YAP pathway is involved in CAR-induced hepatomegaly and liver regeneration.
YAP is a potent regulator of organ size and tissue homeostasis (Kowalik et al., 2011). The role of YAP/TEAD in CAR-induced hepatomegaly was also investigated. The protein levels of total YAP and its downstream targets CTGF, ANKRD1 and CYR61 were measured in hepatomegaly and liver regeneration models. All of these proteins were upregulated in TCPOBOP-treated mice, especially at Day 10 (Figure 3A). The proliferation-related proteins CCNA1, CCND1 and CCNE1 were all significantly upregulated after TCPOBOP treatment. The upregulation of nuclear YAP and the downregulation of cytoplasmic p-YAP suggested that the YAP pathway was activated in this process (Figure S3A).
In the PHx mice model, the protein levels of YAP and its downstream targets ANKRD1 and CYR61 were upregulated, while CTGF showed a slight increase in TCPOBOP-treated mice. The proliferation-related proteins CCNA1, CCND1 and CCNE1 were all significantly upregulated after TCPOBOP treatment, especially at Day 2 after PHx (Figure 3B). Similarly, the nuclear YAP and the cytoplasmic p-YAP showed the same trend as the hepatomegaly model, which indicated that the YAP pathway was activated in these processes (Figure S3B).
Nuclear translocation is essential both for CAR and YAP to activate their downstream targets, thus the possible co-localization of CAR and YAP was examined. HepG2 cells were treated with hCAR selective agonist CITCO. The result suggested that the CAR activation enhanced translocation of YAP (Figure 3C). Co-immunoprecipitation (Co-IP) experiment was then performed to confirm the potential protein-protein interaction between CAR and YAP and a clear interaction between CAR and YAP was observed (Figure 3D).