Rise and Fall of Kir2.2 Current by TLR4 Signaling in Human Monocytes: PKC-Dependent Trafficking and PI3K-Mediated PIP2 Decrease.
LPSs are widely used to stimulate TLR4, but their effects on ion channels in immune cells are poorly known. In THP-1 cells and human blood monocytes treated with LPS, inwardly rectifying K(+) channel current (IKir,LPS) newly emerged at 1 h, peaked at 4 h (-119 ± 8.6 pA/pF), and decayed afterward (-32 ± 6.7 pA/pF at 24 h). Whereas both the Kir2.1 and Kir2.2 mRNAs and proteins were observed, single-channel conductance (38 pS) of IKir,LPS and small interfering RNA-induced knockdown commonly indicated Kir2.2 than Kir2.1. LPS-induced cytokine release and store-operated Ca(2+) entry were commonly decreased by ML-133, a Kir2 inhibitor. Immunoblot, confocal microscopy, and the effects of vesicular trafficking inhibitors commonly suggested plasma membrane translocation of Kir2.2 by LPS. Both IKir,LPS and membrane translocation of Kir2.2 were inhibited by GF109203X (protein kinase C [PKC] inhibitor) or by transfection with small interfering RNA-specific PKCε. Interestingly, pharmacological activation of PKC by PMA induced both Kir2.1 and Kir2.2 currents. The spontaneously decayed IKir,LPS at 24 h was recovered by PI3K inhibitors but further suppressed by an inhibitor of phosphatidylinositol(3,4,5)-trisphosphate (PIP3) phosphatase (phosphatase and tensin homolog). However, IKir,LPS at 24 h was not affected by Akt inhibitors, suggesting that the decreased phosphatidylinositol(4,5)-bisphosphate availability, that is, conversion into PIP3 by PI3K, per se accounts for the decay of IKir,LPS. Taken together, to our knowledge these data are the first demonstrations that IKir is newly induced by TLR4 stimulation via PKC-dependent membrane trafficking of Kir2.2, and that conversion of phosphatidylinositol(4,5)-bisphosphate to PIP3 modulates Kir2.2. The augmentation of Ca(2+) influx and cytokine release suggests a physiological role for Kir2.2 in TLR4-stimulated monocytes.
Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea;
Kyung Soo
KS
Kim
Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea;
Ji Hyun
JH
Jang
Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea;
Haiyue
H
Lin
Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea;
Seong Woo
SW
Choi
Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea;
Hang Rae
HR
Kim
Division of Natural Medical Sciences, College of Health Science, Chosun University, Gwangju 501-759, Republic of Korea; and.
Dong Hoon
DH
Shin
Channelopathy Research Center, Dongguk University College of Medicine, Goyang 410-773, Republic of Korea.
Joo Hyun
JH
Nam
Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea;
Yin Hua
YH
Zhang
Department of Physiology, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 110-799, Republic of Korea; Channelopathy Research Center, Dongguk University College of Medicine, Goyang 410-773, Republic of Korea physiolksj@gmail.com.
Sung Joon
SJ
Kim
D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D008070:Lipopolysaccharides; D008301:Maleimides / Q000494:pharmacology; D009000:Monocytes / Q000276:immunology*; D018408:Patch-Clamp Techniques; D010618:Phenanthrolines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D054801:Phosphoinositide Phospholipase C / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors; D024661:Potassium Channels, Inwardly Rectifying / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D051744:Protein Kinase C-epsilon / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering; D015398:Signal Transduction; D051197:Toll-Like Receptor 4 / Q000378:metabolism*
D002118:Calcium; D007093:Imidazoles; D007211:Indoles; D008070:Lipopolysaccharides; D008301:Maleimides; D010618:Phenanthrolines; D019869:Phosphatidylinositol 3-Kinases; D019269:Phosphatidylinositol 4,5-Diphosphate; D054801:Phosphoinositide Phospholipase C; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010744:Phosphoric Monoester Hydrolases; D024661:Potassium Channels, Inwardly Rectifying; D051744:Protein Kinase C-epsilon; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D051197:Toll-Like Receptor 4; C546026:2-(2-methyl-1H-indol-3-yl)-1H-imidazol(4,5-f)(1,10)phenanthroline; C489457:KCNJ2 protein, human; C489463:Kir2.2 channel; C495345:TLR4 protein, human; C096024:phosphatidylinositol-3,4,5-trisphosphate 5-phosphatase; C070515:bisindolylmaleimide I