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

Abstract

We used isobaric mass tagging (iTRAQ) and lectin 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 Sjögren's Syndrome (pSS) who were enrolled in the Sjögren'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 β2-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.

Mucins and Their Role in Shaping the Functions of Mucus Barriers

“…Altered glycosylation profiles have been reported in other mucin-related diseases such as Sjögren's syndrome (Chaudhury et al 2016, Hall et al 2017, dry eye disease (Stephens & McNamara 2015), and dry mouth (Chaudhury et al 2015). In contrast to the changes in cervical mucus previously described, Chaudhury et al measured a reduction in both the spinnability of saliva samples and the degree of mucin glycosylation (sialic acid residues in particular) in patients with Sjögren's syndrome (Chaudhury et al 2016) and dry mouth (Chaudhury et al 2015).…”

“…In health, mucus appears to play an important role in suppressing virulence of these opportunistic pathogens and in promoting their coexistence as part of a stable microbiota (Swidsinski et al 2005). Defects in mucin expression and mucus production are associated not only with pathologies like CF (Henke et al 2004(Henke et al , 2007Lai et al 2009a), inflammatory bowel disease (IBD) ( Johansson et al 2008), and Sjögren's syndrome (Chaudhury et al 2016, Hall et al 2017 but also with the proliferation of opportunistic pathogens. These diseases are often associated with the formation of biofilms (Cunha-Cruz et al 2013, Singh et al 2000, Swidsinski et al 2005, which are cellular communities of microbes that secrete and surround themselves with a sticky extracellular matrix that can act as a protective barrier against environmental stresses such as antibiotic therapies and the immune system.…”

Comparative Glycomics of Immunoglobulin A and G From Saliva and Plasma Reveals Biomarker Potential

“…Moreover, numerous potential salivary protein-, DNA-, RNA-, and small-molecule-based biomarkers for various diseases have been proposed, as recently reviewed ( 4 ). Furthermore, two studies using global lectin-based profiling of glycans in saliva revealed associations with breast cancer and Sjögren's syndrome ( 5 , 6 ).…”

Inhibitory activity of salivary glycoproteins on phytohemagglutins (PHA): Possible molecules to enhance nutritional quality of red kidney beans

“…Considering the fact that PHA recognizes trisaccharide Gal 1-4GlcNAc1-2Man present in the biantennary galactosylated N-glycans (Nagae et al, 2014), and these Nlinked glycans are also part of mucins (Guile et al, 1998;Ramachandran et al, 2008;Hall et al, 2017), it is quite possible that inhibitory property of saliva may due these Nlinked glycans either in free form or in association with proteins. Results of ammonium sulphate fractionation studies indicated that proteins precipitated at 30-60% of ammonium sulphate have inhibited the PHA activity, suggesting the role of high molecular weight proteins in inhibiting the activity of PHA.…”