Recruitment for the position below will be done together with recruitment for the Gravitation project FLOW. For the recruitment procedure and contact information, please go to the recruitment page of the FLOW website.

Current position

Chaperone buffering in quality control of CFTR

Principal Investigators: Ineke Braakman – Peter van der Sluijs

Key collaborator: Georgios Karras (MD Anderson Cancer Center, Houston, US)

Main research question: How do cytoplasmic chaperones control folding of CFTR variants

Outline of Lumier assay (M. Taipale, G. Karras et al)

Background and goals
The Braakman-van der Sluijs lab studies molecular mechanisms of (membrane) protein folding in the endoplasmic reticulum. Ineke Braakman and Peter van der Sluijs are experts in analysis of newly synthesized protein folding, its regulation by cellular factors, and trafficking pathways in cells. Misfolded proteins are the root cause of many genetic diseases and targeting misfolded proteins with small molecules emerged as a powerful approach to treat disease as shown for cystic fibrosis. Folding of CFTR occurs in three topologically distinct spaces and in this project we will unravel how cytoplasmic chaperone machineries control folding of this multispan
membrane protein. A large number of CFTR patient variants is transported to the cell surface in a misfolded nonfunctional form. How these misfolded proteins escape quality-control mechanisms is not understood.

We have generated a library of triple FLAG-tagged CFTR truncations and missense disease mutants. These will be analyzed for interaction with candidate cytoplasmic chaperones in the in-cell Lumier assay in collaboration with Prof. Karras. Significance of hits for CFTR folding will be confirmed upon overexpression or knockout in combination with our in-cell CFTR folding assay (2). A second question relates to chaperone buffering, in which we hypothesize that misfolded proteins that reach the cell surface do so because chaperone levels are sufficient. We will treat cells with chaperone inhibitors to titrate the activity of cytoplasmic chaperones. The consequences for folding and transport of CFTR variants then will be analyzed (2). Certain mutants may be differentially affected by reduced levels of active chaperones and remain stuck in the ER and targeted for degradation.

Profile/background candidate

We are looking for a postdoc with a background in biochemistry and cell biology. The project can be taken into independence after the post-doc period.

Key references

  1. Van der Sluijs P, Hoelen H, Schmidt A, Braakman I (2024) The folding pathway of ABC transporter CFTR: effective and robust. J Mol Biol Apr 26: 168591. doi: 10.1016/j.jmb.2024.168591.
  2. Im J, Hillenaar T, Yeoh HY, Sahasrabudhe P, Mijnders M, van Willigen M, Hagos A, de Mattos E, van der Sluijs P, Braakman I (2023) ABC-transporter CFTR folds with high fidelity through a modular, stepwise pathway. Cell Mol Life Sci. 80: 33. doi: 10.1007/s00018-022-04671-x.
  3. Kleizen B., van Vlijmen T, de Jonge H, Braakman I (2005). CFTR folds predominantly co-translational. Mol Cell 20:277-87. doi: 10.1016/j.molcel.2005.09.007.