Exogenous H2S prevents the nuclear translocation of PDC-E1 and inhibits vascular smooth muscle cell proliferation in the diabetic state

Hydrogen sulphide (H₂S) inhibits vascular smooth muscle cell (VSMC) proliferation induced by hyperglycaemia and hyperlipidaemia; however, the mechanisms are unclear. Here, we observed lower H₂S levels and higher expression of the proliferation-related proteins PCNA and cyclin D1 in db/db mouse aortae and vascular smooth muscle cells treated with 40 mmol/L glucose and 500 μmol/L palmitate, whereas exogenous H₂S decreased PCNA and cyclin D1 expression. The nuclear translocation of mitochondrial pyruvate dehydrogenase complex-E1 (PDC-E1) was significantly increased in VSMCs treated with high glucose and palmitate, and it increased the level of acetyl-CoA and histone acetylation (H3K9Ac). Exogenous H₂S inhibited PDC-E1 translocation from the mitochondria to the nucleus because PDC-E1 was modified by S-sulfhydration. In addition, PDC-E1 was mutated at Cys101. Overexpression of PDC-E1 mutated at Cys101 increased histone acetylation (H3K9Ac) and VSMC proliferation. Based on these findings, H₂S regulated PDC-E1 S-sulfhydration at Cys101 to prevent its translocation from the mitochondria to the nucleus and to inhibit VSMC proliferation under diabetic conditions.     

Entropic elastic processes in protein mechanisms. II. Simple (passive) and coupled (active) development of elastic forces

The first part of this review on entropic elastic processes in protein mechanisms (Urry, 1988) demonstrated with the polypentapeptide of elastin (Val¹-Pro²-Gly³-Val⁴-Gly⁵)_n that elastic structure develops as the result of an inverse temperature transition and that entropic elasticity is due to internal chain dynamics in a regular nonrandom structure. This demonstration is contrary to the pervasive perspective of entropic protein elasticity of the past three decades wherein a network of random chains has been considered the necessary structural consequence of the occurrence of dominantly entropic elastomeric force. That this is not the case provides a new opportunity for understanding the occurrence and role of entropic elastic processes in protein mechanisms. Entropic elastic processes are considered in two classes: passive and active. The development of elastomeric force on deformation is class I (passive) and the development of elastomeric force as the result of a chemical process shifting the temperature of a transition is class II (active). Examples of class I are elastin, the elastic filament of muscle, elastic force changes in enzyme catalysis resulting from binding processes and resulting in the straining of a scissile bond, and in the turning on and off of channels due to changes in transmembrane potential. Demonstration of the consequences of elastomeric force developing as the result of an inverse temperature transition are seen in elastin, where elastic recoil is lost on oxidation, i.e., on decreasing the hydrophobicity of the chain and shifting the temperature for the development of elastomeric force to temperatures greater than physiological. This is relevant in general to loss of elasticity on aging and more specifically to the development of pulmonary emphysema. Since random chain networks are not the products of inverse temperature transitions and the temperature at which an inverse temperature transition occurs depends on the hydrophobicity of the polypeptide chain, it now becomes possible to consider chemical processes for turning elastomeric force on and off by reversibly changing the hydrophobicity of the polypeptide chain. This is herein called mechanochemical coupling of the first kind; this is the chemical modulation of the temperature for the transition from a less-ordered less elastic state to a more-ordered more elastic state. In the usual considerations to date, development of elastomeric force is the result of a standard transition from a more-ordered less elastic state to a less-ordered more elastic state. When this is chemically modulated, it is herein called mechanochemical coupling of the second kind. For elastin and the polypentapeptide of elastin, since entropic elastomeric force results on formation of a regular nonrandom structure and thermal randomization of chains results in loss of elastic modulus to levels of limited use in protein mechanisms, consideration of regular spiral-like structures rather than ramdom chain networks or random coils are proposed for mechanochemical coupling of the second kind. Chemical processes to effect mechanochemical coupling in biological systems are most obviously phosphorylation-dephosphorylation and changes in calcium ion activity but also changes in pH. These issues are considered in the events attending parturition in muscle contraction and in cell motility.     

Structure and function of muscle myosin

We have studied the primary structures of myosins from chicken muscles in order to clarify the relationship between structure and function of muscle myosin. The primary structures of the various kinds of light chains from chicken muscle myosins have been determined. We also report the primary structure of the 23K fragment of subfragment-1 (S-1) component from the heavy chain of chicken fast skeletal muscle myosin. In addition, antibody was prepared against the 23K fragment. The antibody was found to inhibit the Mg²⁺-ATPase activity and the initial P_i burst of the ATPase in the S-1 component. The antibody suppressed the ATP-induced fluorescence enhancement of S-1, though it did not suppress the binding of ATP to S-1. These results are also discussed.This article was presented during the proceedings of the International Conference on Macromolecular Structure and Function, held at the National Defence Medical College, Tokorozawa, Japan, December 1985.     

Apoptosis repressor with caspase recruitment domain is dramatically reduced in cardiac, skeletal, and vascular smooth muscle during hypertension

Apoptosis repressor with caspase recruitment domain (ARC) is a unique anti-apoptotic protein with a distinct tissue distribution. In addition, unlike most anti-apoptotic proteins which act on one pathway, ARC can inhibit apoptosis mediated by both the death-receptor and mitochondrial signaling pathways. In this study, we confirm previous reports showing high levels of ARC protein in rat heart and skeletal muscle, but demonstrate for the first time that ARC is also expressed in rat aorta. Immunoblot analysis on endothelium-denuded aorta as well as immunohistochemical analysis on intact aorta demonstrated that ARC was highly expressed in smooth muscle. Immunoblot analysis also found that ARC protein was severely downregulated in skeletal muscle (−82%; P < 0.001), heart (−80%; P < 0.001), and aorta (−71%; P < 0.001) of spontaneously hypertensive rats (SHR) compared to normotensive Wistar-Kyoto (WKY) rats. Decreased ARC levels were also confirmed in tissues of hypertensive animals by immunohistochemical analysis. Collectively, this data suggests that ARC protein is expressed in vascular smooth muscle and is significantly reduced in several target tissues during hypertension.     

Electron-microscopic study of innervation of smooth muscle cells surrounding collecting tubules of the fish kidney

Summary The fine structure of the collecting tubules of the trout and killifish kidney was studied. These tubules are surrounded by layers of smooth muscle cells which are commonly innervated. The nerve terminals contain synaptic vesicles and, occasionally, a few dense-cored granules as well. Capillaries occur in the connective tissue space between these smooth muscle cells and the collecting tubule. Epithelial cells of the collecting tubules contain abundant mitochondria and a well developed membrane system displaying parallel arrays, and were considered to be actively involved in the transport of materials. In the trout, the collecting tubules contain peculiar cells in addition to regular tubule cells. The fine structure of these peculiar cells is highly reminiscent of that of gill chloride cells. The significance of these findings may be summarized as follows: If the smooth muscles around the collecting tubule contract under neural influence, intratubular pressure may be increased and, thus affect glomerular filtration rate. The contraction of these muscles may also cause the collapse of peritubular capillaries, affecting the transport activity of tubule cells.     

Binding and Functional Folding (BFF): A Physiological Framework for Studying Biomolecular Interactions and Allostery

EF-hand Ca²⁺-binding proteins (CBPs), such as S100 proteins (S100s) and calmodulin (CaM), are signaling proteins that undergo conformational changes upon increasing intracellular Ca²⁺. Upon binding Ca²⁺, S100 proteins and CaM interact with protein targets and induce important biological responses. The Ca²⁺-binding affinity of CaM and most S100s in the absence of target is weak (^CaK_D > 1 μM). However, upon effector protein binding, the Ca²⁺ affinity of these proteins increases via heterotropic allostery (^CaK_D < 1 μM). Because of the high number and micromolar concentrations of EF-hand CBPs in a cell, at any given time, allostery is required physiologically, allowing for (i) proper Ca²⁺ homeostasis and (ii) strict maintenance of Ca²⁺-signaling within a narrow dynamic range of free Ca²⁺ ion concentrations, [Ca²⁺]^free. In this review, mechanisms of allostery are coalesced into an empirical “binding and functional folding (BFF)” physiological framework. At the molecular level, folding (F), binding and folding (BF), and BFF events include all atoms in the biomolecular complex under study. The BFF framework is introduced with two straightforward BFF types for proteins (type 1, concerted; type 2, stepwise) and considers how homologous and nonhomologous amino acid residues of CBPs and their effector protein(s) evolved to provide allosteric tightening of Ca²⁺ and simultaneously determine how specific and relatively promiscuous CBP-target complexes form as both are needed for proper cellular function.     

Elevated incubation temperature improves later-life swimming endurance in juvenile Chinook salmon,Oncorhynchus tshawytscha

The effect of incubation and rearing temperature on muscle development and swimming endurance under a high-intensity swimming test was investigated in juvenile Chinook salmon (Oncorhynchus tshawytscha) in a hatchery experiment. After controlling for the effects of fork length (L_F) and parental identity, times to fatigue of fish were higher when fish were incubated or reared at warmer temperatures. Significant differences among combinations of pre- and post-emergence temperatures conformed to 15–15°C > 15–9°C > 9–9°C > 7–9°C > 7–7°C in 2011 when swimming tests were conducted at 300 accumulated temperature units post-emergence and 15–9°C > (7–9°C = 7–7°C) in 2012 when swimming tests were conducted at an L_F of c. 40 mm. The combination of pre- and post-emergence temperatures also affected the number and size of muscle fibres, with differences among temperature treatments in mean fibre cross-sectional area persisting after controlling for L_F and parental effects. Nonetheless, neither fibre number nor fibre size accounted for significant variation in swimming endurance. Thus, thermal carryover effects on swimming endurance were not mediated by thermal imprinting of muscle structure. This is the first study to test how temperature, body size and muscle structure interact to affect swimming endurance during early development in salmon.     

Drugs,genes and screens: The ethics of preventing and treating spinal muscular atrophy

Spinal muscular atrophy (SMA) is the most common genetic disease that causes infant mortality. Its treatment and prevention represent the paradigmatic example of the ethical dilemmas of 21st-century medicine. New therapies (nusinersen and AVXS-101) hold the promise of being able to treat, but not cure, the condition. Alternatively, genomic analysis could identify carriers, and carriers could be offered in vitro fertilization and preimplantation genetic diagnosis. In the future, gene editing could prevent the condition at the embryonic stage. How should these different options be evaluated and compared within a health system? In this paper, we discuss the ethical considerations that bear on the question of how to prioritize the different treatments and preventive options for SMA, at a policy level. We argue that despite the tremendous value of what we call ‘ex-post’ approaches to treating SMA (such as using pharmacological agents or gene therapy), there is a moral imperative to pursue ‘ex-ante’ interventions (such as carrier screening in combination with prenatal testing and preimplantation genetic diagnosis, or gene editing) to reduce the incidence of SMA. There are moral reasons relating to autonomy, beneficence and justice to prioritize ex-ante methods over ex-post methods.     

Multiple Sequence Variants in STAC3 Affect Interactions with CaV1.1 and Excitation-Contraction Coupling

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