CSN5 binds to misfolded CFTR and promotes its degradation

AbstractCystic fibrosis is mainly caused by mutations that interfere with the biosynthetic folding of the cystic fibrosis transmembrane conductance regulator (CFTR) protein. The aim of this study was to find cellular proteins interacting with CFTR and regulating its processing. We have used a genetic screen in yeast to identify such proteins and identified CSN5 that interacted with the third cytoplasmic loop of CFTR. CSN5 is the 5th component of the COP9 signalosome, a complex of eight subunits that shares significant homologies to the lid subcomplex of the 26S proteasome and controls the stability of many proteins. The present study shows that CSN5 associates with the core-glycosylated form of CFTR and suggests that this association targets misfolded CFTR to the degradative pathway. Identifying CSN5 as a new component of the degradative pathway is an important step towards the goal of unraveling the sorting between misfolded and correctly folded CFTR proteins

COMMD1-Mediated Ubiquitination Regulates CFTR Trafficking

The CFTR (cystic fibrosis transmembrane conductance regulator) protein is a large polytopic protein whose biogenesis is inefficient. To better understand the regulation of CFTR processing and trafficking, we conducted a genetic screen that identified COMMD1 as a new CFTR partner. COMMD1 is a protein associated with multiple cellular pathways, including the regulation of hepatic copper excretion, sodium uptake through interaction with ENaC (epithelial sodium channel) and NF-kappaB signaling. In this study, we show that COMMD1 interacts with CFTR in cells expressing both proteins endogenously. This interaction promotes CFTR cell surface expression as assessed by biotinylation experiments in heterologously expressing cells through regulation of CFTR ubiquitination. In summary, our data demonstrate that CFTR is protected from ubiquitination by COMMD1, which sustains CFTR expression at the plasma membrane. Thus, increasing COMMD1 expression may provide an approach to simultaneously inhibit ENaC absorption and enhance CFTR trafficking, two major issues in cystic fibrosis

COMMD1-Mediated Ubiquitination Regulates CFTR Trafficking

The CFTR (cystic fibrosis transmembrane conductance regulator) protein is a large polytopic protein whose biogenesis is inefficient. To better understand the regulation of CFTR processing and trafficking, we conducted a genetic screen that identified COMMD1 as a new CFTR partner. COMMD1 is a protein associated with multiple cellular pathways, including the regulation of hepatic copper excretion, sodium uptake through interaction with ENaC (epithelial sodium channel) and NF-kappaB signaling. In this study, we show that COMMD1 interacts with CFTR in cells expressing both proteins endogenously. This interaction promotes CFTR cell surface expression as assessed by biotinylation experiments in heterologously expressing cells through regulation of CFTR ubiquitination. In summary, our data demonstrate that CFTR is protected from ubiquitination by COMMD1, which sustains CFTR expression at the plasma membrane. Thus, increasing COMMD1 expression may provide an approach to simultaneously inhibit ENaC absorption and enhance CFTR trafficking, two major issues in cystic fibrosis

COMMD1 promotes CFTR trafficking through inhibition of ubiquitination

La mucoviscidose (CF, Cystic Fibrosis) est la maladie génétique la plus fréquente dans les populations d’origine caucasienne. Les malades présentent une symptomatologie variée, dominée par une bronchopneumopathie chronique obstructive due à des sécrétions de mucus abondantes et anormalement épaisses et une réponse inflammatoire chronique excessive. La mucoviscidose résulte de mutations dans le gène codant la protéine CFTR (Cystic Fibrosis Transmembrane conductance Regulator), dont la plus fréquente est la délétion d’une phénylalanine en position 508 (F508del) qui est à l’origine d’un adressage défectueux et d’une fonction altérée de la protéine. Afin d’identifier différents partenaires moléculaires de CFTR qui participent à son processus de maturation, à son trafic à la membrane plasmique ou à sa fonction, un criblage double hybride de levure a été effectué en utilisant la troisième boucle intra-cytoplasmique de CFTR (ICL3) comme appât. A l’issue de ce criblage, 14 clones indépendants ont pu être identifiés dont la protéine COMMD1 qui a initialement été décrite comme un régulateur de l’homéostasie du cuivre, de l’absorption sodique et de la voie de signalisation NF-?B. L’objectif principal de ce travail a été de déterminer quel pouvait être l’impact de la protéine COMMD1 sur la maturation et le trafic intracellulaire de CFTR afin de déterminer le rôle de cette protéine dans la physiopathologie de la mucoviscidose. Nous avons montré que la protéine COMMD1 est un nouveau partenaire cytoplasmique du canal CFTR, qui régule le trafic intracellulaire de ce canal par inhibition de l’ubiquitinylation probablement au niveau des endosomes d’endocytose et de recyclage. Notre étude permet de proposer une nouvelle voie de trafic de CFTR via un modèle d’ubiquitinylation régulé par COMMD1. Au cours de cette étude, nous avons également identifié le récepteur 1 de la transferrine (TFR1) comme un nouveau partenaire de COMMD1 dont le mécanisme de régulation semble similaire à celui proposé pour CFTR. Dans un second temps, nous nous sommes intéressés aux propriétés inhibitrices de COMMD1 dans la réaction inflammatoire. COMMD1 a été décrit comme le prototype d’une nouvelle famille de protéines jouant un rôle dans l’inhibition de la voie de signalisation NF-kB. Nous avons observé que la distribution subcellulaire de COMMD1 est différente dans les cellules CF et non-CF. Nous avons mis en évidence que la surexpression de COMMD1 dans les cellules épithéliales bronchiques CF, qui présentent une inflammation excessive, pouvait restaurer un niveau d’inflammation comparable aux cellules non-CF. COMMD1 est impliquée dans plusieurs processus cellulaires altérés dans la physiopathologie de la mucoviscidose, affectant le trafic du canal CFTR, l’absorption de sodium et la réponse inflammatoire. Comprendre comment moduler d’une part le processus d’absorption/sécrétion des ions par le trafic de canaux ioniques et d’autre part, l’inflammation des cellules CF par rapport aux non-CF, devrait permettre d’identifier de nouvelles pistes thérapeutiques. Ces traitements permettraient à la fois de réduire la réaction inflammatoire exacerbée, sans nuire à l’activité essentielle de défense contre les pathogènes, et d’améliorer la sécrétion de fluide chez les patients atteints de mucoviscidoseCystic fibrosis is mainly caused by mutations interfering with the biosynthetic folding of the CFTR protein. The aim of this study was to find proteins able to interact with CFTR and modify its processing. We have identified COMMD1 as a new CFTR partner. COMMD1 is a regulator of copper homeostasis and sodium uptake through interaction with ENaC, as well as the prototype of a new protein family that plays a role in inhibiting NF-?B signalling Co-immunoprecipitation experiments showed that COMMD1 associates with endogenous CFTR in HT29 cells and with F508del-CFTR in heterologously expressing epithelial cells. COMMD1 sub-cellular distribution is both nuclear and cytoplasmic, and more precisely in vesicular cytoplasmic compartments, as assessed by immunocytochemical microscopy. Further studies showed COMMD1 partial codistribution with an early endosomal compartments (TfR). COMMD1 is not involved in CFTR processing (C band) but wt-CFTR cell surface expression was halfreduced when COMMD1 expression was silenced. Unlike F508del-CFTR in temperature rescue, COMMD1 over-expression increased 15% wt-CFTR cell surface expression. Assessment of CFTR ubiquitination showed that COMMD1 over-expression strongly decreased CFTR ubiquitination therefore increasing CFTR cell surface expression. Finally, these data indicate that COMMD1 vesicular compartment is involved in CFTR trafficking through inhibition of CFTR ubiquitination. Understanding how COMMD1 modulation modifies transepithelial transport and inflammation in CF versus non CF cells should give new therapeutic clues to reduce exacerbated inflammation and improve fluid secretion in CF patient

In vitro gamete differentiation from pluripotent stem cells as a promising therapy for infertility

[i]In vitro[/i] gamete differentiation from pluripotent stem cells as a promising therapy for infertilit

Prenatal Diagnosis of a 2.5 Mb De Novo 17q24.1q24.2 Deletion Encompassing KPNA2 and PSMD12 Genes in a Fetus with Craniofacial Dysmorphism, Equinovarus Feet, and Syndactyly

Interstitial 17q24.1 or 17q24.2 deletions were reported after conventional cytogenetic analysis or chromosomal microarray analysis in patients presenting intellectual disability, facial dysmorphism, and/or malformations. We report on a fetus with craniofacial dysmorphism, talipes equinovarus, and syndactyly associated with a de novo 2.5 Mb 17q24.1q24.2 deletion. Among the deleted genes, KPNA2 and PSMD12 are discussed for the correlation with the fetal phenotype. This is the first case of prenatal diagnosis of 17q24.1q24.2 deletion

Two new cases of interstitial 7q35q36.1 deletion including CNTNAP2 and KMT2C

International audienceBackground: Terminal deletions of the long arm of chromosome 7 are well known and frequently associated with syndromic holoprosencephaly due to the involvement of the SHH (aliases HHG1, SMMCI, TPT, TPTPS, and MCOPCB5) gene region. However, interstitial deletions including CNTNAP2 (aliases Caspr2, KIAA0868, and NRXN4) and excluding the SHH region are less common.Methods: We report the clinical and molecular characterization associated with pure 7q35 and 7q35q36.1 deletion in two unrelated patients as detected by oligonucleotide-based array-CGH analysis.Results: The common clinical features were abnormal maternal serum screening during first-trimester pregnancy, low occipitofrontal circumference at birth, hypotonia, abnormal feet, developmental delay, impaired language development, generalized seizures, hyperactive behavior, friendly personality, and cranio-facial dysmorphism. Both deletions occurred de novo and sequencing of CNTNAP2, a candidate gene for epilepsy and autism showed absence of mutation on the contralateral allele.Conclusion: Combined haploinsufficiency of GALNTL5 (alias GalNAc-T5L), CUL1, SSPO (aliases SCO-spondin, KIAA0543, and FLJ36112), AOC1 (alias DAO), RHEB, and especially KMT2C (alias KIAA1506 and HALR) with monoallelic disruption of CNTNAP2 may explain neurologic abnormalities, hypotonia, and exostoses. Haploinsufficiency of PRKAG2 (aliases AAKG, AAKG2, H91620p, WPWS, and CMH6) and KCNH2 (aliases Kv11.1, HERG, and erg1) genes may be responsible of long QT syndrome observed for one patient

COMMD1 regulates CFTR ubiquitination through an ICL3 motif.

<p>(A) HeLa cells were transfected with CFTR constructs (wt, K946R, K951R or K978R-CFTR) and Myc-COMMD1 or empty vector as control (mock). The same quantities of lysates were immunoprecipitated with anti-CFTR mAb (MAB25031). Representative gels for the same experiment where each immunoprecipitation sample was then split in half and loaded onto two 8% SDS-PAGEs for CFTR detection and ubiquitin detection. Both gels were transferred to PVDF membrane and subjected to immunoblotting (IB). Lysates were loaded onto an 11% SDS-PAGE and sequential probing of the membrane was performed (COMMD1, α-tubulin and lastly ubiquitin). Filled and empty arrowheads indicate the fully- (170 kDa) and core-glycosylated (140 kDa) CFTR, respectively. (B) Quantification of ubiquitinated CFTR. Ratio of ubiquitinated CFTR to total CFTR in cells transfected with Myc-COMMD1 compared to the same ratio in mock-transfected cells was reported as 100% for each independent experiment. The means ± S.D. were obtained from five to three independent experiments.* P<0.05 is determined by t-test. (C) Representative gels for the same co-immunoprecipitation experiment between COMMD1 and wt, K946R, K951R or K978R-CFTR in heterologous system. HeLa cells were co-transfected with Myc-COMMD1 or empty vector (mock) and wt, K946R, K951R or K978R-CFTR. Lysates from all these experiments were subjected to SDS-PAGE after CFTR IP. The 8% SDS-PAGE membrane was probed with anti-CFTR mAb and the 11% SDS-PAGE membrane with anti-c-Myc mAb. Both membranes were probed with anti-α-tubulin as control (11% gel is shown). (D) Proposed model of COMMD1 interaction through its COMM domain with the N-terminal end of ICL3 to modulate CFTR ubiquitination.</p

COMMD1 regulates CFTR ubiquitination.

<p>(A) Representative gels for the same CFTR IP experiment with MAB25031 from HeLa cells stably expressing wt-CFTR and separated on 8% SDS-PAGE transferred to PVDF membrane. Half of the membrane was probed with anti-CFTR mAb and the other half with anti-ubiquitin mAb. Lysates were loaded onto an 11% SDS-PAGE and sequential probing of the membrane was performed (COMMD1, α-tubulin and lastly ubiquitin). Filled and empty arrowheads indicate the fully- (170 kDa) and core-glycosylated (140 kDa) CFTR, respectively. (B) Quantification of ubiquitinated CFTR. Ratio of ubiquitinated CFTR to total CFTR in each condition is shown, endogenous COMMD1 expression is referred as 100%. The means ± S.D. were obtained from five independent experiments.* P<0.05 was determined by t-test. (C) Stability of the mature wt-CFTR was determined upon inhibition of protein biosynthesis with cycloheximide (CHX). Cells were incubated in the presence of cycloheximide for the indicated time intervals. (D) Quantification of mature CFTR was normalized to α-tubulin level.</p

COMMD1 and CFTR interact in mammalian cells.

<p>(A) Sequences of ICL3 in other species from fish to primates. Asterisks indicate the position of two class II mutations: S945L and D979A. Identity of amino acids between the different proteins are boxed in black, conserved residues are boxed in dark gray and semi-conserved substitutions in light gray. (B) Representative gels for the same co-immunoprecipitation experiments in HT-29 cells expressing endogenous CFTR and COMMD1. Lysates from HT-29 cells were immunoprecipitated (IP) with either 0.8 µg of anti-COMMD1 mAb (Abnova), 0.8 µg of anti-CFTR mAb (MAB25031, R&D Systems) or with 0.8 µg anti-mouse IgG as a control. Each immunoprecipitation sample was then split in half and loaded onto an 8% SDS-PAGE for CFTR detection and 11% SDS-PAGE for COMMD1 detection. Both gels were transferred to PVDF membrane and subjected to immunoblotting (IB). The 8% SDS-PAGE membrane was probed with anti-CFTR mAb (MM13-4) and the 11% SDS-PAGE membrane with a rabbit anti-COMMD1 pAb (Proteintech Group). Both membranes were probed with anti-α-tubulin as control (11% gel is shown). Filled and empty arrowheads indicate the fully- (170 kDa) and core-glycosylated (140 kDa) CFTR, respectively. * indicates mouse IgG light chain from the antibody used for immunoprecipitation. (C) COMMD1 constructions in pcDNA3.1/Topo plasmid. Two COMMD1 constructs were generated by adding a Myc-tag at the N-terminus of COMMD1: Myc-COMMD1 and a construct with a deletion of the COMM domain named Myc-COMMD1ΔCOMM. (D) Representative gels for the same co-immunoprecipitation experiment between COMMD1 and wt- in heterologous system. HeLa cells stably expressing wt- (spTCF-wt) or empty CFTR vector (spTracer) as control were transfected with Myc-COMMD1. spTCF-wt were transfected with Myc-COMMD1ΔCOMM. Lysates from all these experiments were subjected to SDS-PAGE, as in (B) after CFTR IP. The 8% SDS-PAGE membrane was probed with anti-CFTR mAb and the 11% SDS-PAGE membrane with anti-c-Myc mAb. Both membranes were probed with anti-α-tubulin as control (11% gel is shown).</p