Regulator of Ribosome Synthesis 1 (RRS1) Stabilizes GRP78 and Promotes Breast Cancer Progression

Regulator of ribosome synthesis 1 (RRS1), a crucial regulatory factor in ribosome biogenesis, exerts a remarkable impact on the progression of breast cancer (BC). However, the exact mechanisms and pathways have not yet been fully elucidated. To investigate the impact of RRS1 on BC growth and metastasis, along with its underlying mechanisms. We discovered that RRS1 is overexpressed in BC tissues and cell lines. This study aims to regulate the level of RRS1 through lentiviral transfection technology to explore its potential function in BC cells. Knockdown of RRS1 resulted in the inhibition of cell proliferation, invasion, and migration, whereas overexpression had the opposite effects. We firstly identified the interaction between RRS1 and Glucose-Regulated Protein 78 (GRP78) using Co-immunoprecipitation (Co-IP) combined with mass spectrometry analysis, providing evidences of co-localization and positive regulation between RRS1 and GRP78. We observed that RRS1 inhibited the degradation of GRP78 through the ubiquitin-proteasome pathway, resulting in the stabilization of GRP78. In addition, our findings suggested that RRS1 promoted BC progression by activating the GRP78-mediated phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway. In conclusion, this newly discovered RRS1/GRP78 signaling axis provides a molecular and theoretical basis for further exploring the mechanisms of breast cancer invasion and metastasis.