Biology subjects

McCormick, J. A.

Publications and source records attributed to McCormick, J. A..

5 recordsLinked to original sources

bioRxiv2026

Neuraminidase1 Activity Contributes to Vasopressin Receptor-mediated Augmentation of Water and Electrolyte Retention by the Kidney in Eln Haploinsufficient Mice

Elastin haploinsufficiency is a primary determinant of arteriopathy and hypertension that hallmark Williams syndrome (WS), a rare genetic disorder resulting from microdeletion of genes on human chromosome 7, including the elastin gene (ELN). Accumulating evidence suggests renal dysfunction, including enhanced sodium and water retention as an underlying cause of blood pressure elevation resulting from heterozygous deletion of Eln (Eln+/-) in mice that recapitulates the cardiovascular phenotype of WS. However, the underlying pathophysiological mechanisms are poorly understood. Here, we determined whether the activity of neuraminidase-1 (NEU1) of the elastin receptor complex (ERC) contributes to abnormal handling of water and electrolytes by the kidney in Eln haploinsufficiency. Adult male and female Eln+/+ and Eln+/- mice were subjected to acute extracellular fluid volume expansion with normal saline, combined with pharmacological intervention targeting vasopressin V2 receptor (V2R), NEU1, ENaC, and NKCC2. In male Eln+/+ mice, V2R blockade induced a dose-dependent increase in urine flow rate without affecting sodium excretion. Conversely, V2R stimulation with desmopressin markedly increased urinary sodium excretion in male Eln+/+ but not Eln+/- mice, while both sexes of Eln+/- mice exhibited marked suppression of urine flow rate. Abrogation of ERC signaling through NEU1 inhibition produced a modest increase in urinary sodium excretion in male mice of both genotypes but augmented urine flow rate only in male Eln+/+mice. NEU1 blockade strikingly enhanced the natriuretic effect of furosemide and amiloride in male Eln+/+ and modestly in Eln+/-mice. Taken together, we conclude that Eln haploinsufficiency disrupts vasopressin-dependent modulation of sodium and water reabsorption by sex-dependently altering ERC-mediated modulation of NKCC2 and ENaC. These findings reveal a novel mechanism by which abnormal ERC activity due to Eln haploinsufficiency potentially contributes to renal dysfunction and hypertension. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=120 SRC="FIGDIR/small/731713v1_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@13264fdorg.highwire.dtl.DTLVardef@18453fforg.highwire.dtl.DTLVardef@a6c17eorg.highwire.dtl.DTLVardef@1e9564d_HPS_FORMAT_FIGEXP M_FIG C_FIG AC, adenylyl cyclase; AQP2, aquaporin 2; CD, collecting duct; CNT, connecting tubule; DCT, distal convoluted tubule; EBP, elastin binding protein; Eln, elastin allele; ENaC, epithelial sodium channel; ERC, elastin receptor complex; Gs, stimulatory G subunit; NEU1, neuroaminidase1; NKCC2, sodium-potassium-chloride cotransporter; PPCA, protective protein/ cathepsin A; TAL, loop of Henle thick ascending limb; V2R, vasopressin receptor type 2

physiology↗

bioRxiv2026

Differential Assembly of Native ENaC Complexes Across Mouse Epithelial Tissues

The epithelial sodium channel (ENaC) governs sodium and fluid absorption in the lung, kidney, and colon, but the organization of native ENaC complexes has remained difficult to define because of their low abundance and biochemical instability. To enable direct analysis of native assemblies, we generated a knock-in mouse in which the endogenous {gamma} subunit is fused at its C terminus to mVenus, a 3C protease cleavage site, and a 3xFLAG epitope (ENaC{gamma}-VF). The tag preserves physiological ENaC function, as ENaC{gamma}-VF mice display normal electrolyte handling, benzamil affinity, and amiloride-sensitive Na:K responses indistinguishable from wild-type animals. Using fluorescence-detection size-exclusion chromatography and single-molecule pull-down, we directly monitor intact native ENaC complexes from lung, kidney, and colon and uncover marked tissue-to-tissue differences in channel abundance and apparent complex size. Dual-color analysis with a fluorescent Fab against ENaC marks fully assembled {beta}{gamma} channels, while {gamma}-based fluorescence reports the broader population of {gamma}-containing assemblies. In combination, the ENaC{gamma}-VF line provides a biochemical anchor for identifying regulatory and trafficking proteins that co-purify with native ENaC complexes. These data show that ENaC architecture in vivo is heterogeneous, and establish ENaC{gamma}-VF mice as a platform for dissecting how epithelial environments shape ENaC assembly, composition, and regulation.

biochemistry↗

bioRxiv2025

Ovarian Hormones Moderate Hypertension in Female Eln Haploinsufficient Mice

Hypertension is a hallmark of cardiovascular abnormalities associated with Williams syndrome (WS), a rare genetic disorder involving microdeletion of genes on human chromosome 7, including the elastin gene (ELN). Heterozygous deletion of Eln (Eln+/-) in mice recapitulates hypertension and arteriopathy associated with WS. Previously, differences in blood pressure elevation and sensitivity to dietary sodium were found to be less profound in female Eln+/- mice. Here, we determined whether ovarian hormones play a role in sex-related difference in blood pressure elevation resulting from Eln haploinsufficiency. Female Eln+/+ and Eln+/- mice instrumented with radiotelemetry devices were subjected to sham surgery or ovariectomy (OVX). We found that OVX lowered diastolic but not systolic blood pressure (SBP) in Eln+/- mice, resulting in increased pulse pressure. In Eln+/- mice, diuresis induced by acute volume expansion was blunted, while anti-natriuresis was exaggerated. Furthermore, amiloride lowered SBP and increased urinary Na+ excretion, suggesting that Eln+/--induced hypertension may be Na+-dependent. We conclude that increased Na+ and water retention by the kidney contribute to hypertension resulting from Eln haploinsufficiency. The underlying mechanism involves the alteration of ovarian hormone effects in the kidney and sustained signaling downstream of the V2 receptor, leading to increased ENaC activity and water reabsorption. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=103 SRC="FIGDIR/small/689164v1_ufig1.gif" ALT="Figure 1"> View larger version (15K): org.highwire.dtl.DTLVardef@1ccfa15org.highwire.dtl.DTLVardef@369344org.highwire.dtl.DTLVardef@fe8194org.highwire.dtl.DTLVardef@ed285d_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO CDPC, cortical duct principal cell; ER, estrogen receptor; PR, progesterone receptor; ENaC, epithelial sodium channel; AQP2, aquaporin 2; V2R, vasopressin V2 receptor; ELN, elastin; PKA, protein kinase A; AC, adenylyl cyclase; Gs, stimulatory G protein; ATP, Adenosine triphosphate; cAMP, cyclic AMP; {oplus}, activating; {ominus}, inhibiting C_FIG

physiology↗

bioRxiv2023

Enriched Single-Nucleus RNA-Sequencing reveals unique attributes of distal convoluted tubule cells

BackgroundThe distal convoluted tubule (DCT) comprises two subsegments, DCT1 and DCT2, with different functional and molecular characteristics. The functional and molecular distinction between these segments, however, has been controversial. MethodsTo understand the heterogeneity within the DCT population with better clarity, we enriched for DCT nuclei by using a mouse line combining "Isolation of Nuclei TAgged in specific Cell Types" and NCC (sodium chloride cotransporter)-driven inducible Cre recombinase. We sorted the fluorescently labeled DCT nuclei using Fluorescence-Activated Nucleus Sorting, and performed single nucleus transcriptomics. ResultsAmong 25,183 DCT cells, 70% were from DCT1 and 30% from DCT2. Additionally, there was a small population (<1%) enriched in proliferation-related genes, such asTop2a, Cenpp, and Mki67. Both DCT1 and DCT2 express NCC, magnesium transport genes are more abundant along DCT1; whereas calcium, electrogenic sodium and potassium transport genes are more abundant along DCT2. The transition between these two segments are gradual with a transitional zone where DCT1 and DCT2 cells are interspersed. The expression of the homeobox genes is not consistent between all DCT cells, suggesting that they develop along different trajectories. ConclusionTranscriptomics analysis of an enriched rare cell population using genetically targeted approach offers better clarification of the function and classification. The DCT segment is short, yet, can be separated into two sub-types that serve distinct functions, and are speculated to derive from different origins during development. Significance StatementHigh-resolution snRNAseq data indicate a clear separation between primary sites of calcium and magnesium handling within DCT. Both DCT1 and DCT2 express Slc12a3, but these subsegments serve distinctive functions, with more abundant magnesium handling genes along DCT1 and more calcium handling genes along DCT2. The data also provides insight into the plasticity of the distal nephron-collecting duct junction, formed from cells of separate embryonic origins. By focusing/changing gradients of gene expression, the DCT can morph into different physiological cell states on demand.

physiology↗

bioRxiv2021

Potassium effects on NCC are attenuated during inhibition of Cullin E3-ubiquitin ligases

The thiazide sensitive sodium-chloride co-transporter (NCC) plays a vital role in maintaining sodium (Na+) and potassium (K+) homeostasis. NCC activity is modulated by the with-no-lysine kinases 1 and 4 (WNK1 and WNK4), the abundance of which are controlled by the RING-type E3 ligase Cullin 3 (Cul3) and its substrate adapter Kelch-like protein 3. Dietary K+ intake has an inverse correlation with NCC activity, but the mechanism underlying this phenomenon remains to be fully elucidated. Here, we investigated the involvement of other members of the Cullin family in mediating K+ effects on NCC phosphorylation (active form) and abundance. In kidneys from mice fed diets varying in K+ content, there were negative correlations between NCC (phosphorylated and total) and active (neddylated) forms of Cullins (Cul1, 3, 4 and 5). High dietary K+ effects on phosphorylated NCC were attenuated in Cul3 mutant mice (CUL3-Het/{Delta}9). Short-term (30 min) and long-term (24 h) alterations in the extracellular K+ concentration did not affect Cullin neddylation levels in ex vivo renal tubules. Short-term, the ability of high extracellular K+ to decrease NCC phosphorylation was preserved in the presence of MLN4924 (pan Cullin inhibitor), but the response to low extracellular K+ was absent. Long-term, MLN4924 attenuated the effects of high extracellular K+ on NCC phosphorylation and responses to low extracellular K+ were absent. Our data suggest that in addition to Cul3, other Cullins are involved in mediating the effects of K+ on NCC phosphorylation and abundance.

physiology↗