title: Domain-specific functions of Stardust inDrosophilaembryonic development.
abstract: InDrosophila, the adaptor protein Stardust is essential for the stabilization of the polarity determinant Crumbs in various epithelial tissues, including the embryonic epidermis, the follicular epithelium and photoreceptor cells of the compound eye. In turn, Stardust recruits another adaptor protein, PATJ, to the subapical region to support adherens junction formation and morphogenetic events. Moreover, Stardust binds to Lin-7, which is dispensable in epithelial cells but functions in postsynaptic vesicle fusion. Finally, Stardust has been reported to bind directly to PAR-6, thereby linking the Crumbs-Stardust-PATJ complex to the PAR-6/aPKC complex. PAR-6 and aPKC are also capable of directly binding Bazooka (theDrosophilahomologue of PAR-3) to form the PAR/aPKC complex, which is essential for apical-basal polarity and cell-cell contact formation in most epithelia. However, little is known about the physiological relevance of these interactions in the embryonic epidermis ofDrosophila in vivo. Thus, we performed a structure-function analysis of the annotated domains with GFP-tagged Stardust and evaluated the localization and function of the mutant proteins in epithelial cells of the embryonic epidermis. The data presented here confirm a crucial role of the PDZ domain in binding Crumbs and recruiting the protein to the subapical region. However, the isolated PDZ domain is not capable of being recruited to the cortex, and the SH3 domain is essential to support the binding to Crumbs. Notably, the conserved N-terminal regions (ECR1 and ECR2) are not crucial for epithelial polarity. Finally, the GUK domain plays an important role for the protein's function, which is not directly linked to Crumbs stabilization, and the L27N domain is essential for epithelial polarization independently of recruiting PATJ.
authors.affiliation: Molecular and Cellular Anatomy , University of Regensburg , Universitätsstr. 31, 93053 Regensburg , Germany.
authors.forename: Leonie
authors.initials: L
authors.lastname: Koch
authors.affiliation: Molecular and Cellular Anatomy , University of Regensburg , Universitätsstr. 31, 93053 Regensburg , Germany.
authors.forename: Sabine
authors.initials: S
authors.lastname: Feicht
authors.affiliation: Molecular and Cellular Anatomy , University of Regensburg , Universitätsstr. 31, 93053 Regensburg , Germany.
authors.forename: Rui
authors.initials: R
authors.lastname: Sun
authors.affiliation: Molecular and Cellular Anatomy , University of Regensburg , Universitätsstr. 31, 93053 Regensburg , Germany.
authors.forename: Arnab
authors.initials: A
authors.lastname: Sen
authors.affiliation: Molecular and Cellular Anatomy , University of Regensburg , Universitätsstr. 31, 93053 Regensburg , Germany.
authors.forename: Michael P
authors.identifier: 0000-0001-7718-9890
authors.initials: MP
authors.lastname: Krahn
keywords: Crumbs; Drosophila; PAR-6; Stardust; epithelial polarity