Proteomic and phosphoproteomic analyses identify liver-related signaling in retinal pigment epithelial cells during EMT

Abstract

Epithelial-mesenchymal transition (EMT) of the retinal pigment epithelium (RPE) is associated with several blinding retinal diseases. Using proteomics and phosphoproteomics studies of human induced pluripotent stem cell-derived RPE monolayers with induced EMT, we capture kinase/phosphatase signaling cascades 1 h and 12 h after induction to better understand the pathways mediating RPE EMT. Induction by co-treatment with transforming growth factor b and tumor necrosis factor alpha (TGNF) or enzymatic dissociation perturbs signaling in many of the same pathways, with striking similarity in the respective phosphoproteomes at 1 h. Liver hyperplasia and hepatocyte growth factor (HGF)-MET signaling exhibit the highest overall enrichment. We also observe that HGF and epidermal growth factor signaling, two cooperative pathways inhibited by EMT induction, regulate the RPE transcriptional profile.

IKKβ Inhibition Attenuates Epithelial Mesenchymal Transition of Human Stem Cell-Derived Retinal Pigment Epithelium

“…Given the role of RPE–EMT in PVR and possibly in AMD, efforts have been made to identify inhibitors of RPE–EMT for potential therapeutic use [ 44 , 45 ]. Despite some progress in this field [ 46 , 47 ], since a safe and effective RPE–EMT inhibitor has yet to be reported, we sought to utilize our previously reported RPE–EMT model and transcriptional studies [ 10 , 11 , 12 ] to identify a suitable inhibitor. Our previous transcriptomic [ 11 ], proteomic [ 10 ], and phosphoproteomic [ 12 ] studies identified several malignancy-associated EMT factors that were also significantly altered during RPE–EMT.…”

“…Despite some progress in this field [ 46 , 47 ], since a safe and effective RPE–EMT inhibitor has yet to be reported, we sought to utilize our previously reported RPE–EMT model and transcriptional studies [ 10 , 11 , 12 ] to identify a suitable inhibitor. Our previous transcriptomic [ 11 ], proteomic [ 10 ], and phosphoproteomic [ 12 ] studies identified several malignancy-associated EMT factors that were also significantly altered during RPE–EMT. Although malignancy-associated EMT is controlled by a variety of biological pathways, NF-κB signaling is activated in a wide range of human cancers, and is involved in maintaining epithelial cell plasticity and metastasis via the orchestrated modulation of IKK-2/IκBα/NF-κB [ 26 ].…”

“…To study RPE–EMT, the co-treatment of hRPE cultures with TGF–β/TNF–α, which synergistically activates an EMT program compared with treatment with either cytokine alone [ 7 , 10 , 11 , 12 ], has been used. In our investigation, this model proved useful in conducting molecular-level dissection of the RPE–EMT pathways.…”

“…It has been shown that injury and stress can induce a variety of pathological changes in the RPE, including trans-differentiation and EMT [ 5 , 7 , 10 , 11 , 12 ], and that RPE–EMT is involved in multiple retinal diseases, including proliferative vitreoretinopathy (PVR) [ 4 , 6 , 13 ], neo-vascular (“wet”) age-related macular degeneration (AMD) [ 14 ], and atrophic (“dry”) AMD [ 8 , 15 , 16 ]. To better understand the pathogenesis and help develop therapeutic strategies for these diseases, we have been studying the process of RPE–EMT using human stem cell-derived RPE cells (hRPE) [ 10 , 11 , 12 ]. As an in vitro model of EMT, we and others have been using the co-treatment of hRPE monolayer cultures with TGF–β and TNF–α (TGF–β/TNF–α) to analyze the molecular changes that occur during the progression of EMT and to test the effects of molecules that attenuate EMT [ 7 , 10 , 11 ].…”

Beyond the Liver: Liver-Eye Communication in Clinical and Experimental Aspects

“…In the study of endothelial-mesenchymal transition induction on the RPE layer derived from human induced pluripotent stem cells, it was found that the HGF-MET signal showed the highest overall enrichment. In addition, they also found that HGF signaling plays a role in regulating the transcription profile of RPE (Mertz et al, 2021).Thus, it will be intriguing to study whether altered expression of HGF in liver diseases could exsert distance influence on ocular condition.…”