Cardiomyocyte Expression of ZO-1 Is Essential for Normal Atrioventricular Conduction but Does Not Alter Ventricular Function

Rationale: ZO-1 (Zonula occludens-1), a plasma membrane-associated scaffolding protein regulates signal transduction, transcription, and cellular communication. Global deletion of ZO-1 in the mouse is lethal by embryonic day 11.5. The function of ZO-1 in cardiac myocytes (CM) is largely unknown. Objective: To determine the function of CM ZO-1 in the intact heart, given its binding to other CM proteins that have been shown instrumental in normal cardiac conduction and function. Methods and Results: We generated ZO-1 CM-specific knockout (KO) mice using α-Myosin Heavy Chain-nuclear Cre (ZO-1cKO) and investigated physiological and electrophysiological function by echocardiography, surface ECG and conscious telemetry, intracardiac electrograms and pacing, and optical mapping studies. ZO-1cKO mice were viable, had normal Mendelian ratios, and had a normal lifespan. Ventricular morphometry and function were not significantly different between the ZO-1cKO versus control (CTL) mice, basally in young or aged mice, or even when hearts were subjected to hemodynamic loading. Atrial mass was increased in ZO-1cKO. Electrophysiological and optical mapping studies indicated high-grade atrioventricular (A-V) block in ZO-1cKO comparing to CTL hearts. While ZO-1-associated proteins such as vinculin, connexin 43, N-cadherin, and α-catenin showed no significant change with the loss of ZO-1, Connexin-45 and Coxsackie-adenovirus (CAR) proteins were reduced in atria of ZO-1cKO. Further, with loss of ZO-1, ZO-2 protein was increased significantly in ventricular CM in a presumed compensatory manner but was still not detected in the AV nodal myocytes. Importantly, the expression of the sodium channel protein NaV1.5 was altered in AV nodal cells of the ZO-1cKO versus CTL. Conclusions: ZO-1 protein has a unique physiological role in cardiac nodal tissue. This is in alignment with its known interaction with CAR and Cx45, and a new function in regulating the expression of NaV1.5 in AV node. Uniquely, ZO-1 is dispensable for function of the working myocardium.

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Regulation of the gap junction connexin 43 gene by androgens in the prostate

Journal of Molecular Endocrinology ◽

10.1677/jme.0.0260001 ◽

2001 ◽

Vol 26 (1) ◽

pp. 1-10 ◽

Cited By ~ 18

Author(s):

HT Huynh ◽

L Alpert ◽

DW Laird ◽

G Batist ◽

L Chalifour ◽

...

Keyword(s):

Connexin 43 ◽

Prostate Gland ◽

Physiological Role ◽

Prostate Tissue ◽

Ventral Prostate ◽

Gap Junctional Intercellular Communication ◽

Prostate Carcinogenesis ◽

Cx43 Mrna ◽

And Function ◽

Gap Junctional

Androgens play an important role in prostate gland development and function, and have been implicated in prostate carcinogenesis. We report the regulation of the gap junctional intercellular communication gene connexin 43 (Cx43) by androgens in the prostate gland. In rat ventral prostate tissue, only trace levels of Cx43 mRNA were detected. Castration, however, resulted in a high increase in Cx43 mRNA and protein. Cx32 was unchanged. Castration-induced Cx43 mRNA and protein were abolished by administration of dihydrotestosterone (DHT). Following castration, prostate weights were approximately 16% of sham-treated controls. However, DHT replacement resulted in prostate weights which were not different from sham-treated controls. Under similar castration conditions, Cx43 induction coincided with pronounced apoptosis in the prostate gland cells, and DHT prevented the induction of apoptosis. Given the physiological role of gap junctions and androgens in the regulation of prostate tissue homeostasis, our observations are relevant to the understanding of androgen-dependent prostate carcinogenesis.

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Abstract 253: HSPB7 is Required for Maintaining the Intercalated Disc Structure to Prevent Cardiac Conduction System Failure in Mouse

Circulation Research ◽

10.1161/res.121.suppl_1.253 ◽

2017 ◽

Vol 121 (suppl_1) ◽

Author(s):

Wern-Chir Liao ◽

Liang-Yi Juo ◽

Yen-Hui Chen ◽

Yu-Ting Yan

Keyword(s):

Heart Failure ◽

Gap Junction ◽

Connexin 43 ◽

Adherens Junction ◽

Small Heat Shock Protein ◽

Cardiac Conduction ◽

Nucleotide Polymorphisms ◽

Intercalated Disc ◽

Junction Protein ◽

And Function

HSPB7 is belonged to small heat-shock protein (HSPB) family and considered to function as a co-chaperone, which prevents protein aggregation and maintains protein structure. Single-nucleotide polymorphisms of HSPB7 associated with sporadic cardiomyopathy and heart failure have been identified in human patients. Additionally, HSPB7 is constitutively expressed in heart and rapidly increased in blood plasma after myocardial infarction, suggesting a functional role in the heart. In this study, we found that HSPB7 is highly colocalized with N-cadherin during the assembly and maturation of intercalated disc, suggesting that HSPB7 may involve in organizing and maintaining the cardiac cytoarchitecture. To elucidate the physiological function of HSPB7 in the adult heart, we generated a cardiac-specific inducible HSPB7 knockout mouse. Ablation of HSPB7 in the cardiomyocyte rapidly leads to heart failure, abnormal conduction properties and sudden arrhythmias death. Loss of HSPB7 did not cause significant changes in the organization of contractile proteins in sarcomeres, whereas severe abnormality in the intercalated disc was detected. The expression of connexin 43, a gap-junction protein located at the intercalated disc, was downregulated in HSPB7 knockout cardiomyocytes. Mislocalizations of desmoplakin (desmosomal proteins), and N-cadherin (adherens junction proteins) were also observed in the HSPB7 CKO hearts. Furthermore, filamin C, the interaction protein of HSPB7, was mislocalized and aggregated in HSPB7 mutant cardiomyocytes. The expressivity of the phenotype in the HSPB7 CKO mice is similar to human arrhythmogenic cardiomyopathy patients. Conclusively, we provide the first study characterizing HSPB7 as an intercalated disc protein. Our findings demonstrate that HSPB7 plays an essential role to maintain the structure and function of gap-junction complexes and intercalated disc and has vital implications for human heart disease.

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Molecular architecture and functions of the neuronal cytoskeleton

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100157541 ◽

1990 ◽

Vol 48 (3) ◽

pp. 2-3

Author(s):

Nobutaka Hirokawa

Keyword(s):

Major Elements ◽

Molecular Structures ◽

Organelle Transport ◽

Molecular Architecture ◽

Neuronal Morphogenesis ◽

Microtubule Associated Proteins ◽

Associated Proteins ◽

And Function ◽

Small Clusters

In this symposium I will present our studies about the molecular architecture and function of the cytomatrix of the nerve cells. The nerve cell is a highly polarized cell composed of highly branched dendrites, cell body, and a single long axon along the direction of the impulse propagation. Each part of the neuron takes characteristic shapes for which the cytoskeleton provides the framework. The neuronal cytoskeletons play important roles on neuronal morphogenesis, organelle transport and the synaptic transmission. In the axon neurofilaments (NF) form dense arrays, while microtubules (MT) are arranged as small clusters among the NFs. On the other hand, MTs are distributed uniformly, whereas NFs tend to run solitarily or form small fascicles in the dendrites Quick freeze deep etch electron microscopy revealed various kinds of strands among MTs, NFs and membranous organelles (MO). These structures form major elements of the cytomatrix in the neuron. To investigate molecular nature and function of these filaments first we studied molecular structures of microtubule associated proteins (MAP1A, MAP1B, MAP2, MAP2C and tau), and microtubules reconstituted from MAPs and tubulin in vitro. These MAPs were all fibrous molecules with different length and formed arm like projections from the microtubule surface.

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Significance of Mast Cell Formed Extracellular Traps in Microbial Defense

Clinical Reviews in Allergy & Immunology ◽

10.1007/s12016-021-08861-6 ◽

2021 ◽

Author(s):

Daniel Elieh Ali Komi ◽

Wolfgang M. Kuebler

Keyword(s):

State Of The Art ◽

Extracellular Dna ◽

Cellular Mechanisms ◽

Extracellular Traps ◽

Synthetic Chemicals ◽

Dna Strands ◽

Associated Proteins ◽

Microbial Defense ◽

And Function ◽

Insight Into

AbstractMast cells (MCs) are critically involved in microbial defense by releasing antimicrobial peptides (such as cathelicidin LL-37 and defensins) and phagocytosis of microbes. In past years, it has become evident that in addition MCs may eliminate invading pathogens by ejection of web-like structures of DNA strands embedded with proteins known together as extracellular traps (ETs). Upon stimulation of resting MCs with various microorganisms, their products (including superantigens and toxins), or synthetic chemicals, MCs become activated and enter into a multistage process that includes disintegration of the nuclear membrane, release of chromatin into the cytoplasm, adhesion of cytoplasmic granules on the emerging DNA web, and ejection of the complex into the extracellular space. This so-called ETosis is often associated with cell death of the producing MC, and the type of stimulus potentially determines the ratio of surviving vs. killed MCs. Comparison of different microorganisms with specific elimination characteristics such as S pyogenes (eliminated by MCs only through extracellular mechanisms), S aureus (removed by phagocytosis), fungi, and parasites has revealed important aspects of MC extracellular trap (MCET) biology. Molecular studies identified that the formation of MCET depends on NADPH oxidase-generated reactive oxygen species (ROS). In this review, we summarize the present state-of-the-art on the biological relevance of MCETosis, and its underlying molecular and cellular mechanisms. We also provide an overview over the techniques used to study the structure and function of MCETs, including electron microscopy and fluorescence microscopy using specific monoclonal antibodies (mAbs) to detect MCET-associated proteins such as tryptase and histones, and cell-impermeant DNA dyes for labeling of extracellular DNA. Comparing the type and biofunction of further MCET decorating proteins with ETs produced by other immune cells may help provide a better insight into MCET biology in the pathogenesis of autoimmune and inflammatory disorders as well as microbial defense.

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C. elegans germ granules require both assembly and localized regulators for mRNA repression

Nature Communications ◽

10.1038/s41467-021-21278-1 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Scott Takeo Aoki ◽

Tina R. Lynch ◽

Sarah L. Crittenden ◽

Craig A. Bingman ◽

Marvin Wickens ◽

...

Keyword(s):

Liquid Droplet ◽

Scaffolding Protein ◽

P Granules ◽

C Elegans ◽

Cytoplasmic Rna ◽

And Function ◽

Rnp Granules ◽

Key Residues ◽

Reporter Mrna

AbstractCytoplasmic RNA–protein (RNP) granules have diverse biophysical properties, from liquid to solid, and play enigmatic roles in RNA metabolism. Nematode P granules are paradigmatic liquid droplet granules and central to germ cell development. Here we analyze a key P granule scaffolding protein, PGL-1, to investigate the functional relationship between P granule assembly and function. Using a protein–RNA tethering assay, we find that reporter mRNA expression is repressed when recruited to PGL-1. We determine the crystal structure of the PGL-1 N-terminal region to 1.5 Å, discover its dimerization, and identify key residues at the dimer interface. Mutations of those interface residues prevent P granule assembly in vivo, de-repress PGL-1 tethered mRNA, and reduce fertility. Therefore, PGL-1 dimerization lies at the heart of both P granule assembly and function. Finally, we identify the P granule-associated Argonaute WAGO-1 as crucial for repression of PGL-1 tethered mRNA. We conclude that P granule function requires both assembly and localized regulators.

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Membrane-associated phase separation: organization and function emerge from a two-dimensional milieu

Journal of Molecular Cell Biology ◽

10.1093/jmcb/mjab010 ◽

2021 ◽

Author(s):

Jonathon A Ditlev

Keyword(s):

Phase Separation ◽

Cell Biology ◽

Cellular Environment ◽

Condensate Formation ◽

Associated Proteins ◽

Available Technology ◽

And Function ◽

Surrounding Membrane

Abstract Liquid‒liquid phase separation (LLPS) of biomolecules has emerged as an important mechanism that contributes to cellular organization. Phase separated biomolecular condensates, or membrane-less organelles, are compartments composed of specific biomolecules without a surrounding membrane in the nucleus and cytoplasm. LLPS also occurs at membranes, where both lipids and membrane-associated proteins can de-mix to form phase separated compartments. Investigation of these membrane-associated condensates using in vitro biochemical reconstitution and cell biology has provided key insights into the role of phase separation in membrane domain formation and function. However, these studies have generally been limited by available technology to study LLPS on model membranes and the complex cellular environment that regulates condensate formation, composition, and function. Here, I briefly review our current understanding of membrane-associated condensates, establish why LLPS can be advantageous for certain membrane-associated condensates, and offer a perspective for how these condensates may be studied in the future.

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Loss of dysferlin or myoferlin results in differential defects in excitation–contraction coupling in mouse skeletal muscle

Scientific Reports ◽

10.1038/s41598-021-95378-9 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

David Y. Barefield ◽

Jordan J. Sell ◽

Ibrahim Tahtah ◽

Samuel D. Kearns ◽

Elizabeth M. McNally ◽

...

Keyword(s):

Ryanodine Receptor ◽

Calcium Binding ◽

Physiological Role ◽

Muscle Disease ◽

Calcium Handling ◽

Membrane Repair ◽

Tubule Formation ◽

Ec Coupling ◽

Associated Proteins ◽

Receptor Clusters

AbstractMuscular dystrophies are disorders characterized by progressive muscle loss and weakness that are both genotypically and phenotypically heterogenous. Progression of muscle disease arises from impaired regeneration, plasma membrane instability, defective membrane repair, and calcium mishandling. The ferlin protein family, including dysferlin and myoferlin, are calcium-binding, membrane-associated proteins that regulate membrane fusion, trafficking, and tubule formation. Mice lacking dysferlin (Dysf), myoferlin (Myof), and both dysferlin and myoferlin (Fer) on an isogenic inbred 129 background were previously demonstrated that loss of both dysferlin and myoferlin resulted in more severe muscle disease than loss of either gene alone. Furthermore, Fer mice had disordered triad organization with visibly malformed transverse tubules and sarcoplasmic reticulum, suggesting distinct roles of dysferlin and myoferlin. To assess the physiological role of disorganized triads, we now assessed excitation contraction (EC) coupling in these models. We identified differential abnormalities in EC coupling and ryanodine receptor disruption in flexor digitorum brevis myofibers isolated from ferlin mutant mice. We found that loss of dysferlin alone preserved sensitivity for EC coupling and was associated with larger ryanodine receptor clusters compared to wildtype myofibers. Loss of myoferlin alone or together with a loss of dysferlin reduced sensitivity for EC coupling, and produced disorganized and smaller ryanodine receptor cluster size compared to wildtype myofibers. These data reveal impaired EC coupling in Myof and Fer myofibers and slightly potentiated EC coupling in Dysf myofibers. Despite high homology, dysferlin and myoferlin have differential roles in regulating sarcotubular formation and maintenance resulting in unique impairments in calcium handling properties.

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The Evolving Roles of Cardiac Macrophages in Homeostasis, Regeneration, and Repair

International Journal of Molecular Sciences ◽

10.3390/ijms22157923 ◽

2021 ◽

Vol 22 (15) ◽

pp. 7923

Author(s):

Santiago Alvarez-Argote ◽

Caitlin C. O’Meara

Keyword(s):

Cardiac Injury ◽

Cardiac Regeneration ◽

Normal Function ◽

Cardiac Conduction ◽

Cell Detection ◽

Fate Mapping ◽

The Novel ◽

Functional Roles ◽

Macrophage Populations ◽

And Function

Macrophages were first described as phagocytic immune cells responsible for maintaining tissue homeostasis by the removal of pathogens that disturb normal function. Historically, macrophages have been viewed as terminally differentiated monocyte-derived cells that originated through hematopoiesis and infiltrated multiple tissues in the presence of inflammation or during turnover in normal homeostasis. However, improved cell detection and fate-mapping strategies have elucidated the various lineages of tissue-resident macrophages, which can derive from embryonic origins independent of hematopoiesis and monocyte infiltration. The role of resident macrophages in organs such as the skin, liver, and the lungs have been well characterized, revealing functions well beyond a pure phagocytic and immunological role. In the heart, recent research has begun to decipher the functional roles of various tissue-resident macrophage populations through fate mapping and genetic depletion studies. Several of these studies have elucidated the novel and unexpected roles of cardiac-resident macrophages in homeostasis, including maintaining mitochondrial function, facilitating cardiac conduction, coronary development, and lymphangiogenesis, among others. Additionally, following cardiac injury, cardiac-resident macrophages adopt diverse functions such as the clearance of necrotic and apoptotic cells and debris, a reduction in the inflammatory monocyte infiltration, promotion of angiogenesis, amelioration of inflammation, and hypertrophy in the remaining myocardium, overall limiting damage extension. The present review discusses the origin, development, characterization, and function of cardiac macrophages in homeostasis, cardiac regeneration, and after cardiac injury or stress.

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Interatrial block is related to atrial dysfunction in hypertensive subjects

European Heart Journal - Cardiovascular Imaging ◽

10.1093/ehjci/jeaa356.110 ◽

2021 ◽

Vol 22 (Supplement_1) ◽

Author(s):

L Tirapu Sola ◽

F Loncaric ◽

M Mimbrero ◽

LG Mendieta ◽

L Nunno ◽

...

Keyword(s):

Global Longitudinal Strain ◽

Female Gender ◽

Left Ventricular ◽

P Wave ◽

P Value ◽

Atrial Remodeling ◽

Maximal Volume ◽

Surface Ecg ◽

Interatrial Block ◽

And Function

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): La Marató TV3 Background Interatrial block (IAB), a delay of conduction of the sinus stimulus from right to left atria (LA), is defined as surface ECG P-wave duration ≥120 ms. Arterial hypertension (AH) and IAB have been related to development of atrial fibrillation. Aim To investigate the IAB prevalence in a cohort of AH patients and relate it to LA function. Methods 162 patients with well-regulated AT were included. 12-lead ECG were performed and analysed with a digital caliper. 2D and 3D echocardiography were performed, and LA function assessed with speckle-tracking deformation imaging. Results The median age was 56 ± 6 years, 54% were males. Average duration of AH was 10 ± 6 years. IAB was seen in 25% of AH patients. The comparison between groups is shown in Table 1. There were no differences in demographic characteristics, QRS complex duration (p = 0.179) or left ventricular (LV) size and function between subgroups. LA was enlarged in IAB patients, which was coupled with impairment of the LA reservoir strain. Conclusion Our results show considerable prevalence of IAB in AH patients. The demonstrated LA enlargement and function impairment is not associated with LV dysfunction, therefore suggesting an independent role of IAB in atrial remodeling. Table 1 Interatrial block P value Yes (n= 40) No (n= 142) Age 59 (54-62) 57 (53-61) 0.157 Female gender 16 (40%) 58 (48%) 0.467 Duration of Hypertension (years) 10 (6-12) 8 (5-15) 0.421 Systolic blood pressure (mmHg) 136 (125-150) 136 (127-147) 0.799 Diabetes 3 (8%) 16 (13%) 0.410 LVEDV (mL) 73 (63-91) 71 (57-87) 0.424 E/A 0.98 (0.84-1.25) 0.94 (0.79-1.11) 0.230 E/e’ 7.0 (4.9-8.9) 6.6 (5.2-8.4) 0.779 LVEF (%) 63 ± 7 64 ± 6 0.864 LV global longitudinal strain (%) 21.22 ± 2.63 21.19 ± 2.30 0.932 3D LA maximal volume (mL/m2) 36 (30-39) 30 (26-37) 0.028 3D LA minimal volume (mL/m2) 16 (12-18) 14 (11-17) 0.050 LA reservoir strain (%) 27.64 (24.90-31.23) 29.55 (26.17-32.81) 0.032 LA conduit strain (%) 13.91 (10.71-15.47) 14.37 (11.75-16.72) 0.192 LA contractile strain (%) 14.46 (11.86-16.59) 15.52 (13.66-16.96) 0.079 LVEDV Left Ventricular End Dyastolic Volume

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Expression and Function of Organic Anion Transporting Polypeptides in the Human Brain: Physiological and Pharmacological Implications

Pharmaceutics ◽

10.3390/pharmaceutics13060834 ◽

2021 ◽

Vol 13 (6) ◽

pp. 834

Author(s):

Anima M. Schäfer ◽

Henriette E. Meyer zu Schwabedissen ◽

Markus Grube

Keyword(s):

Organic Anion ◽

Physiological Role ◽

Point Of View ◽

Efflux Transporters ◽

Organic Anion Transporting Polypeptides ◽

Current State ◽

P Glycoprotein ◽

The Central Nervous System ◽

And Function ◽

Uptake Transporters

The central nervous system (CNS) is an important pharmacological target, but it is very effectively protected by the blood–brain barrier (BBB), thereby impairing the efficacy of many potential active compounds as they are unable to cross this barrier. Among others, membranous efflux transporters like P-Glycoprotein are involved in the integrity of this barrier. In addition to these, however, uptake transporters have also been found to selectively uptake certain compounds into the CNS. These transporters are localized in the BBB as well as in neurons or in the choroid plexus. Among them, from a pharmacological point of view, representatives of the organic anion transporting polypeptides (OATPs) are of particular interest, as they mediate the cellular entry of a variety of different pharmaceutical compounds. Thus, OATPs in the BBB potentially offer the possibility of CNS targeting approaches. For these purposes, a profound understanding of the expression and localization of these transporters is crucial. This review therefore summarizes the current state of knowledge of the expression and localization of OATPs in the CNS, gives an overview of their possible physiological role, and outlines their possible pharmacological relevance using selected examples.

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