Quantitation of (a)symmetric inheritance of functional and of oxidatively damaged mitochondrial aconitase in the cell division of old yeast mother cells.
Asymmetric segregation of oxidatively damaged proteins is discussed in the literature as a mechanism in cell division cycles which at the same time causes rejuvenation of the daughter cell and aging of the mother cell. This process must be viewed as cooperating with the cellular degradation processes like autophagy, proteasomal degradation and others. Together, these two mechanisms guarantee survival of the species and prevent clonal senescence of unicellular organisms, like yeast. It is widely believed that oxidative damage to proteins is primarily caused by oxygen radicals and their follow-up products produced in the mitochondria. As we have shown previously, old yeast mother cells in contrast to young cells contain reactive oxygen species and undergo programmed cell death. Here we show that aconitase of the mitochondrial matrix is readily inactivated by oxidative stress, but even in its inactive form is relatively long-lived and retains fluorescence in the Aco1p-eGFP form. The fluorescent protein is distributed between old mothers and their daughters approximately corresponding to the different sizes of mother and daughter cells. However, the remaining active enzyme is primarily inherited by the daughter cells. This indicates that asymmetric distribution of the still active enzyme takes place and a mechanism for discrimination between active and inactive enzyme must exist. As the aconitase remains mitochondrial during aging and cell division, our findings could indicate discrimination between active and no longer active mitochondria during the process.
Klinger
Harald
H
Department of Cell Biology, Division of Genetics, University of Salzburg, Hellbrunnerstrasse 34, Salzburg, Austria.
Rinnerthaler
Mark
M
Lam
Yuen T
YT
Laun
Peter
P
Heeren
Gino
G
Klocker
Andrea
A
Simon-Nobbe
Birgit
B
Dickinson
J Richard
JR
Dawes
Ian W
IW
Breitenbach
Michael
M
D000154:Aconitate Hydratase / Q000235:genetics / Q000378:metabolism*; D017209:Apoptosis; D001483:Base Sequence; D002455:Cell Division / Q000235:genetics / Q000502:physiology*; D017931:DNA Primers / Q000235:genetics; D005800:Genes, Fungal; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism*; D008938:Mitosis; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*
D017931:DNA Primers; D017382:Reactive Oxygen Species; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D000154:Aconitate Hydratase