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Distinct amino acid-sensing mTOR pathways regulate skeletal myogenesis

Mee-Sup Yoon1, Jie Chen

  • 1Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

Molecular Biology of the Cell
|September 27, 2013
PubMed

Insights

Amino acids regulate muscle cell differentiation via mTOR signaling. Rag GTPases and Vps34 have opposing roles, with Vps34 activating a pathway crucial for myogenic differentiation.

Area of Science:

  • Cellular Biology
  • Biochemistry
  • Muscle Development

Background:

  • Mammalian target of rapamycin (mTOR) signaling, influenced by amino acid availability, regulates cellular and developmental processes.
  • mTOR is a key regulator of myogenic differentiation, but the specific amino acid-sensing pathways involved remain unclear.

Purpose of the Study:

  • To investigate the roles of Rag GTPases and Vps34, known mediators of amino acid signals upstream of mTOR complex 1 (mTORC1), in myogenic differentiation.
  • To elucidate the mechanisms by which amino acid availability controls myogenesis.

Main Methods:

  • Utilized C2C12 myoblasts to study myogenic differentiation.
  • Employed knockdown and overexpression techniques for Rag GTPases and active mutants.
  • Investigated the involvement of Vps34, phospholipase D1 (PLD1), and insulin-like growth factor II (IGF-II) signaling pathways.

Main Results:

  • Rag GTPases and Vps34 mediate amino acid activation of mTORC1 in myoblasts but have opposing effects on differentiation.
  • Rag knockdown enhances differentiation, while active Rag mutants impair it by suppressing the IRS1-PI3K-Akt pathway via mTORC1.
  • Vps34 is essential for differentiation, activating a Vps34-PLD1 pathway that produces IGF-II, an autocrine differentiation inducer.

Conclusions:

  • Uncovered distinct amino acid-sensing mechanisms controlling myogenesis.
  • Demonstrated opposing roles for Rag GTPases and Vps34 in myogenic differentiation.
  • Highlighted the context-dependent nature of mTOR signaling in cellular homeostasis and development.

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