CRKL enhances YAP signaling through binding and JNK/JUN pathway activation in liver cancer

Hepatocellular carcinoma (HCC) presents a major health issue due to its rising incidence and limited therapeutic options. The Hippo pathway transducers yes-associated protein (YAP) and WW-domain containing transcription regulator 1 (WWTR1/TAZ) are key regulators of liver tu-morigenesis promoting tumor formation and progression. Although first inhibitors are in clinical trials, targeting the upstream activation of YAP/TAZ could prove equally beneficial. To identify regulators of YAP/TAZ activity, we carried out a proximity labelling approach (BioID) coupled to mass-spectrometry. We verified CRKL as a new YAP-exclusive interaction partner, which is overexpressed in HCC patients correlating with YAP expression and activity as well as poor survival prognosis. In vitro experiments demonstrated CRKL dependent cell survival and loss of YAP binding induced through actin disruption. Moreover, we delineated an activation of the JNK/JUN pathway by CRKL, which promoted YAP transcription. Our data thus illustrated that CRKL not only promoted YAP activity through its binding but also through the induction of YAP transcription by JNK/JUN activation. This highlights the JNK/JUN pathway as a possible target to abrogate YAP expression in HCC patients.