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).