Salivary Cystatins: Exploring New Post-Translational Modifications and Polymorphisms by Top-Down High-Resolution Mass Spectrometry

Manconi, Barbara;Liori, Barbara;Cabras, Tiziana;Vincenzoni, Federica;Iavarone, Federica;Castagnola, Massimo;Messana, Irene;Olianas, Alessandra

2017-01-01

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Abstract

Cystatins are a complex family of cysteine peptidase inhibitors. In the present study, various proteoforms of cystatin A, cystatin B, cystatin S, cystatin SN, and cystatin SA were detected in the acid-soluble fraction of human saliva and characterized by a top-down HPLC-ESI-MS approach. Proteoforms of cystatin D were also detected and characterized by an integrated top-down and bottom-up strategy. The proteoforms derive from coding sequence polymorphisms and post-translational modifications, in particular, phosphorylation, N-terminal processing, and oxidation. This study increases the current knowledge of salivary cystatin proteoforms and provides the basis to evaluate possible qualitative/quantitative variations of these proteoforms in different pathological states and reveal new potential salivary biomarkers of disease. Data are available via ProteomeXchange with identifier PXD007170.