Nuclear protein localization protein 4 homolog

NPLOC4 (Nuclear protein localization protein 4 homolog) is a 608-amino acid protein that functions as a core component of the UFD1-VCP-NPLOC4 ternary complex (UniProt: Q8TAT6). This complex mediates ER-associated protein degradation by binding ubiquitinated substrates and facilitating their export from the endoplasmic reticulum to the cytoplasm for proteasomal degradation. The complex also regulates spindle disassembly during mitosis, nuclear envelope formation, and suppresses type I interferon production by promoting RIG-I degradation.

NPLOC4 participates in fundamental cellular quality-control pathways essential for proteostasis and cellular homeostasis. Its involvement in ERAD and protein trafficking implicates it in cellular processes disrupted across neurodegenerative conditions.

In Alzheimer's Disease, NPLOC4 shows ambiguous regulation across subcellular fractions in post-mortem AD brain tissue compared to age-matched controls (Chaparral AD proteomics). Analysis of two fractions from a four-fraction TMT-labeled proteomics experiment yielded a mean log₂FC of 0.068, indicating minimal overall change but variable direction across fractions. This pattern suggests potential compartment-specific dysregulation in AD neuropathology that warrants further investigation in larger cohorts.