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NBME 24 Answers

nbme24/Block 3/Question#46

A 15-year-old girl with cystic fibrosis has a ...

Endoplasmic reticulum

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submitted by vshummy(46),

I think more generally, protein folding happens at the RER and the stem says the protein doesn’t fold properly. Specifically, the most common CF mutation is a misfolded protein and the protein is retained in the RER and not transported to the cell membrane - FA 2019 pg 60.





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submitted by seagull(362),

I have an issue with this question which also conflicts with UWorld. In order to be degraded by proteosomes the misfolded protein would need to be present in the cytosol for ubuination. It it accumulated in the RER then how does it get tagged? Honestly, so conflicted...

sajaqua1  So ordinarily a misfolded protein does undergo ubiquitination and proteolysis. It is noteable that CFTR misfolding doesn't even allow it escape the ER, so it accumulates in the ER +4