title: Distinct mechanisms controlling rough and smooth endoplasmic reticulum contacts with mitochondria.
abstract: Gp78 (also known as AMFR), an endoplasmic-reticulum (ER)-associated protein degradation (ERAD) E3 ubiquitin ligase, localizes to mitochondria-associated ER and targets the mitofusin (Mfn1 and Mfn2) mitochondrial fusion proteins for degradation. Gp78 is also the cell surface receptor for autocrine motility factor (AMF), which prevents Gp78-dependent mitofusin degradation. Gp78 ubiquitin ligase activity promotes ER-mitochondria association and ER-mitochondria Ca(2+) coupling, processes that are reversed by AMF. Electron microscopy of HT-1080 fibrosarcoma cancer cells identified both smooth ER (SER; ∼8 nm) and wider (∼50-60 nm) rough ER (RER)-mitochondria contacts. Both short hairpin RNA (shRNA)-mediated knockdown of Gp78 (shGp78) and AMF treatment selectively reduced the extent of RER-mitochondria contacts without impacting on SER--mitochondria contacts. Concomitant small interfering RNA (siRNA)-mediated knockdown of Mfn1 increased SER-mitochondria contacts in both control and shGp78 cells, whereas knockdown of Mfn2 increased RER-mitochondria contacts selectively in shGp78 HT-1080 cells. The mitofusins therefore inhibit ER-mitochondria interaction. Regulation of close SER-mitochondria contacts by Mfn1 and of RER-mitochondria contacts by AMF-sensitive Gp78-mediated degradation of Mfn2 define new mechanisms that regulate ER-mitochondria interactions.
authors.affiliation: Departments of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Peter T C
authors.initials: PT
authors.lastname: Wang
authors.affiliation: Department of Zoology, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Pierre O
authors.initials: PO
authors.lastname: Garcin
authors.affiliation: Departments of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Min
authors.initials: M
authors.lastname: Fu
authors.affiliation: Departments of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Matthew
authors.initials: M
authors.lastname: Masoudi
authors.affiliation: Departments of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Pascal
authors.initials: P
authors.lastname: St-Pierre
authors.affiliation: Department of Zoology, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Nelly
authors.initials: N
authors.lastname: Panté
authors.affiliation: Departments of Cellular and Physiological Sciences, Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3 irnabi@mail.ubc.ca.
authors.forename: Ivan R
authors.initials: IR
authors.lastname: Nabi
mesh_terms: D000818:Animals; D019556:COS Cells; D002460:Cell Line; D002522:Chlorocebus aethiops; D018870:Endoplasmic Reticulum, Rough / Q000235:genetics* / Q000378:metabolism; D018871:Endoplasmic Reticulum, Smooth / Q000235:genetics* / Q000378:metabolism; D060746:Endoplasmic Reticulum-Associated Degradation / Q000502:physiology; D020558:GTP Phosphohydrolases / Q000235:genetics*; D006801:Humans; D008928:Mitochondria; D033681:Mitochondrial Membrane Transport Proteins / Q000235:genetics*; D024101:Mitochondrial Proteins / Q000235:genetics*; D034622:RNA Interference; D034741:RNA, Small Interfering; D060285:Receptors, Autocrine Motility Factor / Q000235:genetics*
chemical_list: D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins; D034741:RNA, Small Interfering; C555000:AMFR protein, human; D060285:Receptors, Autocrine Motility Factor; D020558:GTP Phosphohydrolases; C470018:MFN2 protein, human; C470017:Mfn1 protein, human
keywords: AMF; Ca2+ coupling; ER-mitochondria contacts; Gp78 E3 ubiquitin ligase; Mitofusin