Inhibition of Kv2.1 voltage-dependent K+ channels in pancreatic beta-cells enhances glucose-dependent insulin secretion.
Voltage-dependent (Kv) outward K(+) currents repolarize beta-cell action potentials during a glucose stimulus to limit Ca(2+) entry and insulin secretion. Dominant-negative "knockout" of Kv2 family channels enhances glucose-stimulated insulin secretion. Here we show that a putative Kv2.1 antagonist (C-1) stimulates insulin secretion from MIN6 insulinoma cells in a glucose- and dose-dependent manner while blocking voltage-dependent outward K(+) currents. C-1-blocked recombinant Kv2.1-mediated currents more specifically than currents mediated by Kv1, -3, and -4 family channels (Kv1.4, 3.1, 4.2). Additionally, C-1 had little effect on currents recorded from MIN6 cells expressing a dominant-negative Kv2.1 alpha-subunit. The insulinotropic effect of acute Kv2.1 inhibition resulted from enhanced membrane depolarization and augmented intracellular Ca(2+) responses to glucose. Immunohistochemical staining of mouse pancreas sections showed that expression of Kv2.1 correlated highly with insulin-containing beta-cells, consistent with the ability of C-1 to block voltage-dependent outward K(+) currents in isolated mouse beta-cells. Antagonism of Kv2.1 in an ex vivo perfused mouse pancreas model enhanced first- and second-phase insulin secretion, whereas glucagon secretion was unaffected. The present study demonstrates that Kv2.1 is an important component of beta-cell stimulus-secretion coupling, and a compound that enhances, but does not initiate, beta-cell electrical activity by acting on Kv2.1 would be a useful antidiabetic agent.
MacDonald
Patrick E
PE
Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
Sewing
Sabine
S
Wang
Jianli
J
Joseph
Jamie W
JW
Smukler
Simon R
SR
Sakellaropoulos
George
G
Wang
Jing
J
Saleh
Monique C
MC
Chan
Catherine B
CB
Tsushima
Robert G
RG
Salapatek
Anne Marie F
AM
Wheeler
Michael B
MB
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D051668:Delayed Rectifier Potassium Channels; D003981:Diazoxide / Q000494:pharmacology; D005260:Female; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007340:Insulinoma; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D010179:Pancreas / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D015221:Potassium Channels / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D051669:Shab Potassium Channels; D019789:Tetraethylammonium / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D014700:Verapamil / Q000494:pharmacology
D002121:Calcium Channel Blockers; D051668:Delayed Rectifier Potassium Channels; D007328:Insulin; C496988:KCNB1 protein, human; C496990:Kcnb1 protein, mouse; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D011993:Recombinant Fusion Proteins; D051669:Shab Potassium Channels; D019789:Tetraethylammonium; D014700:Verapamil; D005947:Glucose; D003981:Diazoxide; D002118:Calcium