# In vivo conformational space and defects of misfolded CFTR variants by covalent protein painting

## TL;DR

This paper introduces a new method to study protein misfolding in living cells and applies it to understand how faulty CFTR proteins cause Cystic Fibrosis.

## Contribution

The study introduces a novel in vivo structural proteomics method to detect conformational defects in misfolded CFTR variants.

## Key findings

- A previously unreported opening mechanism of CFTR was discovered.
- Misfolding of CFTR variants disrupts conformational changes even with current drug treatments.
- The method suggests ways to stabilize drug-resistant CFTR variants like N1303K.

## Abstract

In vivo characterization of protein structures and structural changes after perturbation is still a major challenge and has impacted our understanding of the molecular events involved in protein misfolding diseases. To identify the true conformational space occupied by proteins in their native state in vivo, we recently developed a structural proteomics method named Covalent Protein Painting (CPP). Here, we show how CPP can be used to identify and quantify the conformational defects of proteins in the misfolding disease Cystic Fibrosis. We first report the discovery of a previously unreported opening mechanism for the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) as well as its conformational changes during biogenesis. Then we further reveal how misfolding of different CFTR variants in Cystic Fibrosis disturbs these conformational changes even upon treatment with current approved drugs and suggest possibilities to stabilize misfolded CFTR variants not or less responsive to these drugs such as N1303K CFTR.

Protein misfolding drives many diseases, but detecting and characterizing misfolding in living cells remains challenging. Here, the authors apply an in vivo structural method to uncover how Cystic Fibrosis-causing CFTR variants misfold, respond to current therapies and uncover an activation mechanism previously missed.