EMC4 (ER membrane protein complex subunit 4) is a crucial component of the endoplasmic reticulum membrane protein complex (EMC) that facilitates energy-independent insertion of newly synthesized membrane proteins into ER membranes, with particular preference for proteins containing weakly hydrophobic transmembrane domains or destabilizing features 123. The protein functions in both cotranslational insertion of multi-pass membrane proteins and post-translational insertion of tail-anchored proteins, controlling membrane protein topology including G protein-coupled receptors 23. Beyond its canonical role, EMC4 serves as a molecular tether between intracellular compartments, facilitating late endosome-to-ER transport by engaging Rab7 and syntaxin18 4. EMC4 also promotes viral membrane fusion during Dengue virus entry by mediating ER-to-endosome phosphatidylserine transfer 5. Disease relevance includes involvement in neuropathic pain, where decreased EMC4 expression was identified as a potential biomarker 6, and roles in α-synuclein aggregation relevant to Parkinson's disease, where EMC4 ablation enhanced autophagic clearance and reduced pathological aggregates 7. Additionally, EMC4 participates in eIF2B-mediated translation regulation and stress response in yeast 8.