IGF-1 up-regulates K+ channels via PI3-kinase, PDK1 and SGK1.
Involvement of voltage-gated (Kv) potassium channels in IGF-1-induced proliferation of HEK293 cells was studied by patch-clamp, RT-PCR and FACS analysis. IGF-1 up-regulated outwardly rectifying whole-cell K+ current starting after 1 h of incubation and reaching a maximum after 4-6 h. The IGF-1-stimulated current was voltage-gated with an activation threshold of -30 mV to -40 mV, a half-maximal activation at +5.3+/-1.8 mV, and time constants for activation and inactivation of 4.5+/-0.4 ms and 43.5+/-5.6 ms ( n=10), respectively. The current was inhibited by TEA, margatoxin, agitoxin-2 and stichodactyla toxin. PCR amplification of different Kv subunits from HEK293 cDNA demonstrated the expression of Kv1.1, Kv1.2, Kv1.3, Kv1.4, Kv3.1 and Kv3.4 mRNA. Quantitative RT-PCR showed up-regulation of Kv1.1, 1.2 and 1.3 mRNA by IGF-1. The effect of IGF-1 on K+ current was blocked by inhibitors of phosphatidylinositol 3-kinase (PI3-kinase), wortmannin and LY294002, and mimicked by overexpression of human 3-phosphoinositide-dependent protein kinase-1 (hPDK1) or serum- and glucocorticoid-dependent kinase-1 (hSGK1), both sequential downstream targets of PI3-kinase. IGF-1-induced proliferation of HEK293 cells was inhibited by both K+ channel blockers and inhibitors of PI3-kinase. In conclusion, IGF-1 through PI3-kinase, PDK1 and SGK1 up-regulates Kv channels, an effect required for the proliferative action of the growth factor.
Gamper
N
N
Sechenov Institute of Evolutionary Physiology and Biochemistry, St. Petersburg, Russia.
Fillon
S
S
Huber
S M
SM
Feng
Y
Y
Kobayashi
T
T
Cohen
P
P
Lang
F
F
D064413:3-Phosphoinositide-Dependent Protein Kinases; D000730:Androstadienes / Q000494:pharmacology; D002455:Cell Division / Q000502:physiology; D002460:Cell Line; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D006801:Humans; D017874:Immediate-Early Proteins; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007668:Kidney / Q000166:cytology; D051664:Kv1.3 Potassium Channel; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009025:Morpholines / Q000494:pharmacology; D009498:Neurotoxins / Q000494:pharmacology; D009687:Nuclear Proteins; D018408:Patch-Clamp Techniques; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000235:genetics* / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D012604:Scorpion Venoms; D015398:Signal Transduction / Q000502:physiology; D000077191:Wortmannin; D000099184:Serum-Glucocorticoid Regulated Kinases
D064413:3-Phosphoinositide-Dependent Protein Kinases; D000730:Androstadienes; D002867:Chromones; D004791:Enzyme Inhibitors; D017874:Immediate-Early Proteins; D007334:Insulin-Like Growth Factor I; D051664:Kv1.3 Potassium Channel; D009025:Morpholines; D009498:Neurotoxins; D009687:Nuclear Proteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011188:Potassium; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger; D012604:Scorpion Venoms; D000077191:Wortmannin; D000099184:Serum-Glucocorticoid Regulated Kinases; C496973:KCNA3 protein, human; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C077910:margatoxin; C578562:PDPK1 protein, human