Abstract

We previously showed in vitro that calcium entry through Trpc1 ion channels regulates myoblast migration and differentiation. In the present work, we used primary cell cultures and isolated muscles from Trpc1(-/-) and Trpc1(+/+) murine model to investigate the role of Trpc1 in myoblast differentiation and in muscle regeneration. In these models, we studied regeneration consecutive to cardiotoxin-induced muscle injury and observed a significant hypotrophy and a delayed regeneration in Trpc1(-/-) muscles consisting in smaller fiber size and increased proportion of centrally nucleated fibers. This was accompanied by a decreased expression of myogenic factors such as MyoD, Myf5, and myogenin and of one of their targets, the developmental MHC (MHCd). Consequently, muscle tension was systematically lower in muscles from Trpc1(-/-) mice. Importantly, the PI3K/Akt/mTOR/p70S6K pathway, which plays a crucial role in muscle growth and regeneration, was down-regulated in regenerating Trpc1(-/-) muscles. Indeed, phosphorylation of both Akt and p70S6K proteins was decreased as well as the activation of PI3K, the main upstream regulator of the Akt. This effect was independent of insulin-like growth factor expression. Akt phosphorylation also was reduced in Trpc1(-/-) primary myoblasts and in control myoblasts differentiated in the absence of extracellular Ca(2+) or pretreated with EGTA-AM or wortmannin, suggesting that the entry of Ca(2+) through Trpc1 channels enhanced the activity of PI3K. Our results emphasize the involvement of Trpc1 channels in skeletal muscle development in vitro and in vivo, and identify a Ca(2+)-dependent activation of the PI3K/Akt/mTOR/p70S6K pathway during myoblast differentiation and muscle regeneration.

Highlights

  • The PI3K/Akt pathway is involved in muscle development and regeneration

  • TRPC1Ϫ/Ϫ Mice Present Delay of Skeletal Muscle Regeneration—We previously showed that TRPC1 protein repression reduces C2C12 myoblast migration and differentiation [23]

  • Activation of the PI3K pathway is well known to induce skeletal muscle hypertrophy defined as an increase in preexisting fiber size as opposed to fiber number

Read more

Summary

Background

The PI3K/Akt pathway is involved in muscle development and regeneration. Results: Knocking out Trpc channels or inhibiting Ca2ϩ fluxes decreases PI3K/Akt activation, slows down myoblasts migration and impairs muscle regeneration. We used primary cell cultures and isolated muscles from Trpc1؊/؊ and Trpc1؉/؉ murine model to investigate the role of Trpc in myoblast differentiation and in muscle regeneration In these models, we studied regeneration consecutive to cardiotoxin-induced muscle injury and observed a significant hypotrophy and a delayed regeneration in Trpc1؊/؊ muscles consisting in smaller fiber size and increased proportion of centrally nucleated fibers. Our results emphasize the involvement of Trpc channels in skeletal muscle development in vitro and in vivo, and identify a Ca2؉-dependent activation of the PI3K/Akt/mTOR/p70S6K pathway during myoblast differentiation and muscle regeneration. We suggest that the entry of Ca2ϩ through Trpc channels enhances the activity of PI3K/Akt/mTOR/p70S6K pathway and accelerates muscle regeneration

EXPERIMENTAL PROCEDURES
RESULTS
DISCUSSION
Full Text
Published version (Free)

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call