Biology subjects

Wei, A.-C.

Publications and source records attributed to Wei, A.-C..

6 recordsLinked to original sources

bioRxiv2025

Cell type specific CaMKII activation patterns revealed by CaMKAR, a bioactivity reporter deployable in living cells

An accurate and precise mechanism for measuring CaMKII activity in living cells is invaluable in the search for effective and targeted CaMKII-based therapeutics. Here, we employ our recently published CaMKII Activity Reporter (CaMKAR) biosensor in order to investigate the spatiotemporal dynamics of CaMKII activation in three different types of cells - cardiac myocytes, skeletal myocytes, and neurons. In doing so, we found a greater rate of CaMKII activation in skeletal muscle compared to cardiac muscle and also delineated CaMKARs ability to measure discrete CaMKII activation events in the presence of individual action potentials. By modifying the original CaMKAR sequence, we generated sensors that can be localized to subcellular compartments and thereby preferentially detect the activity of specific spatially-distributed CaMKII isoforms. Finally, we utilized the live-cell data to generate mathematical models of CaMKII activation kinetics, both as an integrated function across multiple calcium transients and as discrete on-off events following individual depolarizations. By furthering our understanding of CaMKII activity profiles across cell types and within subcellular compartments, we hope to support development of CaMKII inhibitors that are optimally precise and potent.

molecular biology↗

bioRxiv2021

Metabolic Regulation of Mitochondrial Morphologies in Pancreatic Beta Cells: Bioenergetics-Mitochondrial Dynamics Coupling

Cellular bioenergetics and mitochondrial dynamics are crucial for the secretion of insulin by pancreatic beta cells in response to elevated blood glucose concentrations. To obtain better insights into the interactions between energy production and mitochondrial fission/fusion dynamics, we combine live-cell mitochondria imaging with biophysical-based modeling and network analysis to elucidate the principle regulating mitochondrial morphology to match metabolic demand in pancreatic beta cells. A minimalistic differential equation-based model for beta cells was constructed to include glycolysis, oxidative phosphorylation, simple calcium dynamics, and graph-based fission/fusion dynamics controlled by ATP synthase flux and proton leak flux. The model revealed that mitochondrial fission occurs in response to hyperglycemia, starvation, ATP synthase inhibition, uncoupling, and diabetic condition, in which the rate of proton leak exceeds the rate of mitochondrial ATP synthesis. Under these metabolic challenges, the propensities of tip-to-tip fusion events simulated from the microscopic images of the mitochondrial networks were lower than those in the control group and prevented mitochondrial network formation. The modeling and network analysis could serve as the basis for further detailed research on the mechanisms of bioenergetics and mitochondrial dynamics coupling.

systems biology↗

bioRxiv2021

Mathematical Model for the Study of Mitochondrial Retrograde Signaling Dynamics

Mitochondria, semi-autonomous eukaryotic organelles, participate in energy production and metabolism, making mitochondrial quality control crucial. As most mitochondrial proteins are encoded by nuclear genes, quality control depends on proper mitochondria-nucleus communication, designated mitochondrial retrograde signaling. Early studies focused on retrograde signaling participants and specific gene knockouts. However, mitochondrial signal modulation remains elusive. Using yeast, we simulated signal propagation following mitochondrial damage and proposed a mathematical model based ordinary differential equations. Mitochondrial retrograde signaling decisions were described using a Boolean model. Dynamics were analyzed through an ordinary differential equation-based model and extended to evaluate the model response to noisy damage signals. Simulation revealed localized protein concentration dynamics, including waveforms, frequency response, and robustness under noise. Retrograde signaling is bistable with three localized steady states, and increased damage compromises robustness. We elucidated mitochondrial retrograde signaling, thus providing a basis for drug design against yeast and fungi. Author SummaryThe yeast RTG pathway regulates mitochondrial metabolism and mitochondrial quality through passing mitochondrial signal to the nucleus to modulate gene expressions. Using microscopic data of RTG proteins translocation from cytosol to nucleus, the parameters were found by fitting 16 knockout conditions simulated from the proposed differential equation-based model. Further, through dose response, ultrasensitivity, frequency response and noise interference, we demonstrated a switch-like property of RTG pathway activation, a capacity charging property of RTG protein translocation, a low pass filter property of signals in different frequencies, and noise amplification due to mitochondrial signal. The proposed mathematical model enables us to understand the dynamics and mechanisms in mitochondrial retrograde signaling in yeast and provides potential antifungal treatment strategies.

systems biology↗

bioRxiv2020

Mitochondrial CaMKII causes metabolic reprogramming, energetic insufficiency, and dilated cardiomyopathy

Despite the clear association between myocardial injury, heart failure and depressed myocardial energetics, little is known about upstream signals responsible for remodeling myocardial metabolism after pathological stress. We found increased mitochondrial calmodulin kinase II (CaMKII) activation and left ventricular dilation in mice one week after myocardial infarction (MI) surgery. In contrast, mice with genetic mitochondrial CaMKII inhibition were protected from left ventricular dilation and dysfunction after MI. Mice with myocardial and mitochondrial CaMKII over-expression (mtCaMKII) had severe dilated cardiomyopathy and decreased ATP that caused elevated cytoplasmic resting (diastolic) Ca2+ concentration and reduced mechanical performance. We mapped a metabolic pathway that allowed us to rescue disease phenotypes in mtCaMKII mice, providing new insights into physiological and pathological metabolic consequences of CaMKII signaling in mitochondria. Our findings suggest myocardial dilation, a disease phenotype lacking specific therapies, can be prevented by targeted replacement of mitochondrial creatine kinase, or mitochondrial-targeted CaMKII inhibition.

molecular biology↗

bioRxiv2020

Excessive O-GlcNAcylation causes heart failure and sudden death

BackgroundHeart failure is a leading cause of death worldwide and is associated with the rising prevalence of obesity, hypertension and diabetes. O-GlcNAcylation, a post-translational modification of intracellular proteins, serves as a potent transducer of cellular stress. Failing myocardium is marked by increased O-GlcNAcylation, but it is unknown if excessive O-GlcNAcylation contributes to cardiomyopathy and heart failure. The total levels of O-GlcNAcylation are determined by nutrient and metabolic flux, in addition to the net activity of two enzymes, O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA). MethodsWe developed two new transgenic mouse models with myocardial overexpression of OGT and OGA to control O-GlcNAclyation independent of pathological stress. ResultsWe found that OGT transgenic hearts showed increased O-GlcNAcylation, and developed severe dilated cardiomyopathy, ventricular arrhythmias and premature death. In contrast, OGA transgenic hearts had O-GlcNAcylation and cardiac function similar to wild type littermate controls. However, OGA trangenic hearts were resistant to pathological stress induced by pressure overload and had attenuated myocardial O-GlcNAcylation levels, decreased pathological hypertrophy and improved systolic function. Interbreeding OGT with OGA transgenic mice rescued cardiomyopathy and premature death despite persistant elevation of myocardial OGT. Transcriptomic and functional studies revealed disrupted mitochondrial energetics with impairment of complex I activity in hearts from OGT transgenic mice. Complex I activity was rescued by OGA transgenic interbreeding, suggesting an important role for mitochondrial complex I in O-GlcNAc mediated cardiac pathology. ConclusionsOur data provide evidence that excessive O-GlcNAcylation causes cardiomyopathy, at least in part, due to defective energetics. Enhanced OGA activity is well tolerated and attenuation of O-GlcNAcylation is an effective therapy against pressure overload induced heart failure. Attenuation of excessive O-GlcNAcylation may represent a novel therapeutic approach for cardiomyopathy. Clinical PerspectiveO_ST_ABSWhat is new?C_ST_ABSO_LICardiomyopathy from diverse causes is marked by increased O-GlcNAcylation. Here we provide new genetic mouse models to control myocardial O-GlcNAcylation independent of pathological stress. C_LIO_LIGenetically increased myocardial O-GlcNAcylation causes progressive dilated cardiomyopathy and premature death, while genetic reduction of myocardial O-GlcNAcylation is protective against pathological hypertrophy caused by transaortic banding. C_LIO_LIExcessive myocardial O-GlcNAcylation decreases activity and expression of mitochondrial complex I. C_LI What are the clinical implications?O_LIIncreased myocardial O-GlcNAcylation has been shown to be associated with a diverse range of clinical heart failure including aortic stenosis, hypertension, ischemia and diabetes. C_LIO_LIUsing novel genetic mouse models we have provided new proof of concept data that excessive O-GlcNAcylation is sufficient to cause cardiomyopathy. C_LIO_LIWe have shown myocardial over-expression of O-GlcNAcase, an enzyme that reverses O-GlcNAcylation, is well tolerated at baseline, and improves myocardial responses to pathological stress. C_LIO_LIOur findings suggest reversing excessive myocardial O-GlcNAcylation could benefit diverse etiologies of heart failure. C_LI

molecular biology↗

bioRxiv2019

CaMKII oxidation is a performance/disease trade-off in vertebrate evolution

Reactive oxygen species (ROS) contribute to health and disease. CaMKII is a widely expressed enzyme whose activation by oxidation of regulatory domain methionines (ox-CaMKII) contributes to cardiovascular disease, asthma, and cancer. Here we integrate comparative genomic and experimental data to show that CaMKII activation by ROS arose more than half-a-billion years ago on the vertebrate stem lineage where it constituted a bridge between ROS and increased intracellular Ca2+ release, exercise responsive gene transcription, and improved performance in skeletal muscle. These enhancements to fight-or-flight physiology were likely key in facilitating a well-evidenced shift in the behavioural ecology of our immediate chordate ancestors, and, in turn, the evolutionary success of vertebrates. Still, the ox-CaMKII innovation for augmenting performance must be considered a critical evolutionary trade-off, as it rendered us more susceptible to common and often fatal diseases linked to excessive ROS.

evolutionary biology↗