title: Sprouty4 is an endogenous negative modulator of TrkA signaling and neuronal differentiation induced by NGF.
abstract: The Sprouty (Spry) family of proteins represents endogenous regulators of downstream signaling pathways induced by receptor tyrosine kinases (RTKs). Using real time PCR, we detect a significant increase in the expression of Spry4 mRNA in response to NGF, indicating that Spry4 could modulate intracellular signaling pathways and biological processes induced by NGF and its receptor TrkA. In this work, we demonstrate that overexpression of wild-type Spry4 causes a significant reduction in MAPK and Rac1 activation and neurite outgrowth induced by NGF. At molecular level, our findings indicate that ectopic expression of a mutated form of Spry4 (Y53A), in which a conserved tyrosine residue was replaced, fail to block both TrkA-mediated Erk/MAPK activation and neurite outgrowth induced by NGF, suggesting that an intact tyrosine 53 site is required for the inhibitory effect of Spry4 on NGF signaling. Downregulation of Spry4 using small interference RNA knockdown experiments potentiates PC12 cell differentiation and MAPK activation in response to NGF. Together, these findings establish a new physiological mechanism through which Spry4 regulates neurite outgrowth reducing not only the MAPK pathway but also restricting Rac1 activation in response to NGF.
authors.affiliation: Division of Molecular and Cellular Neuroscience, Institute of Cellular Biology and Neuroscience Prof Dr E De Robertis-CONICET, School of Medicine, University of Buenos Aires, Buenos Aires, Argentina.
authors.forename: Fernando C
authors.initials: FC
authors.lastname: Alsina
authors.forename: Dolores
authors.initials: D
authors.lastname: Irala
authors.forename: Paula A
authors.initials: PA
authors.lastname: Fontanet
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Hita
authors.forename: Fernanda
authors.initials: F
authors.lastname: Ledda
authors.forename: Gustavo
authors.initials: G
authors.lastname: Paratcha
mesh_terms: D000818:Animals; D019556:COS Cells; D045744:Cell Line, Tumor; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D020935:MAP Kinase Signaling System; D009154:Mutation; D020932:Nerve Growth Factor / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism*; D016716:PC12 Cells; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D020917:Receptor, trkA / Q000378:metabolism*; D015398:Signal Transduction; D014443:Tyrosine / Q000737:chemistry; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
chemical_list: D009419:Nerve Tissue Proteins; D034741:RNA, Small Interfering; C404992:Spry2 protein, rat; D014443:Tyrosine; D020932:Nerve Growth Factor; D020917:Receptor, trkA; D048049:Extracellular Signal-Regulated MAP Kinases; C499134:Rac1 protein, rat; D020830:rac1 GTP-Binding Protein