title: GPI biosynthesis is essential for rhodopsin sorting at the trans-Golgi network in Drosophila photoreceptors.
abstract: Sorting of integral membrane proteins plays crucial roles in establishing and maintaining the polarized structures of epithelial cells and neurons. However, little is known about the sorting mechanisms of newly synthesized membrane proteins at the trans-Golgi network (TGN). To identify which genes are essential for these sorting mechanisms, we screened mutants in which the transport of Rhodopsin 1 (Rh1), an apical integral membrane protein in Drosophila photoreceptors, was affected. We found that deficiencies in glycosylphosphatidylinositol (GPI) synthesis and attachment processes cause loss of the apical transport of Rh1 from the TGN and mis-sorting to the endolysosomal system. Moreover, Na(+)K(+)-ATPase, a basolateral membrane protein, and Crumbs (Crb), a stalk membrane protein, were mistransported to the apical rhabdomeric microvilli in GPI-deficient photoreceptors. These results indicate that polarized sorting of integral membrane proteins at the TGN requires the synthesis and anchoring of GPI-anchored proteins. Little is known about the cellular biological consequences of GPI deficiency in animals in vivo. Our results provide new insights into the importance of GPI synthesis and aid the understanding of pathologies involving GPI deficiency.
authors.affiliation: Division of Life Science, Graduate School of Integral Arts and Science, Hiroshima University, 1-7-1 Kagamiyama, Higashi-hiroshima 739-8521, Japan.
authors.forename: Takunori
authors.initials: T
authors.lastname: Satoh
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Inagaki
authors.forename: Ziguang
authors.initials: Z
authors.lastname: Liu
authors.forename: Reika
authors.initials: R
authors.lastname: Watanabe
authors.forename: Akiko K
authors.initials: AK
authors.lastname: Satoh
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D029721:Drosophila Proteins / Q000378:metabolism; D004331:Drosophila melanogaster / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D007150:Immunohistochemistry / Q000379:methods; D007700:Kinetics; D008562:Membrane Glycoproteins / Q000378:metabolism; D021962:Membrane Microdomains / Q000378:metabolism; D009154:Mutation; D009474:Neurons / Q000378:metabolism; D017956:Photoreceptor Cells, Invertebrate / Q000378:metabolism*; D012243:Rhodopsin / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D021601:trans-Golgi Network / Q000378:metabolism*
chemical_list: D003902:Detergents; D029721:Drosophila Proteins; D005456:Fluorescent Dyes; D017261:Glycosylphosphatidylinositols; D008562:Membrane Glycoproteins; C055093:chp protein, Drosophila; D012243:Rhodopsin; D000254:Sodium-Potassium-Exchanging ATPase