High impact information on baz

• Thus, antagonism of Bazooka by PAR-1/14-3-3 may represent a general mechanism for establishing complementary cortical domains in polarized cells [1].
• In epithelia, this complex localizes apically and defines the apical membrane, whereas Bazooka lacking PAR-1 phosphorylation/14-3-3 binding sites forms ectopic lateral complexes [1].
• Initially discovered in the landmark genetic screen for Drosophila developmental mutants, bazooka, crumbs, shotgun and stardust mutants exhibit severe disruption in apicobasal polarity in embryonic epithelia, resulting in multilayered epithelia, tissue disintegration, and defects in cuticle formation [2].
• However, for the subset of ectodermal cells that delaminate and form neuroblasts, their polarity requires the function of Bazooka, but not of Stardust or Crumbs [2].
• Bazooka provides an apical cue for Inscuteable localization in Drosophila neuroblasts [3].

Biological context of baz

• Thus, proteins required for establishing the early embryonic epithelial polarity are used later for the morphogenesis of photoreceptors, with Baz and Sdt functioning in different aspects of the formation of the apical-basal cellular architecture [4].
• Requirement for Par-6 and Bazooka in Drosophila border cell migration [5].
• The distributions of several transmembrane proteins required for migration were abnormal following Par-6 or Par-3/Bazooka downregulation, possibly accounting for the migration defects [5].
• The Drosophila protein Bazooka is required for both apical-basal polarity in epithelial cells and directing asymmetric cell division in neuroblasts [6].
• In Drosophila, the multi-PDZ domain protein Bazooka (Baz) is required for establishment of apico-basal polarity in epithelia and in neuroblasts, the stem cells of the central nervous system [7].

Anatomical context of baz

• In light of this functional conservation, we examined the potential role of baz and DaPKC in the regulation of oocyte polarity [8].
• Our analyses reveal germ-line autonomous roles for baz and DaPKC in the establishment of initial anterior-posterior polarity within germ-line cysts and maintenance of oocyte cell fate [8].
• Both in Drosophila and vertebrate epithelial cells, the establishment of apicobasal polarity requires the apically localized, membrane-associated Par-3-Par-6-aPKC protein complex [9].
• Adherens junctions (AJs) often direct this polarity, but we previously found that Bazooka (Baz) acts upstream of AJs as epithelial polarity is first established in Drosophila [10].
• Surprisingly, we found that Baz localizes to an apical domain below its typical binding partners atypical protein kinase C (aPKC) and partitioning defective (PAR)-6 as the Drosophila epithelium first forms [10].

Associations of baz with chemical compounds

• We show that baz is required for Par-1 relocalization within the oocyte and that the distributions of Baz and Par-1 in the Drosophila oocyte are complementary and strikingly reminiscent of the two PAR proteins in the C. elegans embryo [11].

Physical interactions of baz

• The PAR-3/PAR-6/aPKC complex is required to establish polarity in many different cell types, including the C. elegans zygote and epithelial and neuronal cells in Drosophila and mammals [12].
• Mutant analyses revealed that apical Baz accumulations can be established in the absence of AJs, whereas assembly of apical DE-Cad complexes requires Baz [13].
• We show that the lipid phosphatase PTEN directly binds to Baz in vitro and in vivo, and colocalizes with Baz in the apical cortex of epithelia and neuroblasts [14].
• Asymmetric localisation of Inscuteable is initiated during neuroblast delamination by direct binding to Bazooka, an apically localised protein that contains protein-interaction motifs known as PDZ domains [15].

Co-localisations of baz

• DmPAR-6 colocalizes with Bazooka at the apical cell cortex of epithelial cells and neuroblasts, and binds to Bazooka in vitro [6].

Regulatory relationships of baz

• Surprisingly, Bazooka controls asymmetric localization of the Numb-anchoring protein Pon, but not spindle orientation, in pI and all subsequent divisions [16].

Other interactions of baz

• PAR-1 also excludes Bazooka from the posterior of the oocyte, and disruption of this regulation causes anterior-posterior polarity defects [1].
• However, the other apical components, Bazooka-atypical PKC-Par6-Inscuteable, still remain polarized and responsible for asymmetric Miranda localization, suggesting their dominant role in localizing cell-fate determinants [17].
• RESULTS: We show that in photoreceptors Bazooka (D-Par3) recruits the tumor suppressor lipid phosphatase PTEN to developing cell-cell junctions (Zonula Adherens, za). za-localized PTEN controls the spatially restricted accumulation of optimum levels of the lipid PtdIns(3,4,5)P3 within the apical membrane domain [18].
• BACKGROUND: In a specialized epithelial cell such as the Drosophila photoreceptor, a conserved set of proteins is essential for the establishment of polarity, its maintenance, or both--in Drosophila, these proteins include the apical factors Bazooka, D-atypical protein kinase C, and D-Par6 together with D-Ecadherin [18].
• This polarity consists of an enrichment of nonmuscle myosin II at A-P cell borders and Bazooka/PAR-3 protein at the reciprocal D-V cell borders [19].

References