p53 amyloid formation leading to its loss of function: implications in cancer pathogenesis

Abstract

The transcriptional regulator p53 has an essential role in tumor suppression. Almost 50% of human cancers are associated with the loss of p53 functions, where p53 often accumulates in the nucleus as well as in cytoplasm. Although it has been previously suggested that amyloid formation could be a cause of p53 loss-of-function in subset of tumors, the characterization of these amyloids and its structure-function relationship is not yet established. In the current study, we provide several evidences for the presence of p53 amyloid formation (in human and animal cancer tissues); along with its isolation from human cancer tissues and the biophysical characterization of these tissue-derived fibrils. Using amyloid seed of p53 fragment (P8, p53(250-257)), we show that p53 amyloid formation in cells not only leads to its functional inactivation but also transforms it into an oncoprotein. The in vitro studies further show that cancer-associated mutation destabilizes the fold of p53 core domain and also accelerates the aggregation and amyloid formation by this protein. Furthermore, we also show evidence of prion-like cell-to-cell transmission of different p53 amyloid species including full-length p53, which is induced by internalized P8 fibrils. The present study suggests that p53 amyloid formation could be one of the possible cause of p53 loss of function and therefore, inhibiting p53 amyloidogenesis could restore p53 tumor suppressor functions.

p53 reactivation with induction of massive apoptosis-1 (PRIMA-1) inhibits amyloid aggregation of mutant p53 in cancer cells

“…We tested the ability of MDA-MB-231 cell lysates containing mutant p53 to induce aggregation of recombinant WT p53C, and we observed a clear seeding effect indicative of aggregates in the cell extract promoting WTp53C aggregation in a prionlike manner. This result is in agreement with the evidence for a prion-like behavior of aggregates of p53 (7,11,19,65). Lysates obtained from cells treated with PRIMA-1 had a weaker seeding capacity, which corroborates our findings of a reduction in the cellular amyloid-state p53 content after PRIMA-1 treatment.…”

Do Mutations Turn p53 into an Oncogene?

“…Supporting this hypothesis, the TAp63α that in normal conditions acquires a closed conformation in which the TI domain is inaccessible, does not interact with p53R175H [84]. Through this co-aggregation mechanism, mutant p53 proteins may exert a dominant negative effect on p63 and p73, inhibiting their functions [85][86][87]. In particular, the formation of mutant p53/p63 or mutant p53/p73 complexes has been shown to promote invasion through several mechanism.…”

Induction of intracellular wild-type p53 amyloids leading to cellular transformation and tumor formation in mice

“…Next, we hypothesized that similar to mutant p53 (Stein et al, 2019), p53 amyloids can also act as an oncoprotein. Previously, we had demonstrated that p53 amyloids can enhance the existing transformative properties of SH-SY5Y cells (neuroblastoma cell line) (Ghosh et al, 2017). We propose that similar changes might also induce the transformation of normal cells.…”

“…These cells have been used to identify oncogenic agents, which can cause transformation in cells (Imbalzano et al, 2009;Scott et al, 2004;Yusuf and Frenkel, 2010). Since exogenous addition of p53 core amyloid fibrils (seeds) leads to endogenous p53 amyloid formation in cells (Ghosh et al, 2017), we have used this method to induce p53 amyloid formation in these two normal cells. For amyloid seed preparation, p53 core protein was incubated and its aggregation and amyloid formation was confirmed using Circular Dichroism (CD), Thioflavin T (ThT) fluorescence and electron microscopic imaging ( Figure 1A, S1A-C).…”

“…In addition, we have recently demonstrated that p53 amyloid formation leads to loss of p53 functions such as apoptosis, cell cycle arrest in response to DNA damage, and also induces gain of tumorigenic functions. Moreover, similar to many other amyloids associated with neurodegenerative disorders, p53 amyloids also showed prion-like properties in cells (Ghosh et al, 2017). In this study, we ask whether the wild-type p53 amyloid formation can induce the cancerous transformation of normal cells leading to tumor initiation.…”