Developmental regulation of creatine kinase isoenzymes in myogenic cell cultures from chicken. Levels of mRNA for creatine kinase subunits M and B

Proliferation of Human Primary Myoblasts Is Associated with Altered Energy Metabolism in Dependence on Ageing In Vivo and In Vitro

Background. Ageing is associated with suppressed regenerative potential of muscle precursor cells due to decrease of satellite cells and suppressive intramuscular milieu on their activation, associated with ageing-related low-grade inflammation. The aim of the study was to characterize the function of oxidative phosphorylation (OXPHOS), glycolysis, adenylate kinase (AK), and creatine kinase (CK) mediated systems in young and older individuals. Materials and Methods. Myoblasts were cultivated from biopsies taken by transcutaneous conchotomy from vastus lateralis muscle in young (20–29 yrs, n = 7) and older (70–79 yrs, n = 7) subjects. Energy metabolism was assessed in passages 2 to 6 by oxygraphy and enzyme analysis. Results. In myoblasts of young and older subjects the rate of OXPHOS decreased during proliferation from passages 2 to 6. The total activities of CK and AK decreased. Myoblasts of passage 2 cultivated from young muscle showed higher rate of OXPHOS and activities of CK and AK compared to myoblasts from older subjects while hexokinase and pyruvate kinase were not affected by ageing. Conclusions. Proliferation of myoblasts in vitro is associated with downregulation of OXPHOS and energy storage and transfer systems. Ageing in vivo exerts an impact on satellite cells which results in altered metabolic profile in favour of the prevalence of glycolytic pathways over mitochondrial OXPHOS of myoblasts.

DNA immunization utilizing a herpes simplex virus type 2 myogenic DNA vaccine protects mice from mortality and prevents genital herpes

A gene transfer vector for DNA immunization was developed in which the promoter was derived from the murine muscle creatine kinase (MCK) gene; a gene expressed only in differentiated skeletal muscle. In vitro, we observed high-level, but unrestricted, gene expression from the cytomegalovirus (CMV) promoter unlike expression from the MCK promoter which was weak but restricted to myofibers. A myogenic DNA vaccine (MDV) that encoded the glycoprotein D gene from herpes simplex virus type-2 (HSV-2) was used to DNA immunize mice. MDV immunization resulted in virus specific immunity that protected HSV-2 infected mice from mortality and prevented the development of genital herpes. Therefore, we conclude that high-level gene expression or the use of a strong transcription unit was not a prerequisite for an efficacious DNA vaccine and the use of a nonviral tissue specific promoter could suffice.

Ultrastructure of developing muscle in the upper limbs of the human embryo and fetus

BACKGROUND

The ultrastructure of the myogenesis, which proceeds along with the appearance of muscle-specific proteins and isozymes, has not been fully described in the upper limb of staged human embryos.

METHODS

Eight human embryos (Carnegie stage 14-22) and two fetuses (11 and 12 weeks of gestation) were fixed with 5% glutaraldehyde, 4% paraformaldehyde, and 0.2% picric acid in 0.1 M phosphate buffer, pH 7.2. The upper limbs were dissected out and processed for transmission electron microscopy, and sections of the biceps brachii muscle were cut and examined.

RESULTS

At stage 14, the myoblasts were loosely scattered in the ventral proximal region of the upper limb bud and had a small amount of cytoplasm with a few intracellular organelles. At stage 16, the myoblasts were spindle shaped and oriented parallel to the axis of the upper limb bud. These cells had irregularly shaped nuclei with prominent nucleoli, rough endoplasmic reticulum (ER), and mitochondria, but no myofilaments were observed. At stages 17-19, rough ER, free ribosomes, and mitochondria increased in number and thick and thin filaments with faint Z-lines appeared in the peripheral cytoplasm of the myotube. The plasma membranes of some neighboring myotubes were continuous, suggesting that these cells were in the initial stages of the fusion process. At stage 22, the striated pattern of the myofilaments became evident and tubular structures appeared around them and near the plasma membrane. In the fetus at the 11th week, the basal lamina began to surround the myotubes, and T-tubules with sarcoplasmic reticulum were observed. Dyads and triads were observed in the myotube of the 12th week fetus.

CONCLUSION

These findings suggest that rapid myogenesis occurs during the late embryonic period in human upper limbs and that the ultrastructural characteristics of mature myotubes are established during the early fetal period.

Enhancement of skeletal muscle regeneration

We have studied the effect of adding extra satellite cells or soluble factors from crushed muscle on regeneration of minced fragments from rat tibialis muscle. The muscle mince was wrapped in an artificial epimysium to prevent adhesions and cell immigration from adjacent muscles. Regeneration was quantitatively assessed by electrophoretic determination of the muscle-specific form of creatine kinase. Control minces exhibited three periods of change in creatine kinase activity during a 7-week regeneration period. Activity fell rapidly during the first week, then rose gradually from 1-3 weeks and increased more rapidly from 3-7 weeks. To augment the original complement of myogenic cells, satellite cells were isolated from the contralateral muscle, purified by density gradient centrifugation, and expanded in culture for 3 days before adding to the muscle mince. The added cells resulted in a 3-fold enhancement of creatine kinase activity throughout the regeneration period. Soluble muscle extract incorporated into a collagen matrix also stimulated regeneration when added to muscle mince. The extract accelerated the rate of creatine kinase increase during the 1-3 week period beyond that observed in the control or cell augmented mince, suggesting that factors in the extract may facilitate revascularization or reinnervation. The specific activity of creatine kinase was increased in regenerates augmented with both cells and extract, indicating that the effects enhance primarily myogenic processes.

Altering creatine kinase isoenzymes in transgenic mouse muscle by overexpression of the B subunit

To change the levels of expression and isoenzyme distribution of creatine kinase (CK) in muscle, transgenic technology was used to express the B subunit of CK in mouse muscle. Normally, mammalian skeletal muscle contains the MM dimer of CK. The BB dimer and MB heterodimer of CK can be found in brain and heart, respectively. Heterologous genes consisting of skeletal and cardiac muscle-specific actin promoters fused to the genomic coding region of the B form of CK were used to create transgenic mice. Lines were established from the three highest expressing founders. Analysis of skeletal muscle extracts revealed that all three lines had an increase in total CK activity measured under maximal velocity conditions. The highest expressing line, 7001, had a CK activity 150% that of control muscle. Nuclear magnetic resonance saturation transfer was used to measure the in vivo rate of the CK reaction. In 7001 hindlimb muscles, the CK catalyzed reaction was 200% that of control muscle. The elevation in CK activity in transgenic muscle was accompanied by significant changes in the composition of the cytosolic isoenzyme ratio of CK. In control, 100% of CK was MM, whereas 7001 had 60 +/- 18% MM, 32 +/- 10% MB, and 8 +/- 2% BB. There were no changes in ATP, phosphocreatine, Pi, or creatine levels in transgenic muscle compared with control. Immunofluorescence of myofibrils isolated from control and transgenic muscle revealed specific association of CK to the M line. Small amounts of MB CK were detected on myofibrils from transgenic mice. Transgenic mice expressing the B subunit of CK in muscle represent a first step toward altering CK isoforms so as to elucidate the specific roles of these isoforms in energy metabolism.

Expression of the gene encoding human brain creatine kinase depends on sequences immediately following the transcription start point

To localize sequences that are important for regulation of the gene (CK-B) encoding human brain creatine kinase (CK-B), we have functionally dissected the region comprising 1.8 kb of DNA upstream from the main transcription start point (tsp) and the first exon and intron, and made a detailed comparison with the situation in the rat CK-B gene. Upon using the transient chloramphenicol acetyltransferase (CAT) assay in human HeLa and mouse neuroblastoma cells, we have delimited the basal promoter in the human CK-B gene to a segment of 150 nucleotides (nt) immediately preceding the major mRNA cap site. No other essential regulatory sequence is located further upstream. Both from tsp mapping and from mutational inactivation studies, we conclude that of the two T + A-rich motifs in the promoter region, the TTAA motif between nt positions -28 to -25 is of major importance for transcriptional activity. Moreover, and most notably, a region spanning 22 nt of the first exon has a strong stimulatory effect on CK-B/CAT synthesis.

Differential expression of creatine kinase isozymes during development of Xenopus laevis: an unusual heterodimeric isozyme appears at metamorphosis

The creatine kinase (CK) repertoire of Xenopus laevis, which is more complex than that of most other vertebrates, involves at least four genomic loci, all showing developmental and tissue-specific expression. The differential expression of this multilocus CK isozyme system was investigated by immunohistology. Specific monoclonal antibodies (mAb) against the three cytoplasmic CK isozymes of Xenopus laevis were isolated and characterized. Two of these mAbs, anti-CK-IV (DM16) and anti-CK-III (JRM4), were specific for CK-IV and CK-III subunits respectively, as well as for the corresponding homodimeric isozymes, CK-IV/IV and CK-III/III. Anti-CK-II (MRX7) mAb recognizes CK-II subunits and CK-II/III heterodimers; the homodimeric CK-II/III does not occur. Immunohistological localization on larval and adult tissue sections reveals that CK-IV epitopes, beside a generalized tissue distribution, are especially concentrated in the cytoplasm of some particular cells such as the photoreceptors in the outer segment of the retina, certain nerve cells of the spinal cord and spinal ganglia, and in larval hepatocytes. The CK-III III isozyme is specifically expressed in skeletal muscle, its appearance and accumulation occurring in parallel with myoblast differentiation. The CK-II antigen is detected first at the time of metamorphosis is skeletal muscles, as well as in the heart, eyes and brain. In striated musculature the expression of CK-II subunits during metamorphosis results in almost complete replacement of CK-III/III homodimers by CK-II/III heterodimers, as indicated by the progressive masking of CK-III epitope and the corresponding appearance of CK-II antigen. In the adult eyes, CK-II antigens localize at the same particular site of photoreceptors as do CK-IV antigens. Since that antigen represents a heterodimeric CK-II/III isozyme, this implies the activation of both CK-II and CK-III genes, none of which is expressed in larval retina.

Developmental regulation of a cadherin during the differentiation of skeletal myoblasts

Cadherins are a family of integral membrane glycoproteins which mediate calcium-dependent intercellular adhesion in vertebrate species. Here we present evidence that fusion-competent rat L6 myoblasts express a cadherin (Mr 127 kDa). The levels of this cadherin were found to be developmentally regulated. Maximal levels were expressed prior to fusion. The increase in cadherin levels observed during differentiation was prevented by the differentiation inhibitor, 5-bromo-2'-deoxyuridine. L6 myoblasts grown in the presence of anti-cadherin antibodies exhibited an altered morphology in comparison to control cultures, coupled with decreased myoblast fusion. These data indicate that the developmental regulation of cadherin is part of the program of terminal differentiation of skeletal myoblasts, and that cadherins are involved in the process of myoblast fusion.

Developmental expression of creatine kinase isozymes in mammalian lens

Four different isoforms are thought to comprise the creatine kinase of enzymes which regulate energy metabolism through the interconversion of ADP and creatine phosphate. In addition to these well characterized isoforms, MM, MB, BB and mitochondrial creatine kinase, several uncharacterized variants with atypical electrophoretic mobility have been described. In mammalian lens, creatine kinase isoforms exhibit both a regional and developmental pattern of expression. In neonatal rat and human lens, the only isoform expressed is a variant cathodic creatine kinase. Near the time of sexual maturation (11-13 yr) there is a dramatic increase in the expression of BB creatine kinase in human lens. In rat lens, a similar pattern of isoenzyme expression is also seen near the time of sexual maturation (5-6 weeks). In the mature rat lens, in addition to the cathodic variant, there is expression of BB and, to a lesser extent, MM creatine kinase. Using a polyclonal antisera, we have localized BB creatine kinase to the cuboidal epithelial cells of the adult rat lens. This unique pattern of isoenzyme expression and developmental regulation suggests a more complex scheme for the regulation of creatine kinase gene expression than previously postulated.

Skeletal muscle CK-B activity in neurogenic muscular atrophies

Creatine kinase isoenzymes were determined in skeletal muscle biopsy specimens of 34 patients suffering from neurogenic muscular atrophies. The findings were compared: (1) with those of 38 control muscle samples and (2) with those in 41 muscular dystrophies and other myopathic conditions. The measurements were made by electrophoretic separation and elution of the isoenzymes and by immunoinhibition assay. The results showed that the total and specific CK activity were significantly decreased (P less than 0.005) in neurogenic atrophies in contrast to myopathic conditions where no differences from control levels were observed. This decrease was due to a decrease of the CK-M subunit activity, while the CK-B subunit was elevated. The muscle CK-MB activity was considerably elevated in muscular dystrophies (P less than 0.02) and myositis (P less than 0.001), but it was also slightly elevated in neurogenic conditions. The similarity of the muscle CK isoenzyme pattern in neurogenic atrophies and myotonic dystrophy was noted. These findings could possibly reflect considerable difference in the regeneration process of neurogenic atrophies and muscular dystrophies.

Purification and characterization of arginine kinase from sea-urchin eggs

In most invertebrates, creatine kinase is replaced by arginine kinase, which catalyzes reversibly the transfer of a phosphate group between adenosine triphosphate and arginine. In sea-urchin larvae, arginine kinase only is expressed whereas in adult sea-urchins both arginine kinase and creatine kinase can be found in the same tissue. In order to study their developmental regulation and properties, we have purified arginine kinase to homogeneity from the eggs of the sea-urchin Paracentrotus lividus. The purification involves ethanol and ammonium sulfate precipitations, followed by an anion-exchange chromatography, an affinity chromatography and a gel filtration. A 500-fold increase in specific activity leads to a specific activity of 360 IU/mg protein at 25 degrees C. Arginine kinase (pI = 5.7) is rapidly and irreversibly inactivated at 45 degrees C. Amino acid composition and Km values (2.08 mM for phospho-L-arginine and 1.25 mM for ADP) are also given. Determination of molecular mass by gel filtration and separation by SDS/polyacrylamide gel electrophoresis indicate that the enzyme is an 81-kDa dimer of two subunits of 42 kDa.

Distinct tissue specific mitochondrial creatine kinases from chicken brain and striated muscle with a conserved CK framework

cDNA clones for chicken mitochondrial creatine kinase (Mi-CK) were isolated from a lambda gt11 leg muscle cDNA library and sequenced. The deduced amino acid sequence showed 6 blocks of extensive homologies with the cytosolic creatine kinases and contained twenty N-terminal amino acids, with characteristic features of part of a mitochondrial presequence. The mature enzyme contained 380 amino acids with a calculated Mr of 43'195. RNA hybridization analysis showed corresponding Mi-CK transcripts in cardiac and skeletal muscle, but not in brain RNA. Within the 30 N-terminal amino acids purified brain Mi-CK contained 10 changes with respect to cardiac Mi-CK. Thus multiple isoproteins of mitochondrial creatine kinases of brain and striated muscle are encoded by multiple mRNA's.

Structure and expression of the human creatine kinase B gene

Various cDNAs for creatine kinase type B (CK-B) were isolated from human cDNA libraries using a 26-oligonucleotide guess-mer probe. One of the cDNAs appeared to be almost full-length and contained an open reading frame coding for the 381 amino acid residues of the human CK-B polypeptide. The nucleotide sequences of the translated region as well as the primary protein structure show a high degree of homology with known CK-B and CK-M sequences of other vertebrates. The level of CK-B RNA as a measure of CK-B gene activity was determined in various human tissues and cultured cells. Our results confirm that CK-B is expressed in a tissue-specific manner and give support to the previously proposed relation between CK-B gene activity and cell proliferation. Screening of genomic DNA with various cDNA regions as probes revealed that there is only one CK-B gene per haploid genome. Gene cloning and sequencing indicated that CK-B is coded for by a relatively small gene of 3.2 kb in size, which is partially overlapped by an HTF island (A. P. Bird (1986) Nature (London) 321, 557-558) with an extremely high G + C content at its 5' end.

Human creatine kinase: isolation and sequence analysis of cDNA clones for the B subunit, development of subunit specific probes and determination of gene copy number

cDNA clones for human B creatine kinase were isolated from human brain and placenta libraries. The entire coding and 3' untranslated regions, as well as 23 bp of the 5' untranslated region were sequenced. Complete sequence identity was found among the clones, with the exception of an area of heterogeneity among the 3' untranslated region of the brain and placenta clones. A 77.7% nucleotide sequence identity was found between the coding region of human B creatine kinase and our previously reported human M creatine kinase. In contrast, no homology was found in the 3' untranslated regions. Probes were constructed from the nonconserved 3' untranslated regions of human M and B creatine kinase and were shown to be highly specific. Southern transfers of total genomic DNA derived from human placenta and digested to completion with several restriction enzymes were probed with the MCK and BCK specific probes producing single hybridization bands. These results suggest that creatine kinase M and B are single copy genes in the human genome.

Accumulation of creatine kinase mRNA during myogenesis: molecular cloning of a B-creatine kinase cDNA

Cytosolic creatine kinase isoenzymes MM, MB, and BB are assembled from M or B subunits which occur in different relative amounts in specific tissues. The accumulation of mRNAs encoding the M and B subunits was measured during myogenesis in culture. The relative concentration of the two mRNAs was determined by hybridization with a M-CK cDNA probe isolated previously and a B-CK cDNA probe, the cloning and characterization of which is reported here. The B-CK cDNA hybridizes specifically to a 1.6-kb mRNA found in brain and gizzard but not in adult skeletal muscle tissue. The M-CK cDNA hybridizes to a smaller mRNA 1.4-kb long which is specific to skeletal muscle. In culture, the B-CK mRNA is transiently induced and then declines to a low but detectable level.

Serum creatine kinase B subunit levels in neurogenic atrophies

This study is an attempt to determine the creatine kinase B (CK-B) subunit levels in neurogenic atrophies. A group of 69 patients was studied and the results were compared with those in a group of 32 patients with muscle disease. The results showed that the CK-B levels are considerably higher in patients with amyotrophic lateral sclerosis (P less than 0.001) and peroneal muscular atrophy (P less than 0.001). Further studies in the various subgroups of neurogenic atrophies showed that, regardless of the nosological entity, the CK-B activity is considerably higher: (1) in the "widespread" as opposed to "limited" forms (P less than 0.001); (2) in the "chronic" than in the "acute" neurogenic atrophies (P less than 0.001); and (3) in the "active" as opposed to "residual" forms (P less than 0.02). It is suggested that the increase of CK-B in neurogenic atrophies is a strong indication of an active regeneration process in the denervated muscle.

Differential sensitivity of chicken MM-creatine kinase to trypsin and proteinase-K

Under several conditions of SDS-PAGE, the chicken MM-creatine kinase (MM-CK) monomer migrated as a approximately 50,000 dalton polypeptide, approx 25% larger than usually reported. Characterization by sedimentation equilibrium indicated that the anomalous molecular weight was an artifact of electrophoresis. Digestion with trypsin caused only moderate reductions in CK activity, despite extensive degradation of the denatured enzyme revealed by SDS-PAGE. Characterization of trypsinized MM-CK under non-denaturing conditions of electrophoresis and HPLC revealed no fragmentation of the native enzyme, suggesting that MM-CK quaternary structure was maintained despite extensive tryptic nicking. In contrast, much lower concentrations of proteinase-K generated only a single fragment in SDS-PAGE while causing a nearly total loss of enzyme activity.

Isoenzyme-specific localization of M-line bound creatine kinase in myogenic cells

Experiments using isolated fibre bundles or myofibrils of chicken skeletal muscle have shown that a relatively small portion of the muscle-specific MM-type of creatine kinase (CK) (EC 2.7.3.2) is specifically bound to the M-line and yet greatly contributes to the electron-dense M-line structure. Here we demonstrate the presence of M-line bound CK in cultured myogenic cells by removing the unbound sarcoplasmic CK through permeabilization with Triton X-100 and extensive washing of the cells prior to immunofluorescence staining. When stained with antibodies specific for M-CK subunits these cells exhibit bright fluorescence within the M-line region of myofibrils. Occasionally this cross-striated pattern is also observed in mononucleated presumably postmitotic myoblasts. Anti-B-CK incubation, in contrast, results in a weak, diffuse fluorescence at the Z-band. Even though these cells contain appreciable amounts of B-type CK, specific fluorescence at the M-line is never observed with anti-B-CK antibody thus ruling out the presence of BB-type or MB-type CK at this location. Therefore the presence of CK within the M-line structure of myogenic cells which contain all three CK isoenzymes seems to be restricted to the MM-type isoenzyme.

Modulation of in vitro myogenesis by submillimolar concentrations of sodium butyrate

The effects of submillimolar concentrations of sodium butyrate on the differentiation of cultured chick myoblasts have been studied. The continuous presence of 0.5 mM butyrate inhibited myoblast fusion, creatine kinase (CK) isozyme transition, and synthesis of total RNA and protein until the 4th day of myogenesis, after which the fusion index reached control values and total CK activity was elevated. The latter continued to exhibit daily increases over control levels, largely reflecting activity of the MM-CK muscle-specific isozyme which increased to twice the control level by the 8th day. Similar but less striking patterns of early inhibition followed by stimulation were observed for total protein content and synthesis of total protein and RNA. On the other hand, DNA content was slightly but significantly depressed in treated cultures at all times. Butyrate treatment did not reverse 5'-bromodeoxyuridine (BUdR) inhibition of MM-CK differentiation. It was also noted that continuous treatment with 0.5 mM butyrate prevented the unexplained sporadic deterioration of myotubes sometimes observed at the 4th day.

Occurrence of heterogenous forms of the subunits of creatine kinase in various muscle and nonmuscle tissues and their behaviour during myogenesis

Purified, homodimeric creatine kinases from chicken were subjected to two-dimensional gel analysis under dissociating conditions. Each of the subunits M-creatine kinase and B-creatine kinase was resolved into a basic and an acidic subspecies with very similar mobilities in the sodium dodecylsulfate dimension. The M-creatine kinase subspecies were found in myogenic cells, fast muscle, slow muscle and the B-creatine kinase subspecies were present in heart, gizzard and brain. The creatine kinase subunits were identified in these tissues by a variety of methods like immunoreplicas of two-dimensional gels, immunoprecipitations, or coelectrophoresis with purified creatine kinase and all gave the same results. In the course of myogenic development in vitro the subspecies were synthesized coordinately and no indication was found for a differential regulation of any of the subspecies of the creatine kinase subunits. No radioactive phosphorus was incorporated into either one of the subspecies, hence phosphorylation could be ruled out as the source of heterogeneity. Furthermore, peptide mapping analysis of partial proteolytic digests did not reveal differences among the subspecies of the same subunit. Not only chicken but also rat creatine kinase displayed this type of heterogeneity. All subspecies were observed after translation of chicken RNA in a cell-free protein-synthesizing system. The heterogeneity probably might best be explained by the existence of multiple, but closely related genes for the creatine kinase subunits.