title: GIPC is recruited by APPL to peripheral TrkA endosomes and regulates TrkA trafficking and signaling.
abstract: GIPC is a PDZ protein located on peripheral endosomes that binds to the juxtamembrane region of the TrkA nerve growth factor (NGF) receptor and has been implicated in NGF signaling. We establish here that endogenous GIPC binds to the C terminus of APPL, a Rab5 binding protein, which is a marker for signaling endosomes. When PC12(615) cells are treated with either NGF or antibody agonists to activate TrkA, GIPC and APPL translocate from the cytoplasm and bind to incoming, endocytic vesicles carrying TrkA concentrated at the tips of the cell processes. GIPC, but not APPL, dissociates from these peripheral endosomes prior to or during their trafficking from the cell periphery to the juxtanuclear region, where they acquire EEA1. GIPC's interaction with APPL is essential for recruitment of GIPC to peripheral endosomes and for TrkA signaling, because a GIPC PDZ domain mutant that cannot bind APPL or APPL knockdown with small interfering RNA inhibits NGF-induced GIPC recruitment, mitogen-activated protein kinase activation, and neurite outgrowth. GIPC is also required for efficient endocytosis and trafficking of TrkA because depletion of GIPC slows down endocytosis and trafficking of TrkA and APPL to the early EEA1 endosomes in the juxtanuclear region. We conclude that GIPC, following its recruitment to TrkA by APPL, plays a key role in TrkA trafficking and signaling from endosomes.
authors.affiliation: Department of Cellular and Molecular Medicine, University of California-San Diego, George Palade Laboratories Room 210, 9500 Gilman Drive, La Jolla, CA 92093-0651, USA.
authors.forename: Tal
authors.initials: T
authors.lastname: Varsano
authors.forename: Meng-Qiu
authors.initials: MQ
authors.lastname: Dong
authors.forename: Ingrid
authors.initials: I
authors.lastname: Niesman
authors.forename: Hyacynth
authors.initials: H
authors.lastname: Gacula
authors.forename: Xiaojing
authors.initials: X
authors.lastname: Lou
authors.forename: Tianlin
authors.initials: T
authors.lastname: Ma
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Testa
authors.forename: John R
authors.initials: JR
authors.lastname: Yates
authors.forename: Marilyn G
authors.initials: MG
authors.lastname: Farquhar
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism*; D005982:Glutathione Transferase / Q000378:metabolism; D006388:Hemagglutinins / Q000737:chemistry; D006639:Histidine / Q000737:chemistry; D008954:Models, Biological; D008969:Molecular Sequence Data; D020932:Nerve Growth Factor / Q000494:pharmacology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism*; D016716:PC12 Cells; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D051381:Rats; D020917:Receptor, trkA / Q000187:drug effects / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D020696:rab5 GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C492008:Gipc1 protein, rat; D006388:Hemagglutinins; D009479:Neuropeptides; D011994:Recombinant Proteins; D006639:Histidine; D020932:Nerve Growth Factor; D005982:Glutathione Transferase; D020917:Receptor, trkA; D020696:rab5 GTP-Binding Proteins