Date Published: August 14, 2011
Publisher: Impact Journals LLC
Author(s): Sandra Zintel, Dominik Bernhardt, Adelina Rogowska-Wrzesinska, Heinz D. Osiewacz.
A differential mass spectrometry analysis of secreted proteins from juvenile and senescent Podospora anserina cultures revealed age-related differences in protein profiles. Among other proteins with decreased abundance in the secretome of senescent cultures a catalase, termed PaCATB, was identified. Genetic modulation of the abundance of PaCATB identified differential effects on the phenotype of the corresponding strains. Deletion of PaCatB resulted in decreased resistance, over-expression in increased resistance against hydrogen peroxide. While the lifespan of the genetically modified strains was found to be unaffected under standard growth conditions, increased exogenous hydrogen peroxide stress in the growth medium markedly reduced the lifespan of the PaCatB deletion strain but extended the lifespan of PaCatB over-expressors. Overall our data identify a component of the secretome of P. anserina as a new effective factor to cope with environmental stress, stress that under natural conditions is constantly applied on organisms and influences aging processes.
The filamentous fungus Podospora anserina represents a well-studied model organism for aging [1-4]. P. anserina has a small genome  that is completely sequenced , is tractable to experimentation , and is characterized by a short lifespan of a few weeks . During the process of aging, the phenotype changes: the pigmentation of the mycelium increases, the growth rate and fertility decreases, the peripheral hyphae become slender and undulate and finally burst . Aging in P. anserina has been demonstrated to be associated with various pathways including mitochondrial DNA (mtDNA) instability [10-13], respiration [14-17], ROS generation and scavenging [14, 15, 18-22], mitochondrial dynamics , and apoptosis [24-26]. It thus is clear that aging in P. anserina, as in other organisms, is not mono-factorial, but depends on many factors and a network of different, interacting molecular pathways . In aging research the ‘free radical theory of aging’ (FRTA), which states that reactive oxygen species (ROS) generated during normal metabolism are responsible for damaging cellular components and for aging of cells, organs and organisms [28, 29], is one of the major theories and has been extensively studied over decades in various biological systems. It is now well demonstrated that different ROS are generated by different cellular processes (e.g., the respiratory chain) and by specific reactions [30-38]. It is also clear today that low ROS levels are important components in signal transduction and essential for developmental processes. However, increased levels of ROS are excessively damaging all kinds of biomolecules leading to degeneration of biological systems. To avoid imbalanced levels of ROS, all known organisms exhibit a wide variety of scavenging systems like superoxide dismutases, glutathione peroxidases and reductases, peroxiredoxins and catalases [39-41].
P. anserina is a filamentous fungus that is an extensively studied aging model. Studies with this system were generally taking advantage of the possibility to keep the organism under well defined and controlled conditions in the laboratory and to carry out specifically designed manipulations. In this way the successful identification of a variety of individual components and molecular pathways involved in the control of aging and lifespan was possible (for reviews see: [1-4, 58, 59]). However, although very effective, such studies also bear the risk that certain components escape identification, components and pathways that nevertheless are of importance in the complex network governing biological aging.