Identification of multiple transferrin species in the spleen and serum from mice with collagen-induced arthritis which may reflect changes in transferrin glycosylation associated with disease activity: The role of CD38.

UNLABELLED: Collagen type II-induced arthritis (CIA) is an inflammatory and autoimmune disease. Spleen protein extracts were subjected to 2D-DiGE and MS-MALDI-TOF/TOF analysis to identify protein species that differ in abundance in CD38-KO versus B6 WT mice either with arthritis or with inflammation. Using multivariate analyses, in Col-II-immunized mice, 23 distinct spleen protein species were able to discriminate between WT and CD38-KO mice. Among them, several citrullinated proteins and multiple serotransferrin (Tf) species were identified. In contrast, in CFA/IFA-treated mice, the distinct protein profile, which discriminates between CD38-KO and WT mice, was unrelated with Tf, but not with citrullination. Unexpectedly, non-immunized CD38-KO mice showed a distinct proteome profile as compared with that in non-immunized WT mice, and again multiple protein species were identified as Tf. By using a μLC-TOF-MS method to separate and detect Tf glycopeptide glycoforms, increases in fucosylation and glycan branching was observed in sera from mice CIA(+) versus non-immunized, and between WT and CD38-KO with arthritis. Data on 2-DE Tf spots indicated differences in glycosylation related with NeuGc content. Thus, Tf changed significantly in its glycosylation pattern in arthritic mice. The MS data have been deposited to the ProteomeXchange Consortium with the dataset identifiers: PXD002644, PXD002643, PXD003183, and PXD003163. SIGNIFICANCE: 2-DE followed by μLC-TOF-MS could be implemented to identify Tf glycoforms linked to specific protein species, and correlate a particular Tf species to a function. To gain insight into the relationship between transferrin glycoforms and its biological function it is particularly interesting to study putative differences in the glycosylation pattern of Tf in specific tissues associated with the disease (i.e.: joints), or in specific compartments such as exosomes/microvesicles, which are highly enriched in Tf receptors.