mitochondrial import and degradation of amyloid-β peptide

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S2 Mitochondrial structure and dynamics S2.L1 Mitochondrial import and degradation of amyloid-β peptide Elzbieta Glaser, Catarina Moreira Pinho, Pedro Filipe Teixeira Department of Biochemistry and Biophysics, Stockholm University, Arrhenius Laboratories for Natural Sciences, SE-106 91 Stockholm, Sweden E-mail address: [email protected] Mitochondrial dysfunctions associated with amyloid-β peptide (Aβ) accumulation in mitochondria have been observed in Alzheimer's disease (AD) patients' brains and in AD mice models. Aβ is produced by sequential action of β- and γ-secretases cleaving the amyloid precursor protein (APP). The γ-secretase complex was found in mitochondria- associated endoplasmic reticulum membranes (MAM) suggesting that this could be a potential site of Aβ production, from which Aβ is further transported into mitochondria. In vitro,Aβ was shown to be imported into mitochondria through the translocase of the outer membrane (TOM) complex. The mitochondrial presequence protease (PreP) is responsible for Aβ degradation reducing toxic effects of Aβ on mitochondrial functions. The proteolytic activity of PreP is, however, lower in AD brain temporal lobe mitochondria and in AD transgenic mice models, possibly due to an increased reactive oxygen species (ROS) production. We will discuss the intracellular mechanisms of Aβ production, its mitochondrial import and the intra-mitochondrial degradation as well as the implications of a reduced efciency of mitochondrial Aβ clearance for AD. Understanding the underlying mechanisms may provide new insights into mitochondria related pathogenesis of AD and development of drug therapy against AD. doi:10.1016/j.bbabio.2014.05.285 S2.L2 Sub-mitochondrial distribution of the MICOS complex in human cells Stefan Jakobs a , Christian A. Wurm b , Daniel C. Jans b a Department of NanoBiophotonics/Mitochondrial Structure and Dynamics, Max Planck Institute for Biophysical Chemistry, Germany b Max Planck Institute for Biophysical Chemistry, Germany E-mail address: [email protected] The mitochondrial contact site and cristae organizing system (MICOS; previously also named MINOS or MitOS) is a conserved large hetero-oligomeric protein complex in the mitochondrial inner membrane that is crucial for mitochondrial architecture, dynamics, and biogenesis. MICOS has been demonstrated to interact with numerous mitochondrial proteins, and has been linked to several human diseases. However, the spatial arrangement of the MICOS subunits within mitochondria is poorly dened. We used optical super-resolution microscopy and immunogold electron microscopy to investigate the sub-mitochondrial localizations of three known human MICOS subunits (Mic10/MINOS1, Mic19/CHCHD3 and Mic60/ mitolin) in mammalian cells. In cultured cells, MICOS was found to be more abundant in the mitochondria around the nucleus than in the peripheral mitochondria. All three subunits form clusters that were resolvable with super-resolution microscopy, but not with conventional light microscopy. We found that Mic60 is preferentially localized at cristae junctions in human cells. In primary human broblasts, Mic60 labeling uncovered a regularly spaced pattern of clusters arranged in parallel to the cell's growth surface. Likewise, also the cristae junctions were largely horizontally arranged in these mitochondria. The super-resolution images demonstrate a high level of regularity in the nanoscale distribution of the MICOS clusters in mitochondria of cultivated human broblasts. Somewhat unexpect- edly, such highly ordered arrangements of the MICOS clusters were also observed in some other cell types and even tissues. The high level of regularity in the nanoscale distribution of the MICOS complex in human mitochondria further underscores the role of MICOS in the structural organization of the organelle. doi:10.1016/j.bbabio.2014.05.286 S2.O1 Mitochondrial membrane proteins in motion Karin Busch, Timo Appelhans, Wladislaw Kohl University of Osnabrueck, Germany E-mail address: [email protected] Mitochondrial architecture is determined by its main task, energy production by oxidative phosphorylation (OXPHOS) at the inner mitochondrial membrane (IMM). The IMM extrudes into the matrix in variant forms, often disks or tubules, to enlarge the bioenergetic surface. Single cristae are respiratory compartments that are linked to the inner boundary membrane (IBM). Biochemical analyses have established that the composition of cristae membranes is different from the IBM, albeit they form a contiguous sheet connected through cristae junctions. Here, we imaged the distribution and mobility of several IMM proteins, inclusive OXPHOS complexes, over different portions of the IMM/IBM by means of life cell superresolution uorescence microscopy. Proteins were tagged with halo7-tag and specically labeled with the bright and photostable tetramethylrhodamine (TMR-HTL). Sub-stoichiometric labeling enabled the localization and tracking of single molecules in live mammalian cells. We determined local distribution and dynamic proles of OXPHOS complex V (CV, FOF1 ATP synthase) and Tom20, an outer membrane protein, by tracking and localization microscopy Biochimica et Biophysica Acta 1837 (2014) e23e32 Contents lists available at ScienceDirect Biochimica et Biophysica Acta journal homepage: www.elsevier.com/locate/bbabio

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Page 1: Mitochondrial import and degradation of amyloid-β peptide

S2 – Mitochondrial structure and dynamics

S2.L1

Mitochondrial import and degradation of amyloid-β peptideElzbieta Glaser, Catarina Moreira Pinho, Pedro Filipe TeixeiraDepartment of Biochemistry and Biophysics, Stockholm University,Arrhenius Laboratories for Natural Sciences, SE-106 91 Stockholm, SwedenE-mail address: [email protected]

Mitochondrial dysfunctions associatedwith amyloid-β peptide (Aβ)accumulation in mitochondria have been observed in Alzheimer'sdisease (AD) patients' brains and in ADmicemodels. Aβ is produced bysequential action of β- and γ-secretases cleaving the amyloid precursorprotein (APP). The γ-secretase complex was found in mitochondria-associated endoplasmic reticulum membranes (MAM) suggesting thatthis could be a potential site of Aβ production, fromwhich Aβ is furthertransported into mitochondria. In vitro, Aβ was shown to be importedinto mitochondria through the translocase of the outer membrane(TOM) complex. The mitochondrial presequence protease (PreP) isresponsible for Aβ degradation reducing toxic effects of Aβ onmitochondrial functions. The proteolytic activity of PreP is, however,lower in AD brain temporal lobe mitochondria and in AD transgenicmice models, possibly due to an increased reactive oxygen species(ROS) production. We will discuss the intracellular mechanisms ofAβ production, its mitochondrial import and the intra-mitochondrialdegradation as well as the implications of a reduced efficiency ofmitochondrial Aβ clearance for AD. Understanding the underlyingmechanisms may provide new insights into mitochondria relatedpathogenesis of AD and development of drug therapy against AD.

doi:10.1016/j.bbabio.2014.05.285

S2.L2

Sub-mitochondrial distribution of the MICOS complex inhuman cellsStefan Jakobsa, Christian A. Wurmb, Daniel C. JansbaDepartment of NanoBiophotonics/Mitochondrial Structure and Dynamics,Max Planck Institute for Biophysical Chemistry, GermanybMax Planck Institute for Biophysical Chemistry, GermanyE-mail address: [email protected]

The mitochondrial contact site and cristae organizing system(MICOS; previously also named MINOS or MitOS) is a conservedlarge hetero-oligomeric protein complex in the mitochondrial innermembrane that is crucial for mitochondrial architecture, dynamics,and biogenesis. MICOS has been demonstrated to interact withnumerous mitochondrial proteins, and has been linked to severalhuman diseases. However, the spatial arrangement of the MICOS

subunits within mitochondria is poorly defined. We used opticalsuper-resolution microscopy and immunogold electron microscopyto investigate the sub-mitochondrial localizations of three knownhuman MICOS subunits (Mic10/MINOS1, Mic19/CHCHD3 and Mic60/mitofilin) in mammalian cells. In cultured cells, MICOS was foundto be more abundant in the mitochondria around the nucleus thanin the peripheral mitochondria. All three subunits form clusters thatwere resolvable with super-resolution microscopy, but not withconventional light microscopy. We found that Mic60 is preferentiallylocalized at cristae junctions in human cells. In primary humanfibroblasts, Mic60 labeling uncovered a regularly spaced pattern ofclusters arranged in parallel to the cell's growth surface. Likewise, alsothe cristae junctions were largely horizontally arranged in thesemitochondria. The super-resolution images demonstrate a high levelof regularity in the nanoscale distribution of the MICOS clusters inmitochondria of cultivated human fibroblasts. Somewhat unexpect-edly, such highly ordered arrangements of the MICOS clusters werealso observed in some other cell types and even tissues. The high levelof regularity in the nanoscale distribution of the MICOS complex inhuman mitochondria further underscores the role of MICOS in thestructural organization of the organelle.

doi:10.1016/j.bbabio.2014.05.286

S2.O1

Mitochondrial membrane proteins in motionKarin Busch, Timo Appelhans, Wladislaw KohlUniversity of Osnabrueck, GermanyE-mail address: [email protected]

Mitochondrial architecture is determined by its main task, energyproduction by oxidative phosphorylation (OXPHOS) at the innermitochondrial membrane (IMM). The IMM extrudes into the matrix invariant forms, often disks or tubules, to enlarge the bioenergetic surface.Single cristae are respiratory compartments that are linked to the innerboundary membrane (IBM). Biochemical analyses have established thatthe composition of cristae membranes is different from the IBM, albeitthey form a contiguous sheet connected through cristae junctions. Here,we imaged the distribution and mobility of several IMM proteins,inclusiveOXPHOS complexes, over different portions of the IMM/IBMbymeans of life cell superresolution fluorescence microscopy. Proteinswere tagged with halo7-tag and specifically labeled with the brightand photostable tetramethylrhodamine (TMR-HTL). Sub-stoichiometriclabeling enabled the localization and tracking of single molecules inlive mammalian cells. We determined local distribution and dynamicprofiles of OXPHOS complex V (CV, FOF1 ATP synthase) and Tom20,an outer membrane protein, by tracking and localization microscopy

Biochimica et Biophysica Acta 1837 (2014) e23–e32

Contents lists available at ScienceDirect

Biochimica et Biophysica Acta

j ourna l homepage: www.e lsev ie r.com/ locate /bbab io