title: APPL1 associates with TrkA and GIPC1 and is required for nerve growth factor-mediated signal transduction.
abstract: The neurotrophin receptor TrkA plays critical roles in the nervous system by recruiting signaling molecules that activate pathways required for the growth and survival of neurons. Here, we report APPL1 as a TrkA-associated protein. APPL1 and TrkA co-immunoprecipitated in sympathetic neurons. We have identified two routes through which this association can occur. APPL1 was isolated as a binding partner for the TrkA-interacting protein GIPC1 from rat brain lysate by mass spectrometry. The PDZ domain of GIPC1 directly engaged the C-terminal sequence of APPL1. This interaction provides a means through which APPL1 may be recruited to TrkA. In addition, the APPL1 PTB domain bound to TrkA, indicating that APPL1 may associate with TrkA independently of GIPC1. Isolation of endosomal fractions by high-resolution centrifugation determined that APPL1, GIPC1, and phosphorylated TrkA are enriched in the same fractions. Reduction of APPL1 or GIPC1 protein levels suppressed nerve growth factor (NGF)-dependent MEK, extracellular signal-regulated kinase, and Akt activation and neurite outgrowth in PC12 cells. Together, these results indicate that GIPC1 and APPL1 play a role in TrkA function and suggest that a population of endosomes bearing a complex of APPL1, GIPC1, and activated TrkA may transmit NGF signals.
authors.affiliation: Cancer Research Program, Hospital for Sick Children, 555 University Avenue, Toronto M5G 1X8, Ontario, Canada.
authors.forename: Dan C
authors.initials: DC
authors.lastname: Lin
authors.forename: Celia
authors.initials: C
authors.lastname: Quevedo
authors.forename: Natalie E
authors.initials: NE
authors.lastname: Brewer
authors.forename: Alex
authors.initials: A
authors.lastname: Bell
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Testa
authors.forename: Mark L
authors.initials: ML
authors.lastname: Grimes
authors.forename: Freda D
authors.initials: FD
authors.lastname: Miller
authors.forename: David R
authors.initials: DR
authors.lastname: Kaplan
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000256:Adenoviridae / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D019556:COS Cells; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D002999:Clone Cells; D019085:Fluorescent Antibody Technique, Direct; D005982:Glutathione Transferase / Q000378:metabolism; D020932:Nerve Growth Factor / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D009479:Neuropeptides / Q000737:chemistry / Q000378:metabolism*; D016716:PC12 Cells; D017434:Protein Structure, Tertiary; D051381:Rats; D017207:Rats, Sprague-Dawley; D020917:Receptor, trkA / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D017783:Superior Cervical Ganglion / Q000166:cytology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C515694:Appl1 protein, rat; D002352:Carrier Proteins; C492008:Gipc1 protein, rat; D009419:Nerve Tissue Proteins; D009479:Neuropeptides; D011993:Recombinant Fusion Proteins; D020932:Nerve Growth Factor; D005982:Glutathione Transferase; D020917:Receptor, trkA