Nuclear protein localization protein 4 (NPL4)

Nuclear protein localization protein 4 (NPL4, also known as NPLOC4 in humans) is a critical protein cofactor that functions in concert with Ufd1 and p97 (VCP in mammals, Cdc48 in yeast) to recognize and extract polyubiquitylated substrates from membranes, especially in the ER-associated degradation (ERAD) pathway[1][3][4][6][7]. The NPL4-Ufd1-p97 complex is essential for retrotranslocation of misfolded or regulatory proteins from the endoplasmic reticulum into the cytosol for proteasomal degradation, and for the activation of key transcription factors involved in membrane lipid biosynthesis in yeast[2]. NPL4 contains multiple domains including a zinc finger and MPN domain for ubiquitin binding, and is implicated in regulating mitotic spindle disassembly and nuclear envelope reformation in eukaryotic cells[1][3][6]. Dysfunction or mutation of NPL4 can have severe consequences for cell viability and is implicated in several cellular quality control pathways.

Other names

Nuclear protein localization protein 4NPL4NPLOC4 (especially in mammalian contexts)Hrd4 (in yeast, synonymous with ERAD gene HRD4)Npl4p (yeast protein notation)

Drugs or molecules targeting this complex generally act by inhibiting ATPase-mediated retrotranslocation and proteasomal degradation, affecting cellular protein turnover Experimental disruption of NPL4 function can impair ERAD and induce cell death through proteostasis imbalance