K-Ras resides on the Arf6-mediated CIE system and its active type interacted with Arf6T27N

Area of Science:

• Cell Biology
• Molecular Biology
• Oncology

Background:

• Ras proteins are key oncogenes regulating cell signaling.
• Ras signaling occurs not only at the plasma membrane but also in endomembrane compartments.
• Understanding Ras isoform trafficking is crucial for developing anti-Ras drugs.

Purpose of the Study:

• To investigate the role of ADP-ribosylation factor 6 (Arf6) in the intracellular trafficking of K-Ras and H-Ras isoforms.
• To elucidate the molecular mechanisms by which Arf6 influences Ras dynamics and signaling.

Main Methods:

• Co-localization studies using immunofluorescence microscopy.
• Subcellular fractionation experiments.
• RNA interference (siRNA) to deplete Arf6.
• Expression of dominant-active and dominant-negative Arf6 mutants.
• Immunoprecipitation and GST pull-down assays.
• Ras isoform C-terminal swapping experiments.

Main Results:

• K-RasG12V co-localized with Arf6 at the plasma membrane and shared endocytic pathways with H-RasG12V.
• Arf6 depletion reduced plasma membrane presence of endogenous Ras isoforms and inhibited EGF-induced Erk phosphorylation.
• Arf6Q67L expression sequestered both Ras isoforms into PI(4,5)P2-enriched vacuoles.
• K-RasG12V showed greater co-localization with Arf6T27N at tubular endosomes compared to H-RasG12V.
• Direct interaction between K-RasG12V and Arf6T27N was identified, mediated by Ras C-termini.

Conclusions:

• Arf6 plays a significant role in the dynamic regulation of both K-Ras and H-Ras isoforms.
• Arf6 influences Ras localization at the plasma membrane and subsequent endosomal trafficking.
• Specific Arf6 isoforms differentially regulate Ras isoform localization, suggesting isoform-specific therapeutic strategies.