Bélanger Dave, Farah Carole Abi, Nguyen Minh Dang, Lauzon Michel, Cornibert Sylvie, Leclerc Nicole
Département de pathologie et biologie cellulaire, Université de Montréal, Montréal, Québec, Canada, H3T 1J8.
J Cell Sci. 2002 Apr 1;115(Pt 7):1523-39. doi: 10.1242/jcs.115.7.1523.
The expression of microtubule-associated protein 2 (MAP2), developmentally regulated by alternative splicing, coincides with neurite outgrowth. MAP2 proteins contain a microtubule-binding domain (C-terminal) that promotes microtubule assembly and a poorly characterized domain, the projection domain (N-terminal), extending at the surface of microtubules. MAP2b differs from MAP2c by an additional sequence of 1372 amino acids in the projection domain. In this study, we examined the role of the projection domain in the protrusion of microtubules from the cell surface and the subsequent process formation in Sf9 cells. In this system, MAP2b has a lower capacity to induce process formation than MAP2c. To investigate the role of the projection domain in this event, we expressed truncated forms of MAP2b and MAP2c that have partial or complete deletion of their projection domain in Sf9 cells. Our results indicate that process formation is induced by the microtubule-binding domain of these MAP2 proteins and is regulated by their projection domain. Furthermore, the microtubule-binding activity of MAP2b and MAP2c truncated forms as well as the structural properties of the microtubule bundles induced by them do not seem to be the only determinants that control the protrusion of microtubules from the cell surface in Sf9 cells. Rather, our data suggest that microtubule protrusion and process formation are regulated by intramolecular interactions between the projection domain and its microtubule-binding domain in MAP2b.
微管相关蛋白2（MAP2）的表达受可变剪接的发育调控，与神经突生长同时发生。MAP2蛋白包含一个促进微管组装的微管结合结构域（C端）和一个在微管表面延伸的特征不明的结构域，即投射结构域（N端）。MAP2b与MAP2c的区别在于投射结构域中有一个额外的1372个氨基酸的序列。在本研究中，我们研究了投射结构域在微管从细胞表面突出以及随后在Sf9细胞中形成突起过程中的作用。在这个系统中，MAP2b诱导突起形成的能力低于MAP2c。为了研究投射结构域在此过程中的作用，我们在Sf9细胞中表达了投射结构域部分或完全缺失的MAP2b和MAP2c截短形式。我们的结果表明，突起形成是由这些MAP2蛋白的微管结合结构域诱导的，并受其投射结构域的调节。此外，MAP2b和MAP2c截短形式的微管结合活性以及由它们诱导的微管束的结构特性似乎并不是控制微管从Sf9细胞表面突出的唯一决定因素。相反，我们的数据表明，微管突出和突起形成是由MAP2b中投射结构域与其微管结合结构域之间的分子内相互作用调节的。
