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© The Rockefeller University Press,
0021-9525/1999//313 $5.00
The Journal of Cell Biology, Volume 146, Number 2,
, 1999 313-320
Original Article |
N-Glycans Mediate the Apical Sorting of a Gpi-Anchored, Raft-Associated Protein in Madin-Darby Canine Kidney Cells
Simons{at}EMBL-Heidelberg.de
Glycosyl-phosphatidylinositol (GPI)- anchored proteins are preferentially transported to the apical cell surface of polarized Madin-Darby canine kidney (MDCK) cells. It has been assumed that the GPI anchor itself acts as an apical determinant by its interaction with sphingolipid-cholesterol rafts. We modified the rat growth hormone (rGH), an unglycosylated, unpolarized secreted protein, into a GPI-anchored protein and analyzed its surface delivery in polarized MDCK cells. The addition of a GPI anchor to rGH did not lead to an increase in apical delivery of the protein. However, addition of N-glycans to GPI-anchored rGH resulted in predominant apical delivery, suggesting that N-glycans act as apical sorting signals on GPI-anchored proteins as they do on transmembrane and secretory proteins. In contrast to the GPI-anchored rGH, a transmembrane form of rGH which was not raft-associated accumulated intracellularly. Addition of N-glycans to this chimeric protein prevented intracellular accumulation and led to apical delivery.
Key Words: lipid rafts • N-glycans • GPI-anchored proteins • Madin-Darby canine kidney cells • sorting
© 1999 The Rockefeller University Press
1.used in this paper: DAF, decay acceleration factor; DIG, detergent-insoluble glycosphingolipid complex; GPI, glycosyl-phosphatidylinositol; LDL-R, human low density lipoprotein receptor; PLAP, placental alkaline phosphatase; rGH, rat growth hormone; TMD, transmembrane domain; TX-100, Triton X-100
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