Dominant-Negative Form of SIGIRR: SIGIRR^ΔE8 Promotes Tumor Growth Through Regulation of Metabolic Pathways

Area of Science:

• Oncology
• Molecular Biology
• Cell Biology

Background:

• Colorectal carcinoma is a leading cause of cancer mortality.
• Tumor suppressor single immunoglobulin interleukin-1-related receptor (SIGIRR) is frequently inactivated in colorectal cancer.
• A novel SIGIRR isoform, SIGIRR^ΔE8, is overexpressed and shows altered cellular localization and glycosylation.

Purpose of the Study:

• To investigate the molecular mechanisms by which SIGIRR^ΔE8 contributes to colorectal cancer progression.
• To identify the cellular interactions and signaling pathways affected by SIGIRR^ΔE8.

Main Methods:

• Analysis of SIGIRR^ΔE8 C-terminal arginine residues as an endoplasmic reticulum retention signal.
• Investigation of SIGIRR^ΔE8 interaction with ribophorin 1 (RPN1).
• Assessment of SIGIRR^ΔE8's impact on adenosine triphosphate synthase and cellular metabolism in colorectal cancer cells.
• Evaluation of the mammalian target of rapamycin (mTOR) signaling pathway and mitochondrial function in a xenograft model.

Main Results:

• Arginine residues in SIGIRR^ΔE8's C-terminus function as an endoplasmic reticulum retention signal, mediating interaction with RPN1.
• SIGIRR^ΔE8 directly impacts colorectal cancer cell metabolism via interaction with adenosine triphosphate synthase.
• SIGIRR^ΔE8 promotes a metabolic shift, upregulates mTOR signaling, and dysregulates mitochondrial function.
• SIGIRR^ΔE8 expression enhances colon cancer cell survival and proliferation in vivo.

Conclusions:

• SIGIRR^ΔE8 acts as an oncoprotein by hijacking ER-associated protein RPN1 and altering cellular metabolism.
• Targeting SIGIRR^ΔE8 or its downstream pathways may offer novel therapeutic strategies for colorectal cancer.