Jacobson R D, Virág I, Skene J H
J Neurosci. 1986 Jun;6(6):1843-55. doi: 10.1523/JNEUROSCI.06-06-01843.1986.
Development or regeneration of axons in several systems is accompanied by 20-100-fold increases in the synthesis of an acidic, axonally transported membrane protein with an apparent molecular weight of 43-50,000 (Benowitz and Lewis, 1983; Skene and Willard, 1981a, b), which we designate GAP-43. We have proposed that some step(s) in axon growth require production of GAP-43, and perhaps a small number of other "growth-associated proteins," at rates much higher than those typical of mature neurons. This hypothesis predicts that virtually all neurons synthesize GAP-43 at elevated levels during normal CNS development. Here we show that a protein similar to GAP-43 from regenerating toad nerves is prominent among the newly synthesized (35S-methionine-labeled) and total (Coomassie blue-stained) proteins in neonatal rat cerebral cortex and cerebellum, suggesting that synthesis of GAP-43 is indeed a common feature of many developing neurons. Synthesis and accumulation of the protein decline an order of magnitude as animals mature. Antibodies raised against the rat cortex GAP-43 also recognize electrophoretically similar proteins from regenerating toad optic nerves and from developing hamster sensorimotor cortex, indicating that structural features of GAP-43 are conserved in evolution. Cell-free translation of polyadenylated RNA from neonatal and adult cortex suggests that developmental regulation of GAP-43 synthesis is mediated largely through changes in mRNA abundance. These observations together suggest that developmental regulation of GAP-43 gene expression may be common to most vertebrate CNS neurons. GAP-43 remains detectable at a low level in adult rat cortex, and it co-migrates on two-dimensional gels with B-50, a synaptic membrane protein which is a preferred substrate for protein kinase C in adult brains. Phosphorylation of the protein by endogenous kinase(s) in vitro is 4-7-fold greater in growth cone membranes than in mature synaptic membranes, which raises the possibility that local modification of the protein in axon terminals may be synergistic with regulation of GAP-43 synthesis in the cell body.
在多个系统中，轴突的发育或再生伴随着一种酸性的、轴突运输的膜蛋白合成增加20至100倍，该蛋白的表观分子量为43,000至50,000（贝诺维茨和刘易斯，1983年；斯凯内和威拉德，1981年a、b），我们将其命名为GAP - 43。我们提出轴突生长的某些步骤需要以远高于成熟神经元典型水平的速率产生GAP - 43，或许还有少量其他“生长相关蛋白”。这一假说预测，在正常中枢神经系统发育过程中，几乎所有神经元都会以升高的水平合成GAP - 43。在此我们表明，新生大鼠大脑皮层和小脑中，新合成的（用35S - 甲硫氨酸标记）和总的（考马斯亮蓝染色）蛋白质中，与再生蟾蜍神经中GAP - 43类似的一种蛋白质很突出，这表明GAP - 43的合成确实是许多发育中神经元的一个共同特征。随着动物成熟，该蛋白的合成和积累下降一个数量级。针对大鼠皮层GAP - 43产生的抗体也能识别来自再生蟾蜍视神经和发育中仓鼠感觉运动皮层的电泳相似蛋白，表明GAP - 43的结构特征在进化中是保守的。新生和成年皮层多聚腺苷酸化RNA的无细胞翻译表明，GAP - 43合成的发育调控主要是通过mRNA丰度的变化介导的。这些观察结果共同表明，GAP - 43基因表达的发育调控可能是大多数脊椎动物中枢神经系统神经元所共有的。在成年大鼠皮层中，GAP - 43仍可在低水平检测到，并且它在双向凝胶上与B - 50共迁移，B - 50是一种突触膜蛋白，在成年大脑中是蛋白激酶C的优选底物。在体外，生长锥膜中内源性激酶对该蛋白的磷酸化作用比成熟突触膜中强4至7倍，这增加了轴突末端该蛋白的局部修饰可能与细胞体中GAP - 43合成调控协同作用的可能性。
