Protease-Resistant and Cell-Permeable Double-Stapled Peptides Targeting the Rab8a GTPase

Area of Science:

• Chemical Biology
• Medicinal Chemistry
• Molecular Biology

Background:

• Small GTPases are crucial cellular regulators implicated in diseases like cancer.
• Rab-GTPases, a major subfamily, control vesicular transport through protein-protein interactions (PPIs).
• Existing inhibitors, like StRIP3, face limitations in stability and cell permeability.

Purpose of the Study:

• To design a bioavailable analogue of the StRIP3 peptide inhibitor.
• To enhance binding affinity, proteolytic stability, and cellular uptake of the inhibitor.
• To validate the inhibitor's efficacy in targeting Rab GTPases.

Main Methods:

• Design of a double-hydrophobic cross-linked peptide analogue of StRIP3.
• Assessment of binding affinity, proteolytic stability, and cellular uptake.
• Cellular localization studies to confirm target engagement with Rab8a.

Main Results:

• The novel StRIP3 analogue demonstrated increased binding affinity and superior proteolytic stability.
• Robust cellular uptake and accumulation in the same compartments as the target Rab8a protein were observed.
• The modified peptide overcomes the limitations of the original StRIP3.

Conclusions:

• A bioavailable and highly stable peptide inhibitor for Rab GTPases was successfully designed.
• This approach provides a strategy for creating drug-like conformationally constrained peptides.
• The findings offer a promising avenue for targeting previously undruggable GTPase-mediated PPIs.