The Role of ESRP1 in the Regulation of PHGDH in Estrogen Receptor-Positive Breast Cancer

Esrp1 and Esrp2 regulate the stability of tmc1/2a mRNAs in zebrafish sensory hair cells

RNA-binding proteins (RBPs) are important for post-transcriptional RNA processing, including pre-mRNA alternative splicing, mRNA stability, and translation. Several RBPs have been shown to play pivotal roles in the inner ear, whose dysfunction leads to auditory and/or balance impairments. Epithelial splicing-regulatory protein 1 (ESRP1) regulates alternative splicing and mRNA stability, and mutations in ESRP1 gene have been associated with sensorineural hearing loss in humans. In Esrp1 knockout mouse embryos, alternative splicing of its target genes such as Fgfr2 is impaired, which eventually result in cochlear development deficits. However, Esrp1 knockout mice die soon after birth because of complications from cleft-lip and palate defects, impeding further investigations at later postnatal ages. In the present study, we explored the role of ESRP1 in hearing using zebrafish as a model. We showed that esrp1 and its paralog esrp2 are expressed in the inner ear and certain anterior lateral line (ALL) neuromasts. Furthermore, our data suggested that Esrp1 and Esrp2 are required for the mechano-electrical transduction (MET) function of hair cells. RNA sequencing results indicated a significant decrease in the levels of several mRNAs in esrp1/2 double knockout larvae. Among the dysregulated genes are tmc1 and tmc2a, which encode essential subunits of the MET complex. Further investigations demonstrated that Esrp1/2 could directly bind to tmc1 and tmc2a mRNAs and affect their stability. Taken together, we showed here that Esrp1 and Esrp2 regulate the MET function of zebrafish sensory hair cells by modulating the stability of tmc1 and tmc2a mRNAs.Significance statement ESRP1 is an important RNA-binding protein, whose malfunction has been associated with hearing loss in humans. Esrp1 knockout affects alternative splicing of its target mRNAs such as Fgfr2, eventually leading to cochlear development deficits in mice. However, Esrp1 knockout mice die soon after birth, precluding further investigations at later postnatal ages. In this study, we explored the role of ESRP1 in hearing using zebrafish as a model. Our results demonstrated that esrp1 and its paralog esrp2 are expressed in the zebrafish inner ear, and that esrp1/esrp2 double knockout compromised the mechano-electrical transduction (MET) function of hair cells. Additionally, we successfully identified tmc1 and tmc2a mRNAs as the targets of Esrp1/2, which encode essential subunits of the MET complex.

Role of epithelial splicing regulatory protein 1 in cancer progression

As aberrant alternative splicing by either dysregulation or mutations of splicing factors contributes to cancer initiation and progression, splicing factors are emerging as potential therapeutic targets for cancer therapy. Therefore, pharmacological modulators targeting splicing factors have been under development. Epithelial splicing regulatory protein 1 (ESRP1) is an epithelial cell-specific splicing factor, whose downregulation is associated with epithelial-mesenchymal transition (EMT) by regulating alternative splicing of multiple genes, such as CD44, CTNND1, ENAH, and FGFR2. Consistent with the downregulation of ESRP1 during EMT, it has been initially revealed that high ESRP1 expression is associated with favorable prognosis and ESRP1 plays a tumor-suppressive role in cancer progression. However, ESRP1 has been found to promote cancer progression in some cancers, such as breast and ovarian cancers, indicating that it plays a dual role in cancer progression depending on the type of cancer. Furthermore, recent studies have reported that ESRP1 affects tumor growth by regulating the metabolism of tumor cells or immune cell infiltration in the tumor microenvironment, suggesting the novel roles of ESRP1 in addition to EMT. ESRP1 expression was also associated with response to anticancer drugs. This review describes current understanding of the roles and mechanisms of ESRP1 in cancer progression, and further discusses the emerging novel roles of ESRP1 in cancer and recent attempts to target splicing factors for cancer therapy.