AIP1 functions as Arf6-GAP to negatively regulate TLR4 signaling.
Toll-like receptor 4 (TLR4) is unique among the Toll-like receptors in its ability to utilize TLR/IL1R-domain-containing adaptor protein (TIRAP), which recruits TLR4-MyD88 to phosphatidylinositol 4,5-bisphosphate (PIP(2))-rich sites on the plasma membrane, to activate NF-kappaB and MAPK pathways. Here, we show that AIP1 disrupts formation of the TLR4- TIRAP-MyD88 complex without directly binding to any of the complex components. AIP1 via its pleckstrin homology and C2 domains binds to phosphatidylinositol 4-phosphate, a lipid precursor of PIP(2). Knock-out of AIP1 in cells increases and overexpression of AIP1 reduces cellular PIP(2) levels. We further show that AIP1 is a novel GTPase-activating protein (GAP) for Arf6, a small GTPase regulating cellular PIP(2) production and formation of the TLR4-TIRAP-MyD88 complex. Thus, deletion of the GAP domain on AIP1 results in a loss of its ability to mediate the inhibition of Arf6- and TLR4-induced signaling events. We conclude that AIP1 functions as a novel Arf6-GAP to negatively regulate PIP(2)-dependent TLR4-TIRAP-MyD88 signaling.
Wan
Ting
T
From the Interdepartmental Program in Vascular Biology and Therapeutics, Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06520 and; the State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou 510060, China.
Liu
Ting
T
From the Interdepartmental Program in Vascular Biology and Therapeutics, Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06520 and.
Zhang
Haifeng
H
From the Interdepartmental Program in Vascular Biology and Therapeutics, Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06520 and.
Tang
Shibo
S
the State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou 510060, China. Electronic address: tangsb@mail.sysu.edu.cn.
Min
Wang
W
From the Interdepartmental Program in Vascular Biology and Therapeutics, Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06520 and; the State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-Sen University, Guangzhou 510060, China. Electronic address: wang.min@yale.edu.
D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors / Q000235:genetics / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D002460:Cell Line; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism*; D051528:Guanylate Kinases; D006801:Humans; D015151:Immunoblotting; D008070:Lipopolysaccharides / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D011485:Protein Binding; D017472:Receptors, Interleukin-1 / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
D000089982:ADP-Ribosylation Factor 6; D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D020690:GTPase-Activating Proteins; D008070:Lipopolysaccharides; C507779:MYD88 protein, human; D008562:Membrane Glycoproteins; D053594:Myeloid Differentiation Factor 88; D016328:NF-kappa B; D019269:Phosphatidylinositol 4,5-Diphosphate; D017472:Receptors, Interleukin-1; C434984:TIRAP protein, human; D051197:Toll-Like Receptor 4; D020928:Mitogen-Activated Protein Kinases; D051528:Guanylate Kinases; C485777:MAGI2 protein, human; D020727:ADP-Ribosylation Factors; C000715348:ARF6 protein, human; C000715727:Arf6 protein, mouse