title: Differential regulation of TNF-R1 signaling: lipid raft dependency of p42mapk/erk2 activation, but not NF-kappaB activation.
abstract: The TNFR, TNF-R1, is localized to lipid raft and nonraft regions of the plasma membrane. Ligand binding sets in motion signaling cascades that promote the activation of p42(mapk/erk2) and NF-kappaB. However, the role of receptor localization in the activation of downstream signaling events is poorly understood. In this study, we investigated the dynamics of TNF-R1 localization to lipid rafts and the consequences of raft localization on the activation of p42(mapk/erk2) and NF-kappaB in primary cultures of mouse macrophages. Using sucrose density gradient ultracentrifugation and a sensitive ELISA to detect TNF-R1, we show that TNF-R1 is rapidly and transiently recruited to lipid rafts in response to TNF-alpha. Disruption of lipid rafts by cholesterol depletion prevented the TNF-alpha-dependent recruitment of TNF-R1 to lipid rafts and inhibited the activation of p42(mapk/erk2), while the activation of NF-kappaB was unaffected. In addition, phosphorylated p42(mapk/erk2), but not receptor interacting protein, I-kappaB kinase-gamma, or I-kappaBalpha was detected in raft-containing fractions following TNF-alpha stimulation. These findings suggest that TNF-R1 is localized to both lipid raft and nonraft regions of the plasma membrane and that each compartment is capable of initiating different signaling responses. We propose that segregation of TNF-R1 to raft and nonraft regions of the plasma membrane contributes to the diversity of signaling responses initiated by TNF-R1.
authors.affiliation: Program in Cell Biology, Department of Pediatrics, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, CO 80206, USA.
authors.forename: Joyce E S
authors.initials: JE
authors.lastname: Doan
authors.forename: David A
authors.initials: DA
authors.lastname: Windmiller
authors.forename: David W H
authors.initials: DW
authors.lastname: Riches
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000378:metabolism / Q000502:physiology*; D004789:Enzyme Activation; D007700:Kinetics; D021962:Membrane Microdomains / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D021381:Protein Transport; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism / Q000502:physiology*; D047888:Receptors, Tumor Necrosis Factor, Type I; D015398:Signal Transduction; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D015703:Antigens, CD; D016328:NF-kappa B; D018124:Receptors, Tumor Necrosis Factor; D047888:Receptors, Tumor Necrosis Factor, Type I; D014409:Tumor Necrosis Factor-alpha; D019950:Mitogen-Activated Protein Kinase 1