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. Author manuscript; available in PMC: 2024 Apr 28.
Published in final edited form as: Circ Res. 2023 Mar 17;132(9):e116–e133. doi: 10.1161/CIRCRESAHA.122.321858

Figure 6. Ca2+/calmodulin (CaM)-dependent regulation of small-conductance Ca2+-activated K+ (SK)-channels in human right atria (RA).

Figure 6.

A, Schematic representation of the SK-channel macromolecular complex, including phosphorylation-dependent regulation of CaM. B, Western blots of the catalytic subunit of protein phosphatase-2a (PP2Ac), total CaM and Thr80-phosphorylated CaM in RA-cardiomyocytes from Ctl- and cAF-patients. Troponin-C (TnC) was used as loading control. C, Quantification of total and Thr80-phosphorylated calmodulin, as well as relative phosphorylation ratio in RA-cardiomyocytes from Ctl- and cAF-patients. D, Quantification of PP2Ac protein levels in RA-cardiomyocytes from Ctl- and cAF-patients. E, Representative co-immunoprecipitation experiments showing Western blots of SK2 and PP2Ac or SK2 and α-actinin-2 (α-Act2) in lysates (lys) or SK2-immunoprecipitates from RA whole-tissue homogenates of Ctl- or cAF-patients, together with negative control for non-specific binding (NSB). Vertical white lines delineate separate regions on the same gel. F, Quantification of SK2-associated PP2Ac (left) or α-Act2 in RA whole-tissue homogenates of Ctl- and cAF-patients. G, Representative immunostaining and associated line scans (bottom) of SK2 in RA-cardiomyocytes from cAF patients incubated with (right) or without BAPTA-AM (25 μmol/L for 5-hours, left). N-numbers indicate numbers of patients. P-values are based on unpaired Student’s t-test (C,D) or Mann-Whitney tests (F).