Characterization of novel PNLIP variants in congenital pancreatic lipase deficiency

Background/objectives: Studies of a rare homozygous missense mutation identified in two brothers diagnosed with congenital pancreatic lipase deficiency (CPLD) provided the first definitive evidence linking CPLD with missense mutations in the gene of PNLIP. Herein, we investigated the molecular basis for the loss-of-function in the three novel PNLIP variants (c.305G > A, p.(W102∗); c.562C > T, p.(R188C); and c.1257G > A, p.(W419∗)) associated with CPLD. Methods: We characterized three novel PNLIP variants in transfected cells by assessing their secretion, intracellular distribution, and markers of endoplasmic reticulum (ER) stress. Results: All three variants had secretion defects. Notably, the p.R188C and p.W419∗ variants induced misfolding of PNLIP and accumulated as detergent-insoluble aggregates resulting in elevated BiP at both protein and mRNA levels indicating increased ER stress. Conclusions: All three novel PNLIP variants cause a loss-of-function through impaired secretion. Additionally, the p.R188C and p.W419∗ variants may induce proteotoxicity through misfolding and potentially increase the risk for pancreatic acinar cell injury.