Calcium-activated K+ channels increase cell proliferation independent of K+ conductance.
The intermediate-conductance calcium-activated potassium channel (IK1) promotes cell proliferation of numerous cell types including endothelial cells, T lymphocytes, and several cancer cell lines. The mechanism underlying IK1-mediated cell proliferation was examined in human embryonic kidney 293 (HEK293) cells expressing recombinant human IK1 (hIK1) channels. Inhibition of hIK1 with TRAM-34 reduced cell proliferation, while expression of hIK1 in HEK293 cells increased proliferation. When HEK293 cells were transfected with a mutant (GYG/AAA) hIK1 channel, which neither conducts K(+) ions nor promotes Ca(2+) entry, proliferation was increased relative to mock-transfected cells. Furthermore, when HEK293 cells were transfected with a trafficking mutant (L18A/L25A) hIK1 channel, proliferation was also increased relative to control cells. The lack of functional activity of hIK1 mutants at the cell membrane was confirmed by a combination of whole cell patch-clamp electrophysiology and fura-2 imaging to assess store-operated Ca(2+) entry and cell surface immunoprecipitation assays. Moreover, in cells expressing hIK1, inhibition of ERK1/2 and JNK kinases, but not of p38 MAP kinase, reduced cell proliferation. We conclude that functional K(+) efflux at the plasma membrane and the consequent hyperpolarization and enhanced Ca(2+) entry are not necessary for hIK1-induced HEK293 cell proliferation. Rather, our data suggest that hIK1-induced proliferation occurs by a direct interaction with ERK1/2 and JNK signaling pathways.
Faculty of Life Sciences, The University of Manchester, United Kingdom.
Joanne E
JE
Millership
Daniel C
DC
Devor
Kirk L
KL
Hamilton
Corina M
CM
Balut
Jason I E
JI
Bruce
Ian M
IM
Fearon
D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D049109:Cell Proliferation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels / Q000235:genetics / Q000378:metabolism*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism; D062554:NAV1.5 Voltage-Gated Sodium Channel; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism*; D011720:Pyrazoles / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D015222:Sodium Channels / Q000235:genetics / Q000378:metabolism
D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; D009124:Muscle Proteins; D062554:NAV1.5 Voltage-Gated Sodium Channel; D011720:Pyrazoles; C568320:SCN5A protein, human; D015222:Sodium Channels; C411671:TRAM 34; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D011188:Potassium; D002118:Calcium