EMC3 (ER membrane protein complex subunit 3) is an essential component of the endoplasmic reticulum membrane protein complex (EMC) that facilitates energy-independent insertion of newly synthesized membrane proteins into ER membranes 1. The protein preferentially accommodates transmembrane domains with weak hydrophobicity or destabilizing features, and is involved in both cotranslational insertion of multi-pass membrane proteins and post-translational insertion of tail-anchored proteins 1. EMC3 shares structural homology with the Oxa1/Alb3/YidC family of membrane protein insertases and associates with the Sec translocon and ribosomes 1. In disease contexts, EMC3 demonstrates significant clinical relevance. Loss of Emc3 in retinal bipolar cells leads to progressive cell degeneration and reduced electroretinography responses in aged mice, indicating its importance for long-term cell survival 2. Conversely, EMC3 overexpression in hepatocellular carcinoma correlates with poor patient survival and promotes cancer progression through activation of the PI3K/AKT/mTOR signaling pathway 3. Additionally, EMC3 functions as a negative regulator of CD8+ T cell infiltration and has been identified as a potential therapeutic target for enhancing immunotherapy responses 4. These findings establish EMC3 as both a fundamental component of ER protein biogenesis machinery and a clinically relevant factor in cancer and retinal degeneration.