Edem1, also known as endoplasmic reticulum degradation-enhancing α-mannosidase-like protein 1, is a key quality control factor in the endoplasmic reticulum (ER) [1,2,3,4,5,6,7]. It is directly involved in the endoplasmic reticulum-associated degradation (ERAD) process, recognizing terminally misfolded proteins and guiding them to retrotranslocation for proteasomal degradation in the cytosol, thus maintaining ER homeostasis [1,3,6].

In terms of specific functions, in human cells, EDEM1 is an important regulator of amyloid precursor protein (APP) metabolism. Overproduction of EDEM1 reduces APP cellular levels and Aβ40 and Aβ42 secretion, while down-regulation of EDEM1 increases APP levels, suggesting its role in Alzheimer's disease-related processes [1]. In pancreatic β-cells, EDEM1 overexpression inhibits the IRE1/JNK/c-Jun pathway, increasing insulin mRNA levels and insulin secretion, which is relevant to diabetes treatment [2]. In Drosophila, Edem1 in the fat body regulates insulin signalling and metabolic homeostasis by limiting the activity of Drosophila tumor necrosis factor-α Eiger on insulin-producing cells [5]. Also, EDEM1 itself is turned over by ERAD and autophagy, and its degradation is mediated by multiple routes and various ERAD factors [3]. Alterations in EDEM1 functions can enhance ATF6 pro-survival signalling, and EDEM1 can drive misfolded protein degradation via ERAD and use ER-phagy as a backup mechanism when ERAD is impaired [4,6].

In conclusion, Edem1 is crucial for maintaining protein quality control in the ER and has far-reaching impacts on multiple biological processes and disease-related pathways. Its functions in APP metabolism, insulin regulation, and maintaining metabolic homeostasis, as revealed through various studies, highlight its significance in diseases such as Alzheimer's and diabetes. Understanding Edem1 through different research models helps in uncovering the underlying molecular mechanisms of these diseases and potentially developing new treatment strategies.