IGFBP6 Modulates Proteostasis by Activating ATF4 Targets and Reducing ER Retrotranslocon Expression.

Area of Science:

• Molecular Biology
• Cancer Research
• Cell Biology

Background:

• Reduced Insulin-like Growth Factor Binding Protein 6 (IGFBP6) expression correlates with increased breast cancer (BC) metastatic potential.
• Tumor cells exhibit elevated protein synthesis, necessitating compensatory proteostasis adjustments.
• Ribosome-inactivating proteins (RIPs), like viscumin, are tools to study proteostasis by targeting ribosomes.

Purpose of the Study:

• To investigate the impact of IGFBP6 gene knockdown on proteostasis in the MDA-MB-231 breast cancer cell line.
• To elucidate the mechanisms by which IGFBP6 affects protein synthesis and cellular stress responses in BC.

Main Methods:

• Utilized IGFBP6 gene knockdown in the MDA-MB-231 BC cell line.
• Assessed ribosome modification efficiency by viscumin toxin.
• Analyzed expression levels of key proteins involved in ER-associated degradation (ERAD) and unfolded protein response (UPR) pathways.

Main Results:

• MDA-MB-231 cells with IGFBP6 knockdown showed reduced ribosome modification by viscumin.
• This reduced modification is potentially linked to impaired transport of the viscumin catalytic subunit from the ER to the cytoplasm.
• Decreased expression of the HRD1/Derlin subunit (ERAD component) and increased expression of ATF4 target genes (UPR pathway) were observed.

Conclusions:

• IGFBP6 deficiency in breast cancer cells alters proteostasis and cellular stress responses.
• These alterations involve impaired ribosome function, reduced ERAD efficiency, and activation of the UPR pathway.
• Understanding these mechanisms may offer new therapeutic targets for breast cancer metastasis.