title: Nerve growth factor stimulates the concentration of TrkA within lipid rafts and extracellular signal-regulated kinase activation through c-Cbl-associated protein.
abstract: Nerve growth factor (NGF) acts through its receptor, TrkA, to elicit the neuronal differentiation of PC12 cells through the action of extracellular signal-regulated kinase 1 (ERK1) and ERK2. Upon NGF binding, TrkA translocates and concentrates in cholesterol-rich membrane microdomains or lipid rafts, facilitating formation of receptor-associated signaling complexes, activation of downstream signaling pathways, and internalization into endosomes. We have investigated the mechanisms responsible for the localization of TrkA within lipid rafts and its ability to activate ERK1 and ERK2. We report that NGF treatment results in the translocation of activated forms of TrkA to lipid rafts, and this localization is important for efficient activation of the ERKs. TrkA is recruited and retained within lipid rafts through its association with flotillin, an intrinsic constituent of these membrane microdomains, via the adapter protein, c-Cbl associated protein (CAP). Mutant forms of CAP that lack protein interaction domains block TrkA localization to lipid rafts and attenuate ERK activation. Importantly, suppression of endogenous CAP expression inhibited NGF-stimulated neurite outgrowth from primary dorsal root ganglion neurons. These data provide a mechanism for the lipid raft localization of TrkA and establish the importance of the CAP adaptor protein for NGF activation of the ERKs and neuronal differentiation.
authors.affiliation: Department of Neurosciences, Alzheimer Research Laboratory, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4928, USA.
authors.forename: Allison S
authors.initials: AS
authors.lastname: Limpert
authors.forename: J Colleen
authors.initials: JC
authors.lastname: Karlo
authors.forename: Gary E
authors.initials: GE
authors.lastname: Landreth
mesh_terms: D000818:Animals; D002784:Cholesterol / Q000172:deficiency; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D004705:Endocytosis / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005727:Ganglia, Spinal / Q000166:cytology / Q000187:drug effects; D021962:Membrane Microdomains / Q000187:drug effects* / Q000378:metabolism*; D008565:Membrane Proteins; D051379:Mice; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism*; D048053:Mitogen-Activated Protein Kinase 6 / Q000378:metabolism*; D050505:Mutant Proteins / Q000378:metabolism; D020932:Nerve Growth Factor / Q000494:pharmacology*; D016501:Neurites / Q000187:drug effects; D016716:PC12 Cells; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000187:drug effects; D051381:Rats; D020917:Receptor, trkA / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D020664:Son of Sevenless Proteins / Q000378:metabolism; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism
chemical_list: D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D050505:Mutant Proteins; D020664:Son of Sevenless Proteins; C106354:flotillins; D004815:Epidermal Growth Factor; D020932:Nerve Growth Factor; D002784:Cholesterol; D020917:Receptor, trkA; D048052:Mitogen-Activated Protein Kinase 3; D048053:Mitogen-Activated Protein Kinase 6; D020827:rap1 GTP-Binding Proteins