YAP1 and idiopathic pulmonary fibrosis: For example, the GPCR ligand S1P was found to be elevated in IPF [63] and a positive correlation between nuclear YAP and GPCR ligands such as LPA, S1P, thrombin were detected in fibroblasts during TGFβ1-induced fibrotic responses (Table 1) [64], suggesting GPCRs-YAP axis is crucial for fibroblast activation.