The P2Y2 receptor regulates lipoprotein receptor‐related protein 1 expression in smooth muscle cells

Extracellular nucleotides exert various effects in the cardiovascular system. Uridine 5′‐triphosphate (UTP) regulates G‐protein‐coupled P2Y 2 receptor (P2Y 2 R) activation which causes actin cytoskeletal reorganization. We isolated aortic smooth muscle cells (SMC) from wild‐type (WT) and P2Y 2 R−/− mice to investigate whether UTP and the P2Y 2 R modulate expression of low density lipoprotein receptor‐related protein 1 (LRP1) and low density lipoprotein receptor (LDLR). For LRP1 expression, cells were stimulated in the presence or absence of 100 μM UTP overnight. For LDLR mRNA expression, cells were transiently transfected for 24 h with cDNA encoding a hemagglutinin‐tagged WT P2Y 2 R or a mutant P2Y 2 R that does not bind filamin‐A (FLN‐A) and treated with 100 μM UTP overnight. Total RNA was isolated, reversed transcribed to cDNA, and mRNA abundance determined by RT‐PCR using the ΔCt method with GAPDH as a control gene. Results show SMC expressing the P2Y 2 R that lacks the FLN‐A binding domain exhibit 3‐fold lower LDLR expression than SMC expressing the WT P2Y 2 R. However, there was a 3‐fold increase in LRP1 mRNA expression in response to UTP in P2Y 2 R−/− SMC compared to WT. Actinomycin‐D (20 μg/ml) significantly reduced UTP‐induced LRP1 mRNA expression in P2Y 2 R−/− SMC ( P < 0.05). These results might indicate the presence of a P2Y 4 R in P2Y 2 R−/− SMC as a possible cause for the effect of UTP, which is being further investigated.