title: Interplay between toxin transport and flotillin localization.
abstract: The flotillin proteins are localized in lipid domains at the plasma membrane as well as in intracellular compartments. In the present study, we examined the importance of flotillin-1 and flotillin-2 for the uptake and transport of the bacterial Shiga toxin (Stx) and the plant toxin ricin and we investigated whether toxin binding and uptake were associated with flotillin relocalization. We observed a toxin-induced redistribution of the flotillins, which seemed to be regulated in a p38-dependent manner. Our experiments provide no evidence for a changed endocytic uptake of Stx or ricin in cells silenced for flotillin-1 or -2. However, the Golgi-dependent sulfation of both toxins was significantly reduced in flotillin knockdown cells. Interestingly, when the transport of ricin to the ER was investigated, we obtained an increased mannosylation of ricin in flotillin-1 and flotillin-2 knockdown cells. The toxicity of both toxins was twofold increased in flotillin-depleted cells. Since BFA (Brefeldin A) inhibits the toxicity even in flotillin knockdown cells, the retrograde toxin transport is apparently still Golgi-dependent. Thus, flotillin proteins regulate and facilitate the retrograde transport of Stx and ricin.
authors.affiliation: Centre for Cancer Biomedicine, University of Oslo, Oslo, Norway.
authors.forename: Sascha
authors.initials: S
authors.lastname: Pust
authors.forename: Anne Berit
authors.initials: AB
authors.lastname: Dyve
authors.forename: Maria L
authors.initials: ML
authors.lastname: Torgersen
authors.forename: Bo
authors.initials: B
authors.lastname: van Deurs
authors.forename: Kirsten
authors.initials: K
authors.lastname: Sandvig
mesh_terms: D001483:Base Sequence; D002460:Cell Line; D004705:Endocytosis; D004721:Endoplasmic Reticulum / Q000378:metabolism; D055785:Gene Knockdown Techniques; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008853:Microscopy / Q000379:methods; D021381:Protein Transport; D034741:RNA, Small Interfering; D012276:Ricin / Q000378:metabolism* / Q000633:toxicity; D022621:Shiga Toxin / Q000378:metabolism* / Q000633:toxicity
chemical_list: D008565:Membrane Proteins; D034741:RNA, Small Interfering; C106354:flotillins; D022621:Shiga Toxin; D012276:Ricin