In vivo expression of G‐protein β1γ2 dimer in adult mouse skeletal muscle alters L‐type calcium current and excitation–contraction coupling

A number of G-protein-coupled receptors are expressed in skeletal muscle but their roles in muscle physiology and downstream effector systems remain poorly investigated. Here we explored the functional importance of the G-protein βγ (Gβγ) signalling pathway on voltage-controlled Ca2+ homeostasis in single isolated adult skeletal muscle fibres. A GFP-tagged Gβ1γ2 dimer was expressed in vivo in mice muscle fibres. The GFP fluorescence pattern was consistent with a Gβ1γ2 dimer localization in the transverse-tubule membrane. Membrane current and indo-1 fluorescence measurements performed under voltage-clamp conditions reveal a drastic reduction of both L-type Ca2+ current density and of peak amplitude of the voltage-activated Ca2+ transient in Gβ1γ2-expressing fibres. These effects were not observed upon expression of Gβ2γ2, Gβ3γ2 or Gβ4γ2. Our data suggest that the G-protein β1γ2 dimer may play an important regulatory role in skeletal muscle excitation–contraction coupling.