title: CRYP-2/cPTPRO is a neurite inhibitory repulsive guidance cue for retinal neurons in vitro.
abstract: Receptor protein tyrosine phosphatases (RPTPs) are implicated as regulators of axon growth and guidance. Genetic deletions in the fly have shown that type III RPTPs are important in axon pathfinding, but nothing is known about their function on a cellular level. Previous experiments in our lab have identified a type III RPTP, CRYP-2/cPTPRO, specifically expressed during the period of axon outgrowth in the chick brain; cPTPRO is expressed in the axons and growth cones of retinal and tectal projection neurons. We constructed a fusion protein containing the extracellular domain of cPTPRO fused to the Fc portion of mouse immunoglobulin G-1, and used it to perform in vitro functional assays. We found that the extracellular domain of cPTPRO is an antiadhesive, neurite inhibitory molecule for retinal neurons. In addition, cPTPRO had potent growth cone collapsing activity in vitro, and locally applied gradients of cPTPRO repelled growing retinal axons. This chemorepulsive effect could be regulated by the level of cGMP in the growth cone. Immunohistochemical examination of the retina indicated that cPTPRO has at least one heterophilic binding partner in the retina. Taken together, our results indicate that cPTPRO may act as a guidance cue for retinal ganglion cells during vertebrate development.
authors.affiliation: Neuroscience Program, University of Miami School of Medicine, Miami, FL 33136, USA.
authors.forename: L
authors.initials: L
authors.lastname: Stepanek
authors.forename: Q L
authors.initials: QL
authors.lastname: Sun
authors.forename: J
authors.initials: J
authors.lastname: Wang
authors.forename: C
authors.initials: C
authors.lastname: Wang
authors.forename: J L
authors.initials: JL
authors.lastname: Bixby
mesh_terms: D000818:Animals; D001921:Brain / Q000196:embryology; D002448:Cell Adhesion; D002642:Chick Embryo; D005123:Eye / Q000294:innervation*; D020439:Growth Cones / Q000502:physiology*; D006131:Growth Inhibitors / Q000378:metabolism; D009414:Nerve Growth Factors / Q000378:metabolism; D016501:Neurites / Q000502:physiology; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017027:Protein Tyrosine Phosphatases / Q000235:genetics / Q000378:metabolism*; D054631:Receptor-Like Protein Tyrosine Phosphatases, Class 3; D011956:Receptors, Cell Surface / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012160:Retina / Q000166:cytology / Q000196:embryology*
chemical_list: D006131:Growth Inhibitors; D009414:Nerve Growth Factors; D010446:Peptide Fragments; D011956:Receptors, Cell Surface; D011993:Recombinant Fusion Proteins; D017027:Protein Tyrosine Phosphatases; C516890:Ptpro protein, mouse; D054631:Receptor-Like Protein Tyrosine Phosphatases, Class 3