Biology subjects

Luczak, E. D.

Publications and source records attributed to Luczak, E. D..

7 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↗

bioRxiv2024

SGLT2 inhibitors protect against diabetic cardiomyopathy and atrial fibrillation through a CaMKII independent mechanism

Ca2+/calmodulin-dependent protein kinase II (CaMKII) has been implicated as an important mediator of the increasingly evident cardioprotective benefits exerted by sodium- glucose transport protein 2 channel inhibitors (SGLT2i). However, the exact nature of the relationship between CaMKII and SGLT2i remains unclear. Here, we find that empagliflozin but not dapagliflozin attenuated susceptibility to atrial fibrillation (AF) in a type 2 diabetic (T2D) mouse model. However, both empagliflozin and dapagliflozin protected from diabetic cardiomyopathy in T2D mice. We then used real-time microscopy of neonatal rat ventricular cardiomyocytes (NRVMs) with the CaMKII biosensor - CaMKAR to demonstrate that direct inhibition of CaMKII is not essential for the effects of SGLT2i in these cells. Therefore, we conclude that the benefits of SGLT2i in heart disease likely occur through indirect modulation of CaMKII activity, or possibly through an alternative pathway altogether.

molecular biology↗

bioRxiv2023

Genome-wide CRISPR screen reveals genetic modifiers of Ca2+-mediated cell death

Ca2+ is a fundamental determinant of survival in living cells. Excessive intracellular Ca2+ causes cellular toxicity and death but the genetic pathways contributing to Ca2+ induced cell death are incompletely understood. Here, we performed genome-wide CRISPR knock-out screening in human cells challenged with the Ca2+ ionophore ionomycin and identified genes and pathways essential for cell death after Ca2+ overload. We discovered 115 protective gene knockouts, 82 of which are non-essential genes and 21 of which belong to the druggable genome. Notably, members of store operated Ca2+ entry (SOCE), very long-chain fatty acid synthesis, and SWItch/Sucrose Non-Fermentable (SWI/SNF) pathways provided marked protection against Ca2+ toxicity. These results reveal pathways previously unknown to mediate Ca2+-induced cell death and provide a resource for the development of pharmacotherapies against the sequelae of Ca2+ overload in disease.

cell biology↗

bioRxiv2022

Novel Biosensor Identifies Ruxolitinib as a Potent and Cardioprotective CaMKII Inhibitor

Ca2+/Calmodulin-dependent protein kinase II (CaMKII) hyperactivity causes heart injury and arrhythmias--two major sources of mortality worldwide. Despite proven benefits of CaMKII inhibition in numerous preclinical models of heart disease, translation of CaMKII antagonists into humans has been stymied by low potency, toxicity, and an enduring concern for adverse effects on cognition due to an established role of CaMKII in learning and memory. To address these challenges, we asked if any clinically approved drugs, developed for other purposes, were potent CaMKII inhibitors. For this, we engineered a novel fluorescent biosensor, CaMKAR (CaMKII Activity Reporter), which features superior sensitivity, kinetics, and tractability for high throughput screening. Using this tool, we carried a drug repurposing screen (4,475 compounds in clinical use) in human cells expressing autonomously active CaMKII. This yielded five previously unrecognized CaMKII inhibitors with clinically relevant potency: ruxolitinib, baricitinib, silmitasertib, crenolanib, and abemaciclib. Standout among these, ruxolitinib, an orally bioavailable and U.S Food and Drug Administration (FDA)-approved medication, inhibited CaMKII in cultured cardiomyocytes and in mice at concentrations equivalent to human doses. 10-minute treatment in mice was sufficient to prevent atrial fibrillation-- the most common clinical arrhythmia. At cardioprotective doses, ruxolitinib-treated mice behaved normally in established cognitive assays. Our results suggest that human CaMKII inhibition is feasible and safe, and support prompt clinical investigation of ruxolitinib for cardiac indications. One Sentence SummaryWe developed a CaMKII biosensor suitable for high throughput screening and identified ruxolitinib as a CaMKII inhibitor capable of rescuing cardiac arrhythmia.

molecular biology↗

bioRxiv2020

O-GlcNAcylation and oxidation contribute to atrial fibrillation in diabetes by activating CaMKII

Diabetes mellitus and atrial fibrillation (AF) are major unsolved public health problems, and diabetes is an independent risk factor for AF in patients. However, the mechanism(s) underlying this clinical association is unknown. Elevated protein O-GlcNAcylation (OGN) and reactive oxygen species (ROS) are increased in diabetic hearts, and calmodulin kinase II (CaMKII) is a proarrhythmic signal that may be activated by OGN (OGN-CaMKII) and ROS (ox-CaMKII). We induced type 1 (T1D) and type 2 diabetes (T2D) in a portfolio of genetic mouse models capable of dissecting the role of OGN and ROS at CaMKII and the type 2 ryanodine receptor (RyR2), an intracellular Ca2+ channel implicated as an important downstream mechanism of CaMKII- mediated arrhythmias. Here we show that T1D and T2D significantly increased AF, similar to observations in patients, and this increase required CaMKII. While T1D and T2D both require ox-CaMKII to increase AF, they respond differently to loss of OGN-CaMKII or OGN inhibition. Collectively, our data affirm CaMKII as a critical proarrhythmic signal in diabetic AF, and suggest ROS primarily promotes AF by ox-CaMKII, while OGN promotes AF by diverse mechanisms and targets, including CaMKII and RyR2. The proarrhythmic consequences of OGN- and ox-CaMKII differ between T1D and T2D. These results provide new and unanticipated insights into the mechanisms for increased AF in diabetes mellitus, and suggest successful future therapies will need to be different for AF in T1D and T2D.

molecular 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↗