Browsing by Author "Sousa, Marisa"
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- Folding and rescue of a cystic fibrosis transmembrane conductance regulator trafficking mutant identified using human-murine chimeric proteinsPublication . Da Paula, Ana Carina; Sousa, Marisa; Xu, Zhe; Dawson, Elizabeth S.; Boyd, A. Christopher; Sheppard, David N.; Amaral, Margarida D.Impairment of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl channel causes cystic fibrosis, a fatal genetic disease. Here, to gain insight into CFTR structure and function, we exploited interspecies differences between CFTR homologues using human (h)-murine (m) CFTR chimeras containing murine nucleotide-binding domains (NBDs) or regulatory domain on an hCFTR backbone. Among 15 hmCFTR chimeras analyzed, all but two were correctly processed, one containing part of mNBD1 and another containing part of mNBD2. Based on physicochemical distance analysis of divergent residues between human and murine CFTR in the two misprocessed hmCFTR chimeras, we generated point mutations for analysis of respective CFTR processing and functional properties. We identified one amino acid substitution (K584E-CFTR) that disrupts CFTR processing in NBD1. No single mutation was identified in NBD2 that disrupts protein processing. However, a number of NBD2 mutants altered channel function. Analysis of structural models of CFTR identified that although Lys584 interacts with residue Leu581 in human CFTR Glu584 interacts with Phe581 in mouse CFTR. Introduction of the murine residue (Phe581) in cis with K584E in human CFTR rescued the processing and trafficking defects of K584E-CFTR. Our data demonstrate that human-murine CFTR chimeras may be used to validate structural models of full-length CFTR. We also conclude that hmCFTR chimeras are a valuable tool to elucidate interactions between different domains of CFTR.
- HGF Stimulation of Rac1 Signaling Enhances Pharmacological Correction of the Most Prevalent Cystic Fibrosis Mutant F508del-CFTRPublication . Moniz, Sónia; Sousa, Marisa; Moraes, Bruno José; Mendes, Ana Isabel; Palma, Marta; Barreto, Celeste; Fragata, José I.; Amaral, Margarida D; Matos, PauloCystic fibrosis (CF), a major life-limiting genetic disease leading to severe respiratory symptoms, is caused by mutations in CF transmembrane conductance regulator (CFTR), a chloride (Cl(-)) channel expressed at the apical membrane of epithelial cells. Absence of functional CFTR from the surface of respiratory cells reduces mucociliary clearance, promoting airways obstruction, chronic infection, and ultimately lung failure. The most frequent mutation, F508del, causes the channel to misfold, triggering its premature degradation and preventing it from reaching the cell surface. Recently, novel small-molecule correctors rescuing plasma membrane localization of F508del-CFTR underwent clinical trials but with limited success. Plausibly, this may be due to the mutant intrinsic plasma membrane (PM) instability. Herein, we show that restoration of F508del-CFTR PM localization by correctors can be dramatically improved through a novel pathway involving stimulation of signaling by the endogenous small GTPase Rac1 via hepatocyte growth factor (HGF). We first show that CFTR anchors to apical actin cytoskeleton (via Ezrin) upon activation of Rac1 signaling through PIP5K and Arp2/3. We then found that such anchoring retains pharmacologically rescued F508del-CFTR at the cell surface, boosting functional restoration by correctors up to 30% of wild-type channel levels in human airway epithelial cells. Our findings reveal that surface anchoring and retention is a major target pathway for CF pharmacotherapy, namely, to achieve maximal restoration of F508del-CFTR in patients in combination with correctors. Moreover, this approach may also translate to other disorders caused by trafficking-deficient surface proteins.
- Measurements of CFTR-Mediated Cl- Secretion in Human Rectal Biopsies Constitute a Robust Biomarker for Cystic Fibrosis Diagnosis and PrognosisPublication . Sousa, Marisa; Servidoni, Maria F.; Vinagre, Adriana M.; Ramalho, Anabela S.; Bonadia, Luciana C.; Felício, Verónica; Ribeiro, Maria A..; Uliyakina, Inna; Marson A, Fernando; Kmit, Arthur; Cardoso, Silvia R.; Ribeiro, José D.; Bertuzzo, Carmen S.; Sousa, Lisete; Kunzelmann, Karl; Ribeiro, Antônio F.; Amaral, Margarida D.BACKGROUND: Cystic Fibrosis (CF) is caused by ∼1,900 mutations in the CF transmembrane conductance regulator (CFTR) gene encoding for a cAMP-regulated chloride (Cl(-)) channel expressed in several epithelia. Clinical features are dominated by respiratory symptoms, but there is variable organ involvement thus causing diagnostic dilemmas, especially for non-classic cases. METHODOLOGY/PRINCIPAL FINDINGS: To further establish measurement of CFTR function as a sensitive and robust biomarker for diagnosis and prognosis of CF, we herein assessed cholinergic and cAMP-CFTR-mediated Cl(-) secretion in 524 freshly excised rectal biopsies from 118 individuals, including patients with confirmed CF clinical diagnosis (n=51), individuals with clinical CF suspicion (n=49) and age-matched non-CF controls (n=18). Conclusive measurements were obtained for 96% of cases. Patients with "Classic CF", presenting earlier onset of symptoms, pancreatic insufficiency, severe lung disease and low Shwachman-Kulczycki scores were found to lack CFTR-mediated Cl(-) secretion (<5%). Individuals with milder CF disease presented residual CFTR-mediated Cl(-) secretion (10-57%) and non-CF controls show CFTR-mediated Cl(-) secretion ≥ 30-35% and data evidenced good correlations with various clinical parameters. Finally, comparison of these values with those in "CF suspicion" individuals allowed to confirm CF in 16/49 individuals (33%) and exclude it in 28/49 (57%). Statistical discriminant analyses showed that colonic measurements of CFTR-mediated Cl(-) secretion are the best discriminator among Classic/Non-Classic CF and non-CF groups. CONCLUSIONS/SIGNIFICANCE: Determination of CFTR-mediated Cl(-) secretion in rectal biopsies is demonstrated here to be a sensitive, reproducible and robust predictive biomarker for the diagnosis and prognosis of CF. The method also has very high potential for (pre-)clinical trials of CFTR-modulator therapies.
- The contribution of CK2 and spleen tyrosine kinase (SYK) to CFTR trafficking and PKA-induced activityPublication . Luz, Simão; Kongsuphol, Patthara; Mendes, Ana Isabel; Romeiras, Francisco; Sousa, Marisa; Schreiber, Rainer; Matos, Paulo; Jordan, Peter; Mehta, Anil; Amaral, Margarida D.; Kunzelmann, Karl; Farinha, Carlos M.Previously, the pleiotropic “master kinase” casein kinase 2 (CK2) was shown to interact with CFTR, the protein responsible for cystic fibrosis (CF). Moreover, CK2 inhibition abolished CFTR conductance in cell-attached membrane patches, native epithelial ducts, and Xenopus oocytes. CFTR possesses two CK2 phosphorylation sites (S422 and T1471), with unclear impact on its processing and trafficking. Here, we investigated the effects of mutating these CK2 sites on CFTR abundance, maturation, and degradation coupled to effects on ion channel activity and surface expression. We report that CK2 inhibition significantly decreased processing of wild-type (wt) CFTR, with no effect on F508del CFTR. Eliminating phosphorylation at S422 and T1471 revealed antagonistic roles in CFTR trafficking: S422 activation versus T1471 inhibition, as evidenced by a severe trafficking defect for the T1471D mutant. Notably, mutation of Y512, a consensus sequence for the spleen tyrosine kinase (SYK) possibly acting in a CK2 context adjacent to the common CF-causing defect F508del, had a strong effect on both maturation and CFTR currents, allowing the identification of this kinase as a novel regulator of CFTR. These results reinforce the importance of CK2 and the S422 and T1471 residues for regulation of CFTR and uncover a novel regulation of CFTR by SYK, a recognized controller of inflammation.