Abstract
The ability to fight or flee from a threat relies upon an acute adrenergic surge that augments cardiac output, which is dependent upon increased cardiac contractility and heart rate. This cardiac response depends on β-adrenergic-initiated reversal of the small RGK G-protein Rad-mediated inhibition of voltage-gated calcium channels (CaV) acting through the Cavβ subunit. Here, we investigate how Rad couples phosphorylation to augmented Ca2+ influx and increased cardiac contraction. We show that reversal requires phosphorylation of Ser272 and Ser300 within Rad’s polybasic, hydrophobic C-terminal domain (CTD). Phosphorylation of Ser25 and Ser38 in Rad’s N-terminal domain (NTD) alone is ineffective. Phosphorylation of Ser272 and Ser300 or the addition of four Asp to the CTD reduces Rad’s association with the negatively charged, cytoplasmic plasmalemmal surface and with CaVβ, even in the absence of CaVα, measured here by FRET. Addition of a post-translationally prenylated CAAX motif to Rad’s C-terminus, which constitutively tethers Rad to the membrane, prevents the physiological and biochemical effects of both phosphorylation and Asp-substitution. Thus, dissociation of Rad from the sarcolemma, and consequently from CaVβ, is sufficient for sympathetic up-regulation of Ca2+ currents.
Authors
Arianne Papa, Pedro J. del Rivero Morfin, Bi-Xing Chen, Lin Yang, Alex N. Katchman, Sergey I. Zakharov, Guoxia Liu, Michael S. Bohnen, Vivian Zheng, Moshe Katz, Suraj Subramaniam, Joel A. Hirsch, Sharon Weiss, Nathan Dascal, Arthur Karlin, Geoffrey S. Pitt, Henry M. Colecraft, Manu Ben Johny, Steven O. Marx
Abstract
Patients with chronic inflammatory disorders such as psoriasis have an increased risk of cardiovascular disease and elevated levels of LL37, a cathelicidin host defense peptide that has both antimicrobial and proinflammatory properties. To explore if LL37 could contribute to the risk of heart disease, we examined its effects on lipoprotein metabolism and show that LL37 enhances LDL uptake in macrophages through LDLR, SR-B1 and CD36. This interaction led to increased cytosolic cholesterol in macrophages and changes in expression of lipid metabolism genes consistent with increased cholesterol uptake. Structure-function analysis and synchrotron small angle X-ray scattering show structural determinants of the LL37-LDL complex that underlie its ability to bind its receptors and promote uptake. This function of LDL uptake is unique to cathelicidins from humans and some primates and was not observed with cathelicidins from mice or rabbits. Notably, Apoe-/- mice expressing LL37 develop larger atheroma plaques than control mice and a positive correlation between plasma LL37 and OxPL-apoB levels was observed in human subjects with cardiovascular disease. These findings provide evidence that LDL uptake can be increased via interaction with LL37 and may explain the increased risk of cardiovascular disease associated with the chronic inflammatory disorders.
Authors
Yoshiyuki Nakamura, Nikhil N. Kulkarni, Toshiya Takahashi, Haleh Alimohamadi, Tatsuya Dokoshi, Edward L. Liu, Michael Shia, Tomofumi Numata, Elizabeth W.C. Luo, Adrian F. Gombart, Xiaohong Yang, Patrick Secrest, Philip L.S.M. Gordts, Sotirios Tsimikas, Gerard C.L. Wong, Richard L. Gallo
Abstract
Itaconate has emerged as a critical immunoregulatory metabolite. Here, we examined the therapeutic potential of itaconate in atherosclerosis. We found that both itaconate and the enzyme that synthesizes it, aconitate decarboxylase 1 (Acod1, also known as “immune-responsive gene 1”/IRG1) are upregulated during atherogenesis in mice. Deletion of Acod1 in myeloid cells exacerbated inflammation and atherosclerosis in vivo and resulted in an elevated frequency of a specific subset of M1-polarized proinflammatory macrophages in the atherosclerotic aorta. Importantly, Acod1 levels were inversely correlated with clinical occlusion in atherosclerotic human aorta specimens. Treating mice with the itaconate derivative 4-ocytyl itaconate attenuated inflammation and atherosclerosis induced by high cholesterol. Mechanistically, we found that the antioxidant transcription factor, Nuclear factor erythroid-2 Related Factor 2 (Nrf2) was required for itaconate to suppress macrophage activation induced by oxidized lipids in vitro and to decrease atherosclerotic lesion areas in vivo. Overall, our work shows that itaconate suppresses atherogenesis by inducing Nrf2-dependent inhibition of proinflammatory responses in macrophages. Activation of the itaconate pathway may represent an important approach to treat atherosclerosis.
Authors
Jianrui Song, Yanling Zhang, Ryan A. Frieler, Anthony Andren, Sherri C. Wood, Daniel J. Tyrrell, Peter Sajjakulnukit, Jane C. Deng, Costas A. Lyssiotis, Richard M. Mortensen, Morgan Salmon, Daniel R. Goldstein
Abstract
Heterozygous (HET) truncating mutations in the TTN gene (TTNtv) encoding the giant titin protein are the most common genetic cause of dilated cardiomyopathy (DCM). However, the molecular mechanisms by which TTNtv mutations induce DCM are controversial. Here we investigated 127 clinically identified DCM human cardiac samples with next-generation sequencing (NGS), high-resolution gel electrophoresis, Western blot analysis and super-resolution microscopy in order to dissect the structural and functional consequences of TTNtv mutations. The occurrence of TTNtv was found to be 15% in the DCM cohort. Truncated titin proteins matching, by molecular weight, the gene-sequence predictions were detected in the majority of the TTNtv+ samples. Full length titin was reduced in TTNtv+ compared to TTNtv- samples. Proteomic analysis of washed myofibrils and Stimulated Emission Depletion (STED) super-resolution microscopy of myocardial sarcomeres labeled with sequence-specific anti-titin antibodies revealed that truncated titin is structurally integrated in the sarcomere. Sarcomere length-dependent anti-titin epitope position, shape and intensity analyses pointed at possible structural defects in the I/A junction and the M-band of TTNtv+ sarcomeres, which likely contribute, possibly via faulty mechanosensor function, to the development of manifest DCM.
Authors
Dalma Kellermayer, Hedvig Tordai, Balázs Kiss, György Török, Dániel M. Péter, Alex Ali Sayour, Miklós Pólos, István Hartyánszky, Bálint Szilveszter, Siegfried Labeit, Ambrus Gángó, Gábor Bedics, Csaba Bödör, Tamás Radovits, Bela Merkely, Miklós S.Z. Kellermayer
Abstract
Authors
Quentin McAfee, Matthew A. Caporizzo, Keita Uchida, Kenneth C. Bedi Jr., Kenneth B. Margulies, Zolt Arany, Benjamin L. Prosser
Abstract
Interplay between energy-storing white adipose cells and thermogenic beige adipocytes contributes to obesity and insulin resistance. Irrespective of specialized niche, adipocytes require the activity of the nuclear receptor PPARγ for proper function. Exposure to cold or adrenergic signaling enriches thermogenic cells though multiple pathways that act synergistically with PPARγ; however, the molecular mechanisms by which PPARγ licenses white adipose tissue to preferentially adopt a thermogenic or white adipose fate in response to dietary cues or thermoneutral conditions are not fully elucidated. Here, we show that a PPARγ/long noncoding RNA (lncRNA) axis integrates canonical and noncanonical thermogenesis to restrain white adipose tissue heat dissipation during thermoneutrality and diet-induced obesity. Pharmacologic inhibition or genetic deletion of the lncRNA Lexis enhances uncoupling protein 1–dependent (UCP1-dependent) and -independent thermogenesis. Adipose-specific deletion of Lexis counteracted diet-induced obesity, improved insulin sensitivity, and enhanced energy expenditure. Single-nuclei transcriptomics revealed that Lexis regulates a distinct population of thermogenic adipocytes. We systematically map Lexis motif preferences and show that it regulates the thermogenic program through the activity of the metabolic GWAS gene and WNT modulator TCF7L2. Collectively, our studies uncover a new mode of crosstalk between PPARγ and WNT that preserves white adipose tissue plasticity.
Authors
Zhengyi Zhang, Ya Cui, Vivien Su, Dan Wang, Marcus J. Tol, Lijing Cheng, Xiaohui Wu, Jason Kim, Prashant Rajbhandari, Sicheng Zhang, Wei Li, Peter Tontonoz, Claudio J. Villanueva, Tamer Sallam
Abstract
Heart Failure with Preserved Ejection Fraction (HFpEF) is a widespread syndrome with limited therapeutic options and poorly understood immune-pathophysiology. Using a two-hit preclinical model of cardiometabolic HFpEF that induces obesity and hypertension, we found that cardiac T cell infiltration and lymphoid expansion occur concomitantly with cardiac pathology, and that diastolic dysfunction, cardiomyocyte hypertrophy and cardiac phospholamban phosphorylation are T cell-dependent. Heart-infiltrating T cells were not restricted to cardiac antigens and were uniquely characterized by impaired activation of the Inositol-requiring enzyme-1α (IRE1α)-X-box binding protein 1 (XBP1) arm of the unfolded protein response. Notably, selective ablation of XBP1 in T cells enhanced their persistence in the heart and lymphoid organs of mice with preclinical HFpEF. Furthermore, T cell IRE1α-XBP1 activation was restored after withdrawal of the two comorbidities inducing HFpEF, resulting in partial improvement of cardiac pathology. Our results demonstrate that diastolic dysfunction and cardiomyocyte hypertrophy in preclinical HFpEF are T cell-dependent, and that reversible dysregulation of the T cell IRE1α-XBP1 axis is a T cell signature of HFpEF.
Authors
Sasha Smolgovsky, Abraham L. Bayer, Kuljeet Kaur, Erin Sanders, Mark Aronovitz, Mallory E. Filipp, Edward B. Thorp, Gabriele G. Schiattarella, Joseph A. Hill, Robert M. Blanton, Juan R. Cubillos-Ruiz, Pilar Alcaide
Abstract
Cardiovascular diseases are the most common cause of worldwide morbidity and mortality, highlighting the necessity for advanced therapeutic strategies. Ca2+/calmodulin-dependent protein kinase IIδ (CaMKIIδ) is a prominent inducer of various cardiac disorders, which is mediated by two oxidation-sensitive methionine residues within the regulatory domain. We previously showed that ablation of CaMKIIδ oxidation by CRISPR-Cas9 base editing enables the heart to recover function from otherwise severe damage following ischemia/reperfusion (IR) injury. Here, we extended this therapeutic concept toward potential clinical translation. We generated a humanized CAMK2D knockin mouse model, in which the genomic sequence encoding the entire regulatory domain was replaced with the human sequence. This enabled comparison and optimization of two different editing strategies for the human genome in mice. To edit CAMK2D in vivo, we packaged the optimized editing components into an engineered myotropic adeno-associated virus (MyoAAV 2A), which enabled efficient delivery at a very low AAV dose into the humanized mice at the time of IR injury. CAMK2D-edited mice recovered cardiac function, showed improved exercise performance, and were protected from myocardial fibrosis, which was otherwise observed in injured control mice post-IR. Our findings identify a potentially effective strategy for cardioprotection in response to oxidative damage.
Authors
Simon Lebek, Xurde M. Caravia, Leon G. Straub, Damir Alzhanov, Wei Tan, Hui Li, John R. McAnally, Kenian Chen, Lin Xu, Philipp E. Scherer, Ning Liu, Rhonda Bassel-Duby, Eric N. Olson
Abstract
The metabolic syndrome, today affecting more than 20% of the US population, is a group of five conditions that often co-exist and that strongly predispose to cardiovascular disease. How these conditions are linked mechanistically remains unclear, especially two of these: obesity and elevated blood pressure. Here we show that high fat consumption in mice leads to the accumulation of lipid droplets in endothelial cells throughout the organism, and that lipid droplet accumulation in endothelium suppresses endothelial nitric oxide synthase (eNOS), reduces NO production, elevates blood pressure, and accelerates atherosclerosis. Mechanistically, the accumulation of lipid droplets destabilizes eNOS mRNA and activates an endothelial inflammatory signaling cascade that suppresses eNOS and NO production. Pharmacological prevention of lipid droplet formation reverses the suppression of NO production in cell culture and in vivo, and blunts blood pressure elevation in response to high fat diet. These results highlight lipid droplets as a critical and unappreciated component of endothelial cell biology, explain how lipids increase blood pressure acutely, and provide a mechanistic account for the epidemiological link between obesity and elevated blood pressure.
Authors
Boa Kim, Wencao Zhao, Soon Yew Tang, Michael G. Levin, Ayon Ibrahim, Yifan Yang, Emilia M. Roberts, Ling Lai, Jian Li, Richard K. Assoian, Garret A. FitzGerald, Zoltan Arany
Abstract
Identifying branched-chain amino acid (BCAA) oxidation enzymes in the nucleus led us to predict that they are a source of propionyl-CoA that are utilized for histone propionylation and, thereby, regulate gene expression. To investigate the effects of BCAA on the development of cardiac hypertrophy and failure, we applied pressure overload on the heart in mice maintained on a diet with standard levels of BCAA (BCAA-control) versus a BCAA-free diet. The former was associated with an increase in histone H3K23-propionyl (H3K23Pr) at the promoters of upregulated genes [e.g., cell signaling and extracellular matrix genes] and a decrease at the promoters of downregulated genes [e.g., electron transfer complex (ETC I-V) and metabolic genes]. Intriguingly, the BCAA-free diet tempered the increases in promoter-H3K23Pr, thus, reducing collagen gene expression and fibrosis during cardiac hypertrophy. Conversely, the BCAA-free diet inhibited the reductions in promoter-H3K23Pr and abolished the downregulation of ETC I-V subunits, enhanced mitochondrial respiration, and curbed progression of cardiac hypertrophy. Thus, lowering the intake of BCAA reduces pressure overload-induced changes in histone propionylation-dependent gene expression in the heart, which retards the development of cardiomyopathy.
Authors
Zhi Yang, Minzhen He, Julianne Austin, Danish Sayed, Maha Abdellatif
Copyright © 2025 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)