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Abstract #92477 Published in IGR 22-1
A glaucoma- and ALS-associated mutant of OPTN induces neuronal cell death dependent on Tbk1 activity, autophagy and ER stress
Medchalmi S; Tare P; Sayyad Z; Swarup GFEBS Journal 2021; 288: 4576-4595
Mutations in OPTN are associated with glaucoma, an eye disease, and also with amyotrophic lateral sclerosis (ALS), a motor neuron disease. A 2-bp insertion in OPTN (691_692insAG or 2bpIns-OPTN) is associated with both glaucoma and ALS. This mutation results in frame shift after 127 amino acids, giving rise to a protein with C-terminal aberrant sequence. We have explored the mechanism of induction of cell death by this mutant in a motor neuron cell line, NSC-34, and also in a retinal cell line, 661W. Compared to wild-type OPTN, this mutant induced more cell death in NSC-34 and 661W cells. This mutant localizes predominantly in the nucleus whereas normal OPTN localizes in the cytoplasm. Deletion analysis of 2bpIns-OPTN showed that the aberrant sequence was not essential for cell death induction. This mutant interacts with TANK-binding kinase 1 (Tbk1) but not with OPTN and activates Tbk1. This mutant induced ER stress in NSC-34 cells as seen by induction of C/EBP homologous protein (CHOP) and some other genes. Induction of CHOP, autophagosomal protein LC3-II and cell death by this mutant were abrogated by Tbk1 knockdown and also by 4-phenylbutyric acid, that inhibits ER stress. Induction of CHOP and cell death by 2bpIns-OPTN was autophagy dependent as shown by the effect of Atg5 knockdown. This mutant caused increased formation of LC3-positive aggregates. Treatment of cells with autophagy inducer rapamycin reduced LC3-positive aggregates, CHOP and cell death induced by 2bpIns-OPTN. These results suggest that constitutive activation of Tbk1 by 2bpIns-OPTN leads to impaired autophagy that results in ER stress and cell death.
CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India.
Full articleClassification:
3.6 Cellular biology (Part of: 3 Laboratory methods)
3.9 Pathophysiology (Part of: 3 Laboratory methods)
3.4.2 Gene studies (Part of: 3 Laboratory methods > 3.4 Molecular genetics)
3.5 Molecular biology incl. SiRNA (Part of: 3 Laboratory methods)