title: O-linked β-N-acetylglucosamine (O-GlcNAc) site thr-87 regulates synapsin I localization to synapses and size of the reserve pool of synaptic vesicles.
abstract: O-GlcNAc is a carbohydrate modification found on cytosolic and nuclear proteins. Our previous findings implicated O-GlcNAc in hippocampal presynaptic plasticity. An important mechanism in presynaptic plasticity is the establishment of the reserve pool of synaptic vesicles (RPSV). Dynamic association of synapsin I with synaptic vesicles (SVs) regulates the size and release of RPSV. Disruption of synapsin I function results in reduced size of the RPSV, increased synaptic depression, memory deficits, and epilepsy. Here, we investigate whether O-GlcNAc directly regulates synapsin I function in presynaptic plasticity. We found that synapsin I is modified by O-GlcNAc during hippocampal synaptogenesis in the rat. We identified three novel O-GlcNAc sites on synapsin I, two of which are known Ca(2+)/calmodulin-dependent protein kinase II phosphorylation sites. All O-GlcNAc sites mapped within the regulatory regions on synapsin I. Expression of synapsin I where a single O-GlcNAc site Thr-87 was mutated to alanine in primary hippocampal neurons dramatically increased localization of synapsin I to synapses, increased density of SV clusters along axons, and the size of the RPSV, suggesting that O-GlcNAcylation of synapsin I at Thr-87 may be a mechanism to modulate presynaptic plasticity. Thr-87 is located within an amphipathic lipid-packing sensor (ALPS) motif, which participates in targeting of synapsin I to synapses by contributing to the binding of synapsin I to SVs. We discuss the possibility that O-GlcNAcylation of Thr-87 interferes with folding of the ALPS motif, providing a means for regulating the association of synapsin I with SVs as a mechanism contributing to synapsin I localization and RPSV generation.
authors.affiliation: From the Department of Biochemistry, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102.
authors.forename: Yuliya
authors.initials: Y
authors.lastname: Skorobogatko
authors.forename: Ashly
authors.initials: A
authors.lastname: Landicho
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Chalkley
authors.forename: Andrew V
authors.initials: AV
authors.lastname: Kossenkov
authors.forename: Gianluca
authors.initials: G
authors.lastname: Gallo
authors.forename: Keith
authors.initials: K
authors.lastname: Vosseller
mesh_terms: D000117:Acetylglucosamine / Q000235:genetics / Q000378:metabolism*; D020816:Amino Acid Motifs; D000818:Animals; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000235:genetics / Q000378:metabolism; D006031:Glycosylation; D006624:Hippocampus / Q000378:metabolism*; D006801:Humans; D051379:Mice; D017510:Protein Folding; D021381:Protein Transport / Q000502:physiology; D051381:Rats; D016704:Synapsins / Q000235:genetics / Q000378:metabolism*; D013572:Synaptic Vesicles / Q000235:genetics / Q000378:metabolism*
chemical_list: D016704:Synapsins; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D000117:Acetylglucosamine
keywords: Neurobiology; O-GlcNAc; Signal Transduction; Synapses; Synaptic Plasticity