Long-term inhibition of protein tyrosine kinase impairs electrophysiologic activity and a rapid component of exocytosis in pancreatic beta-cells.
Dysfunction of pancreatic beta-cells is a fundamental feature in the pathogenesis of type 2 diabetes. As insulin receptor signaling occurs via protein tyrosine kinase (PTK), we investigated the role of PTK activity in the etiology of beta-cell dysfunction by inhibiting PTK activity in primary cultured mouse pancreatic beta-cells and INS-1 cells with genistein treatment over 24 h. Electrophysiologic recordings showed genistein treatment significantly attenuated ATP-sensitive K(+) (K(ATP)) and voltage-dependent Ca(2+) currents, and depolarized the resting membrane potential in primary beta-cells. When stimulated by high glucose, genistein-treated beta-cells exhibited a time delay of both depolarization and Ca(2+) influx, and were unable to fire action potentials, as well as displaying a reduced level of Ca(2+) influx and a loss of Ca(2+) oscillations. Semiquantitative PCR analysis revealed decreased expression of K(ATP) and L-type Ca(2+) channel mRNA in genistein-treated islets. PTK inhibition also significantly reduced the rapid component of secretory vesicle exocytosis, as indicated by membrane capacitance measurements, and this is likely to be due to the reduced Ca(2+) current amplitude in these cells. These results illustrate that compromised PTK activity contributes to pancreatic beta-cell dysfunction and may be involved in the etiology of type 2 diabetes.
Zhao
Yu-Feng
YF
Prince Henry's Institute of Medical Research, PO Box 5152, Clayton, Victoria 3168, Australia.
Keating
Damien J
DJ
Hernandez
Maria
M
Feng
Dan Dan
DD
Zhu
Yulong
Y
Chen
Chen
C
D000818:Animals; D001483:Base Sequence; D015220:Calcium Channels / Q000187:drug effects / Q000235:genetics; D020013:Calcium Signaling / Q000187:drug effects; D015550:Cell Degranulation / Q000187:drug effects; D002460:Cell Line; D002478:Cells, Cultured; D004247:DNA / Q000235:genetics; D003924:Diabetes Mellitus, Type 2 / Q000209:etiology / Q000235:genetics / Q000503:physiopathology; D004594:Electrophysiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005089:Exocytosis / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects; D019833:Genistein / Q000494:pharmacology; D066298:In Vitro Techniques; D007515:Islets of Langerhans / Q000187:drug effects / Q000201:enzymology* / Q000503:physiopathology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D024661:Potassium Channels, Inwardly Rectifying / Q000187:drug effects / Q000235:genetics; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D022142:Secretory Vesicles / Q000187:drug effects / Q000502:physiology; D000099161:Kcnj11 Channel
D015220:Calcium Channels; D004247:DNA; D004791:Enzyme Inhibitors; D019833:Genistein; D024661:Potassium Channels, Inwardly Rectifying; D011505:Protein-Tyrosine Kinases; D000099161:Kcnj11 Channel