The Cdc48/p97 system in cell cycle regulation and beyond
The abundant hexameric AAA+-type ATPase p97 (also called VCP or Cdc48) has emerged as a key regulatory molecule in many ubiquitin-regulated reactions. It assembles to alternative holo-complexes with diverse ubiquitin adapters and other accessory proteins to act in different cellular processes. On the mechanistic level, it converts the energy of ATP hydrolysis to segregate ubiquitinated target proteins from binding partners or extracts them from cellular surfaces to promote downstream events including proteasomal or lysosomal degradation. This activity ensures cellular homoestasis and controls intracellular signalling pathways with relevance for degenerative diseases and cancer. Key questions regarding the mechanism and cellular relevance of p97 remain to be answered. We aim to identify and characterize new p97-cofactor complexes, understand their function on the mechanistic level and reveal their role in the cell. To achieve this, we use proteomics followed by a combination of structural, biochemical and cell biological approaches.
Regulating the cell cycle and ensuring genomic stability
In a complex with the Ufd1-Npl4 cofactor, p97 controls the cell cycle and is essential for genomic stability. We recently found that the complex extracts the mitotic kinase Aurora B from chromatin to control chromatin condensation and to regulate chromosome segregation during mitosis. We also showed that p97 modulates the response to DNA double strand breaks by extracting proteins at the site of damage. We are using biochemical and live-cell imaging approaches to understand the mechanism of extraction, reveal physical and functional interactions in chromatin-related processes and clarify the relevance for genomic stability in proliferating cells. This work is also aimed to evaluate p97 as a potential cancer drug target.
Sorting of endocytic cargo to the lysosome
Plasma membrane proteins including growth factor receptors are highly regulated as they control intracellular signalling and proliferation. Our proteomics approaches have recently identified a p97 complex with the UBXD1 cofactor, which localises to endosomes and controls sorting of cargo to the lysosome. Using RNAi screening and live cell imaging approaches, we aim to identify specific cofactors involved, understand the underlying mechanism and clarify the relevance for cellular homeostasis and proliferation.