title: Electron microscopic analysis of a spherical mitochondrial structure.
abstract: Mitochondria undergo dynamic structural alterations to meet changing needs and to maintain homeostasis. We report here a novel mitochondrial structure. Conventional transmission electron microscopic examination of murine embryonic fibroblasts treated with carbonyl cyanide m-chlorophenylhydrazone (CCCP), a mitochondrial uncoupler, found that more than half of the mitochondria presented a ring-shaped or C-shaped morphology. Many of these mitochondria seemed to have engulfed various cytosolic components. Serial sections through individual mitochondria indicated that they formed a ball-like structure with an internal lumen surrounded by the membranes and containing cytosolic materials. Notably, the lumen was connected to the external cytoplasm through a small opening. Electron tomographic reconstruction of the mitochondrial spheroids demonstrated the membrane topology and confirmed the vesicular configuration of this mitochondrial structure. The outside periphery and the lumen were defined by the outer membranes, which were lined with the inner membranes. Matrix and cristae were retained but distributed unevenly with less being kept near the luminal opening. Mitochondrial spheroids seem to form in response to oxidative mitochondrial damage independently of mitophagy. The structural features of the mitochondrial spheroids thus represent a novel mitochondrial dynamics.
authors.affiliation: Department of Pharmacology, Toxicology, and Therapeutics, the University of Kansas Medical Center, Kansas City, Kansas 66160, USA. wxding@kumc.edu
authors.forename: Wen-Xing
authors.initials: WX
authors.lastname: Ding
authors.forename: Min
authors.initials: M
authors.lastname: Li
authors.forename: Joanna M
authors.initials: JM
authors.lastname: Biazik
authors.forename: David G
authors.initials: DG
authors.lastname: Morgan
authors.forename: Fengli
authors.initials: F
authors.lastname: Guo
authors.forename: Hong-Min
authors.initials: HM
authors.lastname: Ni
authors.forename: Michael
authors.initials: M
authors.lastname: Goheen
authors.forename: Eeva-Liisa
authors.initials: EL
authors.lastname: Eskelinen
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Yin
mesh_terms: D000818:Animals; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D055032:Electron Microscope Tomography; D004622:Embryo, Mammalian / Q000378:metabolism / Q000648:ultrastructure*; D005347:Fibroblasts / Q000378:metabolism / Q000648:ultrastructure*; D051379:Mice; D008928:Mitochondria / Q000378:metabolism / Q000648:ultrastructure*; D063154:Mitochondrial Dynamics / Q000502:physiology; D061209:Proton Ionophores / Q000494:pharmacology
chemical_list: D061209:Proton Ionophores; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone