Priming of insulin granules for exocytosis by granular Cl(-) uptake and acidification.
ATP-dependent priming of the secretory granules precedes Ca(2+)-regulated neuroendocrine secretion, but the exact nature of this reaction is not fully established in all secretory cell types. We have further investigated this reaction in the insulin-secreting pancreatic B-cell and demonstrate that granular acidification driven by a V-type H(+)-ATPase in the granular membrane is a decisive step in priming. This requires simultaneous Cl(-) uptake through granular ClC-3 Cl(-) channels. Accordingly, granule acidification and priming are inhibited by agents that prevent transgranular Cl(-) fluxes, such as 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and an antibody against the ClC-3 channels, but accelerated by increases in the intracellular ATP:ADP ratio or addition of hypoglycemic sulfonylureas. We suggest that this might represent an important mechanism for metabolic regulation of Ca(2+)-dependent exocytosis that is also likely to be operational in other secretory cell types.
Barg
S
S
Department of Physiological Sciences, Lund University, Sölvegatan 19, SE-223 62 Lund, Sweden.
Huang
P
P
Eliasson
L
L
Nelson
D J
DJ
Obermüller
S
S
Rorsman
P
P
Thévenod
F
F
Renström
E
E
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002478:Cells, Cultured; D018118:Chloride Channels / Q000737:chemistry / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism*; D005089:Exocytosis / Q000187:drug effects; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D017136:Ion Transport / Q000187:drug effects; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008954:Models, Biological; D022142:Secretory Vesicles / Q000187:drug effects / Q000378:metabolism*; D013453:Sulfonylurea Compounds / Q000494:pharmacology; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism
D018118:Chloride Channels; D002712:Chlorides; C115376:ClC-3 channel; D007328:Insulin; D013453:Sulfonylurea Compounds; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D025262:Vacuolar Proton-Translocating ATPases; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid