Functional analysis of choline transporters in rheumatoid arthritis synovial fibroblasts. Issue 6 (2nd November 2017)

• Record Type: Journal Article
• Authors: Seki, Masayuki; Kawai, Yuiko; Ishii, Chikanao; Yamanaka, Tsuyoshi; Odawara, Masato; Inazu, Masato
• Is Part Of: Modern rheumatology. Volume 27:Issue 6(2017)
• Page Start: 995
• Page End: 1003
• Publication Date: 2017-11-02
• Subjects: Choline -- transporter -- rheumatoid arthritis synovial fibroblasts (RASFs) -- apoptosis; Rheumatology -- Periodicals; 616.723005
• DOI: 10.1080/14397595.2017.1280118
• Languages: English
• ISSNs: 1439-7595

Abstract

Abstract: Objectives: In this study, we examined the functional characteristics of choline uptake and sought to identify the transporters in rheumatoid arthritis synovial fibroblasts (RASFs). Methods: The expression of choline transporters was evaluated by quantitative real-time PCR, western blotting, and immunocytochemistry. Time course, Na + -dependency, and kinetics of [ 3 H]choline uptake were investigated. Effects of cationic drugs on the uptake of [ 3 H]choline, cell viability, and caspase-3/7 activity were also examined. Finally, we investigated the influence of choline uptake inhibitor, hemicholinium-3 (HC-3), and choline deficiency on cell viability and caspase-3/7 activity. Results: Choline transporter-like protein 1 (CTL1) and CTL2 mRNA and protein were highly expressed in RASFs and were localized to the plasma membrane. [ 3 H]Choline uptake occurred via a Na + -independent and pH-dependent transport system. The cells have two different [ 3 H]choline transport systems, high- and low-affinity. Various organic cations, HC-3 and choline deficiency inhibited both [ 3 H]choline uptake and cell viability, and enhanced the caspase-3/7 activity. The functional inhibition of choline transporters could promote apoptotic cell death. In RASFs, [ 3 H]choline uptake was significantly increased compared with that in OASFs without a change in gene expression. Conclusions: These results suggest that CTL1 (high-affinity) and CTL2 (low-affinity) are highly expressed in RASFs and choline may be transported by a choline/H + antiport system. Identification of this CTL1- and CTL2-mediated choline transport system should provide a potential new target for RA therapy.