Alterations in the Salivary Proteome and N-Glycome of Sjögren’s Syndrome Patients

We used isobaric mass tagging (iTRAO.) and lectiri affinity capture mass' spectrometry (MS)-based workflows for global analyses of parotid saliva (PS) and whole saliva (WS) samples obtained from patients diagnosed with primary Sjogren's Syndrome (pSS) who were enrolled in the Sjogren's International Collaborative,clinical Alliance (SICCA) as compared with two control groups. The iTRAQ analyses revealed up- and down-regulation of numerous proteins that could be involved in the disease process (e.g., histones) or attempts to mitigate the ensuing damage (e.g., bactericidal/permeability increasing fold containing family (BPIF) members). An immunoblot approach applied to independent sample sets confirmed the pSS associated up regulation of beta 2-microglobulin (in PS) and down-regulation" of carbonic anhydrase VI (in WS) and BPIFB2 (in PS). Beyond the proteome, we profiled the N-glycosites of pSS and control samples. They were enriched for glycopeptides using lectins Aleuria aurantia and wheat germ agglutinin, which recognize fucose and sialic acid/N-acetyl glucosamine, respectively. MS analyses showed that pSS is associated with increased N-glycosylation of numerous salivary glycoproteins in PS and WS. The observed alterations of the salivary proteome and N-glycome could be used as pSS biomarkers enabling easier and earlier detection of this syndrome while lending potential new insights into the disease process.