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Different expression of ? subunits of the KCa1.1 channel by invasive and non-invasive human fibroblast-like synoviocytes.

ABSTRACT: Fibroblast-like synoviocytes (FLS) in rheumatoid arthritis (RA-FLS) contribute to joint inflammation and damage characteristic of the disease. RA-FLS express KCa1.1 (BK, Slo1, MaxiK, KCNMA1) as their major plasma membrane potassium channel. Blocking KCa1.1 reduces the invasive phenotype of RA-FLS and attenuates disease severity in animal models of RA. This channel has therefore emerged as a promising therapeutic target in RA. However, the pore-forming ? subunit of KCa1.1 is widely distributed in the body, and blocking it induces severe side effects, thus limiting its value as a therapeutic target. On the other hand, KCa1.1 channels can also contain different accessory subunits with restricted tissue distribution that regulate channel kinetics and pharmacology. Identification of the regulatory subunits of KCa1.1 expressed by RA-FLS may therefore provide the opportunity for generating a selective target for RA treatment.Highly invasive RA-FLS were isolated from patients with RA, and FLS from patients with osteoarthritis (OA) were used as minimally invasive controls. The ? subunit expression by FLS was assessed by quantitative reverse transcription polymerase chain reactions, Western blotting, and patch-clamp electrophysiology combined with pharmacological agents. FLS were sorted by flow cytometry on the basis of their CD44 expression level for comparison of their invasiveness and with their expression of KCa1.1 ? and ? subunits. ?1 and ?3 subunit expression was reduced with small interfering RNA (siRNA) to assess their specific role in KCa1.1? expression and function and in FLS invasiveness.We identified functional ?1 and ?3b regulatory subunits in RA-FLS. KCa1.1 ?3b subunits were expressed by 70 % of the cells and were associated with highly invasive CD44(high) RA-FLS, whereas minimally invasive CD44(low) RA-FLS and OA-FLS expressed either ?1 subunit. Furthermore, we found that silencing the ?3 but not the ?1 subunit with siRNA reduced KCa1.1 channel density at the plasma membrane of RA-FLS and inhibited RA-FLS invasiveness.Our findings suggest the KCa1.1 channel composed of ? and ?3b subunits as an attractive target for the therapy of RA.

SUBMITTER: Petho Z

PROVIDER: S-EPMC4863321 | biostudies-literature | 2016 May

REPOSITORIES: biostudies-literature

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Different expression of β subunits of the KCa1.1 channel by invasive and non-invasive human fibroblast-like synoviocytes.

Pethő Zoltán Z Tanner Mark R MR Tajhya Rajeev B RB Huq Redwan R Laragione Teresina T Panyi Gyorgy G Gulko Pércio S PS Beeton Christine C

Arthritis research & therapy 20160510 1

<h4>Background</h4>Fibroblast-like synoviocytes (FLS) in rheumatoid arthritis (RA-FLS) contribute to joint inflammation and damage characteristic of the disease. RA-FLS express KCa1.1 (BK, Slo1, MaxiK, KCNMA1) as their major plasma membrane potassium channel. Blocking KCa1.1 reduces the invasive phenotype of RA-FLS and attenuates disease severity in animal models of RA. This channel has therefore emerged as a promising therapeutic target in RA. However, the pore-forming α subunit of KCa1.1 is wi ...[more]

PMID: 27165430

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Project description:BackgroundFibroblast-like synoviocytes (FLS) and CCR7- effector memory T (TEM) cells are two of the major cell types implicated in the progression of rheumatoid arthritis (RA). In particular, FLS become highly invasive, whereas TEM cells proliferate and secrete proinflammatory cytokines, during RA. FLS and T cells may also interact and influence each other's phenotypes. Inhibition of the pathogenic phenotypes of both FLS and TEM cells can be accomplished by selectively blocking the predominant potassium channels that they upregulate during RA: KCa1.1 (BK, Slo1, MaxiK, KCNMA1) upregulated by FLS and Kv1.3 (KCNA3) upregulated by activated TEM cells. In this study, we investigated the roles of KCa1.1 and Kv1.3 in regulating the interactions between FLS and TEM cells and determined if combination therapies of KCa1.1- and Kv1.3-selective blockers are more efficacious than monotherapies in ameliorating disease in rat models of RA.MethodsWe used in vitro functional assays to assess the effects of selective KCa1.1 and Kv1.3 channel inhibitors on the interactions of FLS isolated from rats with collagen-induced arthritis (CIA) with syngeneic TEM cells. We also used flow cytometric analyses to determine the effects of KCa1.1 blockers on the expression of proteins used for antigen presentation on CIA-FLS. Finally, we used the CIA and pristane-induced arthritis models to determine the efficacy of combinatorial therapies of KCa1.1 and Kv1.3 blockers in reducing disease severity compared with monotherapies.ResultsWe show that the interactions of FLS from rats with CIA and of rat TEM cells are regulated by KCa1.1 and Kv1.3. Inhibiting KCa1.1 on FLS reduces the ability of FLS to stimulate TEM cell proliferation and migration, and inhibiting Kv1.3 on TEM cells reduces TEM cells' ability to enhance FLS expression of KCa1.1 and major histocompatibility complex class II protein, as well as stimulates their invasion. Furthermore, we show that combination therapies of selective KCa1.1 and Kv1.3 blockers are more efficacious than monotherapies at reducing signs of disease in two rat models of RA.ConclusionsOur results demonstrate the importance of KCa1.1 and Kv1.3 in regulating FLS and TEM cells during RA, as well as the value of combined therapies targeting both of these cell types to treat RA.

Dataset Information

Different expression of ? subunits of the KCa1.1 channel by invasive and non-invasive human fibroblast-like synoviocytes.

Publications

Different expression of β subunits of the KCa1.1 channel by invasive and non-invasive human fibroblast-like synoviocytes.

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