Centrosome Protein Function

中心体以其组织微管形成间期阵列和有丝分裂纺锤体的能力而闻名。最近的证据表明，中心体参与了细胞质分裂和细胞周期进程。 然而，对参与这些过程的中心体蛋白知之甚少。在之前的资助期间，我们研究了这些未被探索的中心体功能的分子基础。我们发现了一种新的中心体蛋白，称为中心素，它对哺乳动物细胞的胞质分裂是必不可少的。 Centriolin与涉及或参与胞质分裂的蛋白相互作用，包括Snapin(SNARE)、SEC 15(外囊)、MKLP-1(中心纺锤体)和一种新的Rho GTP酶激活蛋白。其中许多蛋白质定位于分裂细胞的中体，当下调时会导致细胞质缺陷。基于这些和其他数据，我们提出了一个模型，在该模型中，中心素作为中体的支架蛋白，协调胞质分裂后期的囊泡融合、微管解聚、沟槽内移和细胞分离。中心素下调引起的胞质分裂缺陷后，细胞发生Gl期停滞。我们出人意料地发现，许多中心体蛋白在下调时会导致GI停滞。然而，这种停滞与胞质分裂或其他中心体功能或中心体结构的缺陷无关。 或者是构图。我们推测，细胞周期停滞是由一个检查点触发的，该检查点监控尚未确定的共同功能中的缺陷，或由中心体上个别蛋白质的减少而引起的“中心体损伤”。GI抑制需要P53和p38的MAP激酶，并诱导激活的P53和p38重新聚集到中心体。基于这些观察，我们提出了两个具体目标。在目标1中，我们将确定中心素及其相关蛋白在胞质分裂中的作用。更具体地说，我们将测试中心素是否将这些蛋白质锚定在中体，以及这些蛋白质的复合体是否控制囊泡融合、微管 中体组织和细胞分离。目的2重点研究中心体蛋白在细胞周期进程和检查点激活中的作用。我们将确定GI停滞的机制，并确定连接中心体蛋白和细胞周期停滞的信号转导途径。

Centrosomes are best known for their ability to organize microtubules to form interphase arrays and mitotic spindles. Recent evidence suggests that centrosomes are involved hi cytokinesis and cell cycle progression. However, little is known about the centrosome proteins that contribute to these processes. In the previous funding period, we examined the molecular basis for these under-explored centrosome functions. We identified a novel centrosome protein called centriolin, which is essential for cytokinesis in mammalian cells. Centriolin interacts with proteins implicated or involved in cytokinesis including snapin (SNARE), sec 15 (exocyst), MKLP-1 (centralspindlin) and a novel GTPase activating protein for Rho GTPases. Many of these proteins localize to the midbody in dividing cells and induce cytokinesis defects when downregulated. Based on these and other data, we propose a model in which centriolin serves as a scaffold protein at the midbody to coordinate vesicle fusion, microtubule depolymerization, furrow ingression and cell separation late in cytokinesis. Defective cytokinesis induced by centriolin downregulation was followed by Gl arrest. We unexpectedly found that many centrosome proteins induced GI arrest when downregulated. However, the arrest did not correlate with defects in cytokinesis or other centrosome functions, or in centrosome structure or composition. We postulate that cell cycle arrest is triggered by a checkpoint that monitors defects in a common function not yet identified, or 'centrosome damage' induced by reduction of individual proteins at centrosomes. GI arrest requires p53 and p38 MAP kinase and induces recruitment of activated p53 and p38 to centrosomes. Based on these observations, we propose two specific aims. In Aim 1 we will determine the role centriolin and associated proteins hi cytokinesis. More specifically, we will test whether centriolin anchors these proteins at the midbody and if a complex of these proteins controls vesicle fusion, microtubule organization and cell separation at the midbody. Aim 2 focuses on the role of centrosome proteins in cell cycle progression and checkpoint activation. We will determine the mechanism of GI arrest and identify the signal transduction pathway that connects centrosome proteins to cell cycle arrest.