Dimerisation of the VIP receptor VIPR2 is essential to its binding VIP and Gαi proteins, and to its functions in breast cancer cells

Abstract Background and Purpose Several G protein‐coupled receptors (GPCRs) are known to homodimerise. Dimeric GPCRs may have different properties from their monomers, but the molecular basis and functional significance of GPCR dimerisation remain largely unknown. We recently found that signalling by the vasoactive intestinal peptide receptor, VIPR2, regulates breast cancer cell migration and proliferation. However, it is unclear whether VIPR2 monomers directly interact with each other and what function the dimeric receptor has. Here, we showed that VIPR2 dimerises and investigated their role in breast cancer progression. Experimental Approach Dimerisation of VIPR2 was assessed by fluorescence resonance energy transfer (FRET) analysis and a pull‐down assay. Breast cancer progression was analysed by orthotopic growth and metastasis of human breast cancers into proper axillary and subiliac lymph‐nodes in mice. Key Results VIPR2 monomers directly interacted with each other through transmembrane domains (TM)3‐4. FRET analysis revealed that VIPR2 moved further apart in cells expressing TM3‐4‐peptides, suggesting that TM3‐4 prevents VIPR2 dimerisation. Breast cancer cells stably expressing TM3‐4 region exhibited suppressed tumour growth and lymph‐node metastasis. Furthermore, ligand‐receptor binding assays revealed that VIP‐FITC bound to cells dose‐dependently, and VIPR2 de‐dimerisation by TM3‐4 expression decreased VIP's affinity to cells. Additionally, TM3‐4 expression decreased Gα i ‐VIPR2 interactions. Conclusion and Implications Dimeric VIPR2 forms the minimal functional unit that effectively promotes growth and metastasis of breast cancer. Therefore, dimeric VIPR2 is a potential therapeutic target for breast cancer, and TM3‐4‐peptides are potential anti‐cancer drug candidates to suppress cancer progression.