Mouse Anti Mouse Robo1 (vertebRate) Hybridoma [wSpcp2]

PURPOSE. The Roundabout (Robo) family of proteins is related to the transmembrane receptors and plays a major role in neurogenesis. However, the role of the Robo proteins in proliferative retinopathy has not yet been defined. This study was conducted to determine whether Robo1 is expressed in the retina of patients with proliferative retinal disease and whether it has a pathobiological role in the disease. METHODS. Immunohistochemistry was used to determine the presence and distribution of Robo1 in the pathologic membranes in proliferative retinopathy. Small interfering (si) RNA technology was used to knockdown Robo1 expression and to study its effects on retinal pigment epithelial (RPE) cells in vitro. The impact on PVR development of blocking Robo1 expression was determined by applying specific siRNA in a PVR rabbit model. The prevalences of PVR and retinal detachment were determined by indirect ophthalmoscope on days 1, 3, 7, 14, 21, and 28 after the injection of RPE cells into the vitreous. RESULTS. Immunohistochemistry showed that Robo1 expression was detected in GFAP-labeled glial cells and cytokeratin-labeled RPE cells in proliferative membranes. Robo1 expression was also detected in CD31-labeled vascular endothelial cells. Knockdown of Robo1 expression not only reduced human RPE cell proliferation in vitro but also effectively suppressed the development of PVR in a rabbit model. CONCLUSIONS. Robo1 is present in the extracellular matrix of proliferative membranes and may be derived from dedifferentiated RPE cells. Silencing the expression of Robo1 in RPE cells inhibited cell proliferation and suppressed the development of PVR in an animal model, indicating a potential therapeutic usefulness in treating PVR. (Invest Ophthalmol Vis Sci. 2010;51:3193-3204) DOI:10.1167/iovs.09-3779

Interaction of transmembrane receptors of the Robo family and the secreted protein Slit provides important signals in the development of the central nervous system and regulation of axonal midline crossing. Heparan sulfate, a sulfated linear polysaccharide modified in a complex variety of ways, serves as an essential co-receptor in Slit-Robo signaling. Previous studies have shown that closely related heparin octasaccharides bind to Drosophila Robo directly, and surface plasmon resonance analysis revealed that Robo1 binds more tightly to full-length unfractionated heparin. For the first time, we utilized electron transfer dissociation-based high spatial resolution hydroxyl radical protein footprinting to identify two separate binding sites for heparin interaction with Robo1: one binding site at the previously identified site for heparin dp8 and a second binding site at the N terminus of Robo1 that is disordered in the x-ray crystal structure. Mutagenesis of the identified N-terminal binding site exhibited a decrease in binding affinity as measured by surface plasmon resonance and heparin affinity chromatography. Footprinting also indicated that heparin binding induces a minor change in the conformation and/or dynamics of the Ig2 domain, but no major conformational changes were detected. These results indicate a second low affinity binding site in the Robo-Slit complex as well as suggesting the role of the Ig2 domain of Robo1 in heparin-mediated signal transduction. This study also marks the first use of electron transfer dissociation-based high spatial resolution hydroxyl radical protein footprinting, which shows great utility for the characterization of protein-carbohydrate complexes.