Biology subjects

Delpire, E.

Publications and source records attributed to Delpire, E..

5 recordsLinked to original sources

bioRxiv2026

Calmodulin mutation N54I causes autosomal dominant CPVT in mice

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is an inherited arrhythmia syndrome characterized by stress- or catecholamine-induced ventricular arrhythmias in the absence of overt structural heart disease. Mutations in RYR2 and CASQ2 account for most genetically defined cases, although pathogenic variants in the three genes encoding calmodulin (CALM1-3) have also been linked to CPVT. Because all three CALM genes encode an identical calmodulin protein, pathogenic calmodulin variants are expected to be expressed in only a small fraction of total cellular calmodulin, raising the question of whether this limited abundance is sufficient to produce an arrhythmogenic phenotype in vivo. We generated a heterozygous mouse model carrying the human disease-associated N54I-equivalent mutation, N54I, in Calm1. Mutant calmodulin accounted for 13.7% of total cardiac calmodulin, consistent with expression from one of six Calm alleles. Under basal conditions, N54I/+ mice exhibited normal growth, survival, cardiac morphology, and surface electrocardiogram parameters. However, cardiomyocytes isolated from N54I/+ mice had increased rates of RyR2-mediated spontaneous calcium release. Following catecholaminergic challenge with isoproterenol and caffeine, N54I/+ mice exhibited significantly more premature ventricular contractions and arrhythmias than wild-type littermates. Exercise challenge in conscious mice similarly provoked ventricular ectopy and ventricular tachycardia. In addition, N54I/+ mice exhibited abnormalities of atrial and sinoatrial electrical activity, including premature atrial contractions, ectopic P waves, atrioventricular conduction slowing, and beat-to-beat variability. These findings demonstrate that expression of the N54I calmodulin variant from a single Calm1 allele is sufficient to produce a CPVT phenotype in vivo. This model provides experimental evidence linking a human disease-associated calmodulin variant to arrhythmogenesis and demonstrates the functional dominance of mutant calmodulin in the heart.

physiology↗

bioRxiv2026

An Alport variant illuminates the bioactivity of the collagen IV α565- α121 scaffold in Bowman's capsule.

Alport syndrome (AS) is a major cause of chronic kidney failure and affects millions of people worldwide. Pathogenic variants in COL4A3, COL4A4, and COL4A5, which encode the collagen IV 345 scaffold, compromise glomerular basement membrane (GBM) structure and function. However, the molecular mechanisms linking the >5,000 reported variants to disease pathology remain poorly understood. To address this gap, we previously examined a distinctive variant, an 8-amino acid "Z-appendage", added to the NC1 domain of the 3 chain. Knock-in mice carrying this variant developed GBM abnormalities and proteinuria, implicating the NC1 hexamer as a critical determinant of GBM function and suggesting that the hexamer surface contains bioactive sites that may mediate signaling and/or organization of macromolecular complexes. Given that approximately 80% of AS cases are associated with COL4A5 variants, including many within the NC1 hexamer, we asked whether relocating the Z-appendage from the 3 NC1 subunit to the 5 subunit produces similar pathology. Strikingly, Col4a5-Z mice did not develop proteinuria and showed only minor changes in GBM morphology. In contrast, the variant induced marked thickening of Bowmans capsule, accompanied by increased deposition of the collagen IV 121 scaffold, increased fibrillar collagen, and cellular deposits. Structural modeling predicts that the collagen IV 565-121 scaffold bearing two Z-appendages adopts an aberrant secondary structure that may stiffen the scaffold and occlude binding sites. Together, these findings reveal a bioactive role for the collagen IV 565-121 scaffold in the Bowmans capsule basement membrane, with potential implications for other 565-121containing tissues such as the aorta and bladder.

molecular biology↗

bioRxiv2025

Kidney kallikrein-1 contributes to cleavage of gamma-ENaC in vivo

The epithelial sodium channel (ENaC) is essential for sodium reabsorption and potassium homeostasis in the distal nephron, where its activity is controlled by mineralocorticoid signaling and downstream proteolytic processing of channel subunits. While cleavage of the {gamma}-ENaC subunit has been implicated in aldosterone-mediated sodium transport, the identity of mineralocorticoid receptor (MR)-regulated proteases responsible for this process remains uncertain. Here, we investigated the role of kallikrein-1 (encoded by Klk1), a serine protease expressed in the connecting tubule and cortical collecting duct (CNT/CCD), as a mediator of ENaC activation. Using CRISPR/Cas9, we generated a conditional Klk1-floxed allele and established mice with CNT/CCD-specific deletion of Klk1 by crossing with Calb1-Cre (CNT-Klk1-/-). On a low sodium, high potassium diet, CNT-Klk1-/- mice exhibited [~]85% less renal kallikrein-1 expression, yet maintained normal serum electrolytes, urinary potassium excretion, and aldosterone responses. Western blot analysis revealed significantly less cleavage of {gamma}-ENaC and -ENaC in CNT-Klk1-/- kidneys, accompanied by more total NCC abundance. Despite impaired ENaC proteolysis, amiloride-sensitive sodium excretion was preserved, indicating intact ENaC function. These findings identify renal kallikrein-1 as a protease that contributes to ENaC subunit processing in vivo. However, the absence of overt sodium or potassium handling defects in CNT-Klk1-/- mice suggests that kallikrein-1 deficiency is not sufficient to disrupt overall ENaC function, likely due to compensatory mechanisms from redundant proteolytic or non-proteolytic pathways. Together, our results refine the role of kallikrein-1 as a modulator, rather than a sole determinant, of ENaC activation and highlight the complexity of aldosterone-dependent sodium transport in the distal nephron. New & NoteworthyUsing a novel connecting tubule / cortical collecting duct specific kallikrein-1 knockout model, we show that {gamma}- and -ENaC cleavage is impaired by loss of renal kallikrein-1 without major disturbances in sodium or potassium handling. These findings highlight redundancy among ENaC regulatory pathways and suggest that proteolytic cleavage, while biochemically evident, may not be an accurate marker of ENaC-mediated sodium transport under physiological stress.

physiology↗

bioRxiv2024

NRBP1 and TSC22D proteins impact distal convoluted tubule physiology through modulation of the WNK pathway

The With No lysine (WNK) kinases regulate processes such as cell volume and epithelial ion transport through the modulation of Cation Chloride Cotransporters such as the NaCl cotransporter, NCC, present in the distal convoluted tubule (DCT) of the kidney. Recently, the interaction of WNKs with Nuclear Receptor Binding Protein 1 (NRBP1) and Transforming Growth Factor {beta}-Stimulated Clone 22 Domain (TSC22D) proteins was reported. Here we explored the effect of NRBP1 and TSC22Ds on WNK signaling in vitro and in the DCT. TSC22D1.1, TSC22D2, and NRBP1 are localized in DCT WNK bodies, which are cytoplasmic biomolecular condensates associated with WNK activation. In HEK293 cells, long TSC22D isoforms and NRBP1 increase WNK4 activity. DCT-specific NRBP1 knockout mice have reduced NCC phosphorylation and activate a compensatory response. Thus, NRBP1 and long TSC22D proteins are positive modulators of WNK signaling and modulate Na+ reabsorption in the kidney. NRBP1 and TSC22Ds likely influence WNK signaling in other tissues, impacting various physiological processes. TeaserThe pseudokinase NRBP1 and its associated TSC22D proteins modulate WNK kinases to regulate sodium reabsorption in the kidney.

physiology↗

bioRxiv2024

Inhibiting CRF Projections from the Central Amygdala to Lateral Hypothalamus and Amygdala Deletion of CRF Alters Binge-Like Ethanol Drinking in a Sex-Dependent Manner

BackgroundBinge alcohol drinking is a dangerous pattern of consumption that can contribute to the development of more severe alcohol use disorders (AUDs). Importantly, the rate and severity of AUDs has historically differed between men and women, suggesting that there may be sex differences in the central mechanisms that modulate alcohol (ethanol) consumption. Corticotropin releasing factor (CRF) is a centrally expressed neuropeptide that has been implicated in the modulation of binge-like ethanol intake, and emerging data highlight sex differences in central CRF systems. MethodsIn the present report we characterized CRF+ neurocircuitry arising from the central nucleus of the amygdala (CeA) and innervating the lateral hypothalamus (LH) in the modulation of binge-like ethanol intake in male and female mice. ResultsUsing chemogenetic tools we found that silencing the CRF+ CeA to LH circuit significantly blunted binge-like ethanol intake in male, but not female, mice. Consistently, genetic deletion of CRF from neurons of the CeA blunted ethanol intake exclusively in male mice. Furthermore, pharmacological blockade of the CRF type-1 receptor (CRF1R) in the LH significantly reduced binge-like ethanol intake in male mice only, while CRF2R activation in the LH failed to alter ethanol intake in either sex. Finally, a history of binge-like ethanol drinking blunted CRF mRNA in the CeA regardless of sex. ConclusionsThese observations provide novel evidence that CRF+ CeA to LH neurocircuitry modulates binge-like ethanol intake in male, but not female mice, which may provide insight into the mechanisms that guide known sex differences in binge-like ethanol intake.

neuroscience↗