VIP17/MAL, a lipid raft-associated protein, is involved in apical transport in MDCK cells.
Apical proteins are sorted and delivered from the trans-Golgi network to the plasma membrane by a mechanism involving sphingolipid-cholesterol rafts. In this paper, we report the effects of changing the levels of VIP17/MAL, a tetraspan membrane protein localized to post-Golgi transport containers and the apical cell surface in MDCK cells. Overexpression of VIP17/MAL disturbed the morphology of the MDCK cell layers by increasing apical delivery and seemingly expanding the apical cell surface domains. On the other hand, expression of antisense RNA directed against VIP17/MAL caused accumulation in the Golgi and/or impaired apical transport of different apical protein markers, i.e., influenza virus hemagglutinin, the secretory protein clusterin (gp80), the transmembrane protein gp114, and a glycosylphosphatidylinositol-anchored protein. However, antisense RNA expression did not affect the distribution of E-cadherin to the basolateral surface. Because VIP17/MAL associates with sphingolipid-cholesterol rafts, these data provide functional evidence that this protein is involved in apical transport and might be a component of the machinery clustering lipid rafts with apical cargo to form apical transport carriers.
Cheong
K H
KH
European Molecular Biology Laboratory, Cell Biology and Biophysics Programme, D69012 Heidelberg and Max Planck Institute for Molecular Cell Biology and Genetics, Dresden, Germany.
Zacchetti
D
D
Schneeberger
E E
EE
Simons
K
K
D000818:Animals; D001483:Base Sequence; D001692:Biological Transport; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D006224:Cricetinae; D004285:Dogs; D017930:Genes, Reporter; D006056:Golgi Apparatus / Q000378:metabolism; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D006801:Humans; D007668:Kidney; D007700:Kinetics; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D009185:Myelin Proteins; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D011510:Proteolipids / Q000235:genetics / Q000378:metabolism*; D016372:RNA, Antisense / Q000235:genetics; D014162:Transfection
D015820:Cadherins; D002352:Carrier Proteins; D019267:Hemagglutinin Glycoproteins, Influenza Virus; C569026:MAL protein, human; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D009185:Myelin Proteins; D062806:Myelin and Lymphocyte-Associated Proteolipid Proteins; D009838:Oligodeoxyribonucleotides; D011510:Proteolipids; D016372:RNA, Antisense