FIGURE 4.
Regulation by recombinant AMPK heterotrimers of whole-cell currents carried by BKCa splice variants expressed in HEK293 cells. Bar charts show the residual whole-cell K+ current (I/Imax; mean ± S.E. (error bars)) carried by the ZERO (A (i)) and STREX (B (i)) splice variants of BKCa and by the S657A mutant (C (i)) after intracellular dialysis (10 min) of a constitutively active AMPK heterotrimer (AMPK; bacterially derived thiophosphorylated α2β2γ1) or an inactive AMPK heterotrimer (iAMPK; bacterially derived kinase-dead α2β2γ1). For the ZERO variant, residual current measured 0.60 ± 0.07 of control (p < 0.01) after 5 ± 0.4 min (n = 8) with AMPK and 0.96 ± 0.08 (n = 3) after 10 min with iAMPK. For the STREX variant, residual current measured 1.17 ± 0.14 (n = 4) of control with AMPK and 1.15 ± 0.1 (n = 3) after 10 min with iAMPK. For the S657A mutant, residual current measured 0.68 ± 0.06 (n = 4) of control (p < 0.01) with AMPK and 0.91 ± 0.08 (n = 3) with iAMPK after 10 min. A–C (ii and iii) show examples of the whole-cell K+ currents recorded after 0 and 10 min (left) and plots of current magnitude against time following intracellular dialysis of AMPK and iAMPK, respectively, to each of the aforementioned BKCa variants (right).