Figure 6.

Regulation of L-type Ca_V1.2 Ca²⁺ channel function by substrate stiffness requires the STREX-containing BK channel. (A) Representative whole-cell recordings of Ba²⁺ currents from HEK293 cells expressing the Ca_V1.2 channel on the soft and stiff substrates. (B) Summary of the mean I-V relationships from 10 cells in three preparations for each case. (C) Voltage dependence of the Ca_V1.2 channel activation determined with tail currents from 10 cells for each case. (D) Voltage dependence of the Ca_V1.2 channel inactivation from recordings in 10 HEK293 cells expressing the Ca_V1.2 channel in three preparations cultured on the soft and stiff substrates. (E) Representative whole-cell recordings of Ba²⁺ currents from HEK293 cells coexpressing the STREX-containing BK channel and the Ca_V1.2 Ca²⁺ channel on the soft and stiff substrates. (F) Summary of the mean I-V relationships from 12 cells in three preparations for each case. (G) Voltage dependence of the Ca_V1.2 channel activation determined with tail currents from 12 cells for each case. (H) Voltage dependence of the Ca_V1.2 channel inactivation from 11 cells in three preparations cultured on the soft and stiff substrates. (I) Representative whole-cell recordings of Ba²⁺ currents from HEK293 cells coexpressing the STREX-deleted BK channel and the Ca_V1.2 channel on the soft and stiff substrates. (J) Summary of the mean I-V relationships from 12 cells in three preparations for each case. (K) Voltage dependence of the Ca_V1.2 channel activation determined with tail currents from 12 cells for each case. (L) Voltage dependence of the Ca_V1.2 channel inactivation from 11 cells in three preparations cultured on the soft and stiff substrates. ^∗p < 0.05, comparison of the current density at the same voltage.