How do organelles such as ribosomes, ER, Golgi and vesicles produce CFTR protein and mucus?

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    $\begingroup$ Can you provide more context? Also can you unpack CFTR? $\endgroup$ – Memming Oct 21 '13 at 2:07
  • $\begingroup$ Also, what is your background knowledge and where are you stuck? $\endgroup$ – fileunderwater Oct 21 '13 at 9:13

CFTR (cystic fibrosis transmembrane conductance regulator) is an integral glycoprotein of the plasma membrane, and mucous is rich in secreted glycoproteins. All proteins are made on ribosomes: CFTR will be cotranslationally inserted into the ER membrane while secretory glycoproteins are cotranslationally sent across the same membrane into the lumen of the ER. In the ER the initial glycans are added to specific amino acid residues. The folding of all proteins is carefully monitored by chaperones in the ER to avoid misfolded proteins reaching the cell surface. Various folding factors also come into play, including peptidyl proline isomerase and protein disulphide isomerase.

Proteins destined for the cell surface leave the ER in COPII-coated vesicles (CFTR will be in the vesicle membrane, secretory glycoproteins in the vesicle lumen) and are targetted to the Golgi where the glycosylation process is completed. Another round of vesicle transport gets the proteins to the cell surface - when these vesicles fuse with the inner surface of the plasma membrane the vesicle content is secreted into the surroundings, while the vesicle membrane proteins enter the plasma membrane.

The classic example of a CFTR defect, resulting in cystic fibrosis, is due to the ΔF508 mutation - the loss of a single amino acid results in misfolding, and the defective protein is held in the ER resulting in loss of CFTR function at the cell surface. Overcoming this retention is one of the targets for CFTR therapy, because if the ΔF508 protein does manage to pass through the secretory pathway to the cell surface it provides sufficient channel function to abolish cystic fibrosis symptoms.

I haven't cited any references here because this is all standard biochemistry/molecular cell biology textbook stuff, so should be easy to confirm.


There are a couple nice videos here: https://synbiota.com/projects/325/

You can also check out some DNA sequences and some protein structures (PDB files) if you want to learn more.


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