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 Ca 2+ 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.
|Number of pages||6|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|Publication status||Published - Dec 9 2003|
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