Disease relevance of Ckm

• Both M-CK(-)/(-) and CK(-)/(-) showed increased phosphomonoester levels during ischemia, most likely reflecting adaptation to a more efficient utilization of glycogenolysis [1].
• In contrast to the cell type- and differentiation-specific expression of the upstream enhancer, the MCK promoter was able to function in myoblasts and myotubes and in nonmyogenic cell lines when combined with the simian virus 40 enhancer [2].
• Transgenic (MCK-CD36) mice had a slightly lower body weight than control litter mates [3].
• 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 [4].
• Therefore, the MCK/SV40 promoter may provide the basis for development of an effective transgene expression cassette for treatment of congenital protein deficiencies in which therapeutic proteins are recognized as foreign by the host immune system [5].

High impact information on Ckm

• To understand the physiological role of the creatine kinase-phosphocreatine (CK-PCr) system in muscle bioenergetics, a null mutation of the muscle CK (M-CK) gene was introduced into the germline of mice [6].
• In vivo protein-DNA interactions at the developmentally regulated enhancer of the mouse muscle creatine kinase (MCK) gene were examined by a newly developed polymerase chain reaction (PCR) footprinting procedure [7].
• Several footprints were detected in terminally differentiated muscle cells where the MCK gene is actively transcribed [7].
• Mice homozygous for this M-CK allele (M-CKI/I) have a 3-fold reduction of dimeric muscle CK enzyme activity, whereas compound heterozygotes with the null M-CK allele (M-CKI/-) display a 6-fold reduction [8].
• In the absence of an authentic target for the MASH proteins, we examined their DNA binding and transcriptional regulatory activity by using a binding site (the E box) from the muscle creatine kinase (MCK) gene, a target of MyoD [9].

Biological context of Ckm

• Transcriptional regulatory element X (Trex) is a positive control site within the Muscle creatine kinase (MCK) enhancer [10].
• It has been proposed that the myogenic factors, MyoD1 and myogenin, directly regulate MCK gene expression in the mouse by binding to its enhancer [11].
• Addition of IGF-I or LiCl stimulated myogenesis, evidenced by increased myotube formation, muscle creatine kinase (MCK) activity, and troponin I (TnI) promoter transactivation during differentiation [12].
• Using targeting constructs based on strain 129/Sv isogenic DNA we managed to ablate the essential exons of the B-CK and M-CK genes at reasonably high frequencies [13].
• Hearts from wild-type, MCK-/-, and M/MtCK-/- mice had comparable baseline function and responded to 10 minutes of increased heart rate and perfusate Ca2+ with similar increases in rate-pressure product (48+/-5%, 42+/-6%, and 51+/-6%, respectively) [14].

Anatomical context of Ckm

• Cell culture and transgenic studies indicate that the Trex site is important for MCK expression in skeletal and cardiac muscle [10].
• Our purpose was to determine whether hearts from mice bioengineered to lack either the M isoform of creatine kinase (MCK-/- mice) or both the M and mitochondrial isoforms (M/MtCK-/- mice) have deficits in cardiac contractile function and energetics, which have previously been reported in skeletal muscle from these mice [14].
• We performed transient transfections of CAT reporter constructs, driven by the MCK promoter with variable lengths of 5'-flanking sequence, into primary cultures of embryonic and fetal muscle cells [15].
• As a test system we compared hindlimb muscle of knockout mice lacking the cytosolic M-type (M-CK(-)/(-)), the mitochondrial ScMit-type (ScCKmit(-)/(-)), or both creatine kinase isoenzymes (CK(-)/(-)), and in vivo 31P-NMR was used to monitor metabolic responses during and after an ischemic period [1].
• Unexpectedly, however, MASH1 and MASH2 also activate transcription of both exogenous and endogenous MCK in transfected C3H/10T1/2 fibroblasts [9].

Associations of Ckm with chemical compounds

• Impaired intracellular energetic communication in muscles from creatine kinase and adenylate kinase (M-CK/AK1) double knock-out mice [16].
• An analysis of actomyosin complexes in vitro demonstrated that one of the consequences of M-CK and AK1 deficiency is hampered phosphoryl delivery to the actomyosin ATPase, resulting in a loss of contractile performance [16].
• To study the physiological role of the creatine kinase/phosphocreatine (CK/PCr) system in cells and tissues with a high and fluctuating energy demand we have concentrated on the site-directed inactivation of the B- and M-CK genes encoding the cytosolic CK protein subunits [13].
• Finally, combined loss of M- and Mt-CK (but not loss of only M-CK) prevented the amount of free energy released from ATP hydrolysis from increasing when pyruvate was provided as a substrate for oxidative phosphorylation [17].
• Finally, overexpression of myogenin rescued the inhibitory effect of rapamycin on MCK gene transcription, whereas it failed to rescue the inhibitory effect of LY294002 and Akt1 [18].

Physical interactions of Ckm

• Like myogenic bHLH proteins, the MASH proteins form heterooligomers with E12 that bind the MCK E box with high affinity in vitro [9].

Regulatory relationships of Ckm

• Notch1 signals were measured by both the activation of the hairy/enhancer of split (HES1) promoter and by the antagonism of MyoD-induced muscle creatine kinase (MCK) promoter activity [19].
• The muscle creatine kinase (MCK) gene whose transcription is induced during muscle differentiation contains p53-binding sites [20].
• Basic fibroblast growth factor (bFGF) prevents myogenesis and represses MCK expression by inhibiting transcriptional activation [21].

Other interactions of Ckm

• The M isoform of creatine kinase (MCK), the striated muscle-specific isoform, is expressed later than BCK [11].
• Herein, we show that simultaneous disruption of the genes for the cytosolic M-CK- and AK1 isoenzymes compromises intracellular energetic communication and severely reduces the cellular capability to maintain total ATP turnover under muscle functional load [16].
• METHODS: CK-deficient mice (CK KO) were examined by cardiac magnetic resonance imaging (MRI) to determine left ventricular volumes, ejection fraction, and mass: ten wild-type (WT), 6 mitochondrial CK KO (Mito-CK-/-), 10 cytosolic CK KO (M-CK-/-), and 10 mice with combined KO (M/Mito-CK-/-) [22].
• The cis-acting elements, MEF-2, E boxes and A/T rich elements present in the enhancer region of the mouse MCK gene are known to regulate the expression of the gene [23].
• Deletion analysis indicated that the C-terminal 15 amino acids of Id3 are critical for the full inhibitory activity while deleting up to 42 residues from the C-terminus of the related protein, Id2, did not affect its ability to inhibit the MCK reporter gene [24].

Analytical, diagnostic and therapeutic context of Ckm

• Fifty-two days after chronic denervation, the number of molecules of MCK/ng total RNA in both muscles (determined with competitive PCR) decreased, with the soleus muscle being more affected [25].
• We have used gel mobility shift assays to characterize the trans-acting factors that interact with a region of the MCK gene containing the 5' enhancer [26].
• Myostatin mRNA and protein, measured by RT-PCR and Western blot, respectively, were significantly higher in gastrocnemius, quadriceps, and tibialis anterior of MCK/Mst-transgenic mice compared with wild-type mice [27].
• Male MCK/Mst-transgenic mice had 18-24% lower hind- and forelimb muscle weight and 18% reduction in quadriceps and gastrocnemius fiber cross-sectional area and myonuclear number (immunohistochemistry) than wild-type male mice [27].
• Proliferating myoblasts and differentiated myofiber cultures were analyzed via SDS-PAGE, immunochemical, and PCR methods for expression of myosin heavy chains (MyHC) and muscle creatine kinase (MCK) as indices of muscle fiber type [28].

References