Inhibition of insulin release by synthetic peptides shows that the H3 region at the C-terminal domain of syntaxin-1 is crucial for Ca(2+)- but not for guanosine 5'-[gamma-thio]triphosphate-induced secretion.
Recently, we have described the presence and possible role of syntaxin in pancreatic beta-cells by using monoclonal antibodies [F. Martin, F. Moya, L. M. Gutierrez, J.A. Reig, B. Soria (1995) Diabetologia 38, 860-863]. In order to characterize further the importance of specific domains of this protein, the functional role of a particular region of the syntaxin-1 molecule has now been investigated by using two synthetic peptides, SynA and SynB, corresponding to two portions of the H3 region at the C-terminal domain of the protein, residues 229-251 and 197-219 respectively. Functional experiments carried out in permeabilized pancreatic beta-cells demonstrate that these peptides inhibit Ca(2+)-dependent insulin release in a dose-dependent manner. This effect is specific because peptides of the same composition but random sequence do not show the same effect. In contrast with this inhibitory effect on Ca(2+)-induced secretion, both peptides increase basal release. However, under the same conditions, SynA and SynB do not affect guanosine 5'-[gamma-thio]triphosphate-induced insulin release. These results demonstrate that specific portions of the H3 region of syntaxin-1 are involved in critical protein-protein interactions specifically during Ca(2+)-induced insulin secretion.
Martin
F
F
Department of Fisiología, Facultad Medicina, Universidad de Alicante, Spain.
Salinas
E
E
Vazquez
J
J
Soria
B
B
Reig
J A
JA
D000595:Amino Acid Sequence; D000818:Animals; D000954:Antigens, Surface / Q000737:chemistry / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D007329:Insulin Antagonists / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology*; D050827:Syntaxin 1
D000954:Antigens, Surface; D007328:Insulin; D007329:Insulin Antagonists; D009419:Nerve Tissue Proteins; D010455:Peptides; C494214:Stx1a protein, mouse; D050827:Syntaxin 1; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D002118:Calcium