Transgenic Mouse Overexpressing Syntaxin-1A as a Diabetes Model

• Published in: Diabetes (New York, N.Y.) Vol. 54; no. 9; pp. 2744 - 2754
• Main Authors: Lam, Patrick P.L., Leung, Yuk-Man, Sheu, Laura, Ellis, James, Tsushima, Robert G., Osborne, Lucy R., Gaisano, Herbert Y.
• Format: Journal Article
• Language: English
• Published: Alexandria, VA American Diabetes Association 01.09.2005
• Subjects: Animals; Biological and medical sciences; Calcium Channels - physiology; Diabetes; Diabetes mellitus; Diabetes Mellitus - genetics; Diabetes Mellitus - physiopathology; Diabetes research; Diabetes. Impaired glucose tolerance; Disease Models, Animal; Endocrine pancreas. Apud cells (diseases); Endocrinopathies; Etiopathogenesis. Screening. Investigations. Target tissue resistance; Exocytosis - physiology; Female; Gene Expression - physiology; Genetic aspects; Glucose; Glucose Tolerance Test; Homeostasis; Insulin; Insulin - metabolism; Insulin Resistance - genetics; Insulin Resistance - physiology; Islands of Langerhans; Islets of Langerhans; Islets of Langerhans - metabolism; Male; Medical sciences; Metabolism; Mice; Mice, Transgenic; Observations; Potassium Channels - physiology; Proteins; Transgenic animals; Canada; Endocrinopathy; Syntaxin; Vertebrata; Mammalia; Mouse; Diabetes mellitus; Rodentia; Transgenic animal; Models
• ISSN: 0012-1797; 1939-327X
• DOI: 10.2337/diabetes.54.9.2744

Transgenic Mouse Overexpressing Syntaxin-1A as a Diabetes Model Patrick P.L. Lam 1 2 , Yuk-Man Leung 1 2 , Laura Sheu 1 2 , James Ellis 3 , Robert G. Tsushima 1 2 , Lucy R. Osborne 1 4 and Herbert Y. Gaisano 1 2 1 Department of Medicine, University of Toronto, Toronto, Canada 2 Department of Physiology, University of Toronto, Toronto, Canada 3 Program in Developmental Biology, Sick Kids Hospital, Toronto, Canada 4 Department of Molecular and Medical Genetics, University of Toronto, Toronto, Canada Address correspondence and reprint requests to Herbert Y. Gaisano, MD, University of Toronto, Room 7226, Medical Science Building, 1 King’s College Circle, Toronto, Ontario, Canada M5S 1A8. E-mail: herbert.gaisano{at}utoronto.ca . Or Lucy R. Osborne, PhD, University of Toronto, Room 7238, Medical Science Building, 1 King’s College Circle, Toronto, Ontario, Canada M5S 1A8. E-mail: lucy.osborne{at}utoronto.ca Abstract Soluble N -ethylmaleimide–sensitive factor (NSF) attachment protein receptor (SNARE) protein syntaxin-1A (STX-1A) plays a role not only in exocytosis, but also binds and regulates Ca 2+ and K + (voltage-gated K + and ATP-sensitive K + channels) to influence the sequence of events leading to secretion. Islet levels of STX-1A and cognate SNARE proteins are reduced in type 2 diabetic rodents, suggesting their role in dysregulated insulin secretion contributing to the abnormal glucose homeostasis. We investigated the specific role of STX-1A in pancreatic β-cells by generating transgenic mice, which express a moderately increased level (∼30% higher) of STX-1A in pancreatic islets (hereafter called STX-1A mice). The STX-1A mice displayed fasting hyperglycemia and a more sustained elevation of plasma glucose levels after an intraperitoneal glucose tolerance test, with correspondingly reduced plasma insulin levels. Surprisingly, β-cells from the STX-1A male mice also exhibited abnormal insulin tolerance. To unequivocally determine the β-cell secretory defects, we used single-cell analyses of exocytosis by patch clamp membrane capacitance measurements and ion channel recordings. Depolarization-evoked membrane capacitance increases were reduced in the STX-1A mouse islet β-cells. The STX-1A mouse also exhibited reduced currents through the Ca 2+ channels but little change in the voltage-gated K + channel or ATP-sensitive K + channel. These results suggest that fluctuation of islet STX-1A levels in diabetes could influence the pathological and differential regulation of β-cell ion channels and the exocytotic machinery, collectively contributing to the impaired insulin secretion. Cm, membrane capacitance GST, glutathione S-transferase IPGTT, intraperitoneal glucose tolerance test KATP channel, ATP-sensitive K+ channel Kv channel, voltage-gated potassium channel NSF, N-ethylmaleimide–sensitive factor SNAP-25, synaptosome-associated protein of 25 kDa SNARE, soluble NSF attachment protein receptor STX-1A, syntaxin-1A TEA, tetraethylammonium VAMP-2, vesicle-associated membrane protein 2 WBS, Williams-Beuren syndrome Footnotes P.P.L.L. and Y.-M.L. contributed equally to this work. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Accepted June 7, 2005. Received November 23, 2004. DIABETES