Shen Wei, Willis Dianna, Zhang Yanping, Schlattner Uwe, Wallimann Theo, Molloy George R
Department of Biological Sciences, University of Delaware, 117 Wolf Hall, Newark, DE 19716, U.S.A.
Biochem J. 2002 Oct 15;367(Pt 2):369-80. doi: 10.1042/BJ20020709.
Transcription and accumulation of brain-type creatine kinase (CKB) mRNA and its protein was examined during postnatal development of rat brain cerebellum, the brain region containing highest CKB mRNA in the adult. CKB protein was extremely low at day 1, increased about 10-fold until week 4 and remained constant until week 10. This time course was paralleled by cerebellar CKB mRNA, which was also extremely low at day 1 and increased 5-fold during the first 3 weeks and then remained constant. High levels of CKB protein were also detected in cultured primary cerebellar granular neurons. Nuclear run-on assays directly showed that CKB mRNA accumulation during postnatal cerebellar development was due to increased transcription. When compared with cerebrum and whole brain, cerebellar CKB mRNA accumulation during postnatal development was temporally delayed. Analysis of myocyte enhancer factor (MEF)-2 and Sp1, factors known to initiate or sustain CKB transcription in tissues other than brain, revealed that MEF-2 in cerebellum was low at week 1 but increased 3.5-fold by week 7, while Sp1 remained unchanged. The increase in CKB protein during cerebellar postnatal development was coincident with that of the ubiquitous mitochondrial CK protein and mRNA, indicating that a functional phosphocreatine energy shuttle probably exists for efficient ATP regeneration in the cerebellum. This should be beneficial for the many energy-demanding requirements during cerebellar development, as indicated by the observed temporal co-expression of CKB with myelin basic protein, which is involved in axon myelination by oligodendrocytes.
在大鼠脑小脑（成年期脑内脑型肌酸激酶（CKB）mRNA含量最高的脑区）出生后的发育过程中，对CKB mRNA及其蛋白质的转录和积累情况进行了检测。出生第1天时，CKB蛋白质含量极低，到第4周时增加了约10倍，并一直保持稳定直至第10周。小脑CKB mRNA的变化趋势与之平行，出生第1天时也极低，在最初3周内增加了5倍，之后保持稳定。在原代培养的小脑颗粒神经元中也检测到了高水平的CKB蛋白质。核转录分析直接表明，出生后小脑发育过程中CKB mRNA的积累是由于转录增加所致。与大脑和全脑相比，出生后小脑发育过程中CKB mRNA的积累在时间上有所延迟。对已知在脑以外组织中启动或维持CKB转录的肌细胞增强因子（MEF）-2和Sp1进行分析发现，小脑MEF-2在第1周时含量较低，但到第7周时增加了3.5倍，而Sp1则保持不变。小脑出生后发育过程中CKB蛋白质的增加与普遍存在的线粒体CK蛋白质和mRNA的增加相一致，这表明可能存在一种功能性的磷酸肌酸能量穿梭机制，以便在小脑中高效再生ATP。这对于小脑发育过程中许多能量需求来说应该是有益的，如观察到的CKB与髓鞘碱性蛋白的时间共表达所示，髓鞘碱性蛋白参与少突胶质细胞对轴突的髓鞘形成。
