Identifying two novel pathways that control the organization and function of the mammalian centrosome.

摘要

In higher eukaryotes, the centrosome is required for the organization of the microtubule cytoskeleton during interphase and the formation of bipolar spindles during mitosis. Centrosomal abnormalities such as centrosome over-amplification and disorganization are common characteristics of cancers found in various organs of the body. However, the mechanisms that control centrosome regulation are only beginning to be understood. The aim of this thesis has been to develop a better understanding of the role centrosome organization has in centrosome function and cell cycle progression.;Previous studies have showed that Golgi proteins are involved in mitotic centrosome function. However, in this thesis we provide the first evidence of a role for a Golgi protein in controlling the organization and function of the interphase centrosome.;In our study of the Golgi protein, GM130 we found that the depletion of this protein had no effect on Golgi structure or function. However, GM130-depleted cells contained disorganized and mispositioned centrosomes that were unable to nucleate microtubules during interphase or mitosis. In a screen to identify GM130 interactors that are involved in centrosome organization, we found that GM130 forms a complex with the Rho GTPase, Cdc42 and its guanine nucleotide exchange factor, Tuba. By forming this trimeric complex at the Golgi, GM130 controls Tuba-mediated activation of Cdc42. Altering the function of Tuba or Cdc42 caused the same centrosome phenotype found in GM130-depleted cells. Moreover, the expression of a constitutively active Cdc42 restored centrosome organization in GM130-depleted cells. These findings indicated that Cdc42 functions downstream of GM130 and Tuba to control the organization and function of the interphase centrosome. Finally, we describe a novel role of the polarity protein Par6alpha in controlling the recruitment of components to the centrosome in a microtubule and dynein-dynactin dependent manner. We found that the centrosomal function of Par6alpha is mediated by its interactions with the centriolar satellite protein PCM-1 and the dynactin component p150-Glued. Together these results provide evidence for two novel pathways that control the organization and function of the interphase centrosome.