title: Thermal Unfolding of the Pertussis Toxin S1 Subunit Facilitates Toxin Translocation to the Cytosol by the Mechanism of Endoplasmic Reticulum-Associated Degradation.
abstract: Pertussis toxin (PT) moves from the host cell surface to the endoplasmic reticulum (ER) by retrograde vesicular transport. The catalytic PTS1 subunit dissociates from the rest of the toxin in the ER and then shifts to a disordered conformation which may trigger its export to the cytosol through the quality control mechanism of ER-associated degradation (ERAD). Functional roles for toxin instability and ERAD in PTS1 translocation have not been established. We addressed these issues with the use of a surface plasmon resonance system to quantify the cytosolic pool of PTS1 from intoxicated cells. Only 3% of surface-associated PTS1 reached the host cytosol after 3 h of toxin exposure. This represented, on average, 38,000 molecules of cytosolic PTS1 per cell. Cells treated with a proteasome inhibitor contained larger quantities of cytosolic PTS1. Stabilization of the dissociated PTS1 subunit with chemical chaperones inhibited toxin export to the cytosol and blocked PT intoxication. ERAD-defective cell lines likewise exhibited reduced quantities of cytosolic PTS1 and PT resistance. These observations identify the unfolding of dissociated PTS1 as a trigger for its ERAD-mediated translocation to the cytosol.
authors.affiliation: Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida, USA.
authors.forename: Tuhina
authors.initials: T
authors.lastname: Banerjee
authors.affiliation: Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida, USA.
authors.forename: Lucia
authors.initials: L
authors.lastname: Cilenti
authors.affiliation: Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Taylor
authors.affiliation: Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida, USA.
authors.forename: Adrienne
authors.initials: A
authors.lastname: Showman
authors.affiliation: Department of Physics, University of Central Florida, Orlando, Florida, USA.
authors.forename: Suren A
authors.initials: SA
authors.lastname: Tatulian
authors.affiliation: Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, Florida, USA kteter@mail.ucf.edu.
authors.forename: Ken
authors.initials: K
authors.lastname: Teter
mesh_terms: D000818:Animals; D016466:CHO Cells; D003412:Cricetulus; D003600:Cytosol / Q000502:physiology*; D060746:Endoplasmic Reticulum-Associated Degradation / Q000502:physiology*; D005786:Gene Expression Regulation; D006358:Hot Temperature; D018832:Molecular Chaperones; D037342:Pertussis Toxin / Q000737:chemistry* / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D058767:Protein Unfolding
chemical_list: D018832:Molecular Chaperones; C083388:pertussis toxin, S1 subunit; D037342:Pertussis Toxin