Fig. 2.

Analysis of the HEK^XBP1s membrane glycoproteome. (A) Heatmap of lectin microarray data generated from HEK^XBP1s membrane glycoproteomes. Full lectin names, print concentration, and sources are listed in Dataset S2A. Color intensity represents normalized log₂ ratio data relative to a pooled sample reference. Each column represents one biological replicate of the indicated sample. Select lectin groups with shared binding specificities are annotated (Right). See also SI Appendix, Fig. S3A and Dataset S3A. (B) Partial MALDI-TOF mass spectra from the HEK^XBP1s membrane proteome. Green and red peaks correspond to tri- and tetraantennary N-glycans with various levels of sialylation. Green- and red-shaded areas highlight the distribution shift of sialylation toward fewer NeuAcs on tri- and tetraantennary N-glycans. Structures above a bracket were not unequivocally defined. “M” and “m” designations indicate major and minor abundances, respectively. Putative structures are based on composition, tandem MS, and knowledge of biosynthetic pathways. All molecular ions are [M+Na]⁺. High-mass spectra are presented in SI Appendix, Fig. S3B, with GC-MS data in SI Appendix, Table S1. (C) Summary of XBP1s-induced changes to the HEK^XBP1s membrane N-glycome (see also SI Appendix, Tables S2 and S3).