Mutant p53 promotes RCP-dependent chemoresistance coinciding with increased delivery of P-glycoprotein to the plasma membrane

Abstract

TP53 is the most frequently mutated gene in cancers. Mutations lead to loss of p53 expression or expression of a mutant protein. Mutant p53 proteins commonly lose wild-type function, but can also acquire novel functions in promoting metastasis and chemoresistance. Previously, we uncovered a role for Rab-coupling protein (RCP) in mutant p53-dependent invasion. RCP promotes endosomal recycling and signalling of integrins and receptor tyrosine kinases. In a screen to identify novel RCP-interacting proteins, we discovered P-glycoprotein (P-gp). Thus, we hypothesised that mutant p53 could promote chemoresistance through RCP-dependent recycling of P-gp. The interaction between RCP and P-gp was verified endogenously and loss of RCP or mutant p53 rendered cells more sensitive to cisplatin and etoposide. In mutant p53 cells we detected an RCP-dependent delivery of P-gp to the plasma membrane upon drug treatment and decreased retention of P-gp substrates. A co-localisation of P-gp and RCP was seen in mutant p53 cells, but not in p53-null cells upon chemotherapeutic exposure. In conclusion, mutant p53 expression enhanced co-localisation of P-gp and RCP to allow for rapid delivery of P-gp to the plasma membrane and increased resistance to chemotherapeutics.

Rab11-FIP1/RCP Functions as a Major Signalling Hub in the Oncogenic Roles of Mutant p53 in Cancer

“…Its response to cisplatin is remarkable, as cisplatin is currently not considered a substrate of P-gp. These data suggest a generic response to chemotherapeutics that promotes plasma membrane localisation of Rab11-FIP1 and its cargo (18).…”

“…As mutant p53 promotes chemoresistance (47)(48)(49), it therefore seemed likely that mutant p53 could promote chemoresistance through the Rab11-FIP1/integrin/EGFR signalling pathway. Indeed, cells in which we knocked-out Rab11-FIP1 appeared to become more sensitive to etoposide and cisplatin (18). However, when inhibiting integrins, the sensitivity was less pronounced compared to loss of Rab11-FIP1 expression, suggesting alternative pathways are involved in this chemoresistance (18).…”

“…Indeed, cells in which we knocked-out Rab11-FIP1 appeared to become more sensitive to etoposide and cisplatin (18). However, when inhibiting integrins, the sensitivity was less pronounced compared to loss of Rab11-FIP1 expression, suggesting alternative pathways are involved in this chemoresistance (18).…”

“…Proposed mechanisms for gain-of-function include binding to new response elements on the DNA and the interaction with many different proteins, including transcription factors such as the p53 family member p63 (15). We have shown previously that mutant p53 inhibits TAp63a function, and in those same conditions, mutant p53 promotes the interaction between integrins, RTKs and the Rab-coupling protein/Rab11-Family Interacting Protein 1 (RCP/Rab11-FIP1), leading to increased invasion, cell scattering, metastasis and chemoresistance (16)(17)(18).…”

“…Interestingly, in a screen to detect novel Rab11-FIP1 interacting proteins, we identified the xenobiotic and chemotherapeutic efflux transporter P-glycoprotein (P-gp/MDR1) (18) as well as the copper and cisplatin transporter ATP7B. We could demonstrate that Rab11-FIP1 promoted membrane localisation of P-gp in response to etoposide and cisplatin and enhanced efflux of its substrates (18). Its response to cisplatin is remarkable, as cisplatin is currently not considered a substrate of P-gp.…”