Nucleus-translocated GCLM promotes chemoresistance in colorectal cancer through a moonlighting function

Area of Science:

• Oncology
• Molecular Biology
• Biochemistry

Background:

• Metabolic enzymes can have non-metabolic roles in cancer progression, including chemoresistance.
• Mechanisms underlying these moonlighting functions are often unclear.
• Glutathione biosynthesis enzyme GCLM's role in chemoresistance is not fully understood.

Purpose of the Study:

• To investigate the nonmetabolic functions of GCLM in colorectal cancer (CRC) chemoresistance.
• To elucidate the molecular mechanisms by which GCLM influences sensitivity to platinum-based chemotherapy.
• To explore the clinical relevance of GCLM expression in CRC patients.

Main Methods:

• Utilized a clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 knockout library screen in CRC cells.
• Investigated protein-protein interactions using biochemical assays.
• Analyzed GCLM phosphorylation and nuclear translocation.
• Correlated GCLM expression with patient prognosis and chemotherapy response.

Main Results:

• Loss of GCLM significantly increased CRC cell sensitivity to platinum-based chemotherapy.
• Nuclear GCLM competitively binds to NF-kappa-B (NF-κB)-repressing factor (NKRF), enhancing NF-κB activity and chemoresistance.
• GCLM phosphorylation by P38 MAPK at T17 mediates its nuclear import via importin a5 upon platinum drug treatment.
• Elevated nuclear GCLM and phospho-GCLM levels correlate with poor prognosis and reduced benefit from chemotherapy.

Conclusions:

• GCLM plays a critical nonmetabolic role in promoting chemoresistance in colorectal cancer.
• A novel posttranslational regulatory mechanism involving GCLM phosphorylation and nuclear translocation enhances NF-κB activity.
• Nuclear GCLM serves as a potential biomarker for predicting chemotherapy response and patient outcomes in CRC.