Transferrin receptor targeting by de novo sheet extension

Area of Science:

• Protein engineering
• Biochemistry
• Drug delivery

Background:

• Designing de novo protein-protein interactions is difficult due to the energetic cost of displacing water from polar groups.
• Exposed polar backbone groups on protein surfaces, particularly at beta sheet edges, present a design challenge.
• The human transferrin receptor (hTfR) is crucial for transporting proteins across the blood-brain barrier (BBB), offering a target for brain drug delivery.

Purpose of the Study:

• To develop a general computational strategy for designing proteins that bind to exposed polar backbone groups at beta sheet edges.
• To create novel protein binders for the human transferrin receptor (hTfR) to facilitate drug delivery across the blood-brain barrier (BBB).

Main Methods:

• Employed a computational design approach to create proteins that geometrically match and complement exposed polar backbone groups.
• Focused on designing binders for an exposed beta sheet on the hTfR.
• Validated the designed protein's binding affinity, stability, and ability to cross a microfluidic BBB model.

Main Results:

• Successfully designed a small protein binder that targets the hTfR.
• The designed protein exhibits a high binding affinity with a dissociation constant (Kd) of 20 nM.
• The protein is hyperstable and demonstrated the ability to traverse an in vitro microfluidic organ-on-a-chip model of the human BBB.

Conclusions:

• The described de novo protein design strategy is effective for targeting proteins with exposed beta edge strands.
• This approach offers a versatile method for creating therapeutic agents capable of crossing the BBB.
• The designed hTfR binder shows potential for future applications in brain drug delivery.