title: Association of a GPI-anchored protein with detergent-resistant membranes facilitates its trafficking through the early secretory pathway.
abstract: Membrane microdomains are implicated in the trafficking and sorting of several membrane proteins. In particular GPI-anchored proteins cluster into Triton X-100 resistant, cholesterol- and sphingolipid-rich membrane microdomains and are sorted to the apical membrane. A growing body of evidence has pointed to the existence of other types of microdomains that are insoluble in detergents, such as Lubrol WX and Tween-20. Here, we report on the role of detergent-resistant membranes formed at early stages in the biosynthesis of membrane dipeptidase (MDP), a GPI-anchored protein, on its trafficking and sorting. Pulse-chase experiments revealed a retarded maturation rate of the GPI-anchor deficient mutant (MDPDeltaGPI) as compared to the wild type protein (wtMDP). However, Golgi to cell surface delivery rate did not show a significant difference between the two variants. On the other hand, early biosynthetic forms of wtMDP were partially insoluble in Tween-20, while MDPDeltaGPI was completely soluble. The lack of association of MDPDeltaGPI with detergent-resistant membranes prior to maturation in the Golgi and the reduction in its trafficking rate strongly suggest the existence of an early trafficking control mechanisms for membrane proteins operating at a level between the endoplasmic reticulum and the cis-Golgi.
authors.affiliation: Department of Physiological Chemistry, University of Veterinary Medicine Hannover, Bünteweg 17, D-30559 Hannover, Germany.
authors.forename: Zeynep
authors.initials: Z
authors.lastname: Hein
authors.forename: Nigel M
authors.initials: NM
authors.lastname: Hooper
authors.forename: Hassan Y
authors.initials: HY
authors.lastname: Naim
mesh_terms: D000818:Animals; D001324:Autoantigens / Q000378:metabolism; D020126:Brefeldin A / Q000494:pharmacology; D019556:COS Cells; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002522:Chlorocebus aethiops; D004150:Dipeptidases / Q000235:genetics / Q000378:metabolism*; D004285:Dogs; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006031:Glycosylation; D017261:Glycosylphosphatidylinositols / Q000502:physiology*; D006056:Golgi Apparatus / Q000378:metabolism; D007700:Kinetics; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D021962:Membrane Microdomains / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism; D009154:Mutation; D017510:Protein Folding; D021381:Protein Transport / Q000187:drug effects / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D013552:Swine; D022161:Transport Vesicles / Q000378:metabolism; D014357:Trypsin / Q000378:metabolism
chemical_list: D001324:Autoantigens; D017261:Glycosylphosphatidylinositols; C097741:Golgin subfamily A member 2; D008164:Luminescent Proteins; D008565:Membrane Proteins; C106354:flotillins; C413663:fluorescent protein 583; D020126:Brefeldin A; D004150:Dipeptidases; C038937:dipeptidase; D014357:Trypsin