Posttranslational Protein Modification in the Salivary Glands of Sjgren's Syndrome Patients

The present study investigated posttranslational reactions in the salivary glands of patients with Sjogren's syndrome. We analysed the biopsies of primary Sjogren's patients using immunohistochemistry and a tag-purified anticyclic citrullinated protein (CCP) antibody to detect citrullinated peptides, and the presence of peptidylarginine deiminase 2 (PAD2) was assessed simultaneously. Thepresent work demonstrated the weak presence of the PAD2 enzyme in some normal salivary glands, although PAD2 expression was increased considerably in Sjogren's patients. The presence of citrullinated proteins was also detected in the salivary tissues of Sjogren's patients, which strongly supports the in situ posttranslational modification of proteins in this setting. Furthermore, the mutual expression of CCP and PAD2 suggests that this posttranslationalmodification is enzyme dependent. In conclusion, patients with Sjogren's syndrome expressed the catalytic machinery to produce posttranslational reactions that may result in autoantigen triggering.