The synovial proteome: analysis of fibroblast-like synoviocytes

Abstract

The present studies were initiated to determine the protein expression patterns of fibroblast-like synovial (FLS) cells derived from the synovia of rheumatoid arthritis patients. The cellular proteins were separated by two-dimensional polyacrylamide gel electrophoresis and the in-gel digested proteins were analyzed by matrix-assisted laser desorption ionization mass spectrometry. A total of 368 spots were examined and 254 identifications were made. The studies identified a number of proteins that have been implicated in the normal or pathological FLS function (e.g. uridine diphosphoglucose dehydrogenase, galectin 1 and galectin 3) or that have been characterized as potential autoantigens in rheumatoid arthritis (e.g. BiP, colligin, HC gp-39). A novel uncharacterized protein product of chromosome 19 open reading frame 10 was also detected as an apparently major component of FLS cells. These results demonstrate the utility of high-content proteomic approaches in the analysis of FLS composition.

Figure 1

Schematic of the method used for the separation and identification of fibroblast-like synovial cellular proteins. MW, molecular weight; pI, isoelectric point.

Figure 2

A representative example of a two-dimensional separation of fibroblast-like synovial cellular proteins. Spot numbers correspond to identifiers in Additional file 1.

Figure 3

Representative examples of matrix-assisted laser desorption ionization quadrupole time of flight mass spectrometer spectra of samples digested in gel with trypsin. (a) Galectin 3 and (b) DDAH2.

Figure 4

Detail of an area of a two-dimensional gel of separated fibroblast-like synovial cellular proteins. The circled areas include the same species of proteins with different mobilities reflecting differences in isoelectric points due post-translational modifications: 215 spot series, vimentin; 237 spot series, beta actin; 278 and 280 spot series, lamin A/C; 279 spot series, caldesmon.

Figure 5

A comparison of the theoretical and observed (a) molecular weights (MW) and (b) isoelectric point (pI) values for the synovial proteins identified in these studies. Note the poor correlation between the expected and the observed values.

Figure 6

Functional categorization of the fibroblast-like synovial proteome based on Swissprot and Tremble assigned functions.

Figure 7

The in-gel locations of synovial proteins of potential functional or pathogenic significance in rheumatoid arthritis. UDPGDH, uridine diphosphoglucose dehydrogenase.