Enhanced phosphatidylinositol 4-phosphate 5-kinase alpha expression and PI(4,5)P2 production in LPS-stimulated microglia.
Microglia are the major glial cells responsible for immune responses against harmful substances in the central nervous system. Type I phosphatidylinositol 4-phosphate 5-kinase alpha (PIP5Kalpha) and its lipid product, phosphatidylinositol 4,5-bisphosphate (PI[4,5]P(2)), regulate important cell surface functions. Here, we report that lipopolysaccharide (LPS) significantly enhanced PIP5Kalpha mRNA and protein expression levels in a time- and concentration-dependent manner in microglia. Furthermore, LPS stimulation led to a robust increase in PI(4,5)P(2) in the plasma membrane, demonstrated by PI(4,5)P(2) immunostaining or PI(4,5)P(2) imaging using a PI(4,5)P(2)-specific probe, tubby (R332H), fused to yellow fluorescent protein. Phosphatidylinositol 3-kinase, p38 mitogen-activated protein kinase (MAPK), p42/44 MAPK, and c-Jun N-terminal kinase signaling pathway inhibitors clearly reduced PIP5Kalpha expression, indicating that these pathways are necessary for LPS-induced PIP5Kalpha expression. In addition, inhibition of nuclear factor-kappaB and Sp1 transcription factors interfered with the LPS-induced upregulation of PIP5Kalpha. Delivery of PI(4,5)P(2) into microglia increased the expression of interleukin-1beta and tumor necrosis factor alpha. These findings indicate that PIP5Kalpha upregulation and the subsequent rise in PI(4,5)P(2) in LPS-stimulated microglia may positively regulate microglial inflammatory responses.
Lee
Sang Yoon
SY
Neuroscience Graduate Program, Ajou University School of Medicine, Suwon, Gyeonggi, Republic of Korea. sangyoon@ajou.ac.kr
Kim
Bokyoung
B
Jeong
Hey-Kyeong
HK
Min
Kyoung-Jin
KJ
Liu
Tian
T
Park
Ji-Young
JY
Joe
Eun-Hye
EH
Jou
Ilo
I
D000818:Animals; D015153:Blotting, Western; D002460:Cell Line; D016207:Cytokines / Q000096:biosynthesis; D005455:Fluorescent Antibody Technique; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008262:Macrophage Activation / Q000187:drug effects; D051379:Mice; D017628:Microglia / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D018613:Microscopy, Confocal; D016328:NF-kappa B / Q000096:biosynthesis; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000096:biosynthesis*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000096:biosynthesis*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013268:Stimulation, Chemical; D014162:Transfection
D016207:Cytokines; D008070:Lipopolysaccharides; D016328:NF-kappa B; D019269:Phosphatidylinositol 4,5-Diphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); C020077:1-phosphatidylinositol-4-phosphate 5-kinase