EIF2AK3 and major depressive disorder: Coincidentally, Chen et al. experimentally identified the endoplasmic reticulum stress kinase PERK [RNA-dependent protein kinase (PKR)-like ER kinase] as a receptor for TMAO, which induces the endoplasmic reticulum stress signaling pathway by binding to the endoplasmic reticulum stress protein PERK (Chen et al., 2019), More importantly, endoplasmic reticulum stress has been shown in many studies to mediate one of the pathogenic mechanisms of psychiatric disorders such as depression (Gold et al., 2013; Xiang et al., 2017).