Biology subjects

Eyster, C. A.

Publications and source records attributed to Eyster, C. A..

3 recordsLinked to original sources

bioRxiv2023

Loss of cardiac PFKFB2 drives Metabolic, Functional, and Electrophysiological Remodeling in the Heart

BackgroundPhosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK-2) is a critical glycolytic regulator responsible for upregulation of glycolysis in response to insulin and adrenergic signaling. PFKFB2, the cardiac isoform of PFK-2, is degraded in the heart in the absence of insulin signaling, contributing to diabetes-induced cardiac metabolic inflexibility. However, previous studies have not examined how the loss of PFKFB2 affects global cardiac metabolism and function. MethodsTo address this, we have generated a mouse model with a cardiomyocyte-specific knockout of PFKFB2 (cKO). Using 9-month-old cKO and control (CON) mice, we characterized impacts of PFKFB2 on cardiac metabolism, function, and electrophysiology. ResultscKO mice have a shortened lifespan of 9 months. Metabolically, cKO mice are characterized by increased glycolytic enzyme abundance and pyruvate dehydrogenase (PDH) activity, as well as decreased mitochondrial abundance and beta oxidation, suggesting a shift toward glucose metabolism. This was supported by a decrease in the ratio of palmitoyl carnitine to pyruvate-dependent mitochondrial respiration in cKO relative to CON animals. Metabolomic, proteomic, and western blot data support the activation of ancillary glucose metabolism, including pentose phosphate and hexosamine biosynthesis pathways. Physiologically, cKO animals exhibited impaired systolic function and left ventricular (LV) dilation, represented by reduced fractional shortening and increased LV internal diameter, respectively. This was accompanied by electrophysiological alterations including increased QT interval and other metrics of delayed ventricular conduction. ConclusionsLoss of PFKFB2 results in metabolic remodeling marked by cardiac ancillary pathway activation. This could delineate an underpinning of pathologic changes to mechanical and electrical function in the heart. Clinical PerspectiveO_ST_ABSWhat is New?C_ST_ABSO_LIWe have generated a novel cardiomyocyte-specific knockout model of PFKFB2, the cardiac isoform of the primary glycolytic regulator Phosphofructokinase-2 (cKO). C_LIO_LIThe cKO model demonstrates that loss of cardiac PFKFB2 drives metabolic reprogramming and shunting of glucose metabolites to ancillary metabolic pathways. C_LIO_LIThe loss of cardiac PFKFB2 promotes electrophysiological and functional remodeling in the cKO heart. C_LI What are the Clinical Implications?O_LIPFKFB2 is degraded in the absence of insulin signaling, making its loss particularly relevant to diabetes and the pathophysiology of diabetic cardiomyopathy. C_LIO_LIChanges which we observe in the cKO model are consistent with those often observed in diabetes and heart failure of other etiologies. C_LIO_LIDefining PFKFB2 loss as a driver of cardiac pathogenesis identifies it as a target for future investigation and potential therapeutic intervention. C_LI

physiology↗

bioRxiv2020

Diabetes induced decreases in PKA signaling in cardiomyocytes: the role of insulin

The cAMP-dependent protein kinase (PKA) signaling pathway is the primary means by which the heart regulates moment-to-moment changes in contractility and metabolism. We have previously found that PKA signaling is dysfunctional in the diabetic heart, yet the underlying mechanisms are not fully understood. The objective of this study was to determine if decreased insulin signaling contributes to a dysfunctional PKA response. To do so, we isolated adult cardiomyocytes (ACMs) from wild type and Akita type 1 diabetic mice. ACMs were cultured in the presence or absence of insulin and PKA signaling was visualized by immunofluorescence microscopy using an antibody that recognizes proteins specifically phosphorylated by PKA. We found significant decreases in proteins phosphorylated by PKA in wild type ACMs cultured in the absence of insulin. Akita ACMs also had decreased PKA signaling in the absence of insulin and this was not rescued by insulin. The decrease in PKA signaling was observed regardless of whether the kinase was stimulated with a beta-agonist, a cell-permeable cAMP analog, or with phosphodiesterase inhibitors. PKA content was unaffected, suggesting that the decrease in PKA signaling may be occurring by the loss of specific PKA substrates. Phospho-specific antibodies were therefore used to discern which potential substrates may be sensitive to the loss of insulin. Contractile proteins were phosphorylated similarly in wild type and Akita ACMs regardless of insulin. However, phosphorylation of the glycolytic regulator, PFK-2, was significantly decreased in an insulin-dependent manner in wild type ACMs and in an insulin-independent manner in Akita ACMs. These results demonstrate a defect in PKA activation in the diabetic heart, mediated in part by deficient insulin signaling, that results in an abnormal activation of a primary metabolic regulator.

cell biology↗

bioRxiv2018

Shugoshin protects centromere pairing and promotes segregation of non-exchange partner chromosomes in meiosis

Faithful chromosome segregation during meiosis I depends upon the formation of connections between homologous chromosomes. Crossovers between homologs connect the partners allowing them to attach to the meiotic spindle as a unit, such that they migrate away from one another at anaphase I. Homologous partners also become connected by pairing of their centromeres in meiotic prophase. This centromere pairing can promote proper segregation at anaphase I of partners that have failed to become joined by a crossover. Centromere pairing is mediated by synaptonemal complex (SC) proteins that persist at the centromere when the SC disassembles. Here, using mouse spermatocyte and yeast model systems, we tested the role of shugoshin in promoting meiotic centromere pairing by protecting centromeric synaptonemal components from disassembly. The results show that shugoshin protects centromeric SC in meiotic prophase and, in anaphase, promotes the proper segregation of partner chromosomes that are not linked by a crossover. SIGNIFICANCEMeiotic crossovers form a connection between homologous chromosomes that allows them to attach to the spindle as a single unit in meiosis I. In humans, failures in this process are a leading cause of aneuploidy. A recently described process, called centromere pairing, can also help connect meiotic chromosome partners in meiosis. Homologous chromosomes become tightly joined by a structure called the synaptonemal complex (SC) in meiotic prophase. After the SC disassembles, persisting SC proteins at the centromeres mediate their pairing. Here, studies in mouse spermatocytes and yeast are used to show that the shugoshin protein helps SC components persist at centromeres and helps centromere pairing promote the proper segregation of yeast chromosomes that fail to become tethered by crossovers.

cell biology↗