Understanding the Role of Rage in Cell Adhesion
Abstract
The Receptor for Advanced Glycation Endproducts (RAGE) is a mammalian specific cell surface receptor. RAGE consists of three extracellular domains (V, C1, and C2), a transmembrane domain, and an intracellular cytoplasmic tail. RAGE has a significant role in human pathogenesis, including neurodegenerative diseases, diabetic complications, and certain cancers. Deregulation of cell adhesion is one of the contributing cellular events common in many of the above listed human pathologies and might be mediated via RAGE signaling. In our study, we aimed to understand the role of RAGE in cell adhesion and to define the importance of the different domains of RAGE in mediating this phenomenon.
For this study, a protein engineering approach was used to express full-length RAGE (FL-RAGE) and a panel of domain deletion constructs ((ΔV-, ΔC1-, ΔC2-, DN-, TmCyto-) RAGE) of the receptor. The necessary expression constructs were assembled in the pcDNA3 vector, and the RAGE variants were expressed in HEK293 cells. The expression and cellular localization of RAGE in HEK 293 cells were analyzed using Western blot, immunofluorescence microscopy, and flow cytometry techniques. Our results show that the cytoplasmic domain of RAGE was sufficient to contribute to cell adhesion to the extracellular matrix to a level comparable to that of the FL-RAGE expressing cells.
The current mechanistic model suggests that RAGE signaling is initiated by ligand binding to the extracellular region, followed by conformational changes in the intracellular domain. Subsequently, this conformation change leads to the recruitment of RAGE-interacting proteins on the intracellular side of the plasma membrane. However, in this thesis, we present evidence of an alternative mechanism of RAGE signaling possibly involving the translocation of RAGE into the nucleus. The results from our study suggest an alternative model for RAGE signaling and will help to better understand RAGE signaling in pathophysiological conditions. Our results could contribute to the development of new small molecule drugs targeting intracellular RAGE or the intracellular RAGE domain as a novel approach for inhibiting RAGE signaling.