Introduction The C2 domain is a Ca²⁺-dependent membrane-targeting motif found in many cellular proteins involved in signal transduction or inflammation pathway. However, the effects of C2 domain-containing proteins in the fibroblast-like synoviocyte (FLS) of rheumatoid arthritis (RA) have not yet been elucidated.

Objectives The aim of this study was to screen novel C2 domain-containing proteins related to aggressiveness of FLS, and confirm the precise roles of target protein in RA.

Methods We transduced RA-FLS with a recombinant adenovirus expressing a C2 domain library. To confirm the effect of phospholipase C-eta2 (PLCH2), as a candidate C2 domain-containing target protein, we established stable MH7A cell lines overexpressing GFP-tagged PLCH2. We also conducted in vitro and in vivo experiments using a recombinant adenovirus expressing the full length form of PLCH2 or C2 domain of PLCH2 (C2-PLCH2).

Results Several C2 domain-containing proteins were identified whose over-expression resulted in reduced proliferation and NF-kB activity of RA-FLS. Among those, we focused on PLCH2 in this study. PLCH2 levels were significantly decreased in RA-FLS and synovium than OA. PLCH2 and C2-PLCH2 suppressed cell invasion and migration, cytokines production, and matrix metalloproteinase secretion in RA-FLS and stable MH7A cell lines compared to control. PLCH2 and C2-PLCH2 sensitised RA-FLS to apoptosis in vitro and in vivo model of matrigel implants engrafted into immunodeficient mice. PLCH2 and C2-PLCH2 further decreased arthritis severity in collagen-induced arthritis (CIA) mouse model.

Conclusions Our results showed that invasive characteristics of RA-FLS and inflammatory arthritis of CIA are reduced by PLCH2 and C2 domain of PLCH2. Therefore C2 domain of PLCH2 may have therapeutic potential for RA.

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Acknowledgements This work was supported by grants (NRF-2014R1A2A1A11051360 and NRF-2015R1A5A2008833) from the National Research Foundation of Korea (NRF) funded by the Korean government (MSIP).

Disclosure of interest None declared