Cravchik A, Reddy D, Matus A
Friedrich Miescher-Institut, Basel, Switzerland.
J Cell Sci. 1994 Mar;107 ( Pt 3):661-72. doi: 10.1242/jcs.107.3.661.
Several microtubule-associated proteins (MAPs) have been shown to bind to microtubules via short sequences with repeated amino acids motifs. A microtubule-binding domain has hitherto not been defined for the adult brain microtubule-associated protein 1A (MAP1A). We have searched for a microtubule-binding domain by expressing different protein regions of MAP1A in cultured cell lines using cDNA constructs. One construct included an area with homology to the microtubule-binding domain of MAP1B (Noble et al. (1989) J. Cell Biol. 109, 437-448), but this did not bind to microtubules in transfected cells. Further investigation of other areas of MAP1A revealed a protein domain, capable of autonomously binding to microtubules, which bears no homology to any previously described microtubule-binding sequence. This MAP1A domain is rich in charged amino acids, as are other mammalian microtubule-binding domains, but unlike them has no identifiable sequence repeats. Whereas all previously described mammalian microtubule-binding domains are basic, this novel microtubule-binding domain of MAP1A is acidic. The expression of this polypeptide in cultured cell lines led to a rearrangement of the microtubules in a pattern distinct from that produced by MAP2 or tau, and increased their resistance to treatment with the microtubule depolymerising agent nocodazole. When the MAP1A microtubule-binding domain was co-expressed in cultured cell lines together with MAP2c, the MAP1A microtubule-binding domain was able to bind to the MAP2c-induced microtubule bundles. These results suggest that different microtubule-binding sequences have a common ability to stabilise microtubules but differ in their influence on microtubule arrangement in the cell. This may be significant in neurons, where microtubule-associated proteins with different microtubule-binding sequences are expressed in different cell compartments and at different times during development.
已有研究表明，几种微管相关蛋白（MAPs）可通过具有重复氨基酸基序的短序列与微管结合。迄今为止，尚未确定成人大脑微管相关蛋白1A（MAP1A）的微管结合结构域。我们通过使用cDNA构建体在培养细胞系中表达MAP1A的不同蛋白区域，来寻找微管结合结构域。一种构建体包含一个与MAP1B的微管结合结构域具有同源性的区域（Noble等人，(1989)《细胞生物学杂志》109, 437 - 448），但该区域在转染细胞中并不与微管结合。对MAP1A其他区域的进一步研究揭示了一个能够自主与微管结合的蛋白结构域，该结构域与任何先前描述的微管结合序列均无同源性。这个MAP1A结构域富含带电荷的氨基酸，其他哺乳动物微管结合结构域也是如此，但与它们不同的是，它没有可识别的序列重复。虽然所有先前描述的哺乳动物微管结合结构域都是碱性的，但MAP1A这个新的微管结合结构域是酸性的。该多肽在培养细胞系中的表达导致微管重排，其模式与MAP2或tau产生的模式不同，并增加了它们对微管解聚剂诺考达唑处理的抗性。当MAP1A微管结合结构域与MAP2c在培养细胞系中共同表达时，MAP1A微管结合结构域能够与MAP2c诱导的微管束结合。这些结果表明，不同的微管结合序列具有稳定微管的共同能力，但在对细胞中微管排列的影响方面存在差异。这在神经元中可能具有重要意义，因为具有不同微管结合序列的微管相关蛋白在发育过程中的不同细胞区室和不同时间表达。
