FIGURE 1.

PTPRG interacts specifically with CNTN3, -4, -5, and -6. A, domain organization of PTPRG and CNTNs. PTPRG includes an inactive N-terminal CA domain, a single FN type III domain, a spacer region, and two intracellular tyrosine phosphatase domains. CNTNs include six Ig domains, four FN domains, and a GPI anchor. B, the extracellular domain of PTPRG associates with CNTN3–6 but not with CNTN1 or CNTN2. HEK293 cells transfected with full-length CNTNs fused to human growth hormone were incubated with an Fc fusion of the CA and FN domains of mouse PTPRG labeled with fluorescein iosothiocyanate (magenta). CNTN-expressing cells were labeled with an antibody conjugated to a green fluorophore. The nuclei were visualized using DAPI. C, interactions between the CA domain of PTPRG with CNTN3–6, as determined by an AlphaScreen bead-based competition assay. The ability of mouse PTPRG(CA) or bovine CAII (control) to inhibit binding between an Fc fusion of full-length mouse CNTN3–6 and biotin-labeled PTPRG(CA) was assessed over a logarithmic dilution series. IC₅₀ values are reported as averages ± S.D. (error bars) from at least three experiments. One representative experiment for each series is shown. See supplemental Table S1 for detailed results. D, one-way ANOVA analysis of the IC₅₀ values measured in C. The means and S.D. values are shown on the graph on the left, whereas the graph on the right shows Tukey 99% confidence intervals for Tukey's multiple comparison tests. Differences between CNTN3 and CNTN4, CNTN4 and CNTN6, and CNTN5 and CNTN6 are statistically significant, whereas the remaining IC₅₀ differences (between CNTN3 and CNTN5, CNTN3 and CNTN6, and CNTN4 and CNTN5) are not. See supplemental Fig. S1.