Yamauchi E, Titani K, Taniguchi H
Department of Biological Chemistry, Faculty of Pharmaceutical Sciences, Nagoya City University, Mizuhoku, Nagoya 467, Japan.
J Biol Chem. 1997 Sep 5;272(36):22948-53. doi: 10.1074/jbc.272.36.22948.
Microtubule-associated protein MAP1B, a major neuronal cytoskeletal protein, is expressed highly during the early stage of brain development and is thought to play an important role in brain development. Although it has been shown that MAP1B localizes both in cytosol and particulate fractions, the underlying molecular mechanism in the membrane localization has yet to be elucidated. In the present study, we show that MAP1B purified from young rat brain can bind to acidic phospholipids, such as phosphatidylserine, but not to a neutral phospholipid, phosphatidylcholine. Furthermore, the binding of MAP1B to taxol-stabilized microtubules was inhibited by the addition of phosphatidylserine or phosphatidylinositol. The addition of phosphatidylcholine showed no effect on the binding of MAP1B to the microtubules. A 120-kDa microtubule-binding fragment of MAP1B was also released from microtubules by the addition of acidic phospholipids. Synthetic peptides derived from the C-terminal half of the tubulin-binding domain, but not that corresponding to the N-terminal half, bound to acidic phospholipids specifically. These results suggest that MAP1B binds to biological membranes through its tubulin-binding site, and the binding may play a regulatory role in MAP1B-microtubule interaction.
微管相关蛋白MAP1B是一种主要的神经元细胞骨架蛋白，在大脑发育早期高度表达，被认为在大脑发育中起重要作用。尽管已表明MAP1B定位于胞质溶胶和颗粒部分，但膜定位的潜在分子机制尚待阐明。在本研究中，我们发现从幼鼠大脑中纯化的MAP1B能与酸性磷脂（如磷脂酰丝氨酸）结合，但不与中性磷脂磷脂酰胆碱结合。此外，添加磷脂酰丝氨酸或磷脂酰肌醇可抑制MAP1B与紫杉醇稳定的微管的结合。添加磷脂酰胆碱对MAP1B与微管的结合无影响。添加酸性磷脂也可从微管中释放出120 kDa的MAP1B微管结合片段。源自微管蛋白结合结构域C端一半的合成肽能特异性地与酸性磷脂结合，而对应于N端一半的合成肽则不能。这些结果表明，MAP1B通过其微管蛋白结合位点与生物膜结合，这种结合可能在MAP1B-微管相互作用中起调节作用。
