The proteasome activity reporter GFP-Cl1 is degraded by autophagy in the aging model Podospora anserina

Abstract

The degradation of damaged proteins is an important vital function especially during aging and stress. The ubiquitin proteasome system is one of the major cellular machineries for protein degradation. Health and longevity are associated with high proteasome activity. To demonstrate such a role in aging of Podospora anserina, we first analyzed the transcript and protein abundance of selected proteasome components in wild-type cultures of different age. No significant differences were observed. Next, in order to increase the overall proteasome abundance we generated strains overexpressing the catalytic proteasome subunits PaPRE2 and PaPRE3. Although transcript levels were strongly increased, no substantial effect on the abundance of the corresponding proteins was observed. Finally, the analysis of the P. anserina strains expressing the sequence coding for the CL1 degron fused to the Gfp gene revealed no evidence for degradation of the GFP-CL1 fusion protein by the proteasome. Instead, our results demonstrate the degradation of the CL1-degron sequence via autophagy, indicating that basal autophagy appears to be a very effective protein quality control pathway in P. anserina.

A Network of Pathways Controlling Cellular Homeostasis Affects the Onset of Senescence in Podospora anserina

“…In western blot experiments, the fusion protein was partly degraded leaving its GFP portion stably retained. Overall, this specific approach did not reveal evidence for the expected function of the UPS in quality control of the CL1 degron as a proteasomal substrate in P. anserina but instead suggested an efficient role of basal autophagy, the vacuolar degradation of proteins [ 66 ]. A role of autophagy in the control of aging was further suggested by a genome-wide transcriptome analysis of the P. anserina wild type.…”