Non-functional role of syntaxin 2 in insulin exocytosis by pancreatic beta cells.
This study was designed in order to examine the expression and functional role of syntaxin 2/epimorphin in pancreatic beta cells. Northern blot analysis revealed that syntaxin 2 mRNA was able to be detected in mouse beta TC3 cells, but not in isolated mouse islets. In agreement with this result, immunoblot analysis detected an appreciable amount of syntaxin 2 protein in beta TC3 cells, but not in mouse islets. Immunohistochemistry of the mouse pancreas demonstrated that syntaxin 2 was little evident in islet cells of Langerhans, and somewhat predominant in exocrine tissues. In order to examine whether syntaxin 2 is anchored to cell surfaces in beta TC3 cells, living cells were incubated with a monoclonal antibody against syntaxin 2 (MC-1). The antibody bound to their surfaces, indicating that syntaxin 2 was localized on cell surfaces. The addition of MC-1 to the culture medium of beta TC3 cells did not affect insulin release under the presence or absence of 11 mM glucose, indicating that syntaxin 2 is not associated with insulin exocytosis. Thus, the expression of syntaxin 2 in islets of Langerhans is very low and the function of this protein is probably unrelated to the insulin exocytosis pathway.
Nagamatsu
S
S
Department of Biochemistry, Kyroin University School of Medicine, Tokyo, Japan. RXB07732@niftyserve.or.jp
Sawa
H
H
Nakamichi
Y
Y
Kondo
Y
Y
Matsushima
S
S
Watanabe
T
T
D000818:Animals; D000911:Antibodies, Monoclonal; D000954:Antigens, Surface / Q000032:analysis / Q000235:genetics* / Q000276:immunology; D005089:Exocytosis / Q000502:physiology*; D015870:Gene Expression / Q000502:physiology; D007328:Insulin / Q000378:metabolism*; D007515:Islets of Langerhans / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism; D008565:Membrane Proteins / Q000032:analysis / Q000235:genetics / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D009419:Nerve Tissue Proteins / Q000032:analysis / Q000235:genetics* / Q000276:immunology; D050827:Syntaxin 1
D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; C504582:Epim protein, mouse; D007328:Insulin; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D050827:Syntaxin 1