Figure 2.

A: Histogram summarizing the results of PPF experiments performed with Ca_v2.2 isoforms carrying mutations of α_1B residues Arg³⁷⁶ and Val⁴¹⁶. Columns show mean PPF values with SE bars for each condition. Human Gβ₁γ₂ was co-expressed in tsA-201 cells with the Ca_v2.2 isoforms for each condition presented except for the negative control ("-Gβ₁γ₂"). Respective mutations in the Ca_v2.2 amino acid sequence are indicated beneath the corresponding columns (see METHODS for full description of the mutations used). Of the various conditions examined only the mutations R376A, R376F, V416A, and the double mutation R376A, V416A resulted in a significant loss of Gβγ-mediated channel inhibition, as measured by the degree of pre-pulse relief following a depolarizing pre-pulse, when compared to WT control (*p < 0.05, t-test, **p < 0.05 one-way ANOVA, Dunnett's method, or Kruskal-Wallis one-way ANOVA on ranks). Numbers in parentheses indicate numbers of cells tested for the respective condition. B: Histogram summarizing the results of PPF experiments using tsA-201 cells co-transfected to express α_1B mutant R376F with Ca_vβ isoforms β_1B, β₂, β₃, and β₄, with or without heterologous human Gβ₁γ₂ as indicated by labels beneath columns. Columns show mean PPF values with SE bars for each condition (see METHODS for full description of the mutations used). Of the conditions examined, coexpression of Ca_vβ_1B and Ca_vβ_2a, and Ca_vβ₄ resulted in statistically significant differences in mean current density for R376F channels expressed with and without heterologous Gβγ (*p < 0.05 using t-test, Mann-Whitney rank sum test, and t-test, respectively).