Schipper H M, Agarwal-Mawal A, Paudel H K
Lady Davis Institute for Medical Research, Sir Mortimer B. Davis-Jewish General Hospital, and Department of Neurology and Neurosurgery, McGill University, Montreal, Quebec, Canada.
Neuroscience. 1999;93(2):585-95. doi: 10.1016/s0306-4522(99)00120-7.
Mitogen-activated protein kinase signal transduction pathway involved in the regulation of proliferation and differentiation of various mammalian cells consists of a sequential activation of three protein kinases, Raf, mitogen-activated protein kinase kinase, and mitogen-activated protein kinase. These kinases are highly expressed in brain and play an important role in neuronal signalling. In this study, to further characterize mitogen-activated protein kinase signalling pathway in brain, we have elucidated the topography and subcellular distribution of mitogen-activated protein kinase kinasel in adult rat brain and differentiating PC12 cells. Our immunohistochemical data indicate that mitogen-activated protein kinase kinase1 is widely distributed throughout the brain and expressed prominently in cortex, hippocampus, brainstem, hypothalamus and cerebellum. In these areas of brain mitogen-activated protein kinase kinasel is exclusively neuronal in origin and is localized within perikarya and dendrites. Confocal microscopy data has determined that a portion of mitogen-activated protein kinase kinase1 in rat brain is co-localized with microtubules. This co-localization was observed only within neuritic shaft and cilia of ventricular ependymal cells. In nerve growth factor-induced differentiating PC12 cells, mitogen-activated protein kinase kinase1 displays co-localization with microtubules within proximal regions of neuritic shafts and their junctions with the cell somas. From bovine brain extract, mitogen-activated protein kinase kinasel co-purifies with microtubules. In vitro kinase assay detected mitogen-activated protein kinase kinase1 activity within purified microtubules. These observations indicate that mitogen-activated protein kinase kinase1 is associated with microtubules within some specialized compartments of the brain and microtubule-associated mitogen-activated protein kinase kinase1 is catalytically active.
丝裂原活化蛋白激酶信号转导途径参与多种哺乳动物细胞增殖和分化的调控，该途径由三种蛋白激酶（Raf、丝裂原活化蛋白激酶激酶和丝裂原活化蛋白激酶）的顺序激活组成。这些激酶在大脑中高度表达，并在神经元信号传导中发挥重要作用。在本研究中，为了进一步表征大脑中的丝裂原活化蛋白激酶信号通路，我们阐明了成年大鼠大脑和分化中的PC12细胞中丝裂原活化蛋白激酶激酶1的拓扑结构和亚细胞分布。我们的免疫组织化学数据表明，丝裂原活化蛋白激酶激酶1广泛分布于整个大脑，在皮质、海马、脑干、下丘脑和小脑中显著表达。在大脑的这些区域，丝裂原活化蛋白激酶激酶1完全起源于神经元，并定位于核周体和树突内。共聚焦显微镜数据确定，大鼠大脑中一部分丝裂原活化蛋白激酶激酶1与微管共定位。这种共定位仅在室管膜细胞的神经突轴和纤毛内观察到。在神经生长因子诱导的分化PC12细胞中，丝裂原活化蛋白激酶激酶1在神经突轴的近端区域及其与细胞体的连接处与微管共定位。从牛脑提取物中，丝裂原活化蛋白激酶激酶1与微管共同纯化。体外激酶测定在纯化的微管中检测到丝裂原活化蛋白激酶激酶1的活性。这些观察结果表明，丝裂原活化蛋白激酶激酶1在大脑的一些特殊区域与微管相关，并且与微管相关的丝裂原活化蛋白激酶激酶1具有催化活性。
