Open AccessKSR induces RAS‐independent MAPK pathway activation and modulates the efficacy of KRAS inhibitors
Author(s) -
Paniagua Guillem,
Jacob Harrys K.C.,
Brehey Oksana,
GarcíaAlonso Sara,
Lechuga Carmen G.,
Pons Tirso,
Musteanu Monica,
Guerra Carmen,
Drosten Matthias,
Barbacid Mariano
Publication year - 2022
Publication title -
molecular oncology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.332
H-Index - 88
eISSN - 1878-0261
pISSN - 1574-7891
DOI - 10.1002/1878-0261.13213
Subject(s) - ectopic expression , mapk/erk pathway , microbiology and biotechnology , cell growth , scaffold protein , biology , protein kinase a , kinase , kras , signal transduction , cancer research , cell culture , biochemistry , mutation , genetics , gene
The kinase suppressor of rat sarcoma (RAS) proteins (KSR1 and KSR2) have long been considered as scaffolding proteins required for optimal mitogen‐activated protein kinase (MAPK) pathway signalling. However, recent evidence suggests that they play a more complex role within this pathway. Here, we demonstrate that ectopic expression of KSR1 or KSR2 is sufficient to activate the MAPK pathway and to induce cell proliferation in the absence of RAS proteins. In contrast, the ectopic expression of KSR proteins is not sufficient to induce cell proliferation in the absence of either rapidly accelerated fibrosarcoma (RAF) or MAPK‐ERK kinase proteins, indicating that they act upstream of RAF. Indeed, KSR1 requires dimerization with at least one member of the RAF family to stimulate proliferation, an event that results in the translocation of the heterodimerized RAF protein to the cell membrane. Mutations in the conserved aspartic acid–phenylalanine–glycine motif of KSR1 that affect ATP binding impair the induction of cell proliferation. We also show that increased expression levels of KSR1 decrease the responsiveness to the KRAS G12C inhibitor sotorasib in human cancer cell lines, thus suggesting that increased levels of expression of KSR may make tumour cells less dependent on KRAS oncogenic signalling.