Fig. 5.
β2 adrenergic regulation of CaV1.2. (A and B) Unlike β1-AR, β2-AR does not up-regulate CaV1.2Δ1821 when activated by Iso. Rad:β2b RNA ratio was 1:2. Records were taken from oocytes of the same batch during a 3-d experiment. DNAs of both receptors were in pGEM-HJ vector. (A) Before-after plots and (B) summary of Iso-induced changes in IBa, without or with either β1-AR or β2-AR. Statistics: A, paired t test; B, one-way ANOVA (F = 9.9, P < 0.001) followed by Dunnett’s test. (C) Basal IBa of CaV1.2Δ1821 is reduced by preincubation with propranolol for 60 to 120 min (10 µM; purple symbols). Rad:β2b RNA ratio was 1:2. One experiment; statistics: t test. (D–F) Iso regulates CaV1.2 via β2-AR following reduction in constitutive activity of the receptor by propranolol preincubation. Representative diary plots (D), Before-after plots (E) and summary of Iso-induced increase in oocytes coexpressing α1CΔ1821, Rad, and β2-AR without and with preincubation with propranolol. One experiment, statistics: paired t test (E), Kruskal–Wallis one-way ANOVA (H = 9.6, P = 0.001) followed by Dunnett’s test (F). (G and H) The S1928A mutation in the distal CT of full-length α1C does not abrogate the β2-AR regulation. Oocytes expressed α1C-WT or α1C-WT S1928A, β2b, α2δ, Rad, and β2-AR and were preincubated in propranolol prior to Iso challenge. Raw data from three experiments are shown in before–after plot (G; statistics: paired t test) and the summary is in H (statistics: Mann–Whitney U test). (I and J) β2-adrenergic regulation of short-NT isoforms of α1C, with or without exon 9*. Oocytes expressed short-NT α1C-wt with or without exon 9*, β2b, α2δ, Rad, and β2-AR and were preincubated in propranolol prior to Iso challenge. Raw data from one experiment are shown in before–after plot (I; statistics: paired t test), and the summary is in J (statistics: t test).