Syntaxin, but not soluble NSF attachment protein (SNAP), biosynthesis by rat pancreatic islets is regulated by glucose in parallel with proinsulin biosynthesis.
Recent studies have revealed that soluble N-ethylmaleimide sensitive factor attachment receptor (SNARE)-related proteins, originally identified in neural tissues, are also expressed in pancreatic beta cells. In this study, we investigated the effect of glucose on syntaxin 1 and alpha/beta SNAP biosynthesis in pancreatic beta cells and we demonstrated that syntaxin 1, but not alpha/beta SNAP biosynthesis by rat isolated pancreatic islets was stimulated specifically by glucose nearly in parallel with proinsulin biosynthesis. Stimulation of syntaxin 1 and proinsulin biosynthesis by glucose was dose-dependent (Km = approximately 8 mmol/l) and reached the maximum (about 8-12 fold) at concentrations over 11 mmol/l. In contrast, 22 mmol/l glucose increased alpha/beta SNAP biosynthesis about 2-fold only, similar to the increase in total protein synthesis. Stimulation of syntaxin 1 biosynthesis by glucose was also time-dependent, taking around 3 h to reach the maximum, and was not affected by actinomycin-D, suggesting regulation at the translational level. On the other hand, glucose had a similar stimulating effect on both syntaxin 1 and alpha/beta SNAP biosynthesis by mouse insulinoma betaTC3 cells as it did on proinsulin biosynthesis. The evidence showing coordinated stimulation of syntaxin 1 and proinsulin biosynthesis by glucose in rat islets suggested the critical functional role of syntaxin 1 in the insulin exocytotic mechanism.
Nagamatsu
S
S
Department of Biochemistry, Kyorin University School of Medicine, Mitaka, Tokyo, Japan.
Nakamichi
Y
Y
Katahira
H
H
D000818:Animals; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000096:biosynthesis*; D002478:Cells, Cultured; D003609:Dactinomycin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D005947:Glucose / Q000008:administration & dosage / Q000494:pharmacology*; D007163:Immunosorbent Techniques; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D011384:Proinsulin / Q000096:biosynthesis*; D050765:Qa-SNARE Proteins; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; D050827:Syntaxin 1; D033921:Vesicular Transport Proteins
D002352:Carrier Proteins; D008565:Membrane Proteins; D019384:Nucleic Acid Synthesis Inhibitors; D050765:Qa-SNARE Proteins; D012333:RNA, Messenger; D052067:Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins; C494214:Stx1a protein, mouse; C494213:Stx1a protein, rat; D050827:Syntaxin 1; D033921:Vesicular Transport Proteins; D003609:Dactinomycin; D011384:Proinsulin; D005947:Glucose