Parkin ubiquitinates phosphoglycerate dehydrogenase to suppress serine synthesis and tumor progression
Juan Liu, … , Wenwei Hu, Zhaohui Feng
Juan Liu, … , Wenwei Hu, Zhaohui Feng
Published May 18, 2020
Citation Information: J Clin Invest. 2020;130(6):3253-3269. https://doi.org/10.1172/JCI132876.
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Research Article Metabolism Oncology

Parkin ubiquitinates phosphoglycerate dehydrogenase to suppress serine synthesis and tumor progression

Abstract

Phosphoglycerate dehydrogenase (PHGDH), the first rate-limiting enzyme of serine synthesis, is frequently overexpressed in human cancer. PHGDH overexpression activates serine synthesis to promote cancer progression. Currently, PHGDH regulation in normal cells and cancer is not well understood. Parkin, an E3 ubiquitin ligase involved in Parkinson’s disease, is a tumor suppressor. Parkin expression is frequently downregulated in many types of cancer, and its tumor-suppressive mechanism is poorly defined. Here, we show that PHGDH is a substrate for Parkin-mediated ubiquitination and degradation. Parkin interacted with PHGDH and ubiquitinated PHGDH at lysine 330, leading to PHGDH degradation to suppress serine synthesis. Parkin deficiency in cancer cells stabilized PHGDH and activated serine synthesis to promote cell proliferation and tumorigenesis, which was largely abolished by targeting PHGDH with RNA interference, CRISPR/Cas9 KO, or small-molecule PHGDH inhibitors. Furthermore, Parkin expression was inversely correlated with PHGDH expression in human breast cancer and lung cancer. Our results revealed PHGDH ubiquitination by Parkin as a crucial mechanism for PHGDH regulation that contributes to the tumor-suppressive function of Parkin and identified Parkin downregulation as a critical mechanism underlying PHGDH overexpression in cancer.

Authors

Juan Liu, Cen Zhang, Hao Wu, Xiao-Xin Sun, Yanchen Li, Shan Huang, Xuetian Yue, Shou-En Lu, Zhiyuan Shen, Xiaoyang Su, Eileen White, Bruce G. Haffty, Wenwei Hu, Zhaohui Feng

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Figure 3

Parkin promotes PHGDH protein degradation through ubiquitination.

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Parkin promotes PHGDH protein degradation through ubiquitination. (A) Tr...
(A) Treatment of proteasome inhibitor MG132 increased PHGDH protein levels and abolished inhibitory effect of Parkin on PHGDH levels in Hs578T cells. Hs578T cells with ectopic expression of WT or C431A Myc-Parkin (upper) and WT or Parkin-KO Hs578T cells (lower) were treated with MG132 (5 μM) or DMSO for 12 hours before Western blot assays. (B) Myc-Parkin expression decreased PHGDH protein half-life (left), whereas knockdown of endogenous Parkin increased PHGDH protein half-life (right) in Hs578T cells. Cells were treated with CHX or DMSO for different hours before Western blot assays. (C) KO of Parkin by CRISPR/Cas9 increased PHGDH protein half-life in Hs578T cells. In B and C, data are presented as mean ± SD. n = 3. (D) Effects of WT and mutant Myc-Parkin on ubiquitination of PHGDH-Flag in Hs578T cells analyzed by in vivo ubiquitination (Ub) assays. (E) GST-Parkin ubiquitinates His-Trx-PHGDH in vitro analyzed by in vitro ubiquitination assays using recombinant proteins. (F) Parkin knockdown by shRNA (left) or Parkin KO by CRISPR/Cas9 (middle and right) reduced ubiquitination of PHGDH-Flag in Hs578T and H1299 cells analyzed by in vivo ubiquitination assays. (G) Parkin knockdown by shRNA reduced ubiquitination of endogenous PHGDH in Hs578T cells analyzed by in vivo ubiquitination assays. (H) T240M and P294S mutations impaired Parkin’s ubiquitination activity toward PHGDH in Hs578T cells analyzed by in vivo ubiquitination assays. (I) T240M and P294S mutations impaired the ability of Myc-Parkin to downregulate PHGDH protein levels in Hs578T and H1299 cells.