Inflammatory signaling is a major component in the development and progression of many lung diseases, including asthma, chronic obstructive pulmonary disorder (COPD), and pulmonary hypertension (PH). This chapter will provide a brief overview of asthma, COPD, and PH and how inflammation plays a vital role in these diseases. Specifically, we will discuss the role of reactive oxygen species (ROS) and Ca2+ signaling in inflammatory cellular responses and how these interactive signaling pathways mediate the development of asthma, COPD, and PH. We will also deliberate the key cellular responses of pulmonary arterial (PA) smooth muscle cells (SMCs) and airway SMCs (ASMCs) in these devastating lung diseases. The analysis of the importance of inflammation will shed light on the key questions remaining in this field and highlight molecular targets that are worth exploring. The crucial findings will not only demonstrate the novel roles of essential signaling molecules such as Rieske iron-sulfur protein and ryanodine receptor in the development and progress of asthma, COPD, and PH but also offer advanced insight for creating more effective and new therapeutic targets for these devastating inflammatory lung diseases.

Rieske iron-sulfur protein (RISP) is a catalytic subunit of the complex III in the mitochondrial electron transport chain. Studies for years have revealed that RISP is essential for the generation of intracellular reactive oxygen species (ROS) via delicate signaling pathways associated with many important molecules such as protein kinase C-ε, NADPH oxidase, and ryanodine receptors. More significantly, mitochondrial RISP-mediated ROS production has been implicated in the development of hypoxic pulmonary vasoconstriction, leading to pulmonary hypertension, right heart failure, and death. Investigations have also shown the involvement of RISP in ROS-dependent cardiac ischemic/reperfusion injuries. Further research may provide novel and valuable information that can not only enhance our understanding of the functional roles of RISP and the underlying molecular mechanisms in the pulmonary vasculature and other systems, but also elucidate whether RISP targeting can act as preventative and restorative therapies against pulmonary hypertension, cardiac diseases, and other disorders.

Isolated complex III (CIII) deficiencies are among the least frequently diagnosed mitochondrial disorders. Clinical symptoms range from isolated myopathy to severe multi-systemic disorders with early death and disability. To date, we know of pathogenic variants in genes encoding five out of 10 subunits and five out of 13 assembly factors of CIII. Here we describe rare bi-allelic variants in the gene of a catalytic subunit of CIII, UQCRFS1, which encodes the Rieske iron-sulfur protein, in two unrelated individuals. Affected children presented with low CIII activity in fibroblasts, lactic acidosis, fetal bradycardia, hypertrophic cardiomyopathy, and alopecia totalis. Studies in proband-derived fibroblasts showed a deleterious effect of the variants on UQCRFS1 protein abundance, mitochondrial import, CIII assembly, and cellular respiration. Complementation studies via lentiviral transduction and overexpression of wild-type UQCRFS1 restored mitochondrial function and rescued the cellular phenotype, confirming UQCRFS1 variants as causative for CIII deficiency. We demonstrate that mutations in UQCRFS1 can cause mitochondrial disease, and our results thereby expand the clinical and mutational spectrum of CIII deficiencies.

Rieske iron-sulfur protein (RISP) is a catalytic subunit of the complex III in the mitochondrial electron transport chain. Studies for years have revealed that RISP is essential for the generation of intracellular reactive oxygen species (ROS) via delicate signaling pathways associated with many important molecules such as protein kinase C-ε, NADPH oxidase, and ryanodine receptors. More significantly, mitochondrial RISP-mediated ROS production has been implicated in the development of hypoxic pulmonary vasoconstriction, leading to pulmonary hypertension, right heart failure, and death. Investigations have also shown the involvement of RISP in ROS-dependent cardiac ischemic/reperfusion injuries. Further research may provide novel and valuable information that can not only enhance our understanding of the functional roles of RISP and the underlying molecular mechanisms in the pulmonary vasculature and other systems, but also elucidate whether RISP targeting can act as preventative and restorative therapies against pulmonary hypertension, cardiac diseases, and other disorders.

Rieske iron-sulfur protein (RISP) is a key protein subunit of mitochondrial complex III which plays an important role in the respiratory electron transport chain. The complete cDNA of RISP was cloned from Spodoptera exigua by real time quantitative PCR and rapid-amplification of cDNA ends (RACE) technology and named as SeRISP (GenBank Accession Number: JN992290). Multiple alignments and the creation of a phylogenetic tree revealed that RISPs are highly conserved among different insects, and the highly conserved region of RISPs is mainly located at the C-terminal which serves as the functional domain. Expression pattern analysis demonstrated that SeRISP is expressed in all developmental stages of S. exigua; the expression levels increased during larval growth, remained stable during development from fourth instar to pupa and reached a peak in the adult. In addition, SeRISP was significantly suppressed at both the mRNA and protein levels by feeding the instar stage with dsRNA; levels of suppression increased with increasing dsRNA concentration and continuous treatment time. The silencing of SeRISP in larvae led to the significant inhibition of ATP synthesis and larval growth, which could result in energy reserve deficiency in pupae and the suppression of fecundity and hatchability in adults. Our findings confirmed that it is possible to silence target genes in S. exigua by simple dsRNA feeding, and provided evidence of the essential role of RISP in the process of ATP synthesis, growth and reproduction.

Hypoxic pulmonary vasoconstriction (HPV) occurs during both fetal and postnatal development and plays a critical role in matching regional alveolar perfusion with ventilation in humans and animals. HPV also contributes significantly to the development of pulmonary hypertension. Although the molecular mechanisms of HPV and pulmonary hypertension remain incompletely understood, increasing evidence demonstrates that hypoxia induces an elevated intracellular reactive oxygen species concentration ([ROS]i) in pulmonary artery smooth muscle cells (PASMCs). The increased [ROS]i is attributed to the mitochondrial electron transport chain (ETC) and plasmalemmal NADPH oxidase (NOX); however, the mitochondrial ETC is a primary source for the elevated [ROS]i. Our studies reveal that mitochondrial ROS can specifically increase the activity of protein kinase C-ε, activate NOX, and then induce more ROS production (i.e., ROS-induced ROS production, RIRP). Mitochondrial ROS production is principally mediated by Rieske iron-sulfur protein (RISP) at the complex III. The increased [ROS]i causes an elevation of intracellular Ca2+ concentration ([Ca2+]i), thereby leading to HPV and associated pulmonary hypertension. Ryanodine receptor-2 (RyR2)/Ca2+ release channel on the sarcoplasmic reticulum (SR) serves as a most valuable player in the elevated [Ca2+]i. Our recent data indicate that RyR2-induced Ca2+ release can enhance RISP-mediated increase in mitochondrial ROS concentration ([ROS]mito), and that the mitochondrial Ca2+ uniporter is involved in elevating [ROS]mito. Based on the existing reports and our unpublished data, we conclude that the cross talk between [ROS]mito and [Ca2+]i, that is RISP-dependent mitochondrial ROS-induced RyR2-mediated SR Ca2+ release (ROS-induced Ca2+ release, RICR) and RyR2-mediated SR Ca2+ release-induced RISP-dependent mitochondrial ROS production (Ca2+-induced ROS production, CIRP), may form a positive reciprocal loop in mediating HPV and also possibly pulmonary hypertension.

We investigated the effects of the herbicide thiobencarb on the growth, photosynthetic activity, and expression profile of photosynthesis-related proteins in the marine diatom Thalassiosira pseudonana. Growth rate was suppressed by 50% at a thiobencarb concentration of 1.26 mg/L. Growth and photosystem II activity (Fv /Fm ratio) were drastically decreased at 5 mg/L, at which the expression levels of 13 proteins increased significantly and those of 11 proteins decreased significantly. Among these proteins, the level of the Rieske iron-sulfur protein was decreased to less than half of the control level. This protein is an essential component of the cytochrome b6 f complex in the photosynthetic electron transport chain. Although the mechanism by which thiobencarb decreased the Rieske iron-sulfur protein level is not clear, these results suggest that growth was inhibited by interruption of the photosynthetic electron transport chain by thiobencarb.

X-ray crystal structures of bc1 complexes obtained over the last 15 years have provided a firm structural basis for our understanding of the complex. For the most part there is good agreement between structures from different species, different crystal forms, and with different inhibitors bound. In this review we focus on some of the remaining unexplained differences, either between the structures themselves or the interpretations of the structural observations. These include the structural basis for the motion of the Rieske iron-sulfur protein in response to inhibitors, a possible conformational change involving tyrosine132 of cytochrome (cyt) b, the presence of cis-peptides at the beginnings of transmembrane helices C, E, and H, the structural insight into the function of the so-called \"Core proteins\", different modelings of the retained signal peptide, orientation of the low-potential heme b, and chirality of the Met ligand to heme c1. This article is part of a Special Issue entitled: Respiratory complex III and related bc complexes.