UBXN2A enhances CHIP-mediated proteasomal degradation of oncoprotein mortalin-2 in cancer cells

Mol Oncol. 2018 Oct;12(10):1753-1777. doi: 10.1002/1878-0261.12372. Epub 2018 Sep 3.


Overexpression of oncoproteins is a major cause of treatment failure using current chemotherapeutic drugs. Drug-induced degradation of oncoproteins is feasible and can improve clinical outcomes in diverse types of cancers. Mortalin-2 (mot-2) is a dominant oncoprotein in several tumors, including colorectal cancer (CRC). In addition to inactivating the p53 tumor suppressor protein, mot-2 enhances tumor cell invasion and migration. Thus, mot-2 is considered a potential therapeutic target in several cancer types. The current study investigated the biological role of a ubiquitin-like protein called UBXN2A in the regulation of mot-2 turnover. An orthogonal ubiquitin transfer technology followed by immunoprecipitation, in vitro ubiquitination, and Magnetic Beads TUBE2 pull-down experiments revealed that UBXN2A promotes carboxyl terminus of the HSP70-interacting protein (CHIP)-dependent ubiquitination of mot-2. We subsequently showed that UBXN2A increases proteasomal degradation of mot-2. A subcellular compartmentalization experiment revealed that induced UBXN2A decreases the level of mot-2 and its chaperone partner, HSP60. Pharmacological upregulation of UBXN2A using a small molecule, veratridine (VTD), decreases the level of mot-2 in cancer cells. Consistent with the in vitro results, UBXN2A+/- mice exhibited selective elevation of mot-2 in colon tissues. An in vitro Anti-K48 TUBE isolation approach showed that recombinant UBXN2A enhances proteasomal degradation of mot-2 in mouse colon tissues. Finally, we observed enhanced association of CHIP with the UBXN2A-mot-2 complex in tumors in an azoxymethane/dextran sulfate sodium-induced mouse CRC model. The existence of a multiprotein complex containing UBXN2A, CHIP, and mot-2 suggests a synergistic tumor suppressor activity of UBXN2A and CHIP in mot-2-enriched tumors. This finding validates the UBXN2A-CHIP axis as a novel and potential therapeutic target in CRC.

Keywords: CHIP E3 ligase; UBXN2A; colorectal cancer; mortalin-2; mouse; veratridine.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Apoptosis
  • Cell Line, Tumor
  • Cell Movement
  • Chaperonin 60 / metabolism
  • Colon / metabolism
  • Colon / pathology
  • Colonic Neoplasms / metabolism
  • Colonic Neoplasms / pathology
  • Female
  • HSP70 Heat-Shock Proteins / metabolism*
  • Haploinsufficiency / genetics
  • Humans
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mitochondria / metabolism
  • Mitochondrial Proteins / metabolism*
  • Multiprotein Complexes / metabolism
  • Phenotype
  • Proteasome Endopeptidase Complex / metabolism*
  • Protein Stability
  • Proteolysis*
  • Substrate Specificity
  • Ubiquitin / metabolism*
  • Ubiquitin-Protein Ligases / metabolism*
  • Ubiquitination
  • Ubiquitins / metabolism*


  • Chaperonin 60
  • HSP70 Heat-Shock Proteins
  • HSPA9 protein, human
  • Hspa9-ps1 protein, mouse
  • Mitochondrial Proteins
  • Multiprotein Complexes
  • UBXN2A protein, human
  • Ubiquitin
  • Ubiquitins
  • Ubxn2a protein, mouse
  • STUB1 protein, human
  • Stub1 protein, mouse
  • Ubiquitin-Protein Ligases
  • Proteasome Endopeptidase Complex