KCNMA1 and rheumatoid arthritis: Since our focus was on the channels expressed at the plasma membrane of FLS, and since coexpression of β subunits with α subunits affects the kinetics and pharmacology of K+ currents through the KCa1.1 channel, we used patch-clamp electrophysiology to assess the expression of functional β subunits at the plasma membrane of RA-FLS.