Biology subjects

Jeong, H.-J.

Publications and source records attributed to Jeong, H.-J..

3 recordsLinked to original sources

bioRxiv2022

Organoid-based human stomach micro-physiological system to recapitulate the dynamic mucosal defense mechanism

Several stomach diseases are attributed to the dysregulation of physiological function of gastric mucosal barrier by pathogens. Gastric organoids are a promising tool to develop treatment strategies for gastric infections. However, their functional features of in vivo gastric mucosal barrier and host-microbe interactions are limited due to the lack of physiological stimuli. Herein, we describe the first human stomach micro-physiological system (hsMPS) with physiologically relevant gastric mucosal defense system based on the combination of organoid and MPS technology. A fluid flow enhanced epithelial-mesenchymal interaction in the hsMPS enables functional maturation of gastric epithelial cells, which allows for the recreation of mesh-like mucus layer containing high level of mucus protective peptides and well-developed epithelial junctional complexes. Furthermore, gastroprotection mechanisms against Helicobacter pylori are successfully demonstrated in our system. Therefore, hsMPS represents a new in vitro tool for research where gastric mucosal defense mechanism is pivotal for developing therapeutic strategies.

bioengineering↗

bioRxiv2021

Calbindin regulates Kv4.1 trafficking and excitability of dentate granule cells via CaMKII-dependent phosphorylation

Calbindin, a major Ca2+ buffer in dentate granule cells (GCs), plays a critical role in shaping Ca2+ signals, yet how it regulates neuronal functions remains largely unknown. Here, we found that calbindin knock-out mice (CBKO) exhibited hyperexcitability in dentate GCs and impaired pattern separation, which was concurrent with reduced K+ current due to downregulated surface expression of Kv4.1. Consistently, manipulation of the calbindin expression in HT22 led to changes in CaMKII activation and the level of surface localization of Kv4.1 through phosphorylation at serine 555, confirming the mechanism underlying neuronal hyperexcitability in CBKO. We also discovered that Ca2+ buffering capacity was significantly reduced in the GCs of Tg2576 to the level of CBKO GCs, and this reduction was restored to normal levels by antioxidants, suggesting that calbindin is a target of oxidative stress. Our data suggest that regulation of CaMKII signaling by Ca2+ buffer is crucial for neuronal excitability regulation.

neuroscience↗

bioRxiv2019

Kv4.1, a key ion channel for low frequency firing of dentate granule cells, is crucial for pattern separation

The dentate gyrus (DG) in the hippocampus may play key roles in remembering distinct episodes through pattern separation, which may be subserved by the sparse firing properties of granule cells (GCs) in the DG. Low intrinsic excitability is characteristic of mature GCs, but ion channel mechanisms are not fully understood. Here, we investigated ionic channel mechanisms for firing frequency regulation in GCs of the rat hippocampus, and identified Kv4.1 as a key player. Immunofluorescence analysis showed that Kv4.1 was preferentially expressed in the DG, and its expression level was higher at 8-week than 3-week-old mice, suggesting a developmental regulation of Kv4.1 expression. With respect to firing frequency, GCs are categorized into two distinctive groups: low frequency (LF) and high frequency (HF) firing GCs. Input resistance (Rin) of most LF-GCs is lower than 200 M{Omega}, suggesting that LF-GCs are fully mature GCs. Kv4.1 channel inhibition by intracellular perfusion of Kv4.1 antibody increased firing rates and gain of the input-output relationship selectively in LF-GCs with no significant effect on resting membrane potential and Rin, but had no effect in HF-GCs. Importantly, mature GCs from mice depleted of Kv4.1 transcripts in the DG showed increased firing frequency, and these mice showed an impairment in contextual discrimination task. Our findings suggest that Kv4.1 expression occurring at late stage of GC maturation is essential for low excitability of DG networks and thereby contributes to pattern separation.

neuroscience↗