GRP75 modulates oncogenic Dbl-driven endocytosis derailed via the CHIP-mediated ubiquitin degradation pathway

Area of Science:

• Cell Biology
• Oncology
• Molecular Biology

Background:

• Chaperone-assisted proteasome degradation is crucial for controlling oncogenic proteins and cancer progression.
• The interplay between chaperones, oncoproteins, and endocytosis pathways remains poorly understood.
• Ovarian cancer progression involves complex regulatory mechanisms of oncogenic signaling and cellular transport.

Purpose of the Study:

• To investigate the novel co-regulatory mechanism between the mitochondrial chaperone GRP75 and the oncoprotein Dbl in ovarian cancer.
• To elucidate the role of GRP75 in modulating Dbl-driven endocytosis and its impact on cancer cell phenotype.
• To explore the potential of targeting the GRP75-Dbl axis for therapeutic intervention in ovarian cancer.

Main Methods:

• Co-immunoprecipitation and immunofluorescence to detect GRP75 and proto-Dbl interactions within endocytosis vesicles.
• Analysis of endocytosis pathways (macropinocytosis, clathrin-mediated, clathrin-independent) using specific inhibitors and knockdown approaches.
• Ubiquitin-proteasome pathway assays to assess the role of GRP75 in Dbl degradation via CHIP.
• Assessment of Rho GTPases activation following GRP75 modulation.

Main Results:

• Proto-Dbl (dbl proto-oncogene product) and mitochondrial chaperone GRP75 were co-enriched in endocytosis vesicles of ovarian cancer cells.
• Oncoprotein Dbl enhanced macropinocytosis while suppressing other endocytosis pathways, indicating a derailed endocytosis phenotype.
• GRP75 promoted proto-Dbl degradation via the CHIP-mediated ubiquitin-proteasome pathway, acting as a cooperator with CHIP and competitor to Hsc70/Hsp90.
• GRP75 knockdown or inhibition reduced oncoprotein Dbl levels, impaired Rho GTPases activation, and shifted the endocytosis-derailed phenotype.

Conclusions:

• A novel GRP75-Dbl regulatory axis controlling endocytosis derailment in ovarian cancer was uncovered.
• GRP75 plays a critical role in modulating oncoprotein Dbl levels and associated endocytic dysregulation.
• Targeting GRP75 with chaperone inhibitors presents a potential therapeutic strategy to counteract oncoprotein-driven endocytosis derailment in cancer.