The crosstalk between MYC and mTORC1 during osteoclastogenesis

Area of Science:

• Cell Biology
• Molecular Biology
• Bone Biology

Background:

• Osteoclasts are crucial for bone resorption, and their differentiation is tightly regulated.
• Aberrant signaling of the mammalian target of rapamycin complex 1 (mTORC1) pathway is linked to bone homeostasis disruption.
• The precise mechanisms governing mTORC1's biphasic regulation during osteoclast differentiation remain unclear.

Purpose of the Study:

• To elucidate the role of MYC in coordinating mTORC1 activation during osteoclastogenesis.
• To investigate the molecular mechanisms by which MYC influences mTORC1 signaling in osteoclasts.
• To understand how the MYC-mTORC1 interplay affects osteoclast activity and bone resorption.

Main Methods:

• Investigated MYC's role in regulating mTORC1 activation during osteoclast differentiation using mouse and human cells.
• Utilized genetic manipulation (MYC-deficiency) and pharmacological inhibition (rapamycin) to assess pathway dynamics.
• Examined the expression of Growth arrest and DNA damage-inducible protein (GADD34) in relation to MYC and mTORC1 activity.

Main Results:

• MYC deficiency disrupted the normal biphasic activation of mTORC1 during osteoclastogenesis.
• Suppression of mTORC1 in mature osteoclasts with rapamycin paradoxically increased bone resorption.
• MYC was found to induce GADD34 expression, which subsequently suppresses mTORC1 activity in the late phase of osteoclastogenesis.

Conclusions:

• A novel MYC-GADD34 signaling axis acts as an upstream regulator of dynamic mTORC1 activation in osteoclasts.
• This axis plays a critical role in controlling osteoclast differentiation and bone resorption activity.
• Understanding this interplay provides new insights into maintaining bone homeostasis and potential therapeutic targets for bone diseases.