title: γ-1-syntrophin mediates trafficking of γ-enolase towards the plasma membrane and enhances its neurotrophic activity.
abstract: Syntrophins are scaffold proteins that can bind several signaling molecules and localize them to the plasma membrane. We demonstrate here that in neuroblastoma SH-SY5Y cells, brain-specific γ1-syntrophin binds the neurotrophic factor γ-enolase through its PDZ domain, and translocates it to the plasma membrane, as shown by immunoprecipitation, surface plasmon resonance, fluorescence colocalization and flow cytometry. Extensive colocalization of γ1-syntrophin and γ-enolase was observed in neurite growth cones in differentiated SH-SY5Y cells. Silencing of the γ1-syntrophin gene by RNA interference significantly reduced the re-distribution of γ-enolase to the plasma membrane and impaired its neurotrophic effects. We demonstrated that an intact C-terminal end of γ-enolase is essential for its γ1-syntrophin-assisted trafficking. The cleavage of two amino acids at the C-terminal end of γ-enolase by the carboxypeptidase cathepsin X prevents binding with the γ1-syntrophin PDZ domain. Collectively, these data demonstrate that γ1-syntrophin participates in γ-enolase translocation towards the plasma membrane, a pre-requisite for its neurotrophic activity. By disrupting this γ1-syntrophin-guided subcellular distribution, cathepsin X reduces γ-enolase-induced neurotrophic signaling.
authors.affiliation: Department of Pharmaceutical Biology, Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia.
authors.forename: Anja
authors.initials: A
authors.lastname: Hafner
authors.forename: Nataša
authors.initials: N
authors.lastname: Obermajer
authors.forename: Janko
authors.initials: J
authors.lastname: Kos
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000502:physiology*; D000595:Amino Acid Sequence; D002454:Cell Differentiation / Q000502:physiology; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D020439:Growth Cones / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D008969:Molecular Sequence Data; D009414:Nerve Growth Factors / Q000378:metabolism* / Q000502:physiology; D009447:Neuroblastoma / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D010751:Phosphopyruvate Hydratase / Q000378:metabolism* / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D015854:Up-Regulation / Q000502:physiology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D009414:Nerve Growth Factors; C432243:SNTG1 protein, human; D010751:Phosphopyruvate Hydratase