title: Rapid Ca2+-dependent decrease of protein ubiquitination at synapses.
abstract: Protein ubiquitination has been implicated in the regulation of axonal growth and synaptic plasticity as well as in the pathogenesis of neurodegenerative diseases. Here we show that depolarization-dependent Ca2+ influx into synaptosomes produces a global, rapid (range of seconds), and reversible decrease of the ubiquitinated state of proteins, which correlates with the Ca2+-dependent dephosphorylation of several synaptic proteins. A similar general decrease in protein ubiquitination was observed in nonneuronal cells on Ca2+ entry induced by ionomycin. Both in synaptosomes and in nonneuronal cells, this decrease was blocked by FK506 (a calcineurin antagonist). Proteins whose ubiquitinated state was decreased include epsin 1, a substrate for the deubiquitinating enzyme fat facets/FAM, which we show here to be concentrated at synapses. These results reveal a fast regulated turnover of protein ubiquitination. In nerve terminals, protein ubiquitination may play a role both in the regulation of synaptic function, including vesicle traffic, and in the coordination of protein turnover with synaptic use.
authors.affiliation: Howard Hughes Medical Institute and Department of Cell Biology, Yale University School of Medicine, New Haven, CT 06510, USA.
authors.forename: Hong
authors.initials: H
authors.lastname: Chen
authors.forename: Simona
authors.initials: S
authors.lastname: Polo
authors.forename: Pier Paolo
authors.initials: PP
authors.lastname: Di Fiore
authors.forename: Pietro V
authors.initials: PV
authors.lastname: De Camilli
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D018076:DNA, Complementary / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D011188:Potassium / Q000737:chemistry; D011233:Precipitin Tests; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D013569:Synapses / Q000378:metabolism*; D013574:Synaptosomes / Q000378:metabolism; D016559:Tacrolimus / Q000494:pharmacology; D013696:Temperature; D013997:Time Factors; D014162:Transfection; D025801:Ubiquitin / Q000378:metabolism*
chemical_list: D018076:DNA, Complementary; D034741:RNA, Small Interfering; D025801:Ubiquitin; D011188:Potassium; D002118:Calcium; D016559:Tacrolimus