title: Endoplasmic Reticulum-Targeted Subunit Toxins Provide a New Approach to Rescue Misfolded Mutant Proteins and Revert Cell Models of Genetic Diseases.
abstract: Many germ line diseases stem from a relatively minor disturbance in mutant protein endoplasmic reticulum (ER) 3D assembly. Chaperones are recruited which, on failure to correct folding, sort the mutant for retrotranslocation and cytosolic proteasomal degradation (ER-associated degradation-ERAD), to initiate/exacerbate deficiency-disease symptoms. Several bacterial (and plant) subunit toxins, retrograde transport to the ER after initial cell surface receptor binding/internalization. The A subunit has evolved to mimic a misfolded protein and hijack the ERAD membrane translocon (dislocon), to effect cytosolic access and cytopathology. We show such toxins compete for ERAD to rescue endogenous misfolded proteins. Cholera toxin or verotoxin (Shiga toxin) containing genetically inactivated (± an N-terminal polyleucine tail) A subunit can, within 2-4 hrs, temporarily increase F508delCFTR protein, the major cystic fibrosis (CF) mutant (5-10x), F508delCFTR Golgi maturation (<10x), cell surface expression (20x) and chloride transport (2x) in F508del CFTR transfected cells and patient-derived F508delCFTR bronchiolar epithelia, without apparent cytopathology. These toxoids also increase glucocerobrosidase (GCC) in N370SGCC Gaucher Disease fibroblasts (3x), another ERAD-exacerbated misfiling disease. We identify a new, potentially benign approach to the treatment of certain genetic protein misfolding diseases.
authors.affiliation: Division of Molecular Structure and Function, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Humaira
authors.initials: H
authors.lastname: Adnan
authors.affiliation: Division of Molecular Structure and Function, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Zhenbo
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Division of Molecular Structure and Function, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Hyun-Joo
authors.initials: HJ
authors.lastname: Park
authors.affiliation: Division of Cell Biology, Research Institute, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Chetankumar
authors.initials: C
authors.lastname: Tailor
authors.affiliation: Division of Molecular Structure and Function, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Clare
authors.initials: C
authors.lastname: Che
authors.affiliation: Division of Molecular Structure and Function, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Mustafa
authors.initials: M
authors.lastname: Kamani
authors.affiliation: ERAD Therapeutics, Caledon, Ontario, Canada.
authors.forename: George
authors.initials: G
authors.lastname: Spitalny
authors.affiliation: Division of Molecular Structure and Function, The Hospital for Sick Children, Toronto, Ontario, Canada.
authors.forename: Beth
authors.initials: B
authors.lastname: Binnington
authors.affiliation: Division of Molecular Structure and Function, The Hospital for Sick Children, Toronto, Ontario, Canada.|Department of Biochemistry, University of Toronto, Ontario, Canada.|Department of Laboratory Medicine & Pathobiology, University of Toronto, Ontario, Canada.
authors.forename: Clifford
authors.identifier: http://orcid.org/0000-0001-9096-0061
authors.initials: C
authors.lastname: Lingwood
mesh_terms: D015153:Blotting, Western; D002772:Cholera Toxin / Q000494:pharmacology; D003550:Cystic Fibrosis / Q000235:genetics / Q000378:metabolism / Q000517:prevention & control; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism; D060746:Endoplasmic Reticulum-Associated Degradation / Q000187:drug effects*; D057809:HEK293 Cells; D006801:Humans; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D009154:Mutation; D017510:Protein Folding / Q000187:drug effects*; D021381:Protein Transport / Q000187:drug effects; D057165:Proteostasis Deficiencies / Q000235:genetics / Q000378:metabolism / Q000517:prevention & control; D022603:Shiga Toxins / Q000494:pharmacology; D014118:Toxins, Biological / Q000145:classification / Q000494:pharmacology*
chemical_list: D022603:Shiga Toxins; D014118:Toxins, Biological; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D002772:Cholera Toxin