The deubiquitinase USP9X regulates RIT1 protein abundance and oncogenic phenotypes

• Published in: iScience Vol. 27; no. 8; p. 110499
• Main Authors: Riley, Amanda K., Grant, Michael, Snell, Aidan, Cromwell, Elizabeth, Vichas, Athea, Moorthi, Sitapriya, Rominger, Callie, Modukuri, Shrikar P., Urisman, Anatoly, Castel, Pau, Wan, Lixin, Berger, Alice H.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 16.08.2024; Elsevier
• Subjects: Cancer; Molecular biology; Proteomics; Molecular biology; Proteomics; Cancer
• ISSN: 2589-0042; 2589-0042
• DOI: 10.1016/j.isci.2024.110499

RIT1 is a rare and understudied oncogene in lung cancer. Despite structural similarity to other RAS GTPase proteins such as KRAS, oncogenic RIT1 activity does not appear to be tightly regulated by nucleotide exchange or hydrolysis. Instead, there is a growing understanding that the protein abundance of RIT1 is important for its regulation and function. We previously identified the deubiquitinase USP9X as a RIT1 dependency in RIT1-mutant cells. Here, we demonstrate that both wild-type and mutant forms of RIT1 are substrates of USP9X. Depletion of USP9X leads to decreased RIT1 protein stability and abundance and resensitizes cells to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors in vitro and in vivo. Our work expands upon the current understanding of RIT1 protein regulation and presents USP9X as a key regulator of RIT1-driven oncogenic phenotypes. [Display omitted] •RIT1-driven drug resistance in vitro and in vivo depends on the deubiquitinase USP9X•USP9X knockout abrogates RIT1-driven proliferation and anchorage-independent growth•USP9X positively regulates RIT1 protein abundance in multiple lung cancer cell lines•USP9X’s catalytic activity controls the ubiquitination of wild-type and mutant RIT1 Molecular biology; Cancer; Proteomics