Disparate molecular mechanisms in cardiac ryanodine receptor channelopathies.

Aims: Mutations in the cardiac ryanodine receptor (RyR2) are associated with catecholaminergic polymorphic ventricular tachycardia (CPVT). This study investigates the underlying molecular mechanisms for CPVT mutations within the RyR2 N-terminus domain (NTD).

Methods And Results: We consulted the high-resolution RyR2 structure in both open and closed configuration to identify mutations G357S/R407I and A77T, which lie within the NTD intra- and inter-subunit interface with the Core Solenoid (CSol), respectively.

Identification of an amino-terminus determinant critical for ryanodine receptor/Ca2+ release channel function.

Aims: The cardiac ryanodine receptor (RyR2), which mediates intracellular Ca2+ release to trigger cardiomyocyte contraction, participates in development of acquired and inherited arrhythmogenic cardiac disease. This study was undertaken to characterize the network of inter- and intra-subunit interactions regulating the activity of the RyR2 homotetramer.

Methods And Results: We use mutational investigations combined with biochemical assays to identify the peptide sequence bridging the β8 with β9 strand as the primary determinant mediating RyR2 N-terminus self-association.

Association of cardiac myosin-binding protein-C with the ryanodine receptor channel - putative retrograde regulation?

The cardiac muscle ryanodine receptor-Ca release channel (RyR2) constitutes the sarcoplasmic reticulum (SR) Ca efflux mechanism that initiates myocyte contraction, while cardiac myosin-binding protein-C (cMyBP-C; also known as MYBPC3) mediates regulation of acto-myosin cross-bridge cycling. In this paper, we provide the first evidence for the presence of direct interaction between these two proteins, forming a RyR2-cMyBP-C complex. The C-terminus of cMyBP-C binds with the RyR2 N-terminus in mammalian cells and the interaction is not mediated by a fibronectin-like domain.

Structural and functional interactions within ryanodine receptor.

The ryanodine receptor/Ca2+ release channel plays a pivotal role in skeletal and cardiac muscle excitation-contraction coupling. Defective regulation leads to neuromuscular disorders and arrhythmogenic cardiac disease. This mini-review focuses on channel regulation through structural intra- and inter-subunit interactions and their implications in ryanodine receptor pathophysiology.

Dantrolene rescues aberrant N-terminus intersubunit interactions in mutant pro-arrhythmic cardiac ryanodine receptors.

Aims: The ryanodine receptor (RyR2) is an intracellular Ca(2+) release channel essential for cardiac excitation-contraction coupling. Abnormal RyR2 channel function results in the generation of arrhythmias and sudden cardiac death. The present study was undertaken to investigate the mechanistic basis of RyR2 dysfunction in inherited arrhythmogenic cardiac disease.

N-terminus oligomerization is conserved in intracellular calcium release channels.

Oligomerization of all three mammalian ryanodine receptor isoforms, a structural requirement for normal intracellular Ca2+ release channel function, is displayed by the discrete N-terminal domain which assembles into homo- and hetero-tetramers. This is demonstrated in yeast, mammalian cells and native tissue by complementary yeast two-hybrid, chemical cross-linking and co-immunoprecipitation assays. The IP3 (inositol 1,4,5-trisphosphate) receptor N-terminus (residues 1-667) similarly exhibits tetrameric association as indicated by chemical cross-linking and co-immunoprecipitation assays.

N-terminus oligomerization regulates the function of cardiac ryanodine receptors.

The ryanodine receptor (RyR) is an ion channel composed of four identical subunits mediating calcium efflux from the endo/sarcoplasmic reticulum of excitable and non-excitable cells. We present several lines of evidence indicating that the RyR2 N-terminus is capable of self-association. A combination of yeast two-hybrid screens, co-immunoprecipitation analysis, chemical crosslinking and gel filtration assays collectively demonstrate that a RyR2 N-terminal fragment possesses the intrinsic ability to oligomerize, enabling apparent tetramer formation.

Evaluation of activity and combination strategies with the microtubule-targeting drug sagopilone in breast cancer cell lines.

Sagopilone, a fully synthetic epothilone, is a microtubule-stabilizing agent optimized for high in vitro and in vivo activity against a broad range of tumor models, including those resistant to paclitaxel and other systemic treatments. Sagopilone development is accompanied by translational research studies to evaluate the molecular mode of action, to recognize mechanisms leading to resistance, to identify predictive response biomarkers, and to establish a rationale for combination with different therapies. Here, we profiled sagopilone activity in breast cancer cell lines.

Cell-based therapy for heart failure: skeletal myoblasts.

Satellite cells are committed precursor cells residing in the skeletal muscle. These cells provide an almost unlimited regeneration potential to the muscle, contrary to the heart, which, although proved to contain cardiac stem cells, possesses a very limited ability for self-renewal. The idea that myoblasts (satellite cell progenies) may repopulate postinfarction scar occurred around the mid-1990s.

Regulation of eNOS expression in HCAEC cell line treated with opioids and proinflammatory cytokines.

Background: Nitric oxide (NO) generated by endothelial nitric oxide synthase (eNOS) plays a crucial role in vascular function and homeostasis. eNOS activity maintains normal vascular tone, regulates leukocyte-endothelial cell interactions, inhibits platelet aggregation, limits smooth muscle cell proliferation and influences cardiac myocyte contractility. The loss of endothelium-derived NO has been shown to result in serious cardiovascular abnormalities, which may indicate eNOS involvement in the origin/development of cardiovascular disorders.