dc.description.abstract |
Animal cells display a variety of shapes and functions that require specific cellular machinery to achieve. For many cells, functions are derived by the molecularly distinct collections of molecules in different regions. For stem cells, partitioning of membrane components is key to producing daughter cells with distinct fates. The evolutionarily conserved Par complex consisting of the kinase aPKC and its adaptor protein Par6 through regulation of the PDZ scaffold Par3 and the small GTPase Cdc42 localizes its activity to the apical cortex of these cells, setting up mutually exclusive domains by inhibiting localization of basal determinants to the Par domain through aPKC kinase activity.
In this work, I have set out to determine the specific, direct interactions that are required to polarize the Par complex. Previously, it had been shown that Par3 and/or Cdc42 were required and sufficient for cortical targeting and polarization of the Par complex in a variety of cell types and organisms. There were also multiple reported interactions between the Par complex and Par3; however the requirement and contribution of each had not been determined.
Through this work, I have shown that there is an additional interaction that aPKC must have for cortical targeting and polarization, the C1 domain of aPKC with cortical phospholipids. Additionally as this domain has the ability to bind constitutively to the cortex, it must be regulated intramolecularly through the PB1 and kinase domains of aPKC.
I have also shown that the previously unidentified Par3 PDZ2:aPKC PBM interaction is required for aPKC polarization in Drosophila neuroblasts, as mutation of the PBM leads to cytoplasmic, inactive aPKC. This suggests that the previously reported reactions are not required, at least in neuroblasts for polarization.
Together these discoveries help us to better understand the minimal interactions that are required for polarization of the Par complex. |
en_US |