CSB428H1F Article #6: Krahn et al. Formation of Baz-Sdt for epithelial polarity
Baz phosphorylation site bind PDZ of Sdt to recruit Sdt to PM.
Phosphorylation of Baz causes it to dissociate from Sdt. Non-phosphorylatable Baz blocks
dissociation causing mutation similar to crb and sdt.
Crb cytoplasmic domain binds PDZ domain of Sdt and Sdt recruit Patj and Lin-7 to apical complex.
Dlg/Lgl/Scrib localize to lateral PM and antagonize Crb-Sdt complex, restricting apical expansion.
BazS980 phosphorylation is required for localization
WT Baz-GFP and Baz -GFP shows the same localization basal to Crb-Sdt.
Phosphorylated BazS980-P was concentrated in most apical part, sometimes with/without Crb-Sdt.
WT Baz-GFP and Baz S98-GFP but not Baz S980-GFP rescued maternal and zygotic baz lethality.
Overexpression of Baz S980-GFP is similar to crb and sdt
Overexpression of Baz S980-GFP caused formation of aggregate containing DE-Cad, Arm, -cat,
Par-6, aPKC, Crb, Sdt, Patj and Lin7. Lateral marker Dlg was normal.
Baz -GFP overexpression caused cells to round up and die of apoptosis.
These dominant-negative effects of Baz -GFP were sell-autonomous. Deletion of Baz CR1 or
PDZ domains did not affect is dominancy. However, those lacking PM targeting signal was not
dominant, showing Baz S980-GFP must be at PM to be dominant.
In neuroblasts and oocytes, Baz -GFP localize apically like WT and cell fate determinants,
spindle orientation, cell division, and viability was not affected.
Baz -GFP mimic crb sdt
crb sdt baz aPKC , and Par-6 mutants secrete only little scraps of cuticle.
Overexpressing Baz S980-GFP caused a cuticle phenotype similar to crb or sdt mutants, but