Endocytosis of the anthrax toxin is mediated by clathrin, actin and unconventional adaptors.
The anthrax toxin is a tripartite toxin, where the two enzymatic subunits require the third subunit, the protective antigen (PA), to interact with cells and be escorted to their cytoplasmic targets. PA binds to cells via one of two receptors, TEM8 and CMG2. Interestingly, the toxin times and triggers its own endocytosis, in particular through the heptamerization of PA. Here we show that PA triggers the ubiquitination of its receptors in a beta-arrestin-dependent manner and that this step is required for clathrin-mediated endocytosis. In addition, we find that endocytosis is dependent on the heterotetrameric adaptor AP-1 but not the more conventional AP-2. Finally, we show that endocytosis of PA is strongly dependent on actin. Unexpectedly, actin was also found to be essential for efficient heptamerization of PA, but only when bound to one of its 2 receptors, TEM8, due to the active organization of TEM8 into actin-dependent domains. Endocytic pathways are highly modular systems. Here we identify some of the key players that allow efficient heptamerization of PA and subsequent ubiquitin-dependent, clathrin-mediated endocytosis of the anthrax toxin.
Abrami
Laurence
L
Global Health Institute, Ecole Polytechnique Fédérale de Lausanne, Faculty of Life Sciences, Lausanne, Switzerland.
Bischofberger
Mirko
M
Kunz
Béatrice
B
Groux
Romain
R
van der Goot
F Gisou
FG
D000199:Actins / Q000378:metabolism*; D033961:Adaptor Protein Complex 1 / Q000378:metabolism*; D033962:Adaptor Protein Complex 2 / Q000378:metabolism; D000818:Animals; D000881:Anthrax / Q000378:metabolism*; D000942:Antigens, Bacterial; D019390:Arrestins / Q000378:metabolism; D001427:Bacterial Toxins / Q000493:pharmacokinetics*; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D016466:CHO Cells; D002966:Clathrin / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D003600:Cytosol / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology; D011992:Endosomes / Q000378:metabolism; D036681:Fluorescence Recovery After Photobleaching; D006367:HeLa Cells; D006801:Humans; D048369:MAP Kinase Kinase 1 / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008840:Microfilament Proteins; D009363:Neoplasm Proteins / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018000:Receptors, Peptide; D053778:Thiazolidines / Q000494:pharmacology; D025801:Ubiquitin / Q000378:metabolism; D000071557:beta-Arrestins
C473287:ANTXR1 protein, human; C447150:ANTXR2 protein, human; D000199:Actins; D033961:Adaptor Protein Complex 1; D033962:Adaptor Protein Complex 2; D000942:Antigens, Bacterial; D019390:Arrestins; D001427:Bacterial Toxins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002966:Clathrin; D008565:Membrane Proteins; D008840:Microfilament Proteins; D009363:Neoplasm Proteins; D011956:Receptors, Cell Surface; D018000:Receptors, Peptide; D053778:Thiazolidines; D025801:Ubiquitin; C030325:anthrax toxin; D000071557:beta-Arrestins; D048369:MAP Kinase Kinase 1; C482125:MAP2K1 protein, human; C037067:latrunculin A