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Title: Human and rat brain lipofuscin proteome

item OTTS, PHILIP - Heinrich-Heine University
item KOPPE, KATHARINA - Heinrich-Heine University
item Onisko, Bruce
item Dynin, Irina
item ARZBERGER, THOMAS - Ludwig-Maximilians University
item KRETZSCHMAR, HANS - Ludwig-Maximilians University
item REQUENA, JESUS - University Of Santiago De Compostela
item Silva, Christopher - Chris
item HUSTON, JOSEPH - Heinrich-Heine University
item KORTH, CARSTEN - Heinrich-Heine University

Submitted to: Proteomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2012
Publication Date: 8/20/2012
Citation: Otts, P., Koppe, K., Onisko, B.C., Dynin, I.A., Arzberger, T., Kretzschmar, H., Requena, J.R., Silva, C.J., Huston, J.P., Korth, C. 2012. Human and rat brain lipofuscin proteome. Proteomics. 12(15-16):2445-2454. doi:10.1002/pmic.201100668.

Interpretive Summary: Lipofuscin is a large fluorescent molecule that is associated with the aging of the brain. Conventional wisdom asserts that lipofuscin is an age-related accumulation of a waste product of incomplete brain metabolism and not evidence of disease. This assumption may not be true since the molecule is associated with age-related macular degeneration and a related molecule is produced in the brains of patients afflicted with an inherited disease. We purified the proteins associated with lipofuscin using a two-step ultracentrifugation process. The lipofuscin-associated proteins were identified by mass spectrometry-based analysis. Forty-nine proteins were identified in human brains and compared to an analogous group of proteins from rat brains. Thirty-two proteins (64 %) were found to be present in both brain samples. Our study is the first to characterize the proteins associated with lipofuscin. The results of this study suggest that there is a small group of proteins associated with lipofuscin, despite the huge differences in the time span of accumulation in rats and humans. Furthermore, the identification of specific proteins will now allow the characterization of age-associated dysfunctional molecular pathways.

Technical Abstract: The accumulation of an autofluorescent pigment called lipofuscin in neurons is an invariable hallmark of brain aging. So far, this material has been considered to be waste material without particular relevance for cellular pathology. However, two lines of evidence argue that lipofuscin may have yet unidentified pathological cellular functions: 1. Genetic forms of premature accumulation of similar autofluorescent material in neuronal ceroid lipofuscinosis point to a direct disease-associated link to lipofuscin, 2. Retinal pigment epithelium cell lipofuscin is mechanistically linked to age-associated macular degeneration.Here, we purified autofluorescent material from the temporal and hippocampal cortex of three different human individuals by a two-step ultracentrifugation on sucrose gradients. For human brain lipofuscin, we could identify 49 proteins present in two out of three experiments that are mainly derived from mitochondria, cytoskeleton and cell membrane. This brain lipofuscin proteome was validated in an interspecies comparison in that whole brain rat lipofuscin purified by the same procedure yielded an overlap of 32 proteins (64%) with that of human lipofuscin. Our study is the first to characterize human and rat brain lipofuscin and identifies high homology pointing to similar cellular mechanisms of age-associated lipofuscin accumulation despite the huge differences in time span of accumulation. The identification of distinct proteins will now allow further characterization of age-associated dysfunctional molecular pathways during lysosomal degradation.