Transmembrane Helices 7 and 8 Confer Aggregation Sensitivity to the Cystic Fibrosis Transmembrane Conductance...

Area of Science:

• Molecular biology
• Protein biochemistry
• Cellular biology

Background:

• The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) is a crucial membrane protein.
• CFTR is known to be prone to misfolding and aggregation, affecting its stability and function.
• Understanding the structural basis of CFTR instability is vital for therapeutic strategies.

Purpose of the Study:

• To pinpoint the specific region within CFTR responsible for its temperature-induced aggregation and instability.
• To elucidate the structural elements contributing to CFTR's limited intracellular stability.

Main Methods:

• Utilized temperature-induced aggregation assays with C-terminally truncated CFTR variants.
• Employed limited proteolysis to identify aggregation-prone structural domains.
• Investigated the degradation rates of isolated CFTR domains (TMD1 and TMD2) in cellular systems.
• Performed in silico predictions of protein aggregation propensity.

Main Results:

• Truncations of CFTR up to the second transmembrane domain (TMD2), including the R region, showed resistance to aggregation.
• A protease-resistant structure comprising TMD2 and part of the Regulatory Region (R) was identified as aggregation-prone.
• The presence of TransMembrane helices 7 (TM7) and 8 significantly increased the aggregation sensitivity of TMD2 fragments.
• Isolated TMD2 was degraded more rapidly in cells compared to isolated TMD1.

Conclusions:

• The N-terminally extended TMD2, incorporating part of the R region, forms a stable, protease-resistant structure.
• This specific structural domain appears to be responsible for inducing heat instability in CFTR.
• The identified region may play a key role in the limited intracellular stability of CFTR, contributing to disease pathology.