Epstein–Barr virus LMP1 protein promotes proliferation and inhibits differentiation of epithelial cells via activation of YAP and TAZ

Abstract

Latent Epstein–Barr virus (EBV) infection promotes undifferentiated nasopharyngeal carcinomas (NPCs) in humans, but the mechanism(s) for this effect has been difficult to study because EBV cannot transform normal epithelial cells in vitro and the EBV genome is often lost when NPC cells are grown in culture. Here we show that the latent EBV protein, LMP1 (Latent membrane protein 1), induces cellular proliferation and inhibits spontaneous differentiation of telomerase-immortalized normal oral keratinocytes (NOKs) in growth factor-deficient conditions by increasing the activity of the Hippo pathway effectors, YAP (Yes-associated protein) and TAZ (Transcriptional coactivator with PDZ-binding motif). We demonstrate that LMP1 enhances YAP and TAZ activity in NOKs both by decreasing Hippo pathway-mediated serine phosphorylation of YAP and TAZ and increasing Src kinase-mediated Y357 phosphorylation of YAP. Furthermore, knockdown of YAP and TAZ is sufficient to reduce proliferation and promote differentiation in EBV-infected NOKs. We find that YAP and TAZ are also required for LMP1-induced epithelial-to-mesenchymal transition. Importantly, we demonstrate that ibrutinib (an FDA-approved BTK inhibitor that blocks YAP and TAZ activity through an off-target effect) restores spontaneous differentiation and inhibits proliferation of EBV-infected NOKs at clinically relevant doses. These results suggest that LMP1-induced YAP and TAZ activity contributes to the development of NPC.

Regulation mechanism of EBV-encoded EBER1 and LMP2A on YAP1 and the impact of YAP1 on the EBV infection status in EBV-associated gastric carcinoma

“…Previously, some studies have reported the relationship between EBV and YAP1 in the occurrence and development of cancer. For example, Singh et al (2023) found that LMP1 encoded by EBV activates the expression and nuclear translocation of Hippo pathway effectors YAP1 and transcriptional co-activator with PDZ-binding motif (TAZ) by reducing Hippo mediated serine phosphorylation of YAP1 and TAZ and increasing Src kinase activity, promoting the proliferation and EMT of telomerase-immortalized normal oral keratinocytes (NOKs), and inhibiting their differentiation. This may be an important mechanism for EBV to promote early NPC ( Singh et al, 2023 ).…”

“…For example, Singh et al (2023) found that LMP1 encoded by EBV activates the expression and nuclear translocation of Hippo pathway effectors YAP1 and transcriptional co-activator with PDZ-binding motif (TAZ) by reducing Hippo mediated serine phosphorylation of YAP1 and TAZ and increasing Src kinase activity, promoting the proliferation and EMT of telomerase-immortalized normal oral keratinocytes (NOKs), and inhibiting their differentiation. This may be an important mechanism for EBV to promote early NPC ( Singh et al, 2023 ). However, their research also found that excessive expression of YAP1 and TAZ may actually induce the lytic form of EBV replication in telomerase-immortalized NOKs ( Singh et al, 2023 ; Van Sciver et al, 2021 ).…”

“…This may be an important mechanism for EBV to promote early NPC ( Singh et al, 2023 ). However, their research also found that excessive expression of YAP1 and TAZ may actually induce the lytic form of EBV replication in telomerase-immortalized NOKs ( Singh et al, 2023 ; Van Sciver et al, 2021 ). In addition, exosomes containing EBV virus products can activate YAP1/fibroblast activation protein α (FAPα) signaling in fibroblasts promotes fibrosis and progression of NPC ( Lee et al, 2022 ).…”

Human cytomegalovirus infection coopts chromatin organization to diminish TEAD1 transcription factor activity

“…Likewise, HPV16 oncoprotein E6 induces cell proliferation by dephosphorylating a serine residue of YAP1 (S379) and preventing its degradation by the proteasome complex 71 . More recently, it has been discovered that Epstein-Barr virus subverts the YAP/TAZ pathway in lytic reactivation in epithelial cells 72,73 .…”

Novel and multiple targets for chimeric antigen receptor-based therapies in lymphoma

“…EBV contributes to pathogenesis and generation of immunosuppressive TME, and can be a marker of relapse ( 233 , 235 ). Latent membrane proteins (LMP1 and LMP2A) are proteins encoded by EBV and participate in oncogenesis ( 236 ). A series of clinical trials were conducted using LMP1/2-specific cytotoxicity T-lymphocytes for cHL, demonstrating an ORR around 30-60% ( 237 ).…”