Provincial Needs Assessment to Determine the Current State of Glomerulonephritis Care in Ontario.

BACKGROUND: Despite its relative rarity, glomerulonephritis (GN) accounts for 20% of prevalent end-stage renal disease patients in Ontario. Early identification and appropriate management of GN to delay progression of disease can reduce patient morbidity and health system costs. As such, a provincial GN needs assessment was conducted to inform on the development of the provincial GN strategic framework in Ontario. OBJECTIVE: To understand the current state of GN care in Ontario from nephrologist, hospital administrator, and patient and family perspectives. DESIGN: Cross-sectional. SETTINGS: 26 regional renal programs in Ontario. PATIENTS: 23 patients and family members living with GN who do not require renal replacement therapy. MEASUREMENTS: Patient and family member interviews as well as a survey of nephrologists. METHODS: The study included 3 components: (1) interviews with patients and family members, (2) a survey of nephrologists, and (3) interviews with regional renal programs. The Ontario Renal Network provincial office developed the needs assessment questions and the physician survey questions after consultation with practicing nephrologists and hospital administrators. Thematic analysis was used to assess interview data and descriptive statistics to assess survey data. RESULTS: Interviews with patients and family members (n = 23) identified gaps in care related to diagnosis and referral to nephrology care, education and decision-making, and psychosocial supports. The survey of nephrologists (n = 74) identified various issues that contribute to unstandardized GN care across Ontario, including a lack of provincial expertise in providing complex GN care, access to medication, multidisciplinary team support as well as patient education, and psychosocial supports. Interviews with regional renal programs aligned with interview and survey findings (n = 11). LIMITATIONS: Interviews with patients and family members were facilitated by 1 interviewer and limited to 20 interviews due to resource limitations. All nephrologists, patients, and family members who participated in the survey and interviews were volunteers and English-speaking, which may have resulted in self-selection bias. CONCLUSIONS: The provincial GN needs assessment emphasized the necessity to develop and implement a provincial GN strategy. The strategic framework includes 4 objectives: (1) ensure patients are supported to make informed decisions, (2) establish a provincial model of care, (3) leverage data to enable planning, decision-making, and monitoring of outcomes, and (4) ensure appropriate access to medication. This is the first Ontario strategy to address provincial gaps in GN care.

CONTEXTE: Malgré sa relative rareté, les glomérulonéphrites (GN) représentent 20 % des cas prévalents d'insuffisance rénale terminale en Ontario. Un diagnostic précoce et une prise en charge adéquate des GN pourraient réduire la morbidité pour les patients et les coûts pour le système de santé. Une analyse des besoins provinciaux (Ontario) en matière de soins des GN a été réalisée pour guider l'élaboration d'un cadre stratégique de gestion de la maladie. OBJECTIF: Connaître l'état actuel des soins en contexte de GN, en Ontario, du point de vue des néphrologues, des directions d'établissements, des patients et de leurs proches. TYPE D'ÉTUDE: Étude transversale. CADRE: 26 programmes régionaux de lutte contre la maladie rénale en Ontario. SUJETS: Un total de 23 individus, soit des patients atteints de GN, mais ne nécessitant pas de thérapie de remplacement rénal, et des membres de leur entourage. MESURES: Des interviews de patients et de membres de leur entourage, ainsi qu'un sondage auprès de néphrologues. MÉTHODOLOGIE: L'étude comportait trois volets: (1) interview des patients et de leur entourage; (2) sondage auprès des néphrologues; (3) entretiens avec les responsables des programmes régionaux de lutte contre la maladie rénale. Le Réseau rénal de l'Ontario a mis au point les questions du sondage et les questions relatives à l'évaluation des besoins après avoir consulté des néphrologues en pratique et des administrateurs d'hôpitaux. Les données recueillies ont été traitées par analyses thématiques (interviews) et par statistiques descriptives (sondage). RÉSULTATS: L'interview des patients et de leur entourage (n = 23) a mis en évidence des lacunes dans les procédures liées au diagnostic et à l'aiguillage en néphrologie, de même que concernant l'éducation des patients, la prise de décisions et le soutien psychosocial. Le sondage des néphrologues (n = 74) a permis de déceler diverses lacunes contribuant à une prestation de soins non normalisée en Ontario, notamment vis-à-vis l'expertise provinciale dans la prestation de soins complexes en GN, l'accès aux médicaments, le soutien d'une équipe multidisciplinaire, l'éducation et le soutien psychosocial des patients. Les entretiens avec les responsables des programmes régionaux de lutte contre la maladie rénale (n = 11) concordaient avec les résultats des deux autres volets. LIMITES: Les interviews avec les patients et leur entourage ont été effectuées par une seule personne et restreintes à une vingtaine en raison de ressources limitées. Les néphrologues, patients et membres de leur entourage étaient tous anglophones et ont participé à l'étude sur une base volontaire, ce qui pourrait introduire un biais d'auto-sélection. CONCLUSION: L'évaluation des besoins provinciaux en matière de soins pour les GN a mis en lumière la nécessité d'élaborer et de mettre en œuvre une stratégie provinciale. Le cadre stratégique comprend quatre objectifs: (1) garantir aux patients le soutien nécessaire pour prendre des décisions éclairées, (2) établir un modèle de soins provincial, (3) exploiter les données pour permettre la planification, la prise de décision et le suivi des résultats, et (4) assurer un accès adéquat aux médicaments. Il s'agit de la première stratégie visant à combler les lacunes provinciales en matière de soins pour les GN en Ontario.

Conformational defects underlie proteasomal degradation of Dent's disease-causing mutants of ClC-5.

Mutations in the CLCN5 (chloride channel, voltage-sensitive 5) gene cause Dent's disease because they reduce the functional expression of the ClC-5 chloride/proton transporter in the recycling endosomes of proximal tubule epithelial cells. The majority (60%) of these disease-causing mutations in ClC-5 are misprocessed and retained in the ER (endoplasmic reticulum). Importantly, the structural basis for misprocessing and the cellular destiny of such ClC-5 mutants have yet to be defined. A ClC-5 monomer comprises a short N-terminal region, an extensive membrane domain and a large C-terminal domain. The recent crystal structure of a eukaryotic ClC (chloride channel) transporter revealed the intimate interaction between the membrane domain and the C-terminal region. Therefore we hypothesized that intramolecular interactions may be perturbed in certain mutants. In the present study we examined two misprocessed mutants: C221R located in the membrane domain and R718X, which truncates the C-terminal domain. Both mutants exhibited enhanced protease susceptibility relative to the normal protein in limited proteolysis studies, providing direct evidence that they are misfolded. Interestingly, the membrane-localized mutation C221R led to enhanced protease susceptibility of the cytosolic N-terminal region, and the C-terminal truncation mutation R718X led to enhanced protease susceptibility of both the cytosolic C-terminal and the membrane domain. Together, these studies support the idea that certain misprocessing mutations alter intramolecular interactions within the full-length ClC-5 protein. Further, we found that these misfolded mutants are polyubiquitinated and targeted for proteasomal degradation in the OK (opossum kidney) renal epithelial cells, thereby ensuring that they do not elicit the unfolded protein response.

ATP induces conformational changes in the carboxyl-terminal region of ClC-5.

ATP binding enhances the activity of ClC-5, the transporter mutated in Dent disease, a disease affecting the renal proximal tubule. Previously, the ATP binding site was revealed in x-ray crystal structures of the cytoplasmic region of this membrane protein. Disruption of this site by mutagenesis (Y617A-ClC-5) reduced the functional expression and ATP-dependent regulation of the full-length transporter in Xenopus oocytes. However, insight into the conformational changes underlying ATP-dependent regulation is lacking. Here, we show that ATP binding induces a change in protein conformation. Specifically, small angle x-ray scattering experiments indicate that ATP binding promotes a clamp-like closure of the isolated ClC-5 carboxyl-terminal region. Limited proteolysis studies show that ATP binding induces conformational compaction of the carboxyl-terminal region in the intact membrane protein as well. In the context of fibroblasts and proximal tubule epithelial cells, disruption of the ATP binding site in full-length ClC-5 (Y617A-ClC-5) led to a defect in processing and trafficking out of the endoplasmic reticulum. These latter findings account for the decrease in functional expression previously reported for this ATP-binding mutant and prompt future study of a model whereby conformational compaction caused by ATP binding promotes biosynthetic maturation.

ClC transporters: discoveries and challenges in defining the mechanisms underlying function and regulation of ClC-5.

The involvement of several members of the chloride channel (ClC) family of membrane proteins in human disease highlights the need to define the mechanisms underlying their function and the consequences of disease-causing mutations. Despite the utility of high-resolution structural models, our understanding of the molecular basis for function of the chloride channels and transporters in the family remains incomplete. In this review, we focus on recent discoveries regarding molecular mechanisms underlying the regulated chloride:proton antiporter activity of ClC-5, the protein mutated in the Dent's disease-a kidney disease presenting with proteinuria and renal failure in severe cases. We discuss the putative role of ClC-5 in receptor-mediated endocytosis and protein uptake by the proximal renal tubule and the possible molecular and cellular consequences of disease-causing mutations. However, validation of these models will require future study of the intrinsic function of this transporter, in situ, in the membranes of recycling endosomes in proximal tubule epithelial cells.