Abstract
The scaffold protein Par-3 ( Drosophila Bazooka) is a central organizer of cell polarity across animals. This review focuses on how the clustering of Par-3 contributes to cell polarity. It begins with the Par-3 homo-oligomerization mechanism and its regulation by Par-1 phosphorylation. The role of polarized cytoskeletal networks in distributing Par-3 clusters to one end of the cell is then discussed, as is the subsequent maintenance of polarized Par-3 clusters through hindered mobility and inhibition from the opposite pole. Finally, specific roles of Par-3 clusters are reviewed, including the bundling of microtubules, the cortical docking of centrosomes, the growth and positioning of cadherin–catenin clusters, and the inhibition of the Par-6–aPKC kinase cassette. Examples are drawn from Drosophila, Caenorhabditis elegans, mammalian cell culture, and biochemical studies.
Highlights
As a scaffold protein central to the polarization of many animal cell types, Par-3 binds numerous molecules both for its recruitment to one pole of the cell and for downstream contributions to polarized cell function[1,2,3]
This review focuses on the clustering of Par-3 and how this clustering contributes to cell polarity
In C. elegans, the actomyosin re-configuration is associated with entry into the polarity maintenance phase as the cell begins mitosis[27], and in Drosophila aPKC initiates the down-regulation of centrosomal microtubules typical of epithelial cells[31,32]
Summary
As a scaffold protein central to the polarization of many animal cell types, Par-3 binds numerous molecules both for its recruitment to one pole of the cell and for downstream contributions to polarized cell function[1,2,3]. In C. elegans, the actomyosin re-configuration is associated with entry into the polarity maintenance phase as the cell begins mitosis[27], and in Drosophila aPKC initiates the down-regulation of centrosomal microtubules typical of epithelial cells[31,32] As these large-scale cytoskeletal assemblies are diminished, other mechanisms become responsible for maintaining the established Par protein polarity[33]. The Goldstein group demonstrated that Polo-like kinase 1 phosphorylates one or more residues in the oligomerization domain of Par-3 to reduce Par-3 clustering after polarity establishment by the contractile actomyosin flow This regulated reduction in Par-3 clustering would presumably allow the release and local dispersion of Par-6–aPKC for the maintenance of anterior–posterior polarity in the C. elegans embryo. Grant information The author(s) declared that no grants were involved in supporting this work
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