Synapsin I, a pre-synaptic marker

Wed, 06/08/2016 - 14:40

Synapsin-I, also called Synapsin 1/Syn1, is an ~80 kDa protein (predicted mol. wt. 74.1 kDa) which belongs to the Synapsin family (Synapsin I, Synapsin II, Synapsin III). Synapsins are the evolutionarily conserved phospho-proteins which are associated with the cytosolic side of the synaptic vesicles. They tether the vesicles to the actin cytoskeleton, thus forming a reserve pool. Synapsins I and II are generally found in mature synapses, whereas, Synapsin III is typically expressed in developing synapses with a relatively lower expression. Synapsins represents the most abundant of neuron-specific phospho-proteins, consisting of 9% of the total amount of all vesicle proteins in neurons wherein they play a critical role in the regulation of neurotransmitter release (Greengard et al. 1993). Phosphorylation at Ser-9 residue (phospho-Ser9 Synapsin I) results in dissociation of Synapsins I from synaptic vesicles which is important for synaptic vesicle neurotransmitter release. Synapsin I influences synaptic plasticity by regulating pre- and post-synaptic vesicular release. Mutations in Synapsin I have been linked to Epilepsy, X-linked, with variable learning disabilities and behavior disorders (XELBD), which is a neurologic disorder characterized by variable combinations of epilepsy, learning difficulties, macrocephaly, and aggressive behavior (Garcia et al. 2004).

Because of Synapsin I's characteristic sub-cellular localization, antibodies against this protein have been used as one of the most reliable markers for pre-synaptic vesicles.  Synapsin I Antibodies from Novus Biologicals have been cited in multiple publications from highly reputed research journals.

Synapsin I antibody NB300-104


Synapsin I antibody PPS084

Synapsin I Antibody [NB300-104]
ICC/IF analysis showing punctate distribution
of Synapsin 1 protein (green) and MAP
protein (red) in cultured rat caudate neurons.


Synapsin I [p ser9] Antibody [PPS084]
WB analysis of rat brain lysate which was
left un-treated (control) or was treated
with lambda-phosphatase: lambda PPase

Dr. Antonio Pisani's team from the Laboratory of Neurophysiology and Synaptic Plasticity (University of Rome Tor Vergata) used Novus' Synapsin I Antibody [NB300-104] for WB analysis of synaptosomal preparations from cerebellar tissues of 14 day old mice. They used Synapsin 1 as well as post synaptic density protein (PSD-95) as synaptic markers and established the localization of Torsin A/TOR1A in the cerebellar synaptosomal enrichments [Puglisi et al. 2013]. A study published in Nature Communications by Dr. Henley's lab from the University of Bristol UK cited the use of Synapsin I Antibody [NB300-104] along with Bassoon as a presynaptic marker. Synapsin I antibody was used at 1:500 dilution for the immunocytochemistry/immunofluorescence analysis of paraformaldehyde fixed embryonic cortical and hippocampal neurons (isolated from Wistar rat's E18 embryos). The results from this study established SUMOylation mediated regulation of Synapsin-Ia/Syn-Ia function and indicated an association of Syn-Ia's decreased SUMOylation with neurological disorders such as autism spectrum disorder/ASD and epilepsy (Tang et al. 2015). Synapsin-I's phosphorylation at Ser-9 residue is highly critical because it leads to its dissociation from the synaptic vesicles. In a recent study published in Neuroscience, Dr. Bozzi's team from University of Trento (Italy) used Novus' Synapsin I [p Ser549] Antibody (NB300-744) at 1:300 dilution for IHC on free floating sections from brains of Wild Type and Engrailed-2 knockout (En2−/−) mice, a model for autism spectrum disorders. The authors observed downregulated levels of SynI and its phosphorylation at Ser549/553 in hilus of mutant mice, before and after Morris water maze /MWM test [Provenzano et al. 2015]. 

Compiled by: Subhash Gangar


  1. Garcia CC, Blair HJ, Seager M et al. 2004. Identification of a mutation in synapsin I, a synaptic vesicle protein, in a family with epilepsy. J Med Genet. 41(3):183-6 [PMID: 14985377].
  2. Greengard P, Valtorta F, Czernik AJ et al. 1993. Synaptic vesicle phosphoproteins and regulation of synaptic function. Science. 259(5096):780-5 [PMID: 8430330]
  3. Provenzano G, Pangrazzi L, Poli A et al. 2015. Reduced phosphorylation of synapsin I in the hippocampus of Engrailed-2 knockout mice, a model for autism spectrum disorders. Neuroscience. 286:122-30 [PMID: 25463523].
  4. Puglisi F, Vanni V, Ponterio G et al. 2013. Torsin A Localization in the Mouse Cerebellar Synaptic Circuitry. PLoS One.  8(6):e68063 [PMID: 23840813]
  5. Tang LT, Craig TJ, Henley JM. 2015. SUMOylation of synapsin Ia maintains synaptic vesicle availability and is reduced in an autism mutation. Nat Commun. 6:7728 [PMID: 26173895].

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