Assessing p53 aggregates over a lifetime: Studies on young, adult, and aged mice.

Abstract

p53 is a tumor-suppressing transcription factor critical to cellular health and function. The importance of intact p53 has been well established over the forty-plus years since its discovery. However, the role of amyloid-like aggregation in p53-related pathologies remains a significant knowledge gap. A growing body of knowledge over the last two decades has connected several mutations prevalent in cancer to the amyloid-like aggregation of p53 into both cross beta-sheet stacked fibrils and non-fibrillar aggregates. Here, non-fibrillar aggregates encompass all non-native p53-p53 (homomeric) complexes currently off-pathway to highly structured low-energy endpoint fibrils. p53 aggregation has reasonably been considered a cancer-centric phenomenon; however, it is unknown whether fibrillar-like structures form throughout the organismal lifespan, analogous to amyloid plaques. Furthermore, it is unclear if these structural states are observable as end-point or transient intermediates, including those either on or off-pathway to fibrillization. Notably, it has been shown that tau aggregates in the frontal cortex of Alzheimer's disease (AD) patients and AD mouse models contained aggregated p53, suggesting p53 aggregation may be more prevalent in aging-related diseases than previously thought. Here, I use immunoprecipitation to isolate p53 from young, adult, and aged mice and compare the aggregation state and propensity using native-page, fluorescence spectroscopy, and electron microscopy. Further, I will compare these data to the aggregation state typically observed in immortalized cell lines. I hypothesize that in mice, WT and mutant p53 may form aggregates over time, although those observed with mutant p53 will appear more fibrillar than WT, and may be distinct from those observed in immortalized cell lines. Together, these experiments help broaden our understanding of p53 aggregation related to age and health in vitro and in vivo.