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Updated: Feb 18, 2026

Purification of Ubiquitinated p53 Proteins from Mammalian Cells
Published on: March 21, 2022
Phosphorylation and Ubiquitination Regulate Protein Phosphatase 5 Activity and Its Prosurvival Role in Kidney Cancer
Natela Dushukyan1, Diana M Dunn1, Rebecca A Sager1
1Department of Urology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY 13210, USA; Upstate Cancer Center, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY 13210, USA; Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, 750 E. Adams St., Syracuse, NY 13210, USA.
Abstract:
The serine/threonine protein phosphatase 5 (PP5) regulates multiple cellular signaling networks. A number of cellular factors, including heat shock protein 90 (Hsp90), promote the activation of PP5. However, it is unclear whether post-translational modifications also influence PP5 phosphatase activity. Here, we show an "on/off switch" mechanism for PP5 regulation. The casein kinase 1δ (CK1δ) phosphorylates T362 in the catalytic domain of PP5, which activates and enhances phosphatase activity independent of Hsp90. Overexpression of the phosphomimetic T362E-PP5 mutant hyper-dephosphorylates substrates such as the co-chaperone Cdc37 and glucocorticoid receptor in cells. Our proteomic approach revealed that the tumor suppressor von Hippel-Lindau protein (VHL) interacts with and ubiquitinates K185/K199-PP5 for proteasomal degradation in a hypoxia- and prolyl-hydroxylation-independent manner. Finally, VHL-deficient clear cell renal cell carcinoma (ccRCC) cell lines and patient tumors exhibit elevated PP5 levels. Downregulation of PP5 causes ccRCC cells to undergo apoptosis, suggesting a prosurvival role for PP5 in kidney cancer.
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