Cloning, characterization, and expression in Escherichia coli of three creatine kinase muscle isoenzyme cDNAs from carp (Cyprinus carpio) striated muscle

Nanozyme-based visual diagnosis and therapeutics for myocardial infarction: The application and strategy

BACKGROUND

Myocardial infarction (MI) is a heart injury caused by ischemia and low oxygen conditions. The occurrence of MI lead to the activation of a large number of neutrophils and macrophages, inducing severe inflammatory injury. Meanwhile, the inflammatory response produces much more free radicals, further exacerbating the inflammatory response and tissue damage. Efforts are being dedicated to developing antioxidants and enzymes, as well as small molecule drugs, for treating myocardial ischemia. However, poor pharmacokinetics and potential side effects limit the clinical application of these drugs. Recent advances in nanotechnology have paved new pathways in biomedical and healthcare environments. Nanozymes exhibit the advantages of biological enzymes and nanomaterials, including with higher catalytic activity and stability than natural enzymes. Thus, nanozymes provide new possibilities for the diagnosis and treatment of oxidative stress and inflammation-related diseases.

AIM OF REVIEW

We describe the application of nanozymes in the diagnosis and therapy of MI, aiming to bridge the gap between the diagnostic and therapeutic needs of MI.

KEY SCIENTIFIC CONCEPTS OF REVIEW

We describe the application of nanozymes in the diagnosis and therapy of MI, and discuss the new strategies for improving the diagnosis and treatment of MI. We review in detail the applications of nanozymes to achieve highly sensitive detection of biomarkers of MI. Due to their unique enzyme catalytic capabilities, nanozymes have the ability to sensitively detect biomolecules through colorimetric, fluorescent, and electrochemical assays. In addition, nanozymes exhibit excellent antioxidase-mimicking activity to treat MI by modulating reduction/oxidation (REDOX) homeostasis. Nanozymes can also passively or actively target MI tissue sites, thereby protecting ischemic myocardial tissue and reducing the infarct area. These innovative applications of nanozymes in the field of biomedicine have shown promising results in the diagnosis and treatment of MI, offering a novel therapeutic strategy.

A Crystal Structure of Pro c 2 Provides Insights into Cross-Reactivity of Aquatic Allergens from the Phosphagen Kinase Family

Arginine kinase (AK) from the phosphagen kinase family is a cross-reactive shellfish allergen. Structurally related cross-reactive allergens are involved in the pathogenesis of allergic symptoms. This study aimed to unravel the cross-reactivity of AK from a structural perspective. The crystal structure of Procambarus clarkii AK (Pro c 2) was resolved at 1.57 Å resolution, which showed a well-conserved structure not only to shellfish AKs but also to fish creatine kinase (CK), another allergen from the phosphagen kinase family. In Western blot, the CK corresponding protein in fish muscles was found to be reactive with AK-specific immunoglobulin (Ig) G. Recombinant Pro c 2 (rPro c 2) and CKs from Lateolabrax japonicus (rCK-L) and Ctenopharyngodon idell (rCK-C) were then produced, and the IgE reactivity of rCK-L and rCK-C, as well as their IgG/IgE cross-reactivity with rPro c 2, was confirmed by immunological assays. This study demonstrated the cross-reactivity among aquatic allergens from the phosphagen kinase family due to their structural similarity.

Tissue and plasma enzyme activities and chemical analytes in Golden Trevally from a public aquarium

OBJECTIVE

Veterinary care of aquatic species, particularly fish, is limited by a lack of knowledge regarding their unique physiology. Tissue enzyme activities measured in plasma are used for assessing function and potential damage to specific organs and tracking disease progression in live animals. The objective of this study was to identify tissue(s) of origin and plasma concentrations for specific enzymes in healthy Golden Trevally Gnathanodon speciosus. We hypothesized that enzymes would exhibit tissue-specific tropisms, with higher activities in one or more tissues compared to others.

METHODS

Six fish were randomly selected from a public aquarium population to obtain antemortem blood samples. The fish were then euthanized, and tissue samples were collected via gross necropsy. Six enzyme activities and two chemical analytes were examined across samples of plasma and 10 tissues from each fish.

RESULT

Enzyme activities exhibited significant organ specificities. Aspartate aminotransferase, lactate dehydrogenase, and creatine kinase levels were highest in skeletal muscle, with variably high levels in gonads. Alkaline phosphatase levels were highest in the kidney, spleen, and liver. Alanine aminotransferase levels had high specificity for the liver. Gamma-glutamyl transferase was only detectable in the kidney and plasma.

CONCLUSION

This work establishes baseline tissue enzyme origins for Golden Trevally, which will aid clinicians in diagnostic interpretation of blood chemistries and improve veterinary care for this understudied fish species.

The relationship between dietary methionine and growth, digestion, absorption, and antioxidant status in intestinal and hepatopancreatic tissues of sub-adult grass carp (Ctenopharyngodon idella)

BACKGROUND

Methionine is an essential amino acid for fish. The present study was conducted to investigate the effects of dietary methionine on growth performance, digestive and absorptive ability, as well as antioxidant capacity in the intestine and hepatopancreas of sub-adult grass carp (Ctenopharyngodon idella).

RESULTS

Dietary methionine deficiency significantly decreased percentage weight gain (PWG), feed intake, feed efficiency and protein efficiency ratio, as well as activities of hepatopancreatic glutamate-oxaloacetate transaminase and muscle glutamate-pyruvate transaminase in sub-adult grass carp (P < 0.05). Furthermore, methionine deficiency significantly reduced activities of trypsin, lipase and amylase in the intestine, Na+/K+-ATPase, alkaline phosphatase and γ-glutamyl transpeptidase in three intestinal segments, and creatine kinase (CK) in the proximal intestine (P < 0.05). However, an unexplained and significant increase in CK activity in the mid intestine was associated with dietary methionine deficiency. Malondialdehyde and protein carbonyl contents in the intestine and hepatopancreas were significantly increased by methionine deficiency (P < 0.05), whereas anti-hydroxyl radical capacity in the hepatopancreas and intestine, and anti-superoxide anion capacity in the intestine, were significantly decreased by methionine deficiency (P < 0.05). Moreover, methionine deficiency significantly decreased superoxide dismutase and glutathione reductase activities, glutathione contents in the hepatopancreas and intestine, as well as glutathione peroxidase activity in the intestine (P < 0.05), whereas it significantly increased activities of catalase in the hepatopancreas and glutathione-S-transferase in the hepatopancreas and intestine (P < 0.05).

CONCLUSIONS

The present results demonstrated that dietary methionine deficiency induced poor growth, and decreased digestive and absorptive function and antioxidant capacity in the hepatopancreas and intestine of sub-adult grass carp. Methionine requirements for sub-adult grass carp (450-1, 170 g) based on PWG, intestinal trypsin, and hepatopancreatic anti-hydroxyl radical activities were estimated to be 6.12 g/kg diet (21.80 g/kg protein), 6.99 g/kg diet (24.90 g/kg protein) and 5.42 g/kg diet (19.31 g/kg protein), respectively, in the presence of 1.50 g cysteine/kg (5.35 g/kg protein).

Effects of glutamate on growth, antioxidant capacity, and antioxidant-related signaling molecule expression in primary cultures of fish enterocytes

The present study explored the effects of glutamate (Glu) on the growth, antioxidant capacity, and gene expression of NF-E2-related nuclear factor 2 (Nrf2) signaling molecule in enterocytes of Jian carp (Cyprinus carpio var. Jian). The enterocytes were incubated in media containing 0, 2, 4, 6, 8, and 10 mM/L Glu for 96 h. The results showed that Glu could promote fish enterocytes proliferation and differentiation. Additionally, activities of alkaline phosphatase, Na(+), K(+)-ATPase, γ-glutamyl transpeptidase, and creatine kinase were significantly improved with the increase in Glu level up to 6 mM/L. Lactic acid dehydrogenase activity and malondialdehyde content in the medium and cellular protein carbonyls were depressed by Glu. Moreover, optimum Glu significantly enhanced glutathione content and the activities and gene expression of catalase, glutathione reductase, and glutathione peroxidase in enterocytes. Finally, the expression level of Nrf2 in enterocytes was significantly elevated by appropriate Glu content in the medium. Furthermore, optimum Glu significantly decreased Kelch-like ECH-associated protein 1 mRNA level in enterocytes. In conclusion, Glu improved the proliferation, function, and antioxidant capacity and regulated antioxidant-related signaling molecule expression of fish enterocytes.

Purification and stability of octameric mitochondrial creatine kinase isoform from herring (Clupea harengus) organ of vision

Creatine kinases (CKs) constitute a large family of isoenzymes that are involved in intracellular energy homeostasis. In cells with high and fluctuating energy requirements ATP level is maintained via phosphocreatine hydrolysis catalyzed by creatine kinase. In contrast to invertebrates and higher vertebrates, in poikilothermic vertebrates the adaptations for the regulation of energy metabolism by changes in the oligomeric state of CK isoforms are not well known. The present study aimed at identification of herring eye CK isoforms and focuses on factors affecting the CK-octamer stability. In addition to the CK octamer, three different dimeric isoforms of CK were detected by cellulose acetate native electrophoresis. Destabilization of octamer was studied in the presence of TSAC substrates and about 50% of octamers dissociated into dimers within 24h. Moreover, we found that the increase of temperature from 4 °C to 30 °C caused rapid inactivation of dimers in TSAC-treated samples but did not affect octameric structures. In a thermostability assay we demonstrated that octamers retain their activity even at 50 °C. Our results indicate that destabilization of the octameric structure can lead to loss of enzyme activity at higher temperatures (above 30 °C). Furthermore, our results based on N-terminal sequence analysis suggest that probably the mitochondrial s-type CK, rather than u-type, is predominantly expressed in herring eye. In conclusion the existence of four various CK isoforms in one organ may reflect complex regulation of energy metabolism in the phototransduction process in teleost fishes.

Analyzing cold tolerance mechanism in transgenic zebrafish (Danio rerio)

Low temperatures may cause severe growth inhibition and mortality in fish. In order to understand the mechanism of cold tolerance, a transgenic zebrafish Tg (smyd1:m3ck) model was established to study the effect of energy homeostasis during cold stress. The muscle-specific promoter Smyd1 was used to express the carp muscle form III of creatine kinase (M3-CK), which maintained enzymatic activity at a relatively low temperature, in zebrafish skeletal muscle. In situ hybridization showed that M3-CK was expressed strongly in the skeletal muscle. When exposed to 13 °C, Tg (smyd1:m3ck) fish maintained their swimming behavior, while the wild-type could not. Energy measurements showed that the concentration of ATP increased in Tg (smyd1:m3ck) versus wild-type fish at 28 °C. After 2 h at 13 °C, ATP concentrations were 2.16-fold higher in Tg (smyd1:m3ck) than in wild-type (P<0.05). At 13 °C, the ATP concentration in Tg (smyd1:m3ck) fish and wild-type fish was 63.3% and 20.0%, respectively, of that in wild-type fish at 28 °C. Microarray analysis revealed differential expression of 1249 transcripts in Tg (smyd1:m3ck) versus wild-type fish under cold stress. Biological processes that were significantly overrepresented in this group included circadian rhythm, energy metabolism, lipid transport, and metabolism. These results are clues to understanding the mechanisms underlying temperature acclimation in fish.

The activity of carp muscle-specific creatine kinase at low temperature is enhanced by decreased hydrophobicity of residue 268

Abstract The muscle-specific forms of creatine kinase in rabbit (RM-CK) and carp (M1-CK) exhibit different temperature-dependent functional properties. Replacing the glycine at residue 268 of RM-CK with asparagine increases the enzyme's activity at 10°C. In this study, we investigated how hydrophobicity of residue 268 affects the biochemical properties of RM-CK and M1-CK at low temperature. We generated three mutants of both RM-CK and M1-CK: Asp268, Lys268, and Leu268. The secondary structures of these mutants were similar, as revealed by their circular dichroism spectra. Similar to the Asn268 mutants, the Asp268 and Lys268 mutants of RM-CK and M1-CK exhibited higher specific activities at 10°C and pH 8.0. However, no such effect was observed for the RM-CK and M1-CK Leu268 mutants. While in the presence of cryoprotectant (sucrose or trehalose), the activities of wild-type RM-CK and M1-CK mutant enzymes with a hydrophobic residue at 268 were higher, and the effect was more profound at pH 8.0. It may be inferred that water molecules affect protein conformation around residue 268, thereby influencing protein stability at low temperature.

Effect of dietary arginine on growth, intestinal enzyme activities and gene expression in muscle, hepatopancreas and intestine of juvenile Jian carp (Cyprinus carpio var. Jian)

The present study was conducted to test the hypothesis that dietary arginine promotes digestion and absorption capacity, and, thus, enhances fish growth. This improvement might be related to the target of rapamycin (TOR) and eIF4E-binding protein (4E-BP). A total of 1200 juvenile Jian carp, Cyprinus carpio var. Jian, with an average initial weight of 6.33 (SE 0.03) g, were fed with diets containing graded concentrations of arginine, namely, 9.8 (control), 12.7, 16.1, 18.5, 21.9 and 24.5 g arginine/kg diet for 9 weeks. An real-time quantitative PCR analysis was performed to determine the relative expression of TOR and 4E-BP in fish muscle, hepatopancreas and intestine. Dietary arginine increased (P < 0.05): (1) glutamate-oxaloacetate transaminase and glutamate-pyruvate transaminase activities in muscle and hepatopancreas; (2) intestine and hepatopancreas protein content, folds height, and trypsin, chymotrypsin, lipase, Na⁺/K⁺-ATPase, alkaline phosphatase, γ-glutamyl transpeptidase and creatine kinase activities in intestine; (3) Lactobacillus counts; (4) relative expression of TOR in the muscle, hepatopancreas and distal intestine (DI); (5) relative expression of 4E-BP in proximal intestine (PI) and mid-intestine (MI), as compared with the control group. In contrast, dietary arginine reduced (P < 0.05): (1) plasma ammonia content; (2) Aeromonas hydrophila and Escherichia coli counts; (3) relative expression of TOR in PI and MI; (4) relative expression of 4E-BP in the muscle, hepatopancreas and DI. The arginine requirement estimated by specific growth rate using quadratic regression analysis was found to be 18.0 g/kg diet. These results indicate that arginine improved fish growth, digestive and absorptive ability and regulated the expression of TOR and 4E-BP genes.

Comparative protein profiles: potential molecular markers from spermatozoa of Acipenseriformes (Chondrostei, Pisces)

Sturgeon and paddlefish (Acipenseriformes), the source of roe consumed as caviar, are a unique and commercially valuable group of ancient fishes. In this study, comparative proteomics was used to analyze protein profiles of spermatozoa from five sturgeon species and one paddlefish: Siberian sturgeon (Acipenser baerii), sterlet (A. ruthenus), Russian sturgeon (A. gueldenstaedtii), starry sturgeon (A. stellatus), beluga (Huso huso), and Mississippi paddlefish (Polyodon spathula). Protein profiles of spermatozoa were determined by isoelectric focusing and two-dimensional electrophoresis (2-DE) high-resolution gels. The peptides, previously selected by 2-DE analysis as potentially species-specific, were obtained by "in-gel" tryptic digestion, followed by matrix-associated laser desorption/ionization time-of-flight/mass spectrometry (MALDI-TOF/MS). Among the 23 protein spots selected, 14 were identified as isoforms of enolase B present in all species, but with different isoelectric points or molecular mass. Exceptions were A. ruthenus and H. huso, species with a close phylogenetic relationship. Glycerol-3-phosphate dehydrogenase was detected exclusively in P. spathula. Phosphoglycerate kinase was detected only in A. ruthenus and H. huso, and 3 additional proteins (fructose bisphosphate aldolase A-2, glycogen phosphorylase type IV and glyceraldehyde-3-phosphate dehydrogenase) were found exclusively in A. gueldenstaedtii and H. huso. This study points to the application of proteomics for differential characterization and comparative studies of acipenseriform species at the molecular level.

Zebrafish HSC70 promoter to express carp muscle-specific creatine kinase for acclimation under cold condition

Zebrafish (Danio rerio) is used as a model system for in vivo studies. To expand the research scope of physical, biochemical and physiological studies, a cold-tolerant model of zebrafish was developed. The common carp (Cyprinus carpio) muscle form of creatine kinase (CK, EC 2.7.3.2) can maintain enzymatic activity at a temperature of around 15°C. However, a cold-inducible promoter of zebrafish, hsc 70 (heat shock protein 70 cognate), is able to increase the expression of gene product by 9.8 fold at a temperature of 16°C. Therefore, the carp CK gene was promoted by hsc 70 and transfected into zebrafish embryos. Resulting transgenic zebrafish survived and could maintain its swimming behavior at 13°C, which was not possible with the wild-type zebrafish. The swimming distance of the transgenic fish was 42% greater than that of the wild type at 13°C. This new transgenic fish model is ideal for studies of ectothermal vertebrates in low-temperature environments.

Activity and function of rabbit muscle-specific creatine kinase at low temperature by mutation at gly268 to asn268

Carp muscle-specific creatine kinase M1 isoenzyme (M1-CK) seems to have evolved to adapt to synchronized changes in body temperature and intracellular pH. When gly(268) in rabbit muscle-specific creatine kinase was substituted with asn(268) as found in carp M1-CK, the rabbit muscle-specific CK G286N mutant specific activity at pH 8.0 and 10°C was more than 2-fold higher than that in the wild-type rabbit enzyme. Kinetic studies showed that K(m) values of the rabbit CK G268N mutant were similar to those of the wild-type rabbit enzyme, yet circular dichroism spectra showed that the overall secondary structures of the mutant enzyme, at pH 8.0 and 5°C, were almost identical to the carp M1-CK enzyme. The X-ray diffraction pattern of the mutant enzyme crystal revealed that amino acid residues involved in substrate binding are closer to one another than in the rabbit enzyme, and the cysteine283 active site of the mutant enzyme points away from the ADP binding site. At pH 7.4-8.0 and 35-10°C, with a smaller substrate, dADP, specific activities of the mutant enzyme were consistently higher than the wild-type rabbit enzyme and more similar to the carp M1-CK enzyme. Thus, the smaller active site of the RM-CK G268N mutant may be one of the reasons for its improved activity at low temperature.

ExprAlign--the identification of ESTs in non-model species by alignment of cDNA microarray expression profiles

Background

Sequence identification of ESTs from non-model species offers distinct challenges particularly when these species have duplicated genomes and when they are phylogenetically distant from sequenced model organisms. For the common carp, an environmental model of aquacultural interest, large numbers of ESTs remained unidentified using BLAST sequence alignment. We have used the expression profiles from large-scale microarray experiments to suggest gene identities.

Results

Expression profiles from ~700 cDNA microarrays describing responses of 7 major tissues to multiple environmental stressors were used to define a co-expression landscape. This was based on the Pearsons correlation coefficient relating each gene with all other genes, from which a network description provided clusters of highly correlated genes as 'mountains'. We show that these contain genes with known identities and genes with unknown identities, and that the correlation constitutes evidence of identity in the latter. This procedure has suggested identities to 522 of 2701 unknown carp ESTs sequences. We also discriminate several common carp genes and gene isoforms that were not discriminated by BLAST sequence alignment alone. Precision in identification was substantially improved by use of data from multiple tissues and treatments.

Conclusion

The detailed analysis of co-expression landscapes is a sensitive technique for suggesting an identity for the large number of BLAST unidentified cDNAs generated in EST projects. It is capable of detecting even subtle changes in expression profiles, and thereby of distinguishing genes with a common BLAST identity into different identities. It benefits from the use of multiple treatments or contrasts, and from the large-scale microarray data.

Proteomic analysis of proteins associated with body mass and length in yellow perch, Perca flavescens

The goal of commercial yellow perch aquaculture is to increase muscle mass which leads to increased profitability. The accumulation and degradation of muscle-specific gene products underlies the variability in body mass (BM) and length observed in pond-cultured yellow perch. Our objective was to apply a combination of statistical and proteomic technologies to identify intact and/or proteolytic fragments of muscle specific gene products involved in muscle growth in yellow perch. Seventy yellow perch randomly selected at 10, 12, 16, 20, and 26 wk of age were euthanized; BM and length were measured and a muscle sample taken. Muscle proteins were resolved using 5-20% gradient SDS-PAGE, stained with SYPRO Ruby and analyzed using TotalLab software. Data were analyzed using stepwise multiple regression with the dependent variables, BM and length and proportional OD of each band in a sample as a potential regressor. Eight bands associated with BM (R(2) = 0.84) and nine bands with length (R(2) = 0.85) were detected. Protein sequencing by nano-LC/MS/MS identified 20 proteins/peptides associated with BM and length. These results contribute the identification of gene products and/or proteolytic fragments associated with muscle growth in yellow perch.

Differential proteome analysis of hagfish dental and somatic skeletal muscles

Hagfish, the plesiomorphic sister group of all vertebrates, are deep-sea scavengers. The large musculus (m.) longitudinalis linguae (dental muscle) is a specialized element of the feeding apparatus that facilitates the efficient ingestion of food. In this article, we compare the protein expression in hagfish dental and somatic (the m. parietalis) skeletal muscles via two-dimensional gel electrophoresis and mass spectrometry in order to characterize the former muscle. Of the 500 proteins screened, 24 were identified with significant differential expression between these muscles. The proteins that were overexpressed in the dental muscle compared to the somatic muscle were troponin C (TnC), glycogen phosphorylase, beta-enolase, fructose-bisphosphate aldolase A (aldolase A), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). In contrast, myosin light chain 1 (MLC 1) and creatine kinase (CK) were over-expressed in the somatic muscle relative to the dental muscle. These results suggest that these two muscles have different energy sources and contractile properties and provide an initial representative map for comparative studies of muscle-protein expression in low craniates.

Purification and some properties of two creatine kinase isoforms from herring (Clupea harengus) spermatozoa

Creatine kinase (CK, EC 2.7.3.2) isoforms play important role in energy homeostasis and together with easily diffusible compounds like creatine and phosphocreatine maintain a cellular energy buffer and intracellular energy transport system. The CK activity in spermatozoa is the highest from all studied tissues in herring. It was detected that the two CK isoforms, CK1 and CK2, are characteristic only for spermatozoa and are not expressed in other herring tissues. Isolation and purification procedures allowed obtaining purified enzymes with specific activity of the 345 micromol/min/mg for CK1 and 511 micromol/min/mg for CK2. Native Mr's of the CK1 and CK2 determined by gel permeation chromatography were about 330,000 and 90,000, respectively. These results indicate that CK1 form has octameric structure and CK2 is a dimer mostly characteristic for cytosolic CK enzymes. In immunoblotting studies with antisera against CK2, the response was observed for CK2 and there was no response for CK1 and two other isoforms from herring skeletal muscle. These findings make the herring isoforms an interesting model for studies on the fish CK biochemical properties.

Comparison of kinetic constants of creatine kinase isoforms

The purpose of this study was to elucidate the functional differences between the CK isoforms by cloning the cDNAs of 12 CK isoforms: the M and B cytoplasmic forms and uMiCK from mouse, the M1, M2 and B cytoplasmic forms from Danio rerio, M1 and M2 cytoplasmic forms from the lower vertebrate Lampetra japonica, a cytoplasmic CK and a MiCK from the marine worm Neanthes diversicolor, and a cytoplasmic CK and a MiCK from the soft coral Dendronephthya gigantea. These were expressed in Escherichia coli as a fusion protein with maltose-binding protein, and kinetic constants (K(m), K(d) and k(cat)) of all the recombinant enzymes, except for the unstable Dendronephthya cytoplasmic CK, were determined for the forward reaction. The kinetic constants of the M- and B-forms of the mouse and Danio cytoplasmic CKs differed significantly, with the K(m) for creatine (K(m)Cr) of M-CK being three- to nine-fold higher than that of B-CK, possibly reflecting differences in the concentration of creatine in muscle and brain cells. The mouse uMiCK had the lowest K(m)Cr value among the CK isoforms. In addition, it also exhibited a strong synergism for substrate binding (K(d)/K(m)=11.8). These results indicate that uMiCK has unique characteristics compared with other CK isoforms. Two subisoforms of M-CK were found in the lower vertebrate L. japonica, and the kinetic constants of recombinant M1- and M2-CKs differed significantly. The M1- and M2-CKs were expressed in skeletal muscle with a ratio of 7:3, while M1-CK was the predominant subisoform in the testis. The kinetic constants of cytoplasmic CK from the marine worm Neanthes were significantly different from those of Neanthes MiCK, possibly indicating that functional differences among CK isoforms occurred at least before the divergence of annelids from other protostome invertebrates.

Protein expression patterns in zebrafish skeletal muscle: initial characterization and the effects of hypoxic exposure

Patterns of protein expression were examined in white skeletal muscle from adult zebrafish (Danio rerio). High resolution two-dimensional gel electrophoresis resolved between 300 and 400 spots with molecular masses between 20 and 120 kDa and isoelectric points between about 5 and 8. Forty spots, representing a range of protein size, charge, and abundance were excised, digested with trypsin, and subjected to matrix-assisted laser-desorption/ionisation-time of flight mass spectrometry for protein identification. Twenty-nine spots were identified, including enzymes of energy metabolism, contractile proteins, an iron transport protein, and a heat shock protein. In addition, several spots matched theoretical proteins predicted from genome sequencing. These theoretical proteins were tentatively identified by similarity to known proteins. Patterns of muscle protein expression were then measured after zebrafish were exposed to low oxygen (16 torr) for 48 h, an exposure previously shown to increase the survival of zebrafish at more severe reductions in oxygen. Exposure to low oxygen (hypoxia) did not change the general pattern of protein expression but did affect the amounts of six low abundance proteins. The relatively subtle effects of hypoxia on patterns of muscle protein expression contrasts the widespread changes previously documented in mRNA levels in this and other species of fish during hypoxic stress. The difference between protein and mRNA expression illustrates the need to integrate both measures for a more complete understanding of gene expression in fish during hypoxic exposure.

Response to acute changes in salinity of two different muscle type creatine kinase isoforms, from euryhaline teleost (Oreochromis mossambicus) gills

Two CKM isoforms (CKM1 and CKM2) from the gills of tilapia (Oreochromis mossambicus) were obtained after transfer from freshwater (FW) to seawater (SW, 25 ppt). Based on the 5' and 3' RACE, the identity of CKM1 and CKM2 was determined to be 59% in the 5'-untranslated region (5'-UTR) and 41.9% in the 3'-UTR. Using Northern blot hybridization with the CKM1 and CKM2 3'-UTR probes, CKM1 and CKM2 were found to be expressed in muscle, heart and gill. The levels of these two different CK isoforms (CKM1 and CKM2) were shown to be different in FW than after acute SW transfer, showing that CKM isoforms respond to changes in salinity.

Elements of the major myofibrillar binding peptide motif are present in the earliest of true muscle type creatine kinases

Most vertebrates possess two genes for cytoplasmic creatine kinase (CK) coding for muscle (M-CK) and brain (B-CK) isoforms which assemble into homo-dimeric (MM, BB) and hetero-dimeric (MB) active enzymes. In mammals and birds, a significant fraction of MM-CK is bound to the myofibrillar M-line where it is thought to facilitate energy buffering and transport. Myofibrillar binding is mediated by major and minor lysine charge clamp motifs (K104/K115 [major] and K8/K24 [minor] in chicken M-CK) located in the N-terminal region [J. Cell Biol. 149 (2000) 1225]. We have obtained the cDNA and deduced amino acid sequences for cytoplasmic CKs from two hagfish, Myxine glutinosa and Eptatretus stoutii, non-vertebrate craniates, and the sequences for two cytoplasmic CKs from the lamprey Lampetra japonica, a jawless true vertebrate. All four cDNAs code for CKs consisting of approximately 380 residues. Phylogenetic analyses showed that the hagfish and lamprey CKs are coded for by genes which are clearly muscle type (M) creatine kinases. Two of these four M-CKs have the K104/K115-equivalent residues of the major myofibrillar binding region while the other two have the K115 equivalent but lack the corresponding K104 residue. All four M-CKs lack the K8/K24 equivalent elements of the minor myofibrillar binding region. Comparison of these sequences to corresponding sequences of cytoplasmic CKs from two protochordates (tunicate, amphioxus) and M- and B-CKs from true fish and above reveal a pattern of acquisition (and loss) of key lysine residues consistent with the physiological context in which these enzymes operate.

Temperature and the expression of seven muscle-specific protein genes during embryogenesis in the Atlantic cod Gadus morhua L

Seven cDNA clones coding for different muscle-specific proteins (MSPs) were isolated from the fast muscle tissue of Atlantic cod Gadus morhua L. In situ hybridization using cRNA probes was used to characterize the temporal and spatial patterns of gene expression with respect to somite stage in embryos incubated at 4 degrees C, 7 degrees C and 10 degrees C. MyoD transcripts were first observed in the presomitic mesoderm prior to somite formation, and in the lateral compartment of the forming somites. MyoD expression was not observed in the adaxial cells that give rise to the slow muscle layer, and expression was undetectable by in situ hybridization in the lateral somitic mesoderm after the 35-somite stage, during development of the final approximately 15 somites. RT-PCR analysis, however, confirmed the presence of low levels of the transcript during these later stages. A phylogenetic comparison of the deduced aminoacid sequences of the full-length MyoD cDNA clone and those from other teleosts, and inference from the in situ expression pattern suggested homology with a second paralogue (MyoD2) recently isolated from the gilthead seabream Sparus aurata. Following MyoD expression, alpha-actin was the first structural gene to be switched on at the 16-somite stage, followed by myosin heavy chain, troponin T, troponin I and muscle creatine kinase. The final mRNA in the series to be expressed was troponin C. All genes were switched on prior to myofibril assembly. The troponin C sequence was unusual in that it showed the greatest sequence identity with the rainbow trout Oncorhynchus mykiss cardiac/slow form, but was expressed in the fast myotomal muscle and not in the heart. In addition, the third TnC calcium binding site showed a lower level of sequence conservation than the rest of the sequence. No differences were seen in the timing of appearance or rate of posterior progression (relative to somite stage) of any MSP transcripts between embryos raised at the different temperatures. It was concluded that myofibrillar genes are activated asynchronously in a distinct temporal order prior to myofibrillar assembly and that this process was highly canalized over the temperature range studied.

Isolation, characterization and nucleotide sequence of the muscle isoforms of creatine kinase from the Antarctic teleost Chaenocephalus aceratus

Creatine kinase (CK) was isolated from the white muscle of the Antarctic icefish Chaenocephalus aceratus, which is deficient in glycolytic capacity. C. aceratus white myotomal creatine kinase (MMCK) displayed an apparent K(m) at 0.5 degrees C of 0.06 mM for ADP and 17 mM for Phosphocreatine. These K(m) values are similar to those reported for other vertebrate MMCKs at their physiologically relevant body temperatures. C. aceratus MMCK exhibited optimal activity at pH of 7.6-7.7 at 0.5 degrees C, in contrast to rabbit MMCK which had optimum activity at pH 6.2 at 30 degrees C. The apparent V(max) of C. aceratus MMCK at 0.5 degrees C is 94+/-4 S.D. (n=9) micromol ATP/min/mg (i.e. U/mg), which is comparable to rabbit MMCK assayed at 20 degrees C and 8-fold greater than rabbit MMCK measured at 0.5 degrees C. DEAE chromatography of C. aceratus white muscle CK resolved two distinct activity peaks. Cloning and sequencing of C. aceratus CK cDNAs confirmed that two muscle-specific isoforms of CK were expressed that were distinct from the mitochondrial and brain isoforms. Icefish MMCK was sensitive to transient temperature elevation, and the DEAE-fractionated forms were highly unstable. These results indicate that C. aceratus MMCK displays significant activity at physiological temperature and intracellular pH of icefish muscle that could contribute to sustaining energy charge during burst-swimming.

Cellular distributions of creatine kinase in branchia of euryhaline tilapia (Oreochromis mossambicus)

Although euryhaline teleosts can adapt to environmental fluctuation of salinity, their energy source for responding to changes in salinity and osmolarity remains unclear. This study examines the cellular localization of creatine kinase (CK) expression in branchia of tilapia (Oreochromis mossambicus). Western blot analysis of muscle-type CK (MM form) revealed a high association with salinity changes, but BB and MB forms of CK in the gills of fish adapted to seawater did not change. With the use of immunocytochemistry, three CK isoforms (MM, MB, and BB) were localized in mitochondria-rich (MR) cells and other epithelial cells of tilapia gills. In addition, staining intensity of MM-form CK in MR cells increased after seawater transfer, whereas BB and MB forms did not significantly change. To our knowledge, this work presents the first evidence of CK expression in MR cells of tilapia gills, highlighting the potential role of CK in providing energy for ion transport.

The carp muscle-specific sub-isoenzymes of creatine kinase form distinct dimers at different temperatures

We have previously cloned three muscle-specific sub-isoforms of creatine kinase (CK, EC 2.7.3.2) from the common carp ( Cyprinus carpio ), designated M1-CK, M2-CK, and M3-CK. The enzyme has a key role in maintaining the energy homoeostasis of cells with fluctuating energy requirements. In the present paper, we report that all three M-CKs in the red and white muscle of different temperature-acclimatized carp were ubiquitously distributed in the cytosol and along membranes. In addition, the expression levels of these isoforms were not significantly altered in response to the temperature acclimatization. Interestingly, our studies showed that the formation of distinct homo- or heterodimers among these three M-CKs was found at various temperatures. At higher temperature, the M1M1-CK and M2M2-CK homodimers, and the M1M3-CK heterodimer are the predominant MM-CKs, whereas the M3M3-CK achieves its homodimeric state at lower temperature. We postulated testable homology models to investigate the chemical properties of these dimeric interfaces. M1M1-CK was used as a reference to compare the structural differences with the M3M3-CK dimer. The calculated solvent accessible surface area that was buried in the contact interfaces of the M1M1-CK and M3M3-CK dimers showed an overall decrease of 12% in the M3M3-CK interface. The modelling analysis also suggested a net decrease of twelve hydrophobic residues and a Phe(3)-->Lys substitution in the M3M3-CK interface. An increase in thermolability of the M3M3-CK homodimer might be due to the decrease in subunit ion pairs and buried surface area in this dimer. Based on our findings, we propose that the carp-muscle-specific CK isoenzymes could undergo shuffling to form distinct M-CK homo- or heterodimers in acclimatization to environmental temperatures.

Acute changes in gill Na+-K+-ATPase and creatine kinase in response to salinity changes in the euryhaline teleost, tilapia (Oreochromis mossambicus)

Some freshwater (FW) teleosts are capable of acclimating to seawater (SW) when challenged; however, the related energetic and physiological consequences are still unclear. This study was conducted to examine the changes in expression of gill Na(+)-K(+)-ATPase and creatine kinase (CK) in tilapia (Oreochromis mossambicus) as the acute responses to transfer from FW to SW. After 24 h in 25 ppt SW, gill Na(+)-K(+)-ATPase activities were higher than those of fish in FW. Fish in 35 ppt SW did not increase gill Na(+)-K(+)-ATPase activities until 1.5 h after transfer, and then the activities were not significantly different from those of fish in 25 ppt SW. Compared to FW, the gill CK activities in 35 ppt SW declined within 1.5 h and afterward dramatically elevated at 2 h, as in 25 ppt SW, but the levels in 35 ppt SW were lower than those in 25 ppt SW. The Western blot of muscle-type CK (MM form) was in high association with the salinity change, showing a pattern of changes similar to that in CK activity; however, levels in 35 ppt SW were higher than those in 25 ppt SW. The activity of Na(+)-K(+)-ATPase highly correlated with that of CK in fish gill after transfer from FW to SW, suggesting that phosphocreatine acts as an energy source to meet the osmoregulatory demand during acute transfer.

Bioenergetics of adaptation to a salinity transition in euryhaline teleost (Oreochromis mossambicus) brain

Freshwater (FW) teleosts are capable of acclimating to seawater (SW) following such a transfer from FW. However, their osmoregulating mechanisms are still unclear, particularly those in the brain. The present study was conducted to examine acute changes that occur in brain Na(+)-K(+)-ATPase activity, creatine kinase (CK) activity, creatine, creatinine contents, and ATP levels of tilapia (Oreochromis mossambicus) in response to this transition. After transfer to SW (25 ppt), the Na(+)-K(+)-ATPase activity was maintained for 8 hr at higher levels than that in FW. In contrast, in 35 ppt SW, Na(+)-K(+)-ATPase was maintained at a even higher level than in FW for the first 2 hr. Brain Na(+)-K(+)-ATPase contents in both the 25 and 35 ppt SW groups were significantly elevated within 1 and 0.5 hr after transfer from FW, respectively. Interestingly, brain CK activities and content (homodimer of the B subunit [BB] form) in both the 25 and 35 ppt SW groups were significantly elevated within 1 hr after transfer from FW. The ATP contents in 35 ppt SW increased abruptly within 0.5 hr, and then gradually decreased during the next 2 hr. Unlike the 35 ppt group that declined in ATP contents, the 25 ppt group leveled off within 24 hr. The elevations in CK activity and creatine levels after transfer from FW to SW imply that abrupt salinity changes alter phosphocreatine/CK ratio. Such changes are needed to satisfy the increases in the energetic requirement of the cotransport mechanisms mediating osmoregulation.

Multiple isoforms and an unusual cathodic isoform of creatine kinase from channel catfish (Ictalurus punctatus)

In vertebrates, the creatine kinase (CK) family consists of two cytosolic and two mitochondrial isoforms. The two cytosolic isoforms are the muscle type (M-CK) and the brain type (B-CK). Here we report multiple CK isoenzymes in the diploid channel catfish (Ictalurus punctatus) with one unusual cathodic isoform that was previously found only in pathological situations in human. The cathodic CK isoform existed only in the channel catfish stomach, ovary, and spleen, but not in any other species analyzed such as tilapia, smallmouth bass, chicken, or rat. Two genes encode the multiple forms of the channel catfish M-CK cDNAs. M-CK1 has three alleles, M-CK1.1, M-CK1.2, and M-CK1.3, while M-CK2 has just one allele as determined by analysis of 17 cDNA clones and by allele-specific PCR. M-CK1 encodes a protein of 381 amino acids and the M-CK2 cDNA encodes a protein of 380 amino acids. The two cDNAs shared an 86% identity and both have the nine diagnostic boxes for cytosolic CKs and thus are of cytosolic origin. The M-CK1 gene was isolated, sequenced, and characterized and its promoter should be useful for transgenic research for muscle-specific expression.

Gene duplication events producing muscle (M) and brain (B) isoforms of cytoplasmic creatine kinase: cDNA and deduced amino acid sequences from two lower chordates

Creatine kinase (CK) is coded for by at least four loci in higher vertebrates--two cytoplasmic isoforms, muscle (M) and brain (B), and two mitochondrial isoforms, sarcomeric and ubiquitous. M is expressed primarily in skeletal muscle, while B is expressed in a variety of cells, including cardiac and smooth muscle fibers, neurons, transport epithelia, and photoreceptors. M and B subunits form very stable homodimers (MM [M-CK], BB [B-CK]) and heterodimers (MB). M-CK is capable of binding to the M line of the myofibril, thereby creating an energy transfer microcompartment; BB and MB CKs are not. M- and B-like CKs are present in all vertebrates yet examined, including fish. Cytoplasmic, dimeric CKs are widely distributed in the invertebrates. The only available amino acid sequence for an invertebrate dimeric CK, that of the protostome polychaete Chaetopterus variopedatus, is just as similar to the vertebrate M isoform as to the B isoform. Echinoderms lack dimeric, cytoplasmic CKs, which appear to be replaced by a dimeric arginine kinase which evolved secondarily from CK. Thus, it is likely that the gene duplication event producing the M and B isoforms occurred after the divergence of the chordates from echinoderms. To narrow down the timing of this duplication event, we obtained the cDNA and deduced amino acid sequences of dimeric CKs from the tunicate Ciona intestinalis (subphylum Urochordata) and the lancelet Branchiostoma floridae (subphylum Cephalochordata). Our results show that these CKs are strikingly similar to both invertebrate and vertebrate CKs. However, phylogenetic analyses by neighbor-joining and parsimony show that these two enzymes appeared to have diverged before the point of divergence of the M and B isoforms. Thus, the gene duplication event for formation of the muscle and brain isoforms of CK most likely occurred during the radiation of the fish, a time noted for gene duplication events at a variety of other loci.

Creatine kinase: a role for arginine-95 in creatine binding and active site organization

Sequence homology analysis reveals that arginine-95 is fully conserved in 29 creatine kinases sequenced to date, but fully conserved as a tyrosine residue in 16 arginine kinases. Site-directed mutants of rabbit muscle creatine kinase (rmCK) were prepared in which R95 was replaced by a tyrosine (R95Y), alanine (R95A), or lysine (R95K). Kinetic analysis of phosphocreatine formation for each purified mutant showed that recombinant native rmCK and all R95 mutants follow a random-order, rapid-equilibrium mechanism. However, we observed no evidence for synergism of substrate binding by the recombinant native enzyme, as reported previously [Maggio et al., (1977) J. Biol. Chem. 252, 1202-1207] for creatine kinase isolated directly from rabbit muscle. The catalytic efficiencies of R95Y and R95A are reduced approximately 3000- and 2000-fold, respectively, compared to native enzyme, but that of R95K is reduced only 30-fold. The major contribution to the reduction of the catalytic efficiency of R95K is a 5-fold reduction in the affinity for creatine. This suggests that while a basic residue is required at position 95 for optimal activity, R95 is not absolutely essential for binding or catalysis in CK. R95Y has a significantly lower affinity for creatine than the native enzyme, but it also displays a somewhat lower affinity for MgATP and 100-fold reduction in k(cat). Interestingly, R95A appears to bind either creatine or MgATP first with affinities similar to those for the native enzyme, but it has a 10-fold lower affinity for the second substrate, suggesting that replacement of R95 by an alanine disrupts the active site organization and reduces the efficiency of formation of the catalytically competent ternary complex.