The unfolded protein response to PI*Z alpha-1 antitrypsin in human hepatocellular and murine models.

Alpha-1 antitrypsin (AAT) deficiency (AATD) is an inherited disease caused by mutations in the serpin family A member 1 (SERPINA1, also known as AAT) gene. The most common variant, PI*Z (Glu342Lys), causes accumulation of aberrantly folded AAT in the endoplasmic reticulum (ER) of hepatocytes that is associated with a toxic gain of function, hepatocellular injury, liver fibrosis, and hepatocellular carcinoma. The unfolded protein response (UPR) is a cellular response to improperly folded proteins meant to alleviate ER stress. It has been unclear whether PI*Z AAT elicits liver cell UPR, due in part to limitations of current cellular and animal models. This study investigates whether UPR is activated in a novel human PI*Z AAT cell line and a new PI*Z human AAT (hAAT) mouse model. A PI*Z AAT hepatocyte cell line (Huh7.5Z) was established using clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 gene editing of the normal ATT (PI*MM) gene in the Huh7.5 cell line. Additionally, novel full-length genomic DNA PI*Z hAAT and PI*M hAAT transgenic mouse models were established. Using these new models, UPR in Huh7.5Z cells and PI*Z mice were comprehensively determined. Robust activation of UPR was observed in Huh7.5Z cells compared to Huh7.5 cells. Activated caspase cascade and apoptosis markers, increased chaperones, and autophagy markers were also detected in Z hepatocytes. Selective attenuation of UPR signaling branches was observed in PI*Z hAAT mice in which the protein kinase R-like ER kinase and inositol-requiring enzyme1α branches were suppressed while the activating transcription factor 6α branch remained active. This study provides direct evidence that PI*Z AAT triggers canonical UPR and that hepatocytes survive pro-apoptotic UPR by selective suppression of UPR branches. Our data improve understanding of underlying pathological molecular mechanisms of PI*Z AATD liver disease.

[Clinico-pathological analysis of vesiculotubular myopathy of adult onset].

The patient was a 50-year-old house wife. There were complicated consanguineous marriages in the family tree. Since 30 years of age, she had suffered from progressive limb muscle weakness, but without myalgia and myasthenia. At present, she was wheelchair-bound. Physical examinations showed obesity, congenital livedo racemosa, epicanthus palpebrae and left renal defect. Neurologically, facial, anterior cervical, and iliopsoas muscles were well preserved, but others were severely involved. Laboratory examinations revealed mildly elevated myogenic serum enzymes, and myogenic changes on needle EMG. In her muscle biopsy from the left rectus femoris muscle, there were no inflammatory changes, but marked variations of the fiber size as well as adipose tissue replacement were recognized. Strickingly, basophilic masses located in the center of the sarcoplasm were present in about 10% of the fibers. Histochemically, the masses were present in both type 1 and 2 fibers, and exhibited almost similar stained patterns to the tubular aggregates, but were dystrophin-, GRP78- and clathrin-positive. Under electron microscopy, the masses consisted of aggregates of the vesiculotubular structure, measuring approximately from 60 nm to more than 6 microns in diameter, which were continuous with T system/sarcoplasmic reticulum and were clearly segregated from myofilaments. This is a chronic progressive muscular disorder of adult onset with the peculiar pathological finding of vesiculotubular structure.