title: {alpha}-Syntrophin regulates ARMS localization at the neuromuscular junction and enhances EphA4 signaling in an ARMS-dependent manner.
abstract: EphA4 signaling has recently been implicated in the regulation of synapse formation and plasticity. In this study, we show that ankyrin repeat-rich membrane spanning (ARMS; also known as a kinase D-interacting substrate of 220 kD), a substrate for ephrin and neurotrophin receptors, was expressed in developing muscle and was concentrated at the neuromuscular junction (NMJ). Using yeast two-hybrid screening, we identified a PDZ (PSD-95, Dlg, ZO-1) domain protein, alpha-syntrophin, as an ARMS-interacting protein in muscle. Overexpression of alpha-syntrophin induced ARMS clustering in a PDZ domain-dependent manner. Coexpression of ARMS enhanced EphA4 signaling, which was further augmented by the presence of alpha-syntrophin. Moreover, the ephrin-A1-induced tyrosine phosphorylation of EphA4 was reduced in C2C12 myotubes after the blockade of ARMS and alpha-syntrophin expression by RNA interference. Finally, alpha-syntrophin-null mice exhibited a disrupted localization of ARMS and EphA4 at the NMJ and a reduced expression of ARMS in muscle. Altogether, our findings suggest that ARMS may play an important role in regulating postsynaptic signal transduction through the syntrophin-mediated localization of receptor tyrosine kinases such as EphA4.
authors.affiliation: Department of Biochemistry, Molecular Neuroscience Center and Biotechnology Research Institute, Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China.
authors.forename: Shuo
authors.initials: S
authors.lastname: Luo
authors.forename: Yu
authors.initials: Y
authors.lastname: Chen
authors.forename: Kwok-On
authors.initials: KO
authors.lastname: Lai
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Arévalo
authors.forename: Stanley C
authors.initials: SC
authors.lastname: Froehner
authors.forename: Marvin E
authors.initials: ME
authors.lastname: Adams
authors.forename: Moses V
authors.initials: MV
authors.lastname: Chao
authors.forename: Nancy Y
authors.initials: NY
authors.lastname: Ip
mesh_terms: D000818:Animals; D019556:COS Cells; D002135:Calcium-Binding Proteins; D002522:Chlorocebus aethiops; D036342:Ephrins / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000254:growth & development* / Q000294:innervation; D009469:Neuromuscular Junction / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017434:Protein Structure, Tertiary / Q000502:physiology; D034622:RNA Interference / Q000502:physiology; D051381:Rats; D036122:Receptor, EphA4 / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D013570:Synaptic Membranes / Q000378:metabolism*; D015854:Up-Regulation / Q000502:physiology
chemical_list: D002135:Calcium-Binding Proteins; D036342:Ephrins; C418610:Kidins220 protein, rat; D008565:Membrane Proteins; D009124:Muscle Proteins; D010750:Phosphoproteins; C091825:syntrophin alpha1; D036122:Receptor, EphA4