The epidermal growth factor receptor regulates YAP signalling and promotes diabetic retinal fibrosis by modulating the degradation of SAV1.

PURPOSE: The epidermal growth factor receptor (EGFR) and Yes-associated protein (YAP) signalling pathways are two intrinsic mechanisms that typically control fibrosis. The intracellular molecules that regulate these two pathways remain unclear. Here, we investigated how EGFR and YAP signalling control retinal Müller cell-related diabetic retinal fibrosis in vivo and in vitro.

METHODS

Human retinal Müller cells (MIO-M1) were transfected in vitro with a Flag-tagged EGFR expression plasmid or an EGFR-targeting siRNA. Western blotting and coimmunoprecipitation (Co-IP) were used to assess the role of EGFR in mediating the interaction between SAV1 and Herc4 and its degradation. In vivo, mice with STZ-induced diabetes received erlotinib (an EGFR inhibitor) intraperitoneally or an intravitreal anti-EGFR antibody. Retinal fibrosis was evaluated via histopathology and YAP signalling analysis.

RESULTS

EGFR inhibited YAP signalling by degrading SAV1 and promoting the interaction between SAV1 and the E3 ligase Herc4. Therefore, EGFR can inhibit the Hippo cascade and promote the nuclear translocation of YAP, thus activating the transcription of downstream Hippo target genes. Pharmacological inhibition of EGFR was found to stimulate the YAP signalling pathway and effectively mitigate retinal fibrosis changes in diabetic mice. Moreover, the intravitreal injection of anti-EGFR antibody markedly inhibited diabetic retinal fibrosis, and initiating this treatment early and administering it multiple times proved to be even more efficacious.

CONCLUSIONS

The results of this study demonstrate that EGFR blocks the Hippo pathway by degrading SAV1 in Müller cells. Targeting EGFR effectively mitigated retinal fibrosis in diabetic mice, highlighting its therapeutic potential.