To understand the effects that Cystic Fibrosis has, it is important to discuss CFTR synthesis and trafficking. Mutations in the CFTR results in protein misfolding, causing a defect in cellular processing and trafficking that targets the protein for degradation and reduces the quantity of CFTR at the cell surface [56]. In order for the CFTR to function correctly, then it must be synthesized, folded, and transported to the apical membrane of the cell without problem. The CFTR passes through quality control systems to get rid of misfolded proteins that would not function properly or that could become damaged [16]. It is apparent that only 33% of CFTR folds correctly and is allowed to leave the endoplasmic reticulum [8]. The nucleus is the site …show more content…
Chaperones are proteins that ensure the correct folding of the CFTR within the endoplasmic reticulum. Hsp70 is an important cytosolic chaperone that complexes with CFTR and reduces aggregation [5]. The CFTR passes through the endoplasmic reticulum-associated degradation (ERAD) after folding in the ER. This quality control system involves the ubiquitin proteasome system (UPS) for which CFTR is a substrate [16]. If a protein is molded and targeted for degradation, then ubiquitin will covalently attach to lysine residues on the CFTR. Three enzymes are required for the process of ubiquitylation: E1 ubiquitin activating enzymes, E2 ubiquitin conjugating enzymes, and E3 ubiquitin protein ligases. E1 enzymes are activated through hydrolysis of ATP, which creates an activated ubiquitin that is transferred to an E2 active site. The activated ubiquitin is then covalently bound to a lysine on the protein by an E3 ligase. A polyubiquitin chain is then formed as ubiquitin molecules link together, and if there are four or more then the misfolded CFTR chain is removed form the ER membrane and targeted for degradation by the 26S proteasome …show more content…
One system detects defects in the cytosolic parts of the CFTR while the other detects defects within the endoplasmic reticulum membrane. It is apparent that ubiquitylating proteins work with specific factors in order to detect misfolding. For example, Hsp70 detects mutations in the cytosolic regions of the CFTR. It is suspected that Hsp70 keeps the CFTR soluble until the E3 ligase CHIP binds with it. The complex that forms between these two redirects the CFTR to the degradation pathway. Derlin-1 is involved with detecting defects in the endoplasmic reticulum membrane and is involved in the retro-translocation of CFTR from the endoplasmic reticulum so that it can be send to the proteasome for degradation [20]. If the CFTR protein is folded correctly within the endoplasmic reticulum, then it is sent to the Golgi apparatus. The coat protein complex II (COPII), which is found within the ER membrane, helps to maintain the correct CFTR structure and location, conformation, and protein-protein interactions as this occurs. Final processing for the CFTR is carried out within the Golgi, as the CFTR replaces a mannose-enriched side chain with a mature complex oligosaccharide side chain. After this is completed, the CFTR is moved to the apical membrane where it has a half-life of 12 to 24 hours. If a CFTR is functioning poorly within the membrane, then it can be recognized by Hsc70 and then
The abnormality in the CFTR gene alters the CFTR protein in people with cystic fibrosis. As a result, one hallmark of CF is the presence of a thick mucus secretion which clogs the bronchial tubes in the lungs and plugs the exit passages from pancreas and intestines, leading to loss of function of these organs.
protein and it deletes a small amount of DNA from the CFTR gene. I am going to explain what
CF happens because two parents have a defect in the CF transmembrane conductor regulator (CFTR) gene. If a child has only one parent that has a
Since we have already known the amino sequence of the protein in previous step, we can narrow down the targeting ubiquitin ligase based on existing research data such as papers, NCBI data.
The Cystic Fibrosis Foundation [CFF] (2010) states the 1400 CFTR gene mutations are classified into 6 groups
CF is caused by a mutation in the cystic fibrosis transmembrane conductance regulator (CTFR) gene, which encodes a chloride ion channel that regulates osmotic balance across the epithelium through the transport of sodium ions and water4. Mutations
Cystic fibrosis (CF) is an inherited disease that affects the lungs and digestive system (National Heart, Blood, and Lung Institute, 2013). CF is caused by mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene located on chromosome 7q31 (Beery & Workman, 2012, p. 192). More than 1600 different mutations in this gene have been identified, but 70% of cystic fibrosis patients have the amino acid ΔF508 defect. This mutation occurs when the CFTR protein is missing three nucleotides at position 508 which codes for the amino acid phenylalanine essential to nutrition (Scott, 2013, p. 493).
Cystic Fibrosis is a genetic disease that causes the body’s lungs to generate a different type of mucus than a non-infected body would. The contaminated lungs will produce mucus that is thick and adhesive which clogs the lungs and leads to an unpleasant and abhorrent lung infection. CF also interferes with the pancreas, disallowing the digestive enzymes from breaking down and absorbing food in the intestine. This can result in low nutrition, feeble growth, excessive sweat production, difficulties in breathing, and sometimes lung disease. When producing extra sweat and mucus, the body loses salt. If too much salt is lost, it can cause abnormal heart rhythms, disturbance of minerals in the blood, and perhaps, shock.
Cystic Fibrosis (CF) is an autosomal recessive gene that causes a wide range of symptoms because there are over 1,000 changes or mutations that can occur within the cystic fibrosis transmembrane receptor (CFTR) protein. The CFTR protein is generally a chloride ion chain “regulated by cyclic adenosine monophosphate and therefore can act as a regulator of other electrolyte channels”(Grossman, S., & Grossman, L. 2005, p. 46). Typically this protein allows chloride ions to exit mucus-producing cells allowing water to flow in and thin the mucus. However, if the CFTR protein has been mutated, such as in cystic fibrosis, chloride ions cannot exit. This causes the mucus to thicken, become sticky, and obstruct the various channels it passes through. This build up of mucus also prevents bacteria from being cleaned from cells thoroughly increasing the patients risk for infections (Grossman, S., & Grossman, L. 2005). However, the severity of CF depends on whether the patients have complete or partial loss of the CFTR gene. If the person has the classic form of CF abnormalities of CFTR will commonly affect “…the respiratory, gastrointestinal, endocrine and metabolic, and genitourinary systems”(Schram, C. 2012). However, if people have atypical forms of CF their genetic disorder may only affect one of the organ systems and may not be found until the patient develops symptoms in their late childhood, early adolescence, or adulthood
In 1989, the CFTR gene was discovered. (Discovery) This gene carries the instructions for the CFTR protein, which sits on the cell surface transporting chloride ions across the cell wall. When the CFTR gene is mutated, the CFTR protein is made incorrectly, and it is unable to exchange chloride ions. The high chlorine concentration inside of the cell is not optimal for normal cell function, so the lung cells naturally begin to pull in water from the mucus to dilute the thick chlorine concentration inside the cells. The result is thick, sticky mucus on the outside of the cells that mats down the cilia in lung airways. Clearing the throat and absorbing nutrients thus becomes extremely difficult and the symptoms of CF arise. (May)
The protein of the cystic fibrosis gene is called the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR). The gene is located on 7q31.2 long arm of chromosome 7 at position 31.2. The CF gene also has 27 exons and is made up of 250,000 DNA nucleotides. CFTR moves chloride ions out of cells which is very important for salt and water balances on the epithelial cells.
Cystic Fibrosis is caused by a genetic defect in Chromosome 7. Chromosome 7 encodes the cystic fibrosis transmembrane conductance regulator, also known as CFTR. There are over 1,000 mutations of this gene causing cystic fibrosis, with each mutation manifesting as a different variation of disease onset and clinical presentation. The most common mutation is the loss of phenylalanine residue at deltaF508. The abnormal functioning CFTR causes impaired chloride transport and more viscous secretions. The defect causes dehydrated secretions in the respiratory tract and gastrointestinal tract. Being dehydrated, these secretions become more difficult to move throughout the body. Along with impaired
Cystic Fibrosis is a disorder where the exocrine glands secrete abnormally thick mucus, leading to obstruction of the pancreas and chronic infections of the lungs, which usually cause death in childhood or early adulthood. Some mildly affected patients may survive longer. Doctors can diagnose the disease by testing the patients perspiration because people with Cystic Fibrosis have high amounts of salt in their perspiration. Those with respiratory infections are treated with antibiotics, with aerosols that relieve constriction of the airways and liquefy the thick mucus, and by physical therapy to help patients cough up the obstructing secretions. Patients with pancreatic insufficiency can take pancreatic enzymes with meals.
Molecular chaperones stabilize unfolded or misfolded proteins until native conformations have been obtained to promote cell survival during and after stress conditions. They do not change or add to the folding principles encoded by a protein because polypeptide chains inherently carry within them all the information that is necessary for achieving the native state of a protein. Instead, they optimize the folding process by stabilizing folding intermediates and are involved in every aspect of proteome maintenance including de novo folding, refolding of stress-induced misfolded proteins, and targeting proteins for degradation (Hartl 2009, Hartl 2011). Chaperones, many of which are induced or upregulated only during stress conditions, work in cooperative networks when protein-aggregate concentration
The fluorescence of RepA70-YFP increased as more RepA70-CFP was produced (Fig. 3C), and this indicated that ClpAP protease could be overloaded and a proteolytic-queue forms similar to what was observed with the LAA tagged proteins targeted to ClpXP8. We also tested two other tags, MarA and MarAn20 (20 amino acids from the N-terminal of MarA), which target proteins to be degraded by the Lon protease. The Lon protease was weakly overloaded by MarA tagged proteins but was overloaded more by MarAn20 tagged proteins (Fig. 3C-D). This made us wonder if Lon could be overloaded when both MarA and MarAn20 were co-produced. Indeed, this was the case (Fig. 3E).