title: Phosphorylation of VAMP/synaptobrevin in synaptic vesicles by endogenous protein kinases.
abstract: VAMP/synaptobrevin (SYB), an integral membrane protein of small synaptic vesicles, is specifically cleaved by tetanus neurotoxin and botulinum neurotoxins B, D, F, and G is thought to play an important role in the docking and/or fusion of synaptic vesicles with the presynaptic membrane. Potential phosphorylation sites for various kinases are present in SYB sequence. We have studied whether SYB is a substrate for protein kinases that are present in nerve terminals and known to modulate neurotransmitter release. SYB can be phosphorylated within the same vesicle by endogenous Ca2+/calmodulin-dependent protein kinase II (CaMKII) associated with synaptic vesicles. This phosphorylation reaction occurs rapidly and involves serine and threonine residues in the cytoplasmic region of SYB. Similarly to CaMKII, a casein kinase II (CasKII) activity copurifying with synaptic vesicles is able to phosphorylate SYB selectively on serine residues of the cytoplasmic region. This phosphorylation reaction is markedly stimulated by sphingosine, a sphingolipid known to activate CasKII and to inhibit CaMKII and protein kinase C. The results show that SYB is a potential substrate for protein kinases involved in the regulation of neurotransmitter release and open the possibility that phosphorylation of SYB plays a role in modulating the molecular interactions between synaptic vesicles and the presynaptic membrane.
authors.affiliation: Department of Experimental Medicine, University of Roma Tor Vergata, Italy.
authors.forename: H B
authors.initials: HB
authors.lastname: Nielander
authors.forename: F
authors.initials: F
authors.lastname: Onofri
authors.forename: F
authors.initials: F
authors.lastname: Valtorta
authors.forename: G
authors.initials: G
authors.lastname: Schiavo
authors.forename: C
authors.initials: C
authors.lastname: Montecucco
authors.forename: P
authors.initials: P
authors.lastname: Greengard
authors.forename: F
authors.initials: F
authors.lastname: Benfenati
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001905:Botulinum Toxins / Q000378:metabolism; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D047390:Casein Kinase II; D015180:Electrophoresis, Gel, Two-Dimensional; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D050683:R-SNARE Proteins; D051381:Rats; D013572:Synaptic Vesicles / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050683:R-SNARE Proteins; D011494:Protein Kinases; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; D011493:Protein Kinase C; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D001905:Botulinum Toxins