title: Mycoplasma pneumoniae CARDS toxin is internalized via clathrin-mediated endocytosis.
abstract: Bacterial toxins possess specific mechanisms of binding and uptake by mammalian cells. Mycoplasma pneumoniae CARDS (Community Acquired Respiratory Distress Syndrome) toxin is a 68 kDa protein, which demonstrates high binding affinity to human surfactant protein-A and exhibits specific biological activities including mono-ADP ribosylation and vacuolization. These properties lead to inflammatory processes in the airway and a range of cytopathologies including ciliostasis, loss of tissue integrity and injury, and cell death. However, the process by which CARDS toxin enters target cells is unknown. In this study, we show that CARDS toxin binds to mammalian cell surfaces and is internalized rapidly in a dose and time-dependent manner using a clathrin-mediated pathway, as indicated by inhibition of toxin internalization by monodansylcadaverine but not by methyl-β-cyclodextrin or filipin. Furthermore, the internalization of CARDS toxin was markedly inhibited in clathrin-depleted cells.
authors.affiliation: Department of Microbiology and Immunology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas, United States of America.
authors.forename: Manickam
authors.initials: M
authors.lastname: Krishnan
authors.forename: T R
authors.initials: TR
authors.lastname: Kannan
authors.forename: Joel B
authors.initials: JB
authors.lastname: Baseman
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001427:Bacterial Toxins / Q000378:metabolism*; D002460:Cell Line; D002966:Clathrin / Q000378:metabolism*; D004705:Endocytosis; D006801:Humans; D011019:Pneumonia, Mycoplasma; D011994:Recombinant Proteins / Q000378:metabolism; D013997:Time Factors
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; C546120:CARDS toxin, Mycoplasma pneumoniae; D002966:Clathrin; D011994:Recombinant Proteins