title: Astrocytic αVβ3 integrin inhibits neurite outgrowth and promotes retraction of neuronal processes by clustering Thy-1.
abstract: Thy-1 is a membrane glycoprotein suggested to stabilize or inhibit growth of neuronal processes. However, its precise function has remained obscure, because its endogenous ligand is unknown. We previously showed that Thy-1 binds directly to α(V)β(3) integrin in trans eliciting responses in astrocytes. Nonetheless, whether α(V)β(3) integrin might also serve as a Thy-1-ligand triggering a neuronal response has not been explored. Thus, utilizing primary neurons and a neuron-derived cell line CAD, Thy-1-mediated effects of α(V)β(3) integrin on growth and retraction of neuronal processes were tested. In astrocyte-neuron co-cultures, endogenous α(V)β(3) integrin restricted neurite outgrowth. Likewise, α(V)β(3)-Fc was sufficient to suppress neurite extension in Thy-1(+), but not in Thy-1(-) CAD cells. In differentiating primary neurons exposed to α(V)β(3)-Fc, fewer and shorter dendrites were detected. This effect was abolished by cleavage of Thy-1 from the neuronal surface using phosphoinositide-specific phospholipase C (PI-PLC). Moreover, α(V)β(3)-Fc also induced retraction of already extended Thy-1(+)-axon-like neurites in differentiated CAD cells as well as of axonal terminals in differentiated primary neurons. Axonal retraction occurred when redistribution and clustering of Thy-1 molecules in the plasma membrane was induced by α(V)β(3) integrin. Binding of α(V)β(3)-Fc was detected in Thy-1 clusters during axon retraction of primary neurons. Moreover, α(V)β(3)-Fc-induced Thy-1 clustering correlated in time and space with redistribution and inactivation of Src kinase. Thus, our data indicates that α(V)β(3) integrin is a ligand for Thy-1 that upon binding not only restricts the growth of neurites, but also induces retraction of already existing processes by inducing Thy-1 clustering. We propose that these events participate in bi-directional astrocyte-neuron communication relevant to axonal repair after neuronal damage.
authors.affiliation: Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, Santiago, Chile.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Herrera-Molina
authors.forename: Renato
authors.initials: R
authors.lastname: Frischknecht
authors.forename: Horacio
authors.initials: H
authors.lastname: Maldonado
authors.forename: Constanze I
authors.initials: CI
authors.lastname: Seidenbecher
authors.forename: Eckart D
authors.initials: ED
authors.lastname: Gundelfinger
authors.forename: Claudio
authors.initials: C
authors.lastname: Hetz
authors.forename: María de la Luz
authors.initials: Mde L
authors.lastname: Aylwin
authors.forename: Pascal
authors.initials: P
authors.lastname: Schneider
authors.forename: Andrew F G
authors.initials: AF
authors.lastname: Quest
authors.forename: Lisette
authors.initials: L
authors.lastname: Leyton
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000166:cytology*; D001369:Axons / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D049109:Cell Proliferation; D002490:Central Nervous System / Q000166:cytology; D018920:Coculture Techniques; D020868:Gene Silencing; D039302:Integrin alphaVbeta3 / Q000378:metabolism*; D051379:Mice; D016501:Neurites / Q000378:metabolism*; D009474:Neurons / Q000166:cytology* / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D018800:Thy-1 Antigens / Q000378:metabolism*
chemical_list: D039302:Integrin alphaVbeta3; D034741:RNA, Small Interfering; D011994:Recombinant Proteins; D018800:Thy-1 Antigens