The pseudokinase NRBP1 activates Rac/Cdc42 via P-Rex1 to drive oncogenic signalling in triple negative breast cancer

ABSTRACT: In an effort to identify oncogenic protein kinase drivers in triple negative breast cancer (TNBC), we undertook mass spectrometry (MS)-based proteomic profiling across a large panel of TNBC cell lines. This revealed marked variation in expression of the multidomain pseudokinase Nuclear Receptor Binding Protein 1 (NRBP1). Interrogation of publicly-available data determined that NRBP1 gene expression is higher in TNBC than in luminal breast cancers and positively associates with poor prognosis in TNBC patients. Gain and loss of function experiments characterized NRBP1 as a positive regulator of TNBC cell migration and invasion. In addition, NRBP1 knockdown reduced colony formation in vitro and moreover, markedly impaired growth of TNBC orthotopic xenografts as well as lung colonization in an experimental metastasis model. To interrogate the signalling mechanism of NRBP1, we applied BioID/MS profiling, identifying P-Rex1, a guanine nucleotide exchange factor for Rac1 and Cdc42, as a NRBP1 binding partner. Importantly, NRBP1 overexpression enhanced levels of GTP-bound Rac1 and Cdc42 in a P-Rex1-dependent manner, while NRBP1 knockdown reduced their activation. In addition, NRBP1 associated with P-Rex1, Rac1 and Cdc42, suggesting a scaffolding function for this pseudokinase. NRBP1-mediated promotion of cell migration and invasion was P-Rex1-dependent, while constitutively-active Cdc42 wholly/or partially rescued the effect of NRBP1 knockdown on cell migration/invasion and colony formation, respectively. Generation of reactive oxygen species via a NRBP1/P-Rex1 pathway was implicated in these oncogenic roles of NRBP1. Overall, these findings define a new function for NRBP1 and a novel oncogenic signalling pathway in TNBC that may be amenable to therapeutic intervention.

INSTRUMENT(S): Q Exactive Plus

ORGANISM(S): Homo Sapiens (human)

DISEASE(S): Breast Cancer

SUBMITTER: Ralf Schittenhelm  

LAB HEAD: Roger Daly

PROVIDER: PXD032168 | Pride | 2023-05-05

REPOSITORIES: Pride