Biology subjects

Kang, J.-S.

Publications and source records attributed to Kang, J.-S..

10 recordsLinked to original sources

bioRxiv2026

Optogenetic Control of cAMP Levels and HCN Channels: Implications in Cardiac Physiology and Parkinsons Disease

Cyclic adenosine monophosphate (cAMP) is a second messenger that regulates various cellular processes, including the activity of hyperpolarization-activated channels (HCN), which are implicated in cardiac physiology and neurodegenerative diseases such as Parkinsons disease (PD). In this study, we used a photoactivated adenylyl cyclase (PAC) S27A mutant to optogenetically control intracellular cAMP levels. We demonstrated that light-induced elevation of cAMP activated HCN4 channels, leading to increased beating rates in cardiomyocytes. Unilateral expression of PAC(S27A) in the substantia nigra pars compacta of mice induced rotation behavior upon light stimulation, which could be attenuated by HCN inhibitors. Furthermore, PAC(S27A) activation partially recovered motor deficits in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model, accompanied by increased HCN2 channel expression in ipsilateral basal ganglia. Our findings highlight the potential of using optogenetics to modulate cAMP and HCN channel activity for the treatment of cardiac and neurological disorders.

cell biology↗

bioRxiv2026

Methodologies for Manipulating Cardiomyocyte Physiology: In Vitro and In Vivo Perspectives

Cardiac tissue is primarily made up of cardiomyocytes, which are regulated by the autonomic nervous system. We have used and developed approaches such as patch clamping and electrical stimulation-combined calcium imaging, computer modeling, optogenetics and chemogenetics combining with video-based Short-Time Fourier transformation (STFT) method to study the physiological activities of cardiomyocytes. The action potential of cardiomyocytes was found to be synchronized with calcium signals, which can be grouped into two categories by STFT. A mathematical model was developed to simulate the changes in electrical activities within cardiomyocytes caused by energy depletion, especially for 2-deoxy-D-glucose (2DG) treatment. Optogenetic and chemogenetics tools, such as ChR2(H134R), OptoXR-{beta}2AR and hM3Dq accelerated beating, while GR, ACR1 and hM4Di inhibited cardiomyocytes beating. A video-based STFT method was developed to visualize the beating frequency during these manipulations. An in vitro co-culture method was developed to study the relationship between sympathetic neuronal firing and calcium dynamics in cardiomyocytes. In vivo, electrocardiograph (ECG) measurements showed that Clozapine N-oxide (CNO) caused heart rates increasement in cTnT-hM3Dq virus injected mouse. However, it had no impact on cTnT-hM4Di virus injected mouse. This study provides comprehensive methodologies for studying cardiomyocyte physiology and manipulating heart rates in vitro and in vivo.

cell biology↗

bioRxiv2026

Optogenetic Regulation of Mitochondrial Function to Modulate Cell Death

Cell death is a critical process involved in physiological and pathological conditions, including neurodegenerative diseases and cancer. This study explores the use of optogenetic techniques to induce cell death by employing light sensitive proteins. By manipulating mitochondrial function with light-sensitive proteins, we investigated three distinct strategies: 1) inhibiting oxidative phosphorylation through Gloeobacter rhodopsin-mediated alkalization, 2) inducing mitochondrial depolarization with reverse proton-pumping rhodopsins (RPPR) and anion-conducting channelrhodopsins, and 3) generating reactive oxygen species (ROS) using mitochondria-targeted miniSOG. Our findings highlight the potential of optogenetic approaches to induce cell death, offering promising avenues for therapeutic interventions in diseases characterized by aberrant cell survival.

cell biology↗

bioRxiv2024

Mitochondrial DNA Release and Activation of the cGAS-STING Pathway in Lethal Stx12 Knockout Mice

STX12 (syntaxin12 or syntaxin13), a member of the SNARE protein family, plays a crucial role in intracellular vesicle transport and membrane fusion. Our previous research has demonstrated that Stx12 knockout mice exhibit perinatal lethality with iron deficiency anemia. Despite its importance, the comprehensive physiological and pathological mechanism of STX12 remain largely unknown. Here, we uncover that STX12 deficiency causes the depolarization of mitochondrial membrane potential in zebrafish embryos and mouse embryonic fibroblasts. Additionally, the loss of STX12 decreases levels of mitochondrial complex subunits, accompanying mitochondrial DNA (mtDNA) release and activating cGAS-STING pathway and Type I interferon pathway in the lung tissue of Stx12-/- mice. Additionally, we have observed a substantial increase in cytokines and neutrophil infiltration within the lung tissues of Stx12 knockout mice, indicating a severe inflammation, which could be a contributing factor for Stx12-/-mortality. Various interventions have failed to rescue the lethal phenotype, suggesting that systemic effects may contribute to lethality. Further research is warranted to elucidate potential intervention strategies. Overall, our findings uncover the critical role of STX12 in maintaining mitochondrial function and mtDNA stability in pulmonary cells, and reveal that STX12 depletion results in pulmonary mtDNA release and activates mtDNA-dependent innate immunity.

molecular biology↗

bioRxiv2024

The earliest allopolyploidization in tracheophytes revealed by phylotranscriptomics and morphology of Selaginellaceae

Selaginellaceae exhibit extraordinary evolutionary history in which they survived and thrived during the Permian-Triassic extinction and did not undergo polyploidization. Here, we reconstructed the phylogenetic relationships of Selaginellaceae by applying large-scale nuclear genes from RNA-seq, and found that each group showed phylogenetic incongruences among single-gene trees with different frequencies. In particular, three different phylogenetic positions of the sanguinolenta group were recovered by different nuclear gene sets. We evaluated the factors that might lead to the phylogenetic incongruence of the sanguinolenta group and concluded that hybridization between each ancestor of two superclades is the most likely cause. We presented the supporting evidence from gene flow test, species network inference, and plastome-based phylogeny. Furthermore, morphological characters and chromosomal evidence also lend support to the hybrid origin of this group. The divergence time estimations, using two gene sets respectively, indicated the splits between the sanguinolenta group and each related superclade happened around the same period, implying that the hybridization event probably occurred during the Early Triassic. This study reveals an ancient allopolyploidization with integrative evidence and robust analyses, which sheds new light on the recalcitrant phylogenetic problem of the sanguinolenta group and reports the polyploidization in the basal vascular plants, Selaginellaceae.

genomics↗

bioRxiv2023

Depletion of SMN Protein in Mesenchymal Progenitors Impairs the Development of Bone and Neuromuscular Junction in Spinal Muscular Atrophy

Spinal Muscular Atrophy (SMA) is a neuromuscular disorder characterized by the deficiency of the survival motor neuron (SMN) protein, which leads to motor neuron dysfunction and muscle atrophy. In addition to the requirement for SMN in motor neurons, recent studies suggest that SMN deficiency in peripheral tissues plays a key role in the pathogenesis of SMA. Using limb mesenchymal progenitor cells (MPCs)-specific SMN-depleted mouse models, we reveal that SMN reduction in chondrocytes and fibro-adipogenic progenitors (FAPs) derived from limb MPCs causes defects in the development of bone and neuromuscular junction (NMJ), respectively. We showed that impaired growth plate homeostasis, which causes skeletal growth defects in SMA, is due to reduced IGF signaling from chondrocytes rather than the liver. Furthermore, the reduction of SMN in FAPs resulted in abnormal NMJ maturation, altered release of neurotransmitters, and NMJ morphological defects. Transplantation of healthy FAPs rescued the morphological deterioration. Our findings highlight the significance of mesenchymal SMN in neuromusculoskeletal pathogenesis in SMA and provide insights into potential therapeutic strategies targeting mesenchymal cells for the treatment of SMA.

neuroscience↗

bioRxiv2021

Impaired pattern separation in Tg2576 mice is associated with hyperexcitable dentate gyrus caused by Kv4.1 downregulation

Alzheimers disease (AD) is a progressive neurodegenerative disorder that causes memory loss. Most AD researches have focused on neurodegeneration mechanisms. Considering that neurodegenerative changes are not reversible, understanding early functional changes before neurodegeneration is critical to develop new strategies for early detection and treatment of AD. We found that Tg2576 mice exhibited impaired pattern separation at the early preclinical stage. Based on previous studies suggesting a critical role of dentate gyrus (DG) in pattern separation, we investigated functional changes in DG of Tg2576 mice. We found that granule cells in DG (DG-GCs) in Tg2576 mice showed increased action potential firing in response to long depolarizations and reduced 4-AP sensitive K+-currents compared to DG-GCs in wild-type (WT) mice. Among Kv4 family channels, Kv4.1 mRNA expression in DG was significantly lower in Tg2576 mice. We confirmed that Kv4.1 protein expression was reduced in Tg2576, and this reduction was restored by antioxidant treatment. Hyperexcitable DG and impaired pattern separation in Tg2576 mice were also recovered by antioxidant treatment. These results highlight the hyperexcitability of DG-GCs as a pathophysiologic mechanism underlying early cognitive deficits in AD and Kv4.1 as a new target for AD pathogenesis in relation to increased oxidative stress.

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↗

bioRxiv2018

Unique unfoldase/aggregase activity of a molecular chaperone that dysregulates a translational elongation factor

The various chaperone activities of heat shock proteins contribute to ensuring cellular proteostasis. Here, we demonstrate the non-canonical unfoldase activity as an inherent functionality of the prokaryotic molecular chaperone Hsp33. The holding-inactive, reduced form of Hsp33 (RHsp33) strongly bound to the translational elongation factor, EF-Tu, and catalyzed the EF-Tu aggregation via evoking its aberrant folding, resulting in its susceptibility to proteolytic degradation by Lon. This interaction was critically mediated by the redox-switch domain of RHsp33 and the guanine nucleotide-binding domain of EF-Tu. The RHsp33-induced in vivo aggregation of EF-Tu upon heat shock was evident in a Lon-deficient strain and inhibited cell growth. Unlike wild-type Escherichia coli, the strain lacking both Hsp33 and Lon showed a non-reduced level of EF-Tu and diminished capability of counteracting heat shock. These findings suggest that the unique unfoldase/aggregase activity of Hsp33 potentially involved in protein turnover confers a cellular survival advantage under heat-stressed conditions.

biochemistry↗

bioRxiv2017

Sympathetic Transmitters Controlling Thermogenic Efficacy of Brown Adipocytes by Modulating Mitochondrial Complex V

Obesity is epidemic worldwide as the results of excessive energy intake or inefficient energy expenditure. It is promising to utilize the thermogenic function of brown adipose tissue for obesity intervention. However, the mechanisms controlling the efficacy of norepinephrine-induced thermogenesis in brown adipocytes remain elusive. Here, we demonstrate that the proton ATPase activity of mitochondrial complex V is a key factor, which antagonizes proton leak by UCP1 and determines the efficacy of norepinephrine-induced thermogenesis in brown adipocytes. Furthermore, to avoid unnecessary and undesired heat production, we reveal that ATP as a sympathetic cotransmitter is necessary for the high efficacy and specificity of norepinephrine-induced thermogenesis in brown adipocytes by upregulating the ATP synthase activity of complex V. Thus, we demonstrate the modulation mechanism of thermogenic efficacy in brown adipocytes. These findings imply new strategies for efficiently utilizing brown adipocytes thermogenic capacity, and therapeutic targets for the treatments of obesity and diabetes.\n\nHighlights1. Norepinephrine (NE) induces heterogeneous responses in brown adipocytes\n\n2. NE activates the H+-ATPase activity of mitochondrial complex V\n\n3. Mitochondrial complex V is a key factor in NE-induced thermogenic efficacy\n\n4. ATP as a sympathetic cotransmitter enhances the NE-induced thermogenic efficacy

cell biology↗