title: Nerve growth factor-mediated neurite outgrowth via regulation of Rab5.
abstract: Nerve growth factor (NGF) induces neurite outgrowth and differentiation in a process that involves NGF binding to its receptor TrkA and endocytosis of the NGF-TrkA complex into signaling endosomes. Here, we find that biogenesis of signaling endosomes requires inactivation of Rab5 to block early endosome fusion. Expression of dominant-negative Rab5 mutants enhanced NGF-mediated neurite outgrowth, whereas a constitutively active Rab5 mutant or Rabex-5 inhibited this process. Consistently, inactivation of Rab5 sustained TrkA activation on the endosomes. Furthermore, NGF treatment rapidly decreased cellular level of active Rab5-GTP, as shown by pull-down assays. This Rab5 down-regulation was mediated by RabGAP5, which was shown to associate with TrkA by coimmunoprecipitation assays. Importantly, RNA interference of RabGAP5 as well as a RabGAP5 truncation mutant containing the TrkA-binding domain blocked NGF-mediated neurite outgrowth, indicating a requirement for RabGAP5 in this process. Thus, NGF signaling down-regulates Rab5 activity via RabGAP5 to facilitate neurite outgrowth and differentiation.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
authors.forename: Jay
authors.initials: J
authors.lastname: Liu
authors.forename: Darija
authors.initials: D
authors.lastname: Lamb
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Chou
authors.forename: Yong-Jian
authors.initials: YJ
authors.lastname: Liu
authors.forename: Guangpu
authors.initials: G
authors.lastname: Li
mesh_terms: D000818:Animals; D015536:Down-Regulation; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D020662:Guanine Nucleotide Exchange Factors / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D009154:Mutation; D020932:Nerve Growth Factor / Q000378:metabolism / Q000494:pharmacology*; D016501:Neurites / Q000187:drug effects / Q000502:physiology*; D016716:PC12 Cells; D051381:Rats; D020917:Receptor, trkA / Q000378:metabolism; D015398:Signal Transduction; D020696:rab5 GTP-Binding Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*
chemical_list: D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; C510870:RabGEF1 protein, mouse; D006160:Guanosine Triphosphate; D020932:Nerve Growth Factor; D020917:Receptor, trkA; D020696:rab5 GTP-Binding Proteins