Abstract
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.
Publication types
-
Research Support, Non-U.S. Gov't
MeSH terms
-
3-Phosphoinositide-Dependent Protein Kinases
-
Androstadienes / pharmacology
-
Cell Division / physiology
-
Cell Line
-
Chromones / pharmacology
-
Enzyme Inhibitors / pharmacology
-
Gene Expression / drug effects
-
Gene Expression / physiology
-
Humans
-
Immediate-Early Proteins
-
Insulin-Like Growth Factor I / pharmacology*
-
Kidney / cytology
-
Kv1.3 Potassium Channel
-
Membrane Potentials / drug effects
-
Membrane Potentials / physiology
-
Morpholines / pharmacology
-
Neurotoxins / pharmacology
-
Nuclear Proteins*
-
Patch-Clamp Techniques
-
Phosphatidylinositol 3-Kinases / metabolism*
-
Phosphoinositide-3 Kinase Inhibitors
-
Potassium / metabolism
-
Potassium Channels / genetics*
-
Potassium Channels / metabolism
-
Potassium Channels, Voltage-Gated*
-
Protein Serine-Threonine Kinases / antagonists & inhibitors
-
Protein Serine-Threonine Kinases / metabolism
-
RNA, Messenger / analysis
-
Scorpion Venoms
-
Signal Transduction / physiology
-
Wortmannin
Substances
-
Androstadienes
-
Chromones
-
Enzyme Inhibitors
-
Immediate-Early Proteins
-
KCNA3 protein, human
-
Kv1.3 Potassium Channel
-
Morpholines
-
Neurotoxins
-
Nuclear Proteins
-
Phosphoinositide-3 Kinase Inhibitors
-
Potassium Channels
-
Potassium Channels, Voltage-Gated
-
RNA, Messenger
-
Scorpion Venoms
-
2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
-
margatoxin
-
Insulin-Like Growth Factor I
-
3-Phosphoinositide-Dependent Protein Kinases
-
PDPK1 protein, human
-
Protein Serine-Threonine Kinases
-
serum-glucocorticoid regulated kinase
-
Potassium
-
Wortmannin