A. Schematic showing domain swap for NLGN4X, NLGN4Y, NLGN4X/Y, and NLGN4Y/X. NLGN4X/Y contains the extracellular domain (ECD) of NLGN4X and the intracellular domain (ICD) of NLGN4Y; NLGN4Y/X contains the ECD of NLGN4Y and the ICD of NLGN4X. B. Surface expression of NLGN4X, NLGN4Y, NLGN4X/Y, and NLGN4Y/X was analyzed by immunoblotting purified surface biotinylated proteins from transfected HEK293T cells. C. Surface intensity level (means ± S.E.M.) normalized to NLGN4X. P values were calculated by ANOVA with Bonferroni’s multiple comparison test. (n=5). D. Immunoblot of transfected NLGN4X (WT, R56Q, N64S, or P93S) and NLGN4Y from HEK293T cells. E. Mature/immature level (means ± S.E.M.) normalized to control. P values were calculated by one-way ANOVA with Bonferroni’s multiple comparison test. (n=7). F. Surface expression of NLGN4X (WT or P93S) and NLGN4Y (WT or S93P) were analyzed by immunoblotting isolated surface biotinylated proteins in transfected HEK293T cells. G. NLGN4X (WT and P93S) and NLGN4Y (WT and S93P) were transfected in HEK293T cells then immunoprecipitated with HA-antibody. Immunoblot was probed for BiP and HA from the immunoprecipitates.