Molecular analysis of peptide export from mitochondria
Final Report Abstract
Dysfunction of mitochondria has severe cellular consequences and is linked to aging and neurodegeneration in human. Several surveillance mechanisms have evolved which prevent the accumutation of non-functional mitochondria and ensure cellular integrity. Whereas irreversibty damaged mitochondria can be selectively removed by autophagy, various intraorganellar proteases degrade non-native mitochondrial proteins and limit mitochondrial damage. Proteolysis by ATP-dependent proteases results in the formation of peptides that are further degraded to free amino acids by oligopeptidases within mitochondria or released from the organelle. The transport of peptides across the inner membrane of mitochondria was found to depend on the ABC-transporter Mdl1 in Sacchammyces cerevisiae. The export of peptides from mitochondria raises the intriguing possibility that these peptides exert a role in interorganellar communication. Therefore, in the frame of the present research project, a potential function of mitochondria-derived peptides for cellular signalling was examined using different experimental strategies. Evidence for a role of peptides released from mitochondria for intracellular signalling was obtained by comparative gene expression profiling in yeast mutants defective in mitochondrial peptide export. The expression of nuclear genes with functions in mitochondrial gene expression and the biogenesis of the respiratory chain were significantly increased in these cells under respiring conditions. Subsequently, a biochemical assay was established allowing the isolation of peptides released from mitochondria and their subsequent identification by mass spectrometry. These experiments established a constant peptide efflux from mitochondria which are generated upon proteolysis of a large fraction of the mitochondrial proteome and led to the identification of novel oligopeptidases within mitochondria. Quantification of the complex pool of released peptides revealed insight into the stability of the mitochondrial proteome under various conditions. Moreover, evidence was provided that proteolysis regulates the abundance of mitochondrial ribosomes and the mitochondrial gene expression apparatus in response to varying growth conditions. However, specific peptides with a rote for intracellular signalling were not identified. Recent experiments in higher eukaryotes linked the function of mitochondria-derived peptides to the mitochondrial unfolded protein response, a stress-induced signalling cascade that is not conserved in yeast. Future studies will therefore focus on the role of the mitochondrial peptide export for stress signalling in higher eukaryotes.
Publications
-
(2004). Reversible assembly of the ATP-binding cassette transporter Mdl1 with the F1F0-ATP synthase in mitochondria. J Biol Chem 279: 38338-38345
Galluhn, D. and Langer, T.
-
(2005). Characterization of peptides released from mitochondria: evidence for constant proteolysis and peptide efflux. J Biol Chem 280: 2691-2699
Augustin, S., Nolden. M., Müller, S., Hardt, O., Arnold, I., and Langer, T.
-
(2005). Rote of the novel metallopeptidase Mop112 and saccharotysin for the complete degradation of proteins residing in different subcompartments of mitochondria. J Biol Chem 280: 20132-20139
Kambacheld, M., Augustin, S., Tatsuta, T., Müller, S., and Langer, T.
-
(2006). Evidence for a novel mitochondria-to-nucleus signalling pathway in respiring cells lacking i-AAA protease and the ABC-transporter Mdl1. Gene 367: 74-88
Arnold, I., Wagner-Ecker, M., Ansorge, W., and Langer, T.
-
(2007). Protein degradation within mitochondria: versatile activities of AAA proteases and other peptidases. Crit Rev Biochem Mol Biol 42:221-242
Koppen, M. and Langer, T.
-
(2007). Quality control of mitochondria - protection against neurodegeneration and ageing. EMBO J 27: 306-314
Tatsuta, T. and Langer T.
-
(2011). Quality control of mitochondrial proteostasis. CSH. Cold Spring Hart Perspect Biol. 3
Baker, M.J., Tatsuta, T., and Langer, T.
-
(2011). Targeting capacity and conservation of PreP homologues localization in mitochondria of different species. J Mol Biol 410:400-10
Alikhani N., Berglund A.K., Engmann T., Spanning E., Vögtle F.N., Pavlov P., Meisinger C., Langer T., Glaser E.
