Protein serine/threonine phosphatase 1 and 2A associate with and dephosphorylate neurofilaments
Protein serine/threonine phosphatase 1 and 2A associate with and dephosphorylate neurofilaments
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DOI：
10.1016/s0169-328x(97)00117-4
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发表时间：
1997-10-03
期刊：
影响因子：
--
通讯作者：
Wadzinski, BE
中科院分区：
文献类型：
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作者：
Strack, S;Westphal, RS;Wadzinski, BE
神经丝的磷酸化状态在细胞骨架完整性、轴突运输和轴突直径的控制中起着重要作用。脊髓的免疫细胞化学分析揭示了所有蛋白磷酸酶亚基的轴突定位。为了确定蛋白磷酸酶是否与轴突神经丝相关，通过凝胶过滤从牛脊髓白质中分离出神经丝蛋白。约占总磷酸化酶 15% 的磷酸酶活性存在于神经丝部分中。通过免疫印迹在神经丝部分中检测到 PPI 和 PP2A 的催化亚基以及 PP2A 的 A 和 B α 调节亚基，而 PP2B 和 PP2C 仅在低分子量可溶性部分中发现。高盐可以使 PP1 和 PP2A 亚基与神经丝部分解离，但磷酸酶抑制剂则不能，表明这种相互作用不涉及催化位点。在神经丝和可溶性部分中，针对外源磷酸化酶 a 的磷酸酶活性的 75% 可归因于 PP2A，其余部分归因于 PPI（如特定抑制剂所示）。神经丝蛋白在体外被相关蛋白激酶磷酸化，这些蛋白激酶似乎包括蛋白激酶A、钙/钙调蛋白依赖性蛋白激酶以及肝素敏感和不敏感的辅因子非依赖性激酶。磷酸化神经丝亚基的去磷酸化主要 (60%) 由相关的 PP2A 催化，PP1 贡献次要活性 (10-20%)。这些研究表明神经丝相关的 PPI 和 PP2A 在神经丝磷酸化的调节中发挥重要作用。 (C) 1997 Elsevier Science B.V.
The phosphorylation state of neurofilaments plays an important role in the control of cytoskeletal integrity, axonal transport, and axon diameter. Immunocytochemical analyses of spinal cord revealed axonal localization of all protein phosphatase subunits. To determine whether protein phosphatases associate with axonal neurofilaments, neurofilament proteins were isolated from bovine spinal cord white matter by gel filtration. approximate to 15% of the total phosphorylase a phosphatase activity was present in the neurofilament fraction. The catalytic subunits of PPI and PP2A, as well as the A and B alpha regulatory subunits of PP2A, were detected in the neurofilament fraction by immunoblotting, whereas PP2B and PP2C were found exclusively in the low molecular weight soluble fractions. PP1 and PP2A subunits could be partially dissociated from neurofilaments by high salt but not by phosphatase inhibitors, indicating that the interaction does not involve the catalytic site. In both neurofilament and soluble fractions, 75% of the phosphatase activity towards exogenous phosphorylase a could be attributed to PP2A, and the remainder to PPI as shown with specific inhibitors. Neurofilament proteins were phosphorylated in vitro by associated protein kinases which appeared to include protein kinase A, calcium/calmodulin-dependent protein kinase, and heparin-sensitive and -insensitive cofactor-independent kinases. Dephosphorylation of phosphorylated neurofilament subunits was mainly (60%) catalyzed by associated PP2A, with PP1 contributing minor activity (10-20%). These studies suggest that neurofilament-associated PPI and PP2A play an important role in the regulation of neurofilament phosphorylation. (C) 1997 Elsevier Science B.V.