Induction of MASH-like pathogenesis in the Nwd1 mouse liver.

Endoplasmic reticulum (ER) stores Ca and plays crucial roles in protein folding, lipid transfer, and it's perturbations trigger an ER stress. In the liver, chronic ER stress is involved in the pathogenesis of metabolic dysfunction-associated steatotic liver disease (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH). Dysfunction of sarco/endoplasmic reticulum calcium ATPase (SERCA2), a key regulator of Ca transport from the cytosol to ER, is associated with the induction of ER stress and lipid droplet formation. We previously identified NACHT and WD repeat domain-containing protein 1 (Nwd1) localized at the ER and mitochondria. However, the physiological significance of Nwd1 outside the brain remains unclear. In this study, we revealed that Nwd1 mice exhibited pathological manifestations comparable to MASH. Nwd1 interacts with SERCA2 near ER membranes. Nwd1 livers exhibited reduced SERCA2 ATPase activity and a smaller Ca pool in the ER, leading to an exacerbated state of ER stress. These findings highlight the importance of SERCA2 activity mediated by Nwd1 in the pathogenesis of MASH.