Therapeutic Targeting of the Soluble Guanylate Cyclase

Abstract

The soluble guanylate cyclase (sGC) is the physiological sensor for nitric oxide and alterations of its function are actively implicated in a wide variety of pathophysiological conditions. Intense research efforts over the past 20 years have provided significant information on its regulation, culminating in the rational development of approved drugs or investigational lead molecules, which target and interact with sGC through novel mechanisms. However, there are numerous questions that remain unanswered. Ongoing investigations, with the critical aid of structural chemistry studies, try to further elucidate the enzyme’s structural characteristics that define the association of “stimulators” or “activators” of sGC in the presence or absence of the heme moiety, respectively, as well as the precise conformational attributes that will allow the design of more innovative and effective drugs. This review relates the progress achieved, particularly in the past 10 years, in understanding the function of this enzyme, and focusses on a) the rationale and results of its therapeutic targeting in disease situations, depending on the state of enzyme (oxidized or not, heme-carrying or not) and b) the most recent structural studies, which should permit improved design of future therapeutic molecules that aim to directly upregulate the activity of sGC.

Mapping of the sGC Stimulator BAY 41-2272 Binding Site on H-NOX Domain and Its Regulation by the Redox State of the Heme

“…H-NOX domains are well-conserved among different organisms, sharing common structural features. Ns H-NOX shares 33.86% sequence identity with Hs sGC β1-subunit H-NOX: 17 out of 27 amino acids that form the heme cavity are identical, making it the most extensively characterized among the H-NOX family domains (Makrynitsa et al, 2019;Wittenborn and Marletta, 2021).…”

“…Mapping these residues on the 3D structure of the Ns H-NOX (PDB ID: 4IAM) (Kumar et al, 2013), shows that the amino acids affected mainly lie on the α 3 and α 4 α-helices as well as on the loop connecting α 2 -α 3 and α 3 -α 4 α-helices, are distributed on the surface of the protein and delineate a binding site juxtaposed to the heme moiety (Figures 1B, 2A). Residues defining the binding surface are conserved in other bacterial H-NOX domains (Makrynitsa et al, 2019) as well as in the β1 Η-ΝΟΧ domain (Supplementary Figure S1A), making it likely that they also play a role in the interaction of BAY 41-2272 with the sGC β1 H-NOX. Moreover, when these results are compared to the reported cryoEM structure of sGC in complex with NO and Riociguat (Liu et al, 2021), it is evident that the residues participating in the binding of the drug are the same in both cases, strengthening the evidence that BAY 41-2272 and related stimulators bind to a conserved pocket in the H-NOX domain (Supplementary Figure S1B).…”

Backbone and side chain NMR assignments of the H-NOX domain from Nostoc sp. in complex with BAY58-2667 (cinaciguat)

“…2a) (Martin et al 2010). Based on the CATH server (Dawson et al 2017), the complex falls into the alpha-beta complex architecture category, a quite typical fold type for H-NOX domains (Makrynitsa et al 2019). However, slight differences are detected, comparing to the TALOS + results of native Ns H-NOX (5 α-helices and 5 β-strands) (Fig.…”

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

“…The 3-D structure of the sGC β-subunit H-NOX domain is remarkably well-conserved among species, while the amino acids of the H-NOX cavity which mediate the interaction of H-NOX with heme are remarkably well-conserved between bacterial and mammalian species (e.g. Nostoc punctiforme, Bos taurus ), being identical by ∼63% (17 of 27, ( Alexandropoulos et al., 2016 ; Makrynitsa et al., 2019 ; Wittenborn and Marletta, 2021 ). This is why rational drug design based on microbial H-NOX structural data and on the very structure of heme has contributed to, and still informs, the development of sGC activator molecules all the way to advanced clinical trials (reviewed in Alexandropoulos et al., 2016 ; Makrynitsa et al., 2019 ; Liu et al., 2021 ; Wittenborn and Marletta, 2021 ).…”

“…Nostoc punctiforme, Bos taurus ), being identical by ∼63% (17 of 27, ( Alexandropoulos et al., 2016 ; Makrynitsa et al., 2019 ; Wittenborn and Marletta, 2021 ). This is why rational drug design based on microbial H-NOX structural data and on the very structure of heme has contributed to, and still informs, the development of sGC activator molecules all the way to advanced clinical trials (reviewed in Alexandropoulos et al., 2016 ; Makrynitsa et al., 2019 ; Liu et al., 2021 ; Wittenborn and Marletta, 2021 ). Despite all this, it is understood that ideally, any conclusions derived from a structural approach using a recombinant microbial domain (in this case Nostoc sp.…”