Question

Question 26 (4 points) Bonus question: The CFTR protein is found in the plasma membrane of individuals unaffected with cystic fibrosis. A common mutation in CFTR causes the protein to be trapped in the ER and eventually degraded. Why does this happen?

Answer 1

Cystic fibrosis (CF) is one of a developing number of human maladies brought about by acquired transformations that upset protein collapsing. It is brought about by brokenness of the Cystic Fibrosis Transmembrane conductance Regulator (CFTR), a cAMP-directed particle divert that dwells in the apical layer of epithelial cells (Riordan, 2008; Lubamba et al., 2012). CFTR brokenness can happen by absconds in protein combination, collapsing, intracellular dealing, channel gating, chloride conductance, or plasma layer steadiness. For each situation, loss of CFTR brings about variations from the norm of water, chloride, and additionally bicarbonate transport that lead to brokenness of target tissues including: pancreatic deficiency, expanded perspiration chloride, intestinal hindrance, and in particular, incessant aspiratory disease, aggravation, and at last passing because of respiratory disappointment (Cohen and Prince, 2012; Ratjen and McColley, 2012). The most predominant CFTR transformation, Phe508del (ΔF508), is found in ∼90% of CF patients (Riordan et al., 1989) where it hinders CFTR collapsing, restrains channel gating, and diminishes plasma film dependability (Lukacs and Verkman, 2012). The systems by which ΔF508 disturbs CFTR collapsing are starting to be comprehended, and little particle modulators that reestablish endoplasmic reticulum (ER) dealing and channel gating hold incredible guarantee for new medicines to address these hidden sub-atomic anomalies in CF patients.

Cystic fibrosis transmembrane conductance controller is a 1480 amino corrosive polytopic glycoprotein in the ABC transporter family (ABCC7) that contains two six-spreading over transmembrane (TM) spaces (TMD1 and TMD2) that structure the channel pore, two cytosolic nucleotide restricting areas (NBD1 and NBD2) that drive channel gating, and a characteristically unstructured administrative (R) area that controls channel action through PKA-interceded phosphorylation (Figure ​(Figure1A).1A). CFTR union has been evaluated to take 9–10 min in eukaryotic cells (Ward and Kopito, 1994), recommending that huge collapsing happens cotranslationally. Like most polytopic film proteins, CFTR biogenesis happens at the ER, and requires composed collapsing of individual areas in three unmistakable cell compartments: the ER layer, the ER lumen, and the cytosol. This compartmentalization happens as the early chain rises up out of the ribosome. Consequent gathering of TMDs and NBDs into the last collapsed structure takes ∼30–120 min and is encouraged by a huge associate of cytosolic and lumenal chaperones including Hsp70, Hsp40, Hsp90, calnexin, and others (Amaral, 2004; Skach, 2006; Wang et al., 2006). On the off chance that CFTR neglects to accomplish its local overlap, chaperones, for example, Hsp70 likewise act to enroll E3 (or potentially E4) ubiquitin-ligases that ubiquitinate CFTR and focus on the freak protein for debasement by the 26S proteasome. In this way, CFTR collapsing is continually observed by cell quality control apparatus all through its biogenesis.