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SMURF2 Facilitates GAP17 Isoform 1 Membrane Displacement to Promote Mutant p53-KRAS Oncogenic Synergy
Paramita Ray1, Shirish Shukla1, Yaqing Zhang2
1Department of Radiation Oncology, The University of Michigan Medical School, Ann Arbor, Michigan.
Abstract:
Cooperativity between mutant p53 and mutant KRAS, although recognized, is poorly understood. In pancreatic cancer, mutant p53 induces splicing factor hnRNPK, causing an isoform switch that produces overexpression of GTPase-activating protein 17 isoform 1 (GAP17-1). GAP17-1 is mislocalized in the cytosol instead of the membrane, owing to the insertion of exon 17 encoding a PPLP motif, thus allowing mutant KRAS to remain in the GTP-bound hyperactive state. However, the role of PPLP in influencing GAP17-1 mislocalization remains unclear. We show that Smad ubiquitination regulatory factor 2 (SMURF2), a known stabilizer of mutant KRAS, interacts with GAP17-1 via the PPLP motif and displaces it from the membrane, facilitating mutant p53-mediated mutant KRAS hyperactivation. We used cell lines with known KRAS and TP53 mutations, characterized SMURF2 expression in multiple pancreatic cancer mouse models (iKras*; iKras*, p53*, and p48-Cre; Kras*), and performed single-cell RNA sequencing and tissue microarray on preclinical and clinical samples. We found that SMURF2 silencing profoundly reduces the survival of mutant TP53; KRAS-driven cells. We show that a GAP17-1 AALA mutant does not bind to SMURF2, stays in the membrane, and keeps mutant KRAS in the GDP-bound state to inhibit downstream signaling. In mouse models, mutant KRAS and SMURF2 upregulation are correlated with pancreatic intraepithelial neoplasia and ductal adenocarcinoma lesions. Furthermore, patients with pancreatic ductal adenocarcinoma who received neoadjuvant therapy and express moderate-to-high SMURF2 show decreased overall survival (P = 0.04).
Implications:
In TP53 and KRAS double-mutated pancreatic cancer, SMURF2-driven GAP17-1 membrane expulsion facilitates mutant p53-KRAS oncogenic synergy.
Insights
Smad ubiquitination regulatory factor 2 (SMURF2) drives mutant p53-KRAS synergy in pancreatic cancer by mislocalizing GTPase-activating protein 17 isoform 1 (GAP17-1). SMURF2 silencing reduces cancer cell survival and correlates with poor patient outcomes.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Genetics
Background:
- Cooperativity between mutant p53 and mutant KRAS is crucial in pancreatic cancer but poorly understood.
- Mutant p53 induces hnRNPK, leading to overexpression of GTPase-activating protein 17 isoform 1 (GAP17-1).
- GAP17-1 mislocalization allows mutant KRAS to remain in a hyperactive state.
Purpose of the Study:
- To elucidate the role of Smad ubiquitination regulatory factor 2 (SMURF2) in mutant p53-KRAS cooperativity.
- To investigate the mechanism of GAP17-1 mislocalization and its impact on mutant KRAS activity.
- To assess the therapeutic potential of targeting SMURF2 in pancreatic cancer.
Main Methods:
- Utilized cell lines with known KRAS and TP53 mutations.
- Examined SMURF2 expression in pancreatic cancer mouse models.
- Performed single-cell RNA sequencing and tissue microarray on preclinical and clinical samples.
Main Results:
- SMURF2 interacts with GAP17-1 via the PPLP motif, displacing it from the membrane and facilitating mutant p53-mediated KRAS hyperactivation.
- SMURF2 silencing significantly reduces the survival of cells with mutant TP53 and KRAS.
- A GAP17-1 mutant unable to bind SMURF2 remains membrane-bound, inhibiting downstream signaling.
- SMURF2 upregulation correlates with pancreatic intraepithelial neoplasia and ductal adenocarcinoma lesions in mouse models.
- High SMURF2 expression in patients with pancreatic ductal adenocarcinoma is associated with decreased overall survival after neoadjuvant therapy.
Conclusions:
- SMURF2 is a key mediator of oncogenic synergy between mutant p53 and mutant KRAS in pancreatic cancer.
- SMURF2-driven GAP17-1 membrane expulsion is critical for maintaining KRAS hyperactivation.
- SMURF2 represents a potential therapeutic target for pancreatic cancer, particularly in patients with TP53 and KRAS mutations.
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