J Physiol Volume 506, Number 3, 589-, February 1, 1998
The Journal of Physiology (1998), 506.3, pp. 589
© Copyright 1998 The Physiological Society
Two forms of triggered endocytosis in regulated secretory cells
Robert D. Burgoyne
The Physiological Laboratory, University of Liverpool, Crown Street, Liverpool L69 3BX, UK
It is likely that during physiological stimulation, exocytosis in regulated secretory cells will be followed by a matched membrane retrieval to maintain a constant cell surface area. Changes in cell surface area during exocytosis and endocytosis can be monitored by patch-clamp recording of plasma membrane capacitance. In such recordings, increases in capacitance due to exocytosis can be readily detected. In whole-cell recordings, membrane retrieval by endocytosis has not always been observed, since a form of endocytosis that recovers exocytosed membrane shows rapid run-down during whole-cell dialysis (Burgoyne, 1995). In some instances, however, with strong stimulation or high intracellular Ca2+ levels, an alternative very rapid form of endocytosis has been observed in whole-cell recordings of chromaffin (Neher & Zucker, 1993; Artalejo et al. 1996) and other cell types (Thomas et al. 1994; Proks & Ashcroft, 1995) that recovers membrane in excess of that inserted during the burst of exocytosis. The relationship between 'compensatory' retrieval and this 'excess' retrieval has now been clarified in two papers on adrenal chromaffin cells (Smith & Neher, 1997; Engisch & Nowycky, 1998, in this issue of The Journal of Physiology) using perforated-patch recording in which compensatory retrieval is maintained. The results of these two studies are in agreement and suggest the presence of two distinct pathways for endocytosis in chromaffin and probably other secretory cells.
Copyright © 1998 The Physiological Society.
