Abstract
Skeletal muscle myoblast differentiation involves elaborate signaling networks, including the activity of various ion channels and transporters. Several K+ and Ca2+ channels have been shown to affect myogenesis, but little is known about roles of Cl- channels in the associated processes. Here, we report that the leucine-rich repeat containing family 8 (LRRC8)/volume-regulated anion channel (VRAC) promotes mouse myoblast differentiation. All LRRC8 subunits of heteromeric VRAC were expressed during myotube formation of murine C2C12 myoblasts. Pharmacological VRAC inhibitors, siRNA-mediated knockdown of the essential VRAC subunit LRRC8A, or VRAC activity-suppressing overexpression of LRRC8A effectively reduced the expression of the myogenic transcription factor myogenin and suppressed myoblast fusion while not affecting myoblast proliferation. We found that inhibiting VRAC impairs plasma membrane hyperpolarization early during differentiation. At later times (more than 6 h after inducing differentiation), VRAC inhibition no longer suppressed myoblast differentiation, suggesting that VRAC acts upstream of K+ channel activation. Consequently, VRAC inhibition prevented the increase of intracellular steady-state Ca2+ levels that normally occurs during myogenesis. Our results may explain the mechanism for the thinning of skeletal muscle bundles observed in LRRC8A-deficient mice and highlight the importance of the LRRC8/VRAC anion channel in cell differentiation.
Highlights
Skeletal muscle myoblast differentiation involves elaborate signaling networks, including the activity of various ion channels and transporters
The thinned skeletal muscle bundles displayed by Lrrc8aϪ/Ϫ mice [22] suggest that lack of LRRC8A may lead to dysfunction of myoblast proliferation, differentiation, or fusion into multinucleated myotubes
We show that consistent with a previous report [44], inhibition of the LRRC8A-containing anion channel volumeregulated anion channel (VRAC) does not impair the proliferation of C2C12 myoblasts
Summary
Becker§, X Ursula Koch§, and X Tobias Stauber‡1 From the ‡Institute of Chemistry and Biochemistry, Freie Universitat Berlin, 14195 Berlin, Germany and §Institute of Biology, Freie Universitat Berlin, 14195 Berlin, Germany
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