Negative regulation of cannabinoid receptor 2‑induced tumorigenic effect by sphingosine‑1‑phosphate receptor 5...

G protein‑coupled receptors (GPCR), also known as seven‑transmembrane proteins, serve a role in transmitting extracellular information into the cellular environment. Type 2 cannabinoid receptors (CB₂) and type 5 sphingosine‑1‑phosphate receptor (S1P₅) are GPCRs that are activated by biolipids and involved in tumor progression in various cancer types. At present, effects of crosstalk between CB₂ and S1P₅ receptors on tumor cell proliferation and migration in gliomas are not fully understood. The present study screened S1Ps for potential interactions with CB₂ using bioluminescence resonance energy transfer analysis. S1P₅ interacted strongly and specifically with CB₂. 293T cells were transfected with CB₂ tagged with Venus and S1P₅ tagged with mCherry to investigate the cellular localization of both receptors. After 24 h, Confocal microscopy analysis revealed that, in the absence of agonists, both receptors were predominantly localized at the plasma membrane. Notably, both receptors were co‑internalized from the membrane to the cytoplasm upon individual and combined activation. The effects of co‑activation of both receptors on tumor progression were investigated using U‑87 MG, the human glioblastoma cell line. Activation of CB₂ induced an increase in cell migration and proliferation, which were downregulated following the co‑activation of S1P₅. Furthermore, activation of S1P₅ significantly attenuated the upregulation of tumor progression‑related genes, including zinc finger protein 91, activating transcription factor 3, Ki67, basic transcription factor 3, and p21, induced by CB₂ activation. This suggests that S1P₅ exerts a negative regulatory effect on CB₂‑mediated tumor progression. The present findings provide evidence of the crosstalk between CB₂ and S1P₅.