title: Stratum, a Homolog of the Human GEF Mss4, Partnered with Rab8, Controls the Basal Restriction of Basement Membrane Proteins in Epithelial Cells.
abstract: The basement membrane (BM), a sheet of extracellular matrix lining the basal side of epithelia, is essential for epithelial cell function and integrity, yet the mechanisms that control the basal restriction of BM proteins are poorly understood. In epithelial cells, a specialized pathway is dedicated to restrict the deposition of BM proteins basally. Here, we report the identification of a factor in this pathway, a homolog of the mammalian guanine nucleotide exchange factor (GEF) Mss4, which we have named Stratum. The loss of Stratum leads to the missecretion of BM proteins at the apical side of the cells, forming aberrant layers in close contact with the plasma membrane. We found that Rab8GTPase acts downstream of Stratum in this process. Altogether, our results uncover the importance of this GEF/Rab complex in specifically coordinating the basal restriction of BM proteins, a critical process for the establishment and maintenance of epithelial cell polarity.
authors.affiliation: Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
authors.forename: Olivier
authors.initials: O
authors.lastname: Devergne
authors.affiliation: Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA.
authors.forename: Gina H
authors.initials: GH
authors.lastname: Sun
authors.affiliation: Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA. Electronic address: schupbac@princeton.edu.
authors.forename: Trudi
authors.initials: T
authors.lastname: Schüpbach
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified / Q000378:metabolism; D001485:Basement Membrane / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D016764:Cell Polarity / Q000502:physiology; D004330:Drosophila / Q000378:metabolism*; D029721:Drosophila Proteins / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism*
chemical_list: D029721:Drosophila Proteins; D020662:Guanine Nucleotide Exchange Factors; D008565:Membrane Proteins; D020558:GTP Phosphohydrolases; C000596969:Rab8 protein, Drosophila
keywords: Drosophila, oogenesis; GEF; Mss4; Rab8; RabIF; basement membrane; cell polarity