BAY 60–2770 activates two isoforms of nitric oxide sensitive guanylyl cyclase: Evidence for stable insertion of activator drugs

Heterozygous gain of function variant in GUCY1A2 may cause autonomous ovarian hyperfunction

PURPOSE

The purpose of this study was to characterize the phenotype associated with a de novo gain-of-function variant in the GUCY1A2 gene.

METHODS

An individual carrying the de novo heterozygous variant c.1458G>T p.(E486D) in GUCY1A2 was identified by exome sequencing. The effect of the corresponding enzyme variant α2E486D/β1 was evaluated using concentration-response measurements with wild-type enzyme and the variant in cytosolic fractions of HEK293 cells, UV-vis absorbance spectra of the corresponding purified enzymes, and examination of overexpressed fluorescent protein-tagged constructs by confocal laser scanning microscopy.

RESULTS

The patient presented with precocious peripheral puberty resembling the autonomous ovarian puberty seen in McCune-Albright syndrome. Additionally, the patient displayed severe intellectual disability. In vitro activity assays revealed an increased nitric oxide affinity for the mutant enzyme. The response to carbon monoxide was unchanged, while thermostability was decreased compared to wild type. Heme content, susceptibility to oxidation, and subcellular localization upon overexpression were unchanged.

CONCLUSION

Our data define a syndromic autonomous ovarian puberty likely due to the activating allele p.(E486D) in GUCY1A2 leading to an increase in cGMP. The overlap with the ovarian symptoms of McCune-Albright syndrome suggests an impact of this cGMP increase on the cAMP pathway in the ovary. Additional cases will be needed to ensure a causal link.

Controlled release of nitric oxide for enhanced tumor drug delivery and reduction of thrombosis risk

Platelets activation and hypercoagulation induced by tumor cell-specific thrombotic secretions such as tissue factor (TF) and cancer procoagulant (CP), microparticles (MPs), and cytokines not only increase cancer-associated thrombosis but also accelerate cancer progress. In addition, the tumor heterogeneity such avascular areas, vascular occlusion and interstitial fluid pressure still challenges efficient drug delivery into tumor tissue. To overcome these adversities, we herein present an antiplatelet strategy based on a proteinic nanoparticles co-assembly of l-arginine (LA) and photosensitizer IR783 for local NO release to inhibit the activation of tumor-associated platelets and normalize angiogenesis, suppressing thrombosis and increasing tumoral accumulation of the nanoagent. In addition, NIR-controlled release localizes the NO spatiotemporally to tumor-associated platelets and prevents undesirable systemic bleeding substantially. Moreover, NO can transform to more cytotoxic peroxynitrite to destroy cancer cells. Our study describes an antiplatelet-directed cancer treatment, which represents a promising area of targeted cancer therapy.

Replacement of heme by soluble guanylate cyclase (sGC) activators abolishes heme-nitric oxide/oxygen (H-NOX) domain structural plasticity

The gasotransmitter nitric oxide (NO) is a critical endogenous regulator of homeostasis, in major part via the generation of cGMP (cyclic guanosine monophosphate) from GTP (guanosine triphosphate) by NO's main physiological receptor, the soluble guanylate cyclase (sGC). sGC is a heterodimer, composed of an α1 and a β1 subunit, of which the latter contains the heme-nitric oxide/oxygen (H-NOX) domain, responsible for NO recognition, binding and signal initiation. The NO/sGC/cGMP axis is dysfunctional in a variety of diseases, including hypertension and heart failure, especially since oxidative stress results in heme oxidation, sGC unresponsiveness to NO and subsequent degradation. As a central player in this axis, sGC is the focus of intense research efforts aiming to develop therapeutic molecules that enhance its activity. A class of drugs named sGC “activators” aim to replace the oxidized heme of the H-NOX domain, thus stabilizing the enzyme and restoring its activity. Although numerous studies outline the pharmacology and binding behavior of these compounds, the static 3D models available so far do not allow a satisfactory understanding of the structural basis of sGC's activation mechanism by these drugs. Herein, application NMR describes different conformational states during the replacement of the heme by a sGC activators. We show that the two sGC activators (BAY 58-2667 and BAY 60-2770) significantly decrease the conformational plasticity of the recombinant H-NOX protein domain of Nostoc sp. cyanobacterium, rendering it a lot more rigid compared to the heme-occupied H-NOX. NMR methodology also reveals, for the first time, a surprising bi-directional competition between reduced heme and these compounds, pointing to a highly dynamic regulation of the H-NOX domain. This competitive, bi-directional mode of interaction is also confirmed by monitoring cGMP generation in A7r5 vascular smooth muscle cells by these activators. We show that, surprisingly, heme's redox state impacts differently the bioactivity of these two structurally similar compounds. In all, by NMR-based and functional approaches we contribute unique experimental insight into the dynamic interaction of sGC activators with the H-NOX domain and its dependence on the heme redox status, with the ultimate goal to permit a better design of such therapeutically important molecules.

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When the heme of Ns H-NOX is replaced by the sGC activators, the protein’s flexibility is significantly reduced.

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Heme causes the conformational exchange of Ns H-NOX, as many residues around the heme adopt invisible conformation.

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L-ascorbate prevents the proper action of BAY 58-2667 and BAY 60-2770 from forming a stable complex with the Ns H-NOX.

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In A7r5 cells, L-ascorbate does not affect cGMP formation induced by BAY 58-2667 and it inhibits the effect of BAY 60-2770.

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BAY molecules act on the H-NOX or the sGC in a bi-directional way, depending on the redox state of the heme.

Redox Switches Controlling Nitric Oxide Signaling in the Resistance Vasculature and Implications for Blood Pressure Regulation: Mid-Career Award for Research Excellence 2020

The arterial resistance vasculature modulates blood pressure and flow to match oxygen delivery to tissue metabolic demand. As such, resistance arteries and arterioles have evolved a series of highly orchestrated cell-cell communication mechanisms between endothelial cells and vascular smooth muscle cells to regulate vascular tone. In response to neurohormonal agonists, release of several intracellular molecules, including nitric oxide, evokes changes in vascular tone. We and others have uncovered novel redox switches in the walls of resistance arteries that govern nitric oxide compartmentalization and diffusion. In this review, we discuss our current understanding of redox switches controlling nitric oxide signaling in endothelial and vascular smooth muscle cells, focusing on new mechanistic insights, physiological and pathophysiological implications, and advances in therapeutic strategies for hypertension and other diseases.

Biomimetic nano-NOS mediated local NO release for inhibiting cancer-associated platelet activation and disrupting tumor vascular barriers

Platelets attribute to the hypercoagulation of blood and maintenance of the tumor vascular integrity, resulting in limited intratumoral perfusion of nanoparticle into solid tumors. To overcome these adversities, we herein present an antiplatelet strategy based on erythrocyte membrane-enveloped proteinic nanoparticles that biomimic nitric oxide synthase (NOS)with co-loading of l-Arginine (LA) and photosensitizer IR783 for local NO release and inhibition of the activation of tumor-associated platelets specifically, thereby enhancing vascular permeability and accumulation of the nanoparticles in tumors. A cRGD-immobolized membrane structure is constructed to actively target platelets and cancer cells respectively, through overexpressed integrin receptors such as integrin α_IIbβ₃ and α_vβ₃, accelerating the inhibition of platelet activation and endocytosis of nanoparticles by tumor cells. Bio-mimicking the arginine/NO pathway in vivo, synergistical delivery of LA and IR783 enables LA molecules readily oxidize to NO with O₂ that is mediated by activated IR783, the resulted NO not only retards the activity of platelets to disrupt the vascular integrity of tumor but also enhances toxicity to cancer cells. In addition, NIR-controlled release localizes the NO spatiotemporally to tumor-associated platelets and prevents undesirable systemic bleeding substantially. The reduction of the hypercoagulable state is further demonstrated by the down-regulation of tissues factor (TF) expression in tumor cells. Our study describes a promising approach to combat cancer, which advances the biomimetic NOS system as the potent therapeutic forces toward clinic applications.

Thermal shift assay: Strengths and weaknesses of the method to investigate the ligand-induced thermostabilization of soluble guanylyl cyclase

Thermal shift assay is a fluorescence dye based biochemical method to determine the melting point of a protein. It can be used to investigate the ligand-induced stabilization of proteins and helps to increase the likelihood of crystallization in biological samples. Dimeric proteins like soluble guanylyl cyclase (sGC) have specific structural and functional properties which may pose a challenge in thermal shift measurements. In this paper, thermal shift assay was used to examine ligand-induced thermostabilization of the dimeric heme-containing protein soluble guanylyl cyclase. Adjustment of the parameters buffer solution, pH, protein / dye ratio and protein amount per well yielded a one-phase melting curve of sGC with a sharp transition and high reproducibility. We found that thermal shift measurement is not affected by heme state or heme content of the enzyme preparation. We used the method to investigate the thermostabilization of sGC induced by the heme-mimetic activator drugs cinaciguat, BAY 60-2770 and BR 11257 in combination with non-hydrolyzable nucleotides. Measurements with the dicarboxylic drugs cinaciguat and BAY 60-2770 yielded steep melting curves with high amplitudes. In contrast, in the presence of the monocarboxylic sGC activator BR 11257, melting curves appear flattened in the dye-based measurements. In the present paper, we show that activity-based thermostability measurements are superior to dye-based measurements in detecting the thermostabilizing influence of sGC activator drugs.

cGMP modulation therapeutics for sickle cell disease

IMPACT STATEMENT

Sickle cell disease (SCD) is one of the most common inherited diseases and is associated with a reduced life expectancy and acute and chronic complications, including frequent painful vaso-occlusive episodes that often require hospitalization. At present, treatment of SCD is limited to hematopoietic stem cell transplant, transfusion, and limited options for pharmacotherapy, based principally on hydroxyurea therapy. This review highlights the importance of intracellular cGMP-dependent signaling pathways in SCD pathophysiology; modulation of these pathways with soluble guanylate cyclase (sGC) stimulators or phosphodiesterase (PDE) inhibitors could potentially provide vasorelaxation and anti-inflammatory effects, as well as elevate levels of anti-sickling fetal hemoglobin.

Discovery and development of next generation sGC stimulators with diverse multidimensional pharmacology and broad therapeutic potential

Nitric oxide (NO)-sensitive soluble guanylyl cyclase (sGC), an enzyme that catalyzes the conversion of guanosine-5'-triphosphate (GTP) to cyclic guanosine-3',5'-monophophate (cGMP), transduces many of the physiological effects of the gasotransmitter NO. Upon binding of NO to the prosthetic heme group of sGC, a conformational change occurs, resulting in enzymatic activation and increased production of cGMP. cGMP modulates several downstream cellular and physiological responses, including but not limited to vasodilation. Impairment of this signaling system and altered NO-cGMP homeostasis have been implicated in cardiovascular, pulmonary, renal, gastrointestinal, central nervous system, and hepatic pathologies. sGC stimulators, small molecule drugs that synergistically increase sGC enzyme activity with NO, have shown great potential to treat a variety of diseases via modulation of NO-sGC-cGMP signaling. Here, we give an overview of novel, orally available sGC stimulators that Ironwood Pharmaceuticals is developing. We outline the non-clinical and clinical studies, highlighting pharmacological and pharmacokinetic (PK) profiles, including pharmacodynamic (PD) effects, and efficacy in a variety of disease models.

Methods to investigate structure and activation dynamics of GC-1/GC-2

Soluble guanylyl cyclase (sGC) is a heterodimeric enzyme consisting of one α and one β subunit. The α1β1 (GC-1) and α2β1 (GC-2) heterodimers are important for NO signaling in humans and catalyse the conversion from GTP to cGMP. Each sGC subunit consists of four domains. Several crystal structures of the isolated domains are available. However, crystals of full-length sGC have failed to materialise. In consequence, the detailed three dimensional structure of sGC remains unknown to date. Different techniques including stopped-flow spectroscopy, Förster-resonance energy transfer, direct fluorescence, analytical ultracentrifugation, chemical cross-linking, small-angle X-ray scattering, electron microscopy, hydrogen-deuterium exchange and protein thermal shift assays, were used to collect indirect information. Taken together, this circumstantial evidence from different groups brings forth a plausible model of sGC domain arrangement, spatial orientation and dynamic rearrangement upon activation. For analysis of the active conformation the stable binding mode of sGC activators has a significant methodological advantage over the transient, elusive, complex and highly concentration dependent effects of NO in many applications. The methods used and the results obtained are reviewed and discussed in this article.