Figure 5.
Overexpression of otoferlin in chromaffin cells does not change kinetics or amount of exocytosis and does not restore synchronous exocytosis in Syt1-deficient cells. A, TIRF image of the footprint of a chromaffin cell, which had been transfected with an otoferlin–eGFP fusion construct. Individual fluorescent spots most probably represent otoferlin–eGFP-tagged chromaffin granules. Scale bar, 1 μm. B, Average ΔCm in response to the first flash in control (n = 20; black) and otoferlin-expressing (n = 20; gray) bovine chromaffin cells. The first flash was delivered 120–180 s after establishment of the whole-cell configuration. C, Exocytic responses of a wild-type (Wt) nontransfected mouse chromaffin cell (black) and mean response of five Syt1-deficient chromaffin cells that had been transfected to express the otoferlin–eGFP fusion construct: lack of the fast component of the exocytic burst. Inset, Representative exocytotic response from wild-type (black, postflash [Ca2+]i: 16.31 μm) and Syt1 knock-out (gray, postflash [Ca2+]i: 15.5 μm).