ENGINEERED PEPTIDES CORRESPONDING TO SEGMENTS OF THE H3 DOMAIN OF SYNTAXIN INHIBIT INSULIN RELEASE BOTH IN INTACT AND PERMEABILIZED MOUSE PANCREATIC BETA-CELLS

Syntaxin is one of the proteins involved in the exocytotic event throu gh sequential binding to specific proteins, including SNAP25 and synap tobrevin. In a previous work in digitonin-permeabilized beta cells, we characterized the functional role of two segments: synA and synB of t he H3 domain of syntaxin. As a continuation of these experiments in th e present study we have initially outlined a zone of 17 residues as th e very effective uncoupling element of the synA segment. Further funct ional studies have been accomplished in intact pancreatic beta cells w ith a specific myristoylated (myr) 13-mer peptide comprised in this ac tive zone. These experiments showed a concentration-dependent inhibiti on of glucose-induced insulin release (IC50=4 mu M) of this engineered peptide that was specific since a myristoylated random peptide with t he same composition was ineffective. A second myristoylated 13-mer pep tide comprised into the synB segment was shown to be even more potent promoting a selective inhibition of insulin release. These data show f or the first time, that nutrient-induced secretory process can be spec ifically uncoupled in intact beta cells demonstrating at the same time that syntaxin plays a central role in this mechanism. (C) 1998 Academ ic Press.