The G protein coupled receptor CXCR4 designed by the QTY code becomes more hydrophilic and retains cell signaling activity

Lotta Tegler,Horst Pick,Horst Vogel,Karolina Corin,Jennifer Brookes,Michael Skuhersky,Shuguang Zhang

doi:10.1038/s41598-020-77659-x

Abstract

G protein-coupled receptors (GPCRs) are vital for diverse biological functions, including vision, smell, and aging. They are involved in a wide range of diseases, and are among the most important targets of medicinal drugs. Tools that facilitate GPCR studies or GPCR-based technologies or therapies are thus critical to develop. Here we report using our QTY (glutamine, threonine, tyrosine) code to systematically replace 29 membrane-facing leucine, isoleucine, valine, and phenylalanine residues in the transmembrane α-helices of the GPCR CXCR4. This variant, CXCR4QTY29, became more hydrophilic, while retaining the ability to bind its ligand CXCL12. When transfected into HEK293 cells, it inserted into the cell membrane, and initiated cellular signaling. This QTY code has the potential to improve GPCR and membrane protein studies by making it possible to design functional hydrophilic receptors. This tool can be applied to diverse α-helical membrane proteins, and may aid in the development of other applications, including clinical therapies.

Highlights

G protein-coupled receptors (GPCRs) are arguably the most important class of proteins
One problem currently hampering the development of membrane protein-based, and GPCRbased, technologies is the need to stabilize them with detergents outside of the cell membrane
We previously reported an alternative approach for designing hydrophilic GPCRs, which we call the “QTY code”[23]

Summary

Introduction

G protein-coupled receptors (GPCRs) are arguably the most important class of proteins. A computational approach was typically used[18,19,20], one group substituted charged residues for hydrophobic ones[21], and a second group “grafted” the hydrophilic face of a soluble protein onto the hydrophobic membrane-facing section of a membrane protein[22]. These strategies either require significant computational resources to design a water-soluble receptor, or may have limitations when applied to other membrane proteins. Detergents may still be needed for p urification[18]

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Results

Conclusion