About this Research Topic
NO-stimulated guanylyl cyclases (sGC or GC1/GC2) are heterodimeric enzymes specialized to produce cGMP in large quantities upon reversible NO binding to a prosthetic haem-group. Two isoforms are existing, GC1 and GC2. GC1 is the predominant isoform in most of the cell types, except in neurons where both isoforms are expressed equally. The enzymes are tuned to detect even short, low-amplitude NO signals and transduce them at several hundred-fold amplification, such that activation of a small fraction of intact sGC (~2%) is sufficient to elicit a physiological effect. NO/sGC signaling is involved in the regulation of many organ systems, with the cardiovascular being the most extensively studied. Here it exerts a continuous influence on the adjustment of vascular tone and local blood flow, as well as platelet and leukocyte reactivity. Accordingly, impaired NO/sGC signaling is associated with decreased vascular relaxation, development of hypertension, and increased risk of myocardial infarction.
Activity of sGC depends on the redox state of the haem-group. Only sGC with a reduced haem iron (Fe2+) respond to NO, whereas sGC with an oxidized one (Fe3+) is not activated by NO. Notably, sGC does not bind oxygen, leading to haem oxidation through NO deoxygenation in other haem proteins, which points to a self-protective mechanism from oxidation. With the advent of sGC activators, compounds that target the oxidized/haem-free form of sGC, as demonstrated using purified enzyme, the previously unknown existence of distinct sGC redox states in cells has been suggested; increased sensitivity of the sGC signaling to these compounds was judged as an increase in oxidized/haem-free sGC and conversely, a decrease in sensitivity was taken as an indicator of sGC-haem reduction. Accordingly, it is proposed that the level of oxidized/haem-free sGC is elevated in disease states associated with oxygen/nitrogen species. Concomitantly, it has also been shown that endogenous antioxidants such as methaemoglobin reductase and hydrogen sulfide can reverse sGC-haem oxidation. At the same time, redox regulation of sGC can also occur through specific cysteine residues, leading to a higher level of complexity regarding possible redox-based modifications of sGC, their regulation, and their impact on sGC signaling.
This Research Topic aims to assemble a series of articles on the redox regulation of sGC through haem and cysteine residues and its impact on sGC signaling. We welcome contributions in the form of original research, reviews, and scientific-based essays/short communications, which will help to extend and consolidate our knowledge. Since most of the work has been conducted in in vitro systems we want to focus on integrative approaches explore the in vivo redox regulation of sGC in physiology and disease. Many fundamental questions also remain unanswered, including: (1) in what ratio do the different redox-based modifications of sGC coexist? (2) To what extent can their relationship be shifted by endogenous factors? (3) And, what is the biological consequence of this?
Activity of sGC depends on the redox state of the haem-group. Only sGC with a reduced haem iron (Fe2+) respond to NO, whereas sGC with an oxidized one (Fe3+) is not activated by NO. Notably, sGC does not bind oxygen, leading to haem oxidation through NO deoxygenation in other haem proteins, which points to a self-protective mechanism from oxidation. With the advent of sGC activators, compounds that target the oxidized/haem-free form of sGC, as demonstrated using purified enzyme, the previously unknown existence of distinct sGC redox states in cells has been suggested; increased sensitivity of the sGC signaling to these compounds was judged as an increase in oxidized/haem-free sGC and conversely, a decrease in sensitivity was taken as an indicator of sGC-haem reduction. Accordingly, it is proposed that the level of oxidized/haem-free sGC is elevated in disease states associated with oxygen/nitrogen species. Concomitantly, it has also been shown that endogenous antioxidants such as methaemoglobin reductase and hydrogen sulfide can reverse sGC-haem oxidation. At the same time, redox regulation of sGC can also occur through specific cysteine residues, leading to a higher level of complexity regarding possible redox-based modifications of sGC, their regulation, and their impact on sGC signaling.
This Research Topic aims to assemble a series of articles on the redox regulation of sGC through haem and cysteine residues and its impact on sGC signaling. We welcome contributions in the form of original research, reviews, and scientific-based essays/short communications, which will help to extend and consolidate our knowledge. Since most of the work has been conducted in in vitro systems we want to focus on integrative approaches explore the in vivo redox regulation of sGC in physiology and disease. Many fundamental questions also remain unanswered, including: (1) in what ratio do the different redox-based modifications of sGC coexist? (2) To what extent can their relationship be shifted by endogenous factors? (3) And, what is the biological consequence of this?
Keywords: sGC, guanylyl cyclase, nitric oxide, cGMP, redox regulation, haem, cystein, signalling, vascular relaxation, blood pressure
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