Boyne L J, Martin K, Hockfield S, Fischer I
Department of Anatomy and Neurobiology, Medical College of Pennsylvania, Philadelphia 19129, USA.
J Neurosci Res. 1995 Mar 1;40(4):439-50. doi: 10.1002/jnr.490400403.
Microtubule associated proteins (MAPs) interact with tubulin to modulate neurite stability and growth during development. The phosphorylated form of one of these MAPs, MAP1B (MAP1B-P) is hypothesized to be of particular importance for the regulation of neurite outgrowth. To investigate the mechanisms by which MAP1B and MAP1B-P contribute to this regulation, we used a new antibody against an isoform of MAP1B-P to determine its pattern of expression during neuronal development in vitro. We examined cultured hippocampal neurons because these provide a well-established system to evaluate the development of axons and dendrites. MAP1B, MAP1B-P and MAP2 colocalized to the cell bodies and minor processes during the first 24 hours of culture, but MAP1B-P also extended well into the growth cones. As neurite outgrowth and differentiation proceeded, MAP1B and MAP1B-P became localized to the cell bodies and axons, and MAP2 to the cell bodies and dendrites. After 3 days, MAP1B-P declined in the cell body and was segregated to the distal axon; MAP1B remained in the cell body, but was also concentrated in the distal axon. Over 5-9 days in culture, MAP1B-P levels decreased and became undetectable; MAP1B levels decreased later (19-23 days). MAP2 levels, however, remained high through the entire culture period in cell bodies and dendrites. These results are consistent with the hypothesis that MAP1B-P plays an important role in the initiation and elongation of axons by regulating the dynamics of microtubules near the growth cone: MAP1B-P expression is greatest during the period of active neurite extension, is particularly prominent in growth cones where axon outgrowth is most active, and decreases along with the decline in active axon extension.
微管相关蛋白（MAPs）与微管蛋白相互作用，以调节发育过程中神经突的稳定性和生长。这些MAPs之一的磷酸化形式，即MAP1B（MAP1B-P），被认为对神经突生长的调节尤为重要。为了研究MAP1B和MAP1B-P参与这种调节的机制，我们使用了一种针对MAP1B-P异构体的新抗体，以确定其在体外神经元发育过程中的表达模式。我们检查了培养的海马神经元，因为它们提供了一个成熟的系统来评估轴突和树突的发育。在培养的最初24小时内，MAP1B、MAP1B-P和MAP2共定位于细胞体和小的突起，但MAP1B-P也大量延伸至生长锥。随着神经突的生长和分化进行，MAP1B和MAP1B-P定位于细胞体和轴突，而MAP2定位于细胞体和树突。3天后，MAP1B-P在细胞体中减少并被分隔到轴突远端；MAP1B仍留在细胞体中，但也集中在轴突远端。在培养5-9天期间，MAP1B-P水平下降并变得无法检测到；MAP1B水平稍后下降（19-23天）。然而，MAP2水平在整个培养期间在细胞体和树突中保持较高。这些结果与以下假设一致，即MAP1B-P通过调节生长锥附近微管的动力学，在轴突的起始和延伸中起重要作用：MAP1B-P的表达在神经突活跃延伸期间最高，在轴突生长最活跃的生长锥中尤为突出，并随着活跃轴突延伸的下降而降低。
