The Glycoproteome of Loxosceles Venom Reveals an Expanded Landscape of Animal Toxins

Spider venoms of the genus Loxosceles constitute a complex mixture of bioactive proteins and peptides associated with the major clinical manifestations of loxoscelism. Although significant advances have been made in the proteomic characterization of these toxins, studies addressing post-translational modifications, particularly glycosylation, and their potential impact on venom properties remain scarce. Here, we investigated the occurrence and characteristics of N-glycosylation in the venoms of Loxosceles gaucho, Loxosceles intermedia, and Loxosceles laeta. Using two-dimensional electrophoresis combined with glycoprotein-specific staining and LC-MS/MS, we identified glycosylation in different proteins biologically relevant to envenomation, predominantly belonging to the phospholipase D family, with distinct profiles among the species analyzed. Bottom-up glycoproteomic analysis of crude venoms using Byonic and a customized sequence database identified 88 N-glycosylated peptide sequences, primarily associated with lyases and hydrolases. Extensive microheterogeneity was detected at individual glycosylation sites, with paucimannosidic structures predominating alongside oligomannose and hybrid/complex N-glycans. Complementary enzyme-linked lectin assays supported the presence of distinct carbohydrate epitopes, including mannose, galactose, and N-acetylgalactosamine containing structures, and revealed α2,6-sialic acid-reactive motifs in two species. These findings establish N-glycosylation as an additional layer of molecular heterogeneity in Loxosceles venoms and provide a foundation for investigating its potential contribution to toxin properties and venom diversity.