Fig. 2

Protein-protein interaction networks of upregulated proteins associated with primary Sjögren’s syndrome identified in stimulated whole saliva. Two distinct protein-protein interaction networks are visualised. One is involved in metabolism and redox reactions, while the other plays a central role in both innate and adaptive immunity and contains the most upregulated protein in the patient group, namely neutrophil gelatinase-associated lipocalin (LCN2). The five most upregulated proteins in the patient group (Table 3) are indicated with red circles. The Search Tool for the Retrieval of Interacting Genes/Proteins (http://string-db.org/) was used to generate the networks, where potential interactions of proteins with medium confidence are shown. The different clusters are indicated by the same colour. The colour of the connecting lines indicates the type of evidence used in predicting the associations (red gene fusion, yellow text-mining extracted from literature, purple protein-protein interaction datasets, light blue protein interaction groups, black linked across species). CALM calmodulin, CALML5 calmodulin-like protein 5, GRN granulin adipocyte plasma, APMAP membrane-associated protein, GNA13 guanine nucleotide-binding protein subunit alpha-13, WDR1 WD repeat-containing protein 1, SIRPA tyrosine-protein phosphatase non-receptor type substrate 1, LSP1 lymphocyte-specific protein 1