Membrane cycling after the excess retrieval mode of rapid endocytosis in mouse chromaffin cells

A.E. PEREZ BAY ; A.V. BELINGHERI ; Y. D. ALVAREZ; F.D. MARENGO

ACTA PHYSIOLOGICA

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2012 vol. 204 p. 403 - 418

1748-1708

AIM: After exocytosis, neuroendocrine cells and neurones keep constant the plasma membrane and the releasable vesicle pools by performing endocytosis and vesicular cycling. Patch-clamp capacitance measurements on chromaffin cells showed that strong Ca(+2) entry activates excess retrieval: a rapid endocytosis process that retrieves more membrane than the one fused by preceding exocytosis. The main purpose of the present experiments was to study the recycling pathway that follows excess retrieval, which is unknown. METHODS: Membrane recycling after exocytosis-endocytosis can be studied by fluorescence imaging assays with FM1-43 (Perez Bay et al. Am J Physiol Cell Physiol 2007; 293, C1509). In this work, we used this assay in combination with fluorescent dextrans and specific organelle-targeted antibodies to study the membrane recycling after excess retrieval in mouse chromaffin cells. RESULTS: Excess retrieval was observed after the application of high-K(+) or cholinergic agonists during 15 or 30 s in the presence of FM1-43. We found that the excess retrieval membrane pool (defined as endocytosis-exocytosis) was associated with the generation of a non-releasable fraction of membrane (up to 30% of plasma membrane surface) colocalizing with the lysosomal compartment. The excess retrieval membrane pool followed a saturable cytosolic Ca(2+) dependency, and it was suppressed by inhibitors of L-type Ca(2+) channels, endoplasmic reticulum Ca(2+) release and PKC.