De novo reconstitution reveals the proteins required for skeletal muscle voltage-induced Ca 2+ release.

Skeletal muscle contraction is triggered by Ca ²⁺ release from the sarcoplasmic reticulum (SR) in response to plasma membrane (PM) excitation. In vertebrates, this depends on activation of the RyR1 Ca ²⁺ pore in the SR, under control of conformational changes of Ca _V 1.1, located ∼12 nm away in the PM. Over the last ∼30 y, gene knockouts have revealed that Ca _V 1.1/RyR1 coupling requires additional proteins, but leave open the possibility that currently untested proteins are also necessary. Here, we demonstrate the reconstitution of conformational coupling in tsA201 cells by expression of Ca _V 1.1, β1a, Stac3, RyR1, and junctophilin2. As in muscle, depolarization evokes Ca ²⁺ transients independent of external Ca ²⁺ entry and having amplitude with a saturating dependence on voltage. Moreover, freeze-fracture electron microscopy indicates that the five identified proteins are sufficient to establish physical links between Ca _V 1.1 and RyR1. Thus, these proteins constitute the key elements essential for excitation-contraction coupling in skeletal muscle.
Competing Interests: The authors declare no conflict of interest.