Efficient trafficking of ceramide from the endoplasmic reticulum to the Golgi apparatus requires a VAMP-associated protein-interacting FFAT motif of CERT.
Ceramide is synthesized at the endoplasmic reticulum (ER) and transported to the Golgi apparatus by CERT for its conversion to sphingomyelin in mammalian cells. CERT has a pleck-strin homology (PH) domain for Golgi targeting and a START domain catalyzing the intermembrane transfer of ceramide. The region between the two domains contains a short peptide motif designated FFAT, which is supposed to interact with the ER-resident proteins VAP-A and VAP-B. Both VAPs were actually co-immunoprecipitated with CERT, and the CERT/VAP interaction was abolished by mutations in the FFAT motif. These mutations did not affect the Golgi targeting activity of CERT. Whereas mutations of neither the FFAT motif nor the PH domain inhibited the ceramide transfer activity of CERT in a cell-free system, they impaired the ER-to-Golgi transport of ceramide in intact and in semi-intact cells at near endogenous expression levels. By contrast, when overexpressed, both the FFAT motif and the PH domain mutants of CERT substantially supported the transport of ceramide from the ER to the site where sphingomyelin is produced. These results suggest that the Golgi-targeting PH domain and ER-interacting FFAT motif of CERT spatially restrict the random ceramide transfer activity of the START domain in cells.
Kawano
Miyuki
M
Department of Biochemistry and Cell Biology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan.
Kumagai
Keigo
K
Nishijima
Masahiro
M
Hanada
Kentaro
K
D020816:Amino Acid Motifs / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport / Q000235:genetics; D016466:CHO Cells; D002518:Ceramides / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D017354:Point Mutation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D017434:Protein Structure, Tertiary / Q000235:genetics; D050683:R-SNARE Proteins / Q000378:metabolism*
D002518:Ceramides; D050683:R-SNARE Proteins; C119090:CERT1 protein, human; D017346:Protein Serine-Threonine Kinases