Calcium influx selects the fast mode of endocytosis in the synaptic terminal of retinal bipolar cells
AUTOR(ES)
Neves, Guilherme
FONTE
The National Academy of Sciences
RESUMO
To investigate the regulation of endocytosis by Ca2+, we have made capacitance measurements in the synaptic terminal of depolarizing bipolar cells from the retina of goldfish. After a brief depolarization, all of the excess membrane was retrieved rapidly (τ ≈1 s). But when the rise in free [Ca2+] was reduced by the introduction of Ca2+ buffers [1,2-bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetate (BAPTA) or EGTA], a large fraction of the membrane was retrieved by a second, slower mechanism (τ ≥ 10 s). The block of fast endocytosis by EGTA could be overcome by increasing the amplitude of the Ca2+ current, demonstrating that Ca2+ influx was the trigger for fast endocytosis. These manipulations of the Ca2+ signal altered the relative proportions of fast and slow endocytosis but did not modulate the rate constants of these processes. A brief stimulus that triggered fast endocytosis did not generate a significant rise in the spatially averaged [Ca2+], indicating that Ca2+ regulated endocytosis through an action close to the active zone. The slow mode of retrieval occurred at the resting [Ca2+]. These results demonstrate that Ca2+ influx couples fast endocytosis and exocytosis at this synapse.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=65021Documentos Relacionados
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