Cereblon (CRBN), a substrate receptor for Cullin-ring E3 ubiquitin ligase (CRL), is a major target protein of immunomodulatory drugs. An earlier study demonstrated that CRBN directly interacts with the catalytic α subunit of AMP-activated protein kinase (AMPK), a master regulator of energy homeostasis, down-regulating the enzymatic activity of AMPK. However, it is not clear how CRBN modulates AMPK activity. To investigate the mechanism of CRBN-dependent AMPK inhibition, we measured protein levels of each AMPK subunit in brains, livers, lungs, hearts, spleens, skeletal muscles, testes, kidneys, and embryonic fibroblasts from wild-type and Crbn-/- mice. Protein levels and stability of the regulatory AMPKγ subunit were increased in Crbn-/- mice. Increased stability of AMPKγ in Crbn-/- MEFs was dramatically reduced by exogenous expression of Crbn. In wild-type MEFs, the proteasomal inhibitor MG132 blocked degradation of AMPKγ. We also found that CRL4CRBN directly ubiquitinated AMPKγ. Taken together, these findings suggest that CRL4CRBN regulates AMPK through ubiquitin-dependent proteasomal degradation of AMPKγ.

中文翻译：

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Cereblon 对 AMPK γ 亚基的泛素依赖性蛋白酶体降解抑制 AMPK 活性。

Cereblon (CRBN) 是 Cullin 环 E3 泛素连接酶 (CRL) 的底物受体，是免疫调节药物的主要靶蛋白。早期的一项研究表明，CRBN 直接与 AMP 活化蛋白激酶 (AMPK) 的催化 α 亚基相互作用，AMPK 是能量稳态的主要调节剂，下调 AMPK 的酶活性。然而，目前尚不清楚 CRBN 如何调节 AMPK 活性。为了研究 CRBN 依赖性 AMPK 抑制的机制，我们测量了来自野生型和 Crbn-/- 小鼠的大脑、肝脏、肺、心脏、脾脏、骨骼肌、睾丸、肾脏和胚胎成纤维细胞中每个 AMPK 亚基的蛋白质水平. 在 Crbn-/- 小鼠中，调节性 AMPKγ 亚基的蛋白质水平和稳定性增加。Crbn-/- MEFs 中 AMPKγ 稳定性的增加被 Crbn 的外源表达显着降低。在野生型 MEFs 中，蛋白酶体抑制剂 MG132 阻止了 AMPKγ 的降解。我们还发现 CRL4CRBN 直接泛素化 AMPKγ。总之，这些发现表明 CRL4CRBN 通过 AMPKγ 的泛素依赖性蛋白酶体降解来调节 AMPK。