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Article #5 Summary


Department
Cell and Systems Biology
Course Code
CSB428H1
Professor
U.Tepass

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CSB428H1F Article #5: Morais-de-Sa et al.aPKC phosphorylation of Bazooka
Introduction
Baz localizes below Par-6/aPKC and excluded from apical domain by aPKC phosphorylation that
disrupts Baz/aPKC binding, which is also helped by the Crb complex.
Both Crb and Sdt bind directly to PDZ of Par-6. Two C’ Thr of Crb are phosphorylated by aPKC and
is required for Crb activity.
Baz binds Arm and DE-Cad and Echinoid of AJ.
In the absence of aPKC phosphorylation, Baz recruits AJ to apical, and expands lateral domain.
In neuroblasts, Baz recruits Par-6/aPKC to the apical cortex and aPKC phosphorylation of Numb
and Mira exclude them from apical domain. Baz directly binds Numb.
Scrib, Dlg and Lgl localize below apical lateral junctions to antagonize Crb complex.
Baz can bind Par-6-aPKC using CR3 and PDZ domains, but is excluded from Par-6/aPKC domains.
Baz is below Par-6/aPKC in follicular epithelium
aPKC is apical and Baz is more basal with Arm and AJ. Removal of Baz abolishes apical aPKC/Par-
6 and Arm/DE-Cad localization. aPKC and Par-6 lack apical pool of Baz, but junctional pool is
normal.
Loss of aPKC disrupts localization of Crb and Patj and loss of Crb disrupts localization of aPKC
and Par-6; apical Baz pool was lost.
aPKC phosphorylation excludes Baz from AP domain
Native aPKC phosphorylated Baz on conserved S980 aPKC binding site, but not S980A.
S980-P-specific antibody detected BazS980-P at apical side and no staining is observed after
phosphatase treatment or in aPKC or baz mutants.
Non-phosphorylatable BazS980A-GFP localized to apical domain with aPKC but phospho-mimic
BazS980E-GFP localized to AJ.
More aPKC co-precipitate with BazS980A-GFP than WT Baz or BazS980E-GFP, indicating aPKC
phosphorylation prevents Baz from binding with aPKC and excludes Baz from apical domain.
In aPKC mutant, BazS980A-GFP is no longer at apical, but accumulates at apical-lateral boundary.
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