Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02115, USA.
Proc Natl Acad Sci U S A. 2010 Dec 7;107(49):21022-7. doi: 10.1073/pnas.1014664107. Epub 2010 Nov 19.
Centrosomes are primary microtubule (MT)-organizing centers (MTOCs). During mitosis, they dramatically increase their size and MT-nucleating activity and participate in spindle assembly from spindle poles. These events require the serine/threonine kinase, Aurora A (AurA), and the centrosomal protein of 192 kDa (Cep192)/spindle defective 2 (Spd-2), but the underlying mechanism remains unclear. We have found that Cep192, unlike targeting protein for Xklp2 (TPX2), a known MT-localizing AurA activator, is an AurA cofactor in centrosome-driven spindle assembly. Cep192, through a direct interaction, targets AurA to mitotic centrosomes where the locally accumulating AurA forms homodimers or oligomers. The dimerization of endogenous AurA, in the presence of bound Cep192, triggers potent kinase activation that, in turn, drives MT assembly. Depletion of Cep192 or specific interference with AurA-Cep192 binding did not prevent AurA oligomerization on MTs but abrogated AurA recruitment to centrosomes and its activation by either sperm nuclei or anti-AurA antibody (αAurA)-induced dimerization. In these settings, MT assembly by both centrosomes and αAurA-coated beads was also abolished or severely compromised. Hence, Cep192 activates AurA by a mechanism different from that previously described for TPX2. The Cep192-mediated mechanism maximizes AurA activity at centrosomes and appears essential for the function of these organelles as MTOCs.
中心体是微管（MT）组织中心（MTOC）的主要组成部分。在有丝分裂过程中，它们的大小和 MT 成核活性显著增加，并参与纺锤体从纺锤体极的组装。这些事件需要丝氨酸/苏氨酸激酶 Aurora A（AurA）和 192kDa 中心体蛋白（Cep192）/纺锤体缺陷 2（Spd-2），但潜在的机制尚不清楚。我们发现，Cep192 与靶向蛋白 Xklp2（TPX2）不同，TPX2 是一种已知的 MT 定位 AurA 激活剂，Cep192 是中心体驱动的纺锤体组装中 AurA 的共因子。Cep192 通过直接相互作用将 AurA 靶向有丝分裂中心体，局部积累的 AurA 在那里形成同源二聚体或寡聚体。内源性 AurA 的二聚化，在结合 Cep192 的情况下，触发强烈的激酶激活，进而驱动 MT 组装。Cep192 的耗竭或 AurA-Cep192 结合的特异性干扰并没有阻止 AurA 在 MT 上的寡聚化，但阻止了 AurA 向中心体的募集及其被精子核或抗 AurA 抗体（α AurA）诱导的二聚化激活。在这些情况下，中心体和α AurA 包被珠的 MT 组装也被废除或严重受损。因此，Cep192 通过与以前描述的 TPX2 不同的机制激活 AurA。Cep192 介导的机制最大限度地提高了中心体处的 AurA 活性，并且似乎对于这些细胞器作为 MTOC 的功能至关重要。
