The Nogo-B receptor promotes Ras plasma membrane localization and activation

Abstract

The localization of prenylated Ras at the plasma membrane promotes activation of Ras by receptor tyrosine kinases and stimulates oncogenic signaling by mutant Ras. The Nogo-B receptor (NgBR) is a transmembrane receptor that contains a conserved hydrophobic pocket. Here, we demonstrate that the NgBR promotes the membrane accumulation of Ras by directly binding prenylated Ras at the plasma membrane. We show that NgBR knockdown diminishes the membrane localization of Ras in multiple cell types. NgBR overexpression in NIH-3T3 fibroblasts increases membrane-associated Ras, induces the transformed phenotype in vitro, and promotes the formation of fibrosarcoma in nude mice. NgBR knockdown in human breast cancer cells reduces Ras membrane localization, inhibits EGF-stimulated Ras signaling, and diminishes tumorigenesis of xenografts in nude mice. Our data demonstrate that NgBR is a unique receptor that promotes accumulation of prenylated Ras at the plasma membrane and promotes EGF pathways.

Nogo‑B receptor in relevant carcinoma: Current achievements, challenges and aims (Review)

“…In addition, the downregulation of NgBR decreases the EGF-stimulated phosphorylation of ERK and Akt (43). These results are sufficient to suggest that the overexpression of NgBR is able to enhance the EGF-mediated activation of Ras and its downstream kinases, including Akt and ERK (28). That NgBR is essential for the accumulation of Ras in the tumour cell membrane indicates that NgBR serves a pivotal role in the oncogenic function of Ras in tumour growth.…”

“…Zhao et al (27) revealed that the inhibition of NgBR is able to attenuate the activation of the Akt signalling pathway and subsequently decrease cellular growth, migration, survival and proliferation. A follow-up study revealed that the overexpression of NgBR enhanced the phosphorylation of Akt in MDA-MB-231 cells (28). Pula et al (20) revealed that NgBR is substantially increased in IDC at the protein and mRNA levels and concluded that a low expression of NgBR in IDC is able to downregulate the PI3K/Akt/mechanistic target of rapamycin (mTOR) signalling pathway and subsequently reduce cancer cell proliferation, migration, adhesion, survival and invasiveness.…”

“…This signalling pathway is involved in the dysregulation of cell differentiation, proliferation and apoptosis, and tumorigenesis likely involves multiple mutations in this pathway (40). Dysregulation of this signalling pathway may be overactivated by the abnormal expression of numerous cell factors, including NgBR, the mutational activation of EGF-like ligands, and the mutation and overexpression of Ras (28).…”

“…Caveolin-1 has a membranedocking site in its lipid raft domains that binds to guanosine diphosphate (GDP)-loaded H-Ras (42). The hydrophobic cytoplasmic domain of NgBR has a docking site for binding to prenylated Ras, and this binding promotes the translocation of GDP/GTP-bound H-Ras and K-Ras to the plasmalemma, a step that has a pivotal role in oncogenic signalling by these GTPases (28).…”

“…A recent cancer pathogenesis study revealed that NgBR preferentially binds to farnesylated H-Ras, and its carboxyl terminus composed of hydrophobic residues is essential for integrating with farnesylated Ras to form a steady complex that mediates H-Ras signalling (28,43). Through a cell surface biotinylation assay, Zhao et al (28) revealed that the upregulation of NgBR enhances the amounts of membrane-associated K-Ras and H-Ras without changing their total levels. It has been reported that NgBR only mediates the accumulation of Ras at the plasma membrane and does not enhance the levels of Ras (43).…”