Regulation of calcium-permeable TRPV2 channel by insulin in pancreatic beta-cells.
OBJECTIVE
Calcium-permeable cation channel TRPV2 is expressed in pancreatic beta-cells. We investigated regulation and function of TRPV2 in beta-cells.


METHODS
Translocation of TRPV2 was assessed in MIN6 cells and cultured mouse beta-cells by transfecting TRPV2 fused to green fluorescent protein or TRPV2 containing c-Myc tag in the extracellular domain. Calcium entry was assessed by monitoring fura-2 fluorescence.


RESULTS
In MIN6 cells, TRPV2 was observed mainly in cytoplasm in an unstimulated condition. Addition of exogenous insulin induced translocation and insertion of TRPV2 to the plasma membrane. Consistent with these observations, insulin increased calcium entry, which was inhibited by tranilast, an inhibitor of TRPV2, or by knockdown of TRPV2 using shRNA. A high concentration of glucose also induced translocation of TRPV2, which was blocked by nefedipine, diazoxide, and somatostatin, agents blocking glucose-induced insulin secretion. Knockdown of the insulin receptor attenuated insulin-induced translocation of TRPV2. Similarly, the effect of insulin on TRPV2 translocation was not observed in a beta-cell line derived from islets obtained from a beta-cell-specific insulin receptor knockout mouse. Knockdown of TRPV2 or addition of tranilast significantly inhibited insulin secretion induced by a high concentration of glucose. Likewise, cell growth induced by serum and glucose was inhibited by tranilast or by knockdown of TRPV2. Finally, insulin-induced translocation of TRPV2 was observed in cultured mouse beta-cells, and knockdown of TRPV2 reduced insulin secretion induced by glucose.


CONCLUSIONS
TRPV2 is regulated by insulin and is involved in the autocrine action of this hormone on beta-cells.
Hisanaga
Etsuko
E
Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan.
Nagasawa
Masahiro
M
Ueki
Kohjiro
K
Kulkarni
Rohit N
RN
Mori
Masatomo
M
Kojima
Itaru
I
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D005822:Genetic Vectors; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology*; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D021381:Protein Transport / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
D015220:Calcium Channels; D007004:Hypoglycemic Agents; D007328:Insulin; D050916:TRPV Cation Channels; C485717:Trpv2 protein, mouse; D002118:Calcium