Biology subjects

Su, X.-T.

Publications and source records attributed to Su, X.-T..

5 recordsLinked to original sources

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

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↗

bioRxiv2025

Distinct cell types along thick ascending limb express pathways for monovalent and divalent cation transport

Kidney thick ascending limb cells reabsorb sodium, potassium, calcium, and magnesium and contribute to urinary concentration. These cells are typically viewed as of a single type that recycles potassium across the apical membrane and generates a lumen-positive transepithelial voltage driving calcium and magnesium reabsorption, although variability in potassium channel expression has been reported. Additionally, recent transcriptomic analyses suggest that different cell types exist along this segment, but classifications have varied and have not led to a new consensus model. We used immunolocalization, electrophysiology and enriched single nucleus RNA-Seq to identify thick ascending limb cell types in rat, mouse and human. We identified three major TAL cell types defined by expression of potassium channels and claudins. One has apical potassium channels, low basolateral potassium conductance, and is bordered by a sodium-permeable claudin. A second lacks apical potassium channels, has high basolateral potassium conductance and is bordered by calcium- and magnesium-permeable claudins. A third type also lacks apical potassium channels and has a high basolateral potassium conductance, but these cells are ringed by sodium-permeable claudins. The recognition of diverse cell types resolves longstanding questions about how solute transport can be modulated selectively and how disruption of these cells leads to human disease.

physiology↗

bioRxiv2023

A resource for probing influences of perinatal factors on neurodevelopment in 3-10-years-old Chinese children

Adverse perinatal factors can disrupt the normal development of the brain, with potential long-term impacts on childrens overall development. Currently, the neuropathological mechanisms by which these factors lead to various neurodevelopmental disorders (NDDs) remain largely unknown. An open resource that integrate perinatal factors with brain and mental health development is essential for investigating NDD-related aetiology. In this Data Descriptor, we introduce a multicentre database containing information on perinatal factors that influence childrens brain-mind development, namely, periCBD, that combines neuroimaging and behavioural phenotypes with perinatal factors associated with a high incidence of NDDs at county/region/central district hospitals. PeriCBD was designed to establish a platform for the investigation of individual differences in brain-mind development among children aged 3-10 years are associated with perinatal factors. Ultimately, our goal was to develop an early prediction and screening model for NDDs that leverages normative data to facilitate NDD aetiology research. Herein, we provide a systematic overview of the data acquisition/cleaning/quality control/sharing, processes of periCBD and present preliminary brain-mind associations.

neuroscience↗

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↗