b [20].

Analytical, diagnostic and therapeutic context of SYN1


  1. Synapsin is a novel Rab3 effector protein on small synaptic vesicles. I. Identification and characterization of the synapsin I-Rab3 interactions in vitro and in intact nerve terminals. Giovedì, S., Vaccaro, P., Valtorta, F., Darchen, F., Greengard, P., Cesareni, G., Benfenati, F. J. Biol. Chem. (2004) [Pubmed]
  2. Phosphorylation of synapsin I at a novel site by proline-directed protein kinase. Hall, F.L., Mitchell, J.P., Vulliet, P.R. J. Biol. Chem. (1990) [Pubmed]
  3. Ganglioside-induced adherence of botulinum and tetanus neurotoxins to adducin. Schengrund, C.L., DasGupta, B.R., Hughes, C.A., Ringler, N.J. J. Neurochem. (1996) [Pubmed]
  4. Synapsins contain O-linked N-acetylglucosamine. Lüthi, T., Haltiwanger, R.S., Greengard, P., Bähler, M. J. Neurochem. (1991) [Pubmed]
  5. Cellular immune crossreactivity between myelin basic protein and synapsin in rats with experimental allergic encephalomyelitis. De Santis, M.L., Roth, G.A., Cumar, F.A. J. Neurosci. Res. (1992) [Pubmed]
  6. Synapsin or protein 4.1 in chromaffin cells. Burgoyne, R.D., Baines, A.J. Nature (1987) [Pubmed]
  7. Synapsin I is a microtubule-bundling protein. Baines, A.J., Bennett, V. Nature (1986) [Pubmed]
  8. Synapsin I is a spectrin-binding protein immunologically related to erythrocyte protein 4.1. Baines, A.J., Bennett, V. Nature (1985) [Pubmed]
  9. Electrostatic and hydrophobic interactions of synapsin I and synapsin I fragments with phospholipid bilayers. Benfenati, F., Greengard, P., Brunner, J., Bähler, M. J. Cell Biol. (1989) [Pubmed]
  10. Interactions of synapsin I with phospholipids: possible role in synaptic vesicle clustering and in the maintenance of bilayer structures. Benfenati, F., Valtorta, F., Rossi, M.C., Onofri, F., Sihra, T., Greengard, P. J. Cell Biol. (1993) [Pubmed]
  11. Dephosphorylated synapsin I anchors synaptic vesicles to actin cytoskeleton: an analysis by videomicroscopy. Ceccaldi, P.E., Grohovaz, F., Benfenati, F., Chieregatti, E., Greengard, P., Valtorta, F. J. Cell Biol. (1995) [Pubmed]
  12. Synapsin is a novel Rab3 effector protein on small synaptic vesicles. II. Functional effects of the Rab3A-synapsin I interaction. Giovedì, S., Darchen, F., Valtorta, F., Greengard, P., Benfenati, F. J. Biol. Chem. (2004) [Pubmed]
  13. Synapsin I in nerve terminals: selective association with small synaptic vesicles. Navone, F., Greengard, P., De Camilli, P. Science (1984) [Pubmed]
  14. Protein p38: an integral membrane protein specific for small vesicles of neurons and neuroendocrine cells. Navone, F., Jahn, R., Di Gioia, G., Stukenbrok, H., Greengard, P., De Camilli, P. J. Cell Biol. (1986) [Pubmed]
  15. Effects of the neuronal phosphoprotein synapsin I on actin polymerization. II. Analytical interpretation of kinetic curves. Fesce, R., Benfenati, F., Greengard, P., Valtorta, F. J. Biol. Chem. (1992) [Pubmed]
  16. Characterization of synapsin I fragments produced by cysteine-specific cleavage: a study of their interactions with F-actin. Bähler, M., Benfenati, F., Valtorta, F., Czernik, A.J., Greengard, P. J. Cell Biol. (1989) [Pubmed]
  17. Acidic calmodulin binding protein, ACAMP-81, is MARCKS protein interacting with synapsin I. Mizutani, A., Tokumitsu, H., Hidaka, H. Biochem. Biophys. Res. Commun. (1992) [Pubmed]
  18. Mammalian brain phosphoproteins as substrates for calcineurin. King, M.M., Huang, C.Y., Chock, P.B., Nairn, A.C., Hemmings, H.C., Chan, K.F., Greengard, P. J. Biol. Chem. (1984) [Pubmed]
  19. Myelin basic protein domains involved in the interaction with actin. Roth, G.A., Gonzalez, M.D., Monferran, C.G., De Santis, M.L., Cumar, F.A. Neurochem. Int. (1993) [Pubmed]
  20. Protein substrate specificity of a calmodulin-dependent protein kinase isolated from bovine heart. Kloepper, R.F., Landt, M. Cell Calcium (1984) [Pubmed]
  21. Synapsin I is a highly surface-active molecule. Ho, M.F., Bähler, M., Czernik, A.J., Schiebler, W., Kézdy, F.J., Kaiser, E.T., Greengard, P. J. Biol. Chem. (1991) [Pubmed]
  22. Phylogenetic survey of proteins related to synapsin I and biochemical analysis of four such proteins from fish brain. Goelz, S.E., Nestler, E.J., Greengard, P. J. Neurochem. (1985) [Pubmed]
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