The glycoproteomics of hawk and caiman tears

Background Glycoproteins are important tear components that participate in the stability of the ocular surface. However, the glycopeptides that are present in the tears of wild animals have not yet been described. This work aimed to describe the glycoproteomic profile of roadside hawk (Rupornis magnirostris) and caiman (Caiman latirostris) tears. Methods Tears collected from 10 hawks and 70 caimans using Schirmer tear test strips were used in this study. The samples were submitted to trypsin digestion and separated using a reverse-phase column coupled to a mass spectrometer associated to a nanospray ionization source. The glycoproteins were categorized as: cellular components, biological processes and molecular function, according to the UniProt Knowledgebase. Results As shown by the liquid chromatography–mass spectrometry, all glycopeptides found were classified as N-type. Of the 51 glycoproteins that were identified in the hawk tear film, the most abundant were ovotransferrin, globulins and complement system proteins. In the caiman tear film, 29 glycoproteins were identified. The most abundant caiman glycoproteins were uncharacterized proteins, ATPases, globulins and proteasome components. Ontological characterization revealed that the glycoproteins were extracellular, and the most identified molecular function was endopeptidase activity for both species. Conclusion Glycoproteins are abundant in the tear film of the bird and reptile species studied herein, and all these molecules were shown to have N-type modifications. Location at the extracellular space and an endopeptidase inhibitor activity were the main cell component and molecular function for both species, respectively. These profiles showed differences when compared to human tears, are possibly linked to adaptive processes and can be the basis for further studies on the search of disease biomarkers.

Ganglioside GM2: a potential biomarker for cholangiocarcinoma

Objective To investigate the expression of glycosphingolipids in serum and tissue from patients with cholangiocarcinoma compared with healthy controls. Methods Nanospray ionization-linear ion trap mass spectrometry (NSI-MSn) was used to demonstrate the comparative structural glycomics of glycosphingolipids in serum from patients with cholangiocarcinoma (n=15), compared with healthy controls (n = 15). GM2 expression in cholangiocarcinoma tissues (n = 60) was evaluated by immunohistochemistry. Results Eleven glycosphingolipids were detected by NSI-MSn: CMH (ceramide monohexose), Lac-Cer (galactose (Gal)β1-4 glucose (Glc)β1-1'-ceramide), Gb3 (Galα1-4Galβ1-4Glcβ1-1'-ceramide), Gb4/Lc4 (N-acetylgalactosamine (GalNAc)β1-3Galα1-4Galβ1-4Glcβ1-1'-ceramide/Galβ1-4 N-acetylglucosamine (GlcNAc)β1-3Galβ1-4Glcβ1-1'-ceramide), GM3 (N-acetylneuraminic acid (NeuAc)2-3Galβ1-4Glcβ1-1'-ceramide), GM2 (GalNAcβ1-4[NeuAc2-3]Galβ1-4Glcβ1-1'-ceramide), GM1 (Galβ1-3GalNAcβ1-4[NeuAc2-3]Galβ1-4Glcβ1-1'-ceramide), hFA (hydroxylated fatty acid)-CMH, hFA-Lac-Cer, hFA-Gb3, and hFA-GM3. Lac-Cer was the most abundant structure among the lactosides and globosides (normal, 24.40% ± 0.11%; tumor, 24.61% ± 2.10%), while GM3 predominated among the gangliosides (normal, 29.14% ± 1.31%; tumor, 30.53% ± 4.04%). The two glycosphingolipids that significantly differed between healthy controls and patients with cholangiocarcinoma were Gb3 and GM2. High expression of GM2 was associated with vascular invasion in tissue from patients with cholangiocarcinoma. Conclusions Altered expression of glycosphingolipids in tissue and serum from patients with cholangiocarcinoma may contribute to tumor growth and progression. The ganglioside GM2, which significantly increased in the serum of patients with cholangiocarcinoma, represents a promising target as a biomarker for cholangiocarcinoma.