title: Rab22 controls NGF signaling and neurite outgrowth in PC12 cells.
abstract: Rab22 is a small GTPase that is localized on early endosomes and regulates early endosomal sorting. This study reports that Rab22 promotes nerve growth factor (NGF) signaling-dependent neurite outgrowth and gene expression in PC12 cells by sorting NGF and the activated/phosphorylated receptor (pTrkA) into signaling endosomes to sustain signal transduction in the cell. NGF binding induces the endocytosis of pTrkA into Rab22-containing endosomes. Knockdown of Rab22 via small hairpin RNA (shRNA) blocks NGF-induced pTrkA endocytosis into the endosomes and gene expression (VGF) and neurite outgrowth. Overexpression of human Rab22 can rescue the inhibitory effects of the Rab22 shRNA, suggesting a specific Rab22 function in NGF signal transduction, rather than off-target effects. Furthermore, the Rab22 effector, Rabex-5, is necessary for NGF-induced neurite outgrowth and gene expression, as evidenced by the inhibitory effect of shRNA-mediated knockdown of Rabex-5. Disruption of the Rab22-Rabex-5 interaction via overexpression of the Rab22-binding domain of Rabex-5 in the cell also blocks NGF-induced neurite outgrowth, suggesting a critical role of Rab22-Rabex-5 interaction in the biogenesis of NGF-signaling endosomes to sustain the signal for neurite outgrowth. These data provide the first evidence for an early endosomal Rab GTPase as a positive regulator of NGF signal transduction and cell differentiation.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
authors.forename: Liang
authors.initials: L
authors.lastname: Wang
authors.forename: Zhimin
authors.initials: Z
authors.lastname: Liang
authors.forename: Guangpu
authors.initials: G
authors.lastname: Li
mesh_terms: D000818:Animals; D002450:Cell Communication / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D004705:Endocytosis / Q000502:physiology; D011992:Endosomes / Q000378:metabolism*; D015870:Gene Expression; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D055785:Gene Knockdown Techniques; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D020932:Nerve Growth Factor / Q000235:genetics / Q000378:metabolism*; D016501:Neurites / Q000502:physiology* / Q000648:ultrastructure; D055495:Neurogenesis / Q000502:physiology*; D016716:PC12 Cells; D010766:Phosphorylation; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D060888:Real-Time Polymerase Chain Reaction; D020917:Receptor, trkA / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D034741:RNA, Small Interfering; C484189:Rab31 protein, rat; D020932:Nerve Growth Factor; D020917:Receptor, trkA; D020691:rab GTP-Binding Proteins