title: Eph-dependent tyrosine phosphorylation of ephexin1 modulates growth cone collapse.
abstract: Ephs regulate growth cone repulsion, a process controlled by the actin cytoskeleton. The guanine nucleotide exchange factor (GEF) ephexin1 interacts with EphA4 and has been suggested to mediate the effect of EphA on the activity of Rho GTPases, key regulators of the cytoskeleton and axon guidance. Using cultured ephexin1-/- mouse neurons and RNA interference in the chick, we report that ephexin1 is required for normal axon outgrowth and ephrin-dependent axon repulsion. Ephexin1 becomes tyrosine phosphorylated in response to EphA signaling in neurons, and this phosphorylation event is required for growth cone collapse. Tyrosine phosphorylation of ephexin1 enhances ephexin1's GEF activity toward RhoA while not altering its activity toward Rac1 or Cdc42, thus changing the balance of GTPase activities. These findings reveal that ephexin1 plays a role in axon guidance and is regulated by a switch mechanism that is specifically tailored to control Eph-mediated growth cone collapse.
authors.affiliation: Neurobiology Program, Children's Hospital, Boston, Massachusetts 02115, USA.
authors.forename: Mustafa
authors.initials: M
authors.lastname: Sahin
authors.forename: Paul L
authors.initials: PL
authors.lastname: Greer
authors.forename: Michael Z
authors.initials: MZ
authors.lastname: Lin
authors.forename: Heather
authors.initials: H
authors.lastname: Poucher
authors.forename: Johann
authors.initials: J
authors.lastname: Eberhart
authors.forename: Susanne
authors.initials: S
authors.lastname: Schmidt
authors.forename: Tracy M
authors.initials: TM
authors.lastname: Wright
authors.forename: Steven M
authors.initials: SM
authors.lastname: Shamah
authors.forename: Sinead
authors.initials: S
authors.lastname: O'connell
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Cowan
authors.forename: Linda
authors.initials: L
authors.lastname: Hu
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Goldberg
authors.forename: Anne
authors.initials: A
authors.lastname: Debant
authors.forename: Gabriel
authors.initials: G
authors.lastname: Corfas
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Krull
authors.forename: Michael E
authors.initials: ME
authors.lastname: Greenberg
mesh_terms: D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002478:Cells, Cultured; D002642:Chick Embryo; D003599:Cytoskeleton / Q000378:metabolism; D020439:Growth Cones / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D007150:Immunohistochemistry; D051379:Mice; D010766:Phosphorylation; D036082:Receptor, EphA1 / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014443:Tyrosine / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000378:metabolism
chemical_list: D000199:Actins; D020662:Guanine Nucleotide Exchange Factors; C504479:Ngef protein, mouse; D014443:Tyrosine; D036082:Receptor, EphA1; D020741:rho GTP-Binding Proteins