Dissimilarity in the folding of human cytosolic creatine kinase isoenzymes

Molecular Characterization, Expression Profile, and A 21-bp Indel within the ASB9 Gene and Its Associations with Chicken Production Traits

A growing number of studies have shown that members of the ankyrin repeat and suppressors of cytokine signaling (SOCS) box-containing protein (ASB) family are extensively involved in biological processes such as cell growth, tissue development, insulin signaling, ubiquitination, protein degradation, and skeletal muscle membrane protein formation, while the specific biological role of ankyrin-repeat and SOCS box protein 9 (ASB9) remains unclear. In this study, a 21 bp indel in the intron of ASB9 was identified for the first time in 2641 individuals from 11 different breeds and an F₂ resource population, and differences were observed among individuals with different genotypes (II, ID, and DD). An association study of a cross-designed F₂ resource population revealed that the 21-bp indel was significantly related to growth and carcass traits. The significantly associated growth traits were body weight (BW) at 4, 6, 8, 10, and 12 weeks of age; sternal length (SL) at 4, 8, and 12 weeks of age; body slope length (BSL) at 4, 8, and 12 weeks of age; shank girth (SG) at 4 and 12 weeks of age; tibia length (TL) at 12 weeks of age; and pelvic width (PW) at 4 weeks of age (p < 0.05). This indel was also significantly correlated with carcass traits including semievisceration weight (SEW), evisceration weight (EW), claw weight (CLW), breast muscle weight (BMW), leg weight (LeW), leg muscle weight (LMW), claw rate (CLR), and shedding weight (ShW) (p < 0.05). In commercial broilers, the II genotype was the dominant genotype and underwent extensive selection. Interestingly, the ASB9 gene was expressed at significantly higher levels in the leg muscles of Arbor Acres broilers than those of Lushi chickens, while the opposite was true for the breast muscles. In summary, the 21-bp indel in the ASB9 gene significantly influenced the expression of the ASB9 gene in muscle tissue and was associated with multiple growth and carcass traits in the F₂ resource population. These findings suggested that the 21-bp indel within the ASB9 gene could be used in marker-assisted selection breeding for traits related to chicken growth.

Evaluation of antifatigue and antioxidant activities of the marine microalgae Isochrysis galbana in mice

The present work aimed to estimate the possible anti-fatigue effect and potential mechanism of Isochrysis galbana (IG) in mice. The anti-fatigue activity of IG (100, 200, and 400 mg/kg) was elucidated by a weight-loaded forced swimming test, and the potential mechanism was explored by determination of fatigue-related biochemical parameters. The results showed that pretreatment with IG significantly extended the exhaustive swimming time and increased the levels of liver glycogen, muscle glycogen and blood glucose in a dose-dependent manner. Besides, the increased levels of alanine aminotransferase, aspartate aminotransferase, blood lactic acid, lactic dehydrogenase, creatine kinase, and blood urea nitrogen by exhausted swimming, were dramatically attenuated by pretreatment with IG. Furthermore, supplementation with IG significantly enhanced the glutathione peroxidase and superoxide dismutase levels, while attenuated the level of malonaldehyde. Taken together, IG possessed appreciable efficacy to alleviate fatigue, and the mechanism might be associated with favorably modulating the process of energy consumption, metabolism, and attenuating oxidative stress injury.

Model of the Ankyrin and SOCS Box Protein, ASB9, E3 Ligase Reveals a Mechanism for Dynamic Ubiquitin Transfer

Cullin-RING E3 ligases (CRLs) are elongated and bowed protein complexes that transfer ubiquitin over 60 Å to proteins targeted for proteasome degradation. One such CRL contains the ankyrin repeat and SOCS box protein 9 (ASB9), which binds to and partially inhibits creatine kinase (CK). While current models for the ASB9-CK complex contain some known interface residues, the overall structure and precise interface of the ASB9-CK complex remains unknown. Through an integrative modeling approach, we report a third-generation model that reveals precisely the interface interactions and also fits the shape of the ASB9-CK complex as determined by small-angle X-ray scattering. We constructed an atomic model for the entire CK-targeting CRL to uncover dominant modes of motion that could permit ubiquitin transfer. Remarkably, only the correctly docked CK-containing E3 ligase and not incorrectly docked structures permitted close approach of ubiquitin to the CK substrate.

Cardioprotective effect of Salvianolic acid B on acute myocardial infarction by promoting autophagy and neovascularization and inhibiting apoptosis

OBJECTIVES

The aim of this study was to investigate the cardioprotective effect of salvianolic acid B (Sal B) on acute myocardial infarction (AMI) in rats and its potential mechanisms.

METHODS

The AMI model was established in rats to study the effect of Sal B on AMI. Haematoxylin-eosin (HE) staining was used to evaluate the pathological change in AMI rats. Immunofluorescence and TUNEL staining were used to detect autophagy and apoptosis of myocardial cells in hearts of AMI rats, respectively. Protein expression of apoptosis-related, autophagy-related and angiogenesis-related proteins were examined by Western blot.

KEY FINDINGS

Sal B attenuated myocardial infarction significantly compared with that of the model group. Rats administered with Sal B showed higher inhibition rate of infarction and lower infarct size than those of the model group. Moreover, Sal B decreased the serum levels of creatine kinase, lactate dehydrogenase and malondialdehyde, while increased such level of superoxide dismutase significantly compared with those of the model group. Sal B inhibited the expression of Bax, cleaved caspase-9 and cleaved PARP, while promoted the expression of Bcl-2, LC3-II, Beclin1 and VEGF.

CONCLUSIONS

Sal B has cardioprotective effect on AMI and Sal B may be a promising candidate for AMI treatment.

A single residue substitution accounts for the significant difference in thermostability between two isoforms of human cytosolic creatine kinase

Creatine kinase (CK) helps maintain homeostasis of intracellular ATP level by catalyzing the reversible phosphotransfer between ATP and phosphocreatine. In humans, there are two cytosolic CK isoforms, the muscle-type (M) and the brain-type (B), which frequently function as homodimers (hMMCK and hBBCK). Interestingly, these isoenzymes exhibit significantly different thermostabilities, despite high similarity in amino acid sequences and tertiary structures. In order to investigate the mechanism of this phenomenon, in this work, we first used domain swapping and site-directed mutagenesis to search for the key residues responsible for the isoenzyme-specific thermostability. Strikingly, the difference in thermostability was found to principally arise from one single residue substitution at position 36 (Pro in hBBCK vs. Leu in hMMCK). We then engaged the molecular dynamics simulations to study the molecular mechanism. The calculations imply that the P36L substitution introduces additional local interactions around residue 36 and thus further stabilizes the dimer interface through a complex interaction network, which rationalizes the observation that hMMCK is more resistant to thermal inactivation than hBBCK. We finally confirmed this molecular explanation through thermal inactivation assays on Asp36 mutants that were proposed to devastate the local interactions and thus the dimer associations in both isoenzymes.

Effect of SNPs on creatine kinase structure and function: identifying potential molecular mechanisms for possible creatine kinase deficiency diseases

Single-nucleotide polymorphisms (SNPs) are common genetic material changes that often occur naturally. SNPs can cause amino acid replacements that may lead to severe diseases, such as the well-known sickle-cell anemia. We constructed eight SNP mutants of human brain-type creatine kinase (CKB) based on bioinformatics predictions. The biochemical and biophysical characteristics of these SNP mutants were determined and compared to those of the wild-type creatine kinase to explore the potential molecular mechanisms of possible creatine kinase SNP-induced diseases. While the reactivation of six SNP mutants after heat shock dropped more than 45%, only three of them showed notable increases in ANS fluorescence intensity and decreases in catalytic efficiency. Among them, H26Y and P36T bind substrates as well as the wild-type form does, but the melting temperatures (T_m) dropped below body temperature, while the T59I mutant exhibited decreased catalytic activity that was most likely due to the much reduced binding affinity of this mutant for substrates. These findings indicate that SNPs such as H26Y, P36T and T59I have the potential to induce genetic diseases by different mechanisms.

Folding studies on muscle type of creatine kinase from Pelodiscus sinensis

A folding study of creatine kinase from Pelodiscus sinensis has not yet been reported. To gain more insight into structural and folding mechanisms of P. sinensis CK (PSCK), denaturants such as SDS, guanidine HCl, and urea were applied in this study. We purified PSCK from the muscle of P. sinensis and conducted inhibition kinetics with structural unfolding studies under various conditions. The results revealed that PSCK was completely inactivated at 1.8 mM SDS, 1.05 M guanidine HCl, and 7.5 M urea. The kinetics via time-interval measurements showed that the inactivation by SDS, guanidine HCl, and urea were all first-order reactions with kinetic processes shifting from monophase to biphase at increasing concentrations. With respect to tertiary structural changes, PSCK was unfolded in different ways; SDS increased the hydrophobicity but retained the most tertiary structural conformation, while guanidine HCl and urea induced conspicuous changes in tertiary structures and initiated kinetic unfolding mechanisms. Our study provides information regarding PSCK and enhances our knowledge of the reptile-derived enzyme folding.