ZNRF4 is an E3 ubiquitin-protein ligase that functions as a negative regulator of innate immune signaling and endoplasmic reticulum (ER) homeostasis. As an E3 ligase, ZNRF4 catalyzes K48-linked ubiquitination of target proteins, marking them for proteasomal degradation 1. Its primary characterized function is negative regulation of NOD2 signaling through ubiquitination and degradation of RIPK2 (RIP2), the adaptor protein essential for NOD2-mediated NF-κB activation 1. This ZNRF4-mediated RIP2 degradation promotes NOD2-induced tolerance and fine-tunes antibacterial immune responses 1. Additionally, ZNRF4 localizes to the ER membrane where it regulates the turnover of calnexin, an ER-resident chaperone, through direct interaction and ubiquitin-dependent proteasomal degradation 2. This ER-associated degradation function supports proper ER proteostasis and homeostasis. While the physiological role in spermatogenesis remains unclear, ZNRF4 belongs to a RING-finger protein family with potential reproductive functions 3. The clinical significance of ZNRF4 dysregulation extends to immune-mediated diseases and inflammatory disorders due to its role in NOD2 signaling modulation 4. However, specific disease associations remain incompletely characterized.