Renal expression of parvalbumin is critical for NaCl handling and response to diuretics

Abstract

The distal convoluted tubule (DCT) plays an essential role in the reabsorption of NaCl by the kidney, a process that can be inhibited by thiazide diuretics. Parvalbumin (PV), a Ca 2؉ -binding protein that plays a role in muscle fibers and neurons, is selectively expressed in the DCT, where its role remains unknown. We therefore investigated the renal phenotype of PV knockout mice (Pvalb ؊/؊ ) vs. wild-type (Pvalb ؉/؉ ) littermates. PV colocalized with the thiazidesensitive Na ؉ -Cl ؊ cotransporter (NCC) in the early DCT. The Pvalb ؊/؊ mice showed increased diuresis and kaliuresis at baseline with higher aldosterone levels and lower lithium clearance. Acute furosemide administration increased diuresis and natriuresis/kaliuresis, but, surprisingly, did not increase calciuria in Pvalb ؊/؊ mice. NaCl supplementation of Pvalb ؊/؊ mice increased calciuria at baseline and after furosemide. The Pvalb ؊/؊ mice showed no significant diuretic response to hydrochlorothiazide, but an accentuated hypocalciuria. A decreased expression of NCC was detected in the early DCT of Pvalb ؊/؊ kidneys in the absence of ultrastructural and apoptotic changes. The PV-deficient mice had a positive Ca 2؉ balance and increased bone mineral density. Studies in mouse DCT cells showed that endogenous NCC expression is Ca 2؉ -dependent and can be modulated by the levels of PV expression. These results suggest that PV regulates the expression of NCC by modulating intracellular Ca 2؉ signaling in response to ATP in DCT cells. They also provide insights into the Ca 2؉ -sparing action of thiazides and the pathophysiology of distal tubulopathies.distal convoluted tubule ͉ kidney ͉ salt-losing nephropathy ͉ sodium-chloride cotransport P arvalbumin (PV) belongs to the superfamily of EF-hand Ca 2ϩ -binding proteins that play a role in multiple cellular processes, including gene transcription, ion transport, protein phosphorylation, and enzymatic activities (1). These proteins possess well conserved helix-loop-helix motifs that bind Ca 2ϩ ions with high affinity, leading to conformational changes. The conformational plasticity and the cell-specific expression of these Ca 2ϩ sensor or buffer proteins contribute to the versatility of Ca 2ϩ signaling (2). PV is a 109-aa cytosolic protein that contains a pair of functional EF-hand motifs forming a stable unit that binds two Ca 2ϩ ions (3). This Ca 2ϩ buffer is expressed in a restricted number of vertebrate tissues, including fast-contracting/relaxing skeletal muscle fibers and GABA neurons in the brain (4). The generation of PV knockout (Pvalb Ϫ/Ϫ ) mice confirmed the important role played by PV in muscle and brain (5). The fast muscles of Pvalb Ϫ/Ϫ mice exhibit a decreased relaxation rate of the twitch (5), suggesting that PV facilitates Ca 2ϩ diffusion from myofibrils to the sarcoplasmic reticulum (6). The lack of PV in the brain induces changes in short-term synaptic plasticity and modified network properties, resulting in increased susceptibility to epileptic seizures (7). Although no human disease is ass...

Parvalbumine et régulation du transport ionique dans le tube contourné distal du rein

“…Dans le rein, la parvalbumine est exclusivement exprimée dans la partie proximale du TCD, étroitement colocalisée avec NCC [8,9]. L'analyse phénotypique des souris Pvalb -/-a permis de mieux comprendre le rôle de la parvalbumine dans les mécanismes de transport opérant dans le TCD [9].…”

“…L'analyse phénotypique des souris Pvalb -/-a permis de mieux comprendre le rôle de la parvalbumine dans les mécanismes de transport opérant dans le TCD [9]. En effet, les souris Pvalb -/-présentent un phénotype associant perte sodique modérée, hyperaldostéronisme secondaire et kaliurie augmentée, diminution de la clairance du lithium endogène suggérant une réabsorption compensatrice de sodium au niveau du tube proximal, et une hypocalciurie associée à une densité osseuse majorée.…”

“…Ces travaux, menés sur une lignée dérivée du TCD de souris (mTCD) ont démontré que l'induction d'une diminution (knock-down) de l'expression de la parvalbumine par divers siARN se traduit par une diminution spécifique de l'expression endogène de NCC. Par ailleurs, à l'instar de son rôle de tampon calcique dans les cellules musculaires et neuronales, la parvalbumine est capable de moduler l'amplitude des courants calciques induits par les agonistes purinergiques (ATP et UTP) ainsi que le niveau d'expression de NCC dans les cellules mTCD [9]. Ces résultats sont conformes à des travaux antérieurs suggérant que le néphron distal répond à l'ATP via des récepteurs purinergiques qui inhibent le transport de sodium [10].…”

Protein Phosphatase 1 Inhibitor-1 Deficiency Reduces Phosphorylation of Renal NaCl Cotransporter and Causes Arterial Hypotension

“…WNK1 and WNK4 are serine/ threonine kinases that interact in a complex cascade with the STE20-related proline-alanine-rich kinase (SPAK) to regulate NCC phosphorylation (e.g., Thr44, Thr53, Thr58, and Ser71 in mouse NCC) and finally, activity. 8,[10][11][12] In addition to the WNK-SPAK pathway, several other proteins were identified to control NCC, including parvalbumin (PV), 13 serum and glucocorticoid-inducible kinase Sgk1, ubiquitin ligase Nedd4-2, [14][15][16] kelch-like 3 (KLHL3), 17,18 cullin 3, 17,18 and protein phosphatase (PP) 4. 19 Remarkably, several of the above listed regulatory proteins are highly abundant in the DCT (e.g., WNK4, KS-WNK1, SPAK, PV, and KLHL3).…”

The inositol Inpp5k 5-phosphatase affects osmoregulation through the vasopressin-aquaporin 2 pathway in the collecting system

“…Water handling at baseline and during various protocols was assessed in individual metabolic cages, after appropriate training, as described [1,5]. Plasma samples and 24-h urine collections were obtained at baseline, and urinary concentrating ability was tested after 24-h water deprivation.…”