Similar effects of alpha- and beta-SNAP on Ca(2+)-regulated exocytosis.
Soluble N-ethylmaleimide-sensitive fusion protein attachment proteins (SNAP) proteins function in Ca(2+)-regulated exocytosis. Recent work (Schiavo et al. (1996) Nature 378, 733-736) based on in vitro protein interactions has raised the possibility that alpha- and beta-SNAPs have distinct roles in exocytosis. We have examined this possibility by comparing the activities of recombinant alpha- and beta-SNAPs. Both of these proteins were able to similarly bind NSF and activate its ATPase activity but to a lesser extent than gamma-SNAP. When introduced into digitoninpermeabilised chromaffin cells, both alpha- and beta-SNAP stimulated Ca(2+)-regulated exocytosis in a MgATP-dependent manner. The dose-response relationships for these proteins were essentially the same and addition of both proteins did not lead to any further increase in exocytosis above that due to each protein alone. We conclude that alpha- and beta-SNAPs are interchangeable isoforms with similar functions in regulated exocytosis.
Sudlow
A W
AW
Physiological Laboratory, University of Liverpool, UK.
McFerran
B W
BW
Bodill
H
H
Barnard
R J
RJ
Morgan
A
A
Burgoyne
R D
RD
D000251:Adenosine Triphosphatases / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000313:Adrenal Medulla; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000494:pharmacology*; D002395:Catecholamines / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D019439:Chromaffin Cells / Q000187:drug effects / Q000378:metabolism*; D005089:Exocytosis; D007700:Kinetics; D008565:Membrane Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000494:pharmacology*; D051379:Mice; D016133:Polymerase Chain Reaction; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000494:pharmacology; D016324:Sequence Tagged Sites; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; D033921:Vesicular Transport Proteins
D002352:Carrier Proteins; D002395:Catecholamines; D008565:Membrane Proteins; D011994:Recombinant Proteins; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; D033921:Vesicular Transport Proteins; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D002118:Calcium