Cell
Volume 160, Issue 4, 12 February 2015, Pages 715-728
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Article
Degradation of AMPK by a Cancer-Specific Ubiquitin Ligase

https://doi.org/10.1016/j.cell.2015.01.034Get rights and content
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Highlights

  • MAGE-A3/6 are normally testis restricted and aberrantly expressed in many cancers

  • MAGE-A3/6 are driver oncogenes competent to transform cells

  • MAGE-A3/6-TRIM28 ubiquitinates and degrades the AMPK tumor suppressor

  • MAGE-A3/6-TRIM28 suppresses autophagy and potentiates mTOR signaling

Summary

AMP-activated protein kinase (AMPK) is a master sensor and regulator of cellular energy status. Upon metabolic stress, AMPK suppresses anabolic and promotes catabolic processes to regain energy homeostasis. Cancer cells can occasionally suppress the growth-restrictive AMPK pathway by mutation of an upstream regulatory kinase. Here, we describe a widespread mechanism to suppress AMPK through its ubiquitination and degradation by the cancer-specific MAGE-A3/6-TRIM28 ubiquitin ligase. MAGE-A3 and MAGE-A6 are highly similar proteins normally expressed only in the male germline but frequently re-activated in human cancers. MAGE-A3/6 are necessary for cancer cell viability and are sufficient to drive tumorigenic properties of non-cancerous cells. Screening for targets of MAGE-A3/6-TRIM28 revealed that it ubiquitinates and degrades AMPKα1. This leads to inhibition of autophagy, activation of mTOR signaling, and hypersensitization to AMPK agonists, such as metformin. These findings elucidate a germline mechanism commonly hijacked in cancer to suppress AMPK.

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