Journal Article

A Crohn’s disease variant in Atg16l1 enhances its degradation by caspase 3

Reichelt, Mike, Diehl, Lauri, Graham, Robert R., Li, Yun, Katakam, Anand Kumar, van Lookeren Campagne, Menno, Roose-Girma, Merone, Noubade, Rajkumar, Peng, Ivan, Murthy, Aditya, DeVoss, Jason

2014

Overview

Crohn’s disease is a debilitating inflammatory bowel disease (IBD) that can involve the entire digestive tract. A single-nucleotide polymorphism (SNP) encoding a missense variant in the autophagy gene ATG16L1 (rs2241880, Thr300Ala) is strongly associated with the incidence of Crohn’s disease. Numerous studies have demonstrated the effect of ATG16L1 deletion or deficiency; however, the molecular consequences of the Thr300Ala (T300A) variant remains unknown. Here we show that amino acids 296–299 constitute a caspase cleavage motif in ATG16L1 and that the T300A variant (T316A in mice) significantly increases ATG16L1 sensitization to caspase-3-mediated processing. We observed that death-receptor activation or starvation-induced metabolic stress in human and murine macrophages increased degradation of the T300A or T316A variants of ATG16L1, respectively, resulting in diminished autophagy. Knock-in mice harbouring the T316A variant showed defective clearance of the ileal pathogen Yersinia enterocolitica and an elevated inflammatory cytokine response. In turn, deletion of the caspase-3-encoding gene, Casp3 , or elimination of the caspase cleavage site by site-directed mutagenesis rescued starvation-induced autophagy and pathogen clearance, respectively. These findings demonstrate that caspase 3 activation in the presence of a common risk allele leads to accelerated degradation of ATG16L1, placing cellular stress, apoptotic stimuli and impaired autophagy in a unified pathway that predisposes to Crohn’s disease. The Crohn’s disease risk-conferring T300A variant in the autophagy protein ATG16L1 increases its sensitivity to caspase-3-mediated cleavage; this decreases the induction of autophagy in response to metabolic stress or pathogen infection, leading to increased secretion of inflammatory cytokines. The genetics of Crohn's disease The Thr 300-to-Ala (T300A) polymorphism in the autophagy gene ATG16L1 has been recognized as a significant susceptibility factor for Crohn's disease, a chronic inflammatory bowel disease that is emerging as a significant health problem in industrialized countries. This study demonstrates that Thr 300 resides at the P1′ position of a caspase-cleavage site in human ATG16L, where it increases ATG16L1 sensitivity to caspase-3-mediated cleavage. This decreases the induction of autophagy in response to metabolic stress or death receptor stimulation leading to increased secretion of inflammatory cytokines. These observations raise the possibility that therapeutic inhibition of caspase 3 activation pathways may restore autophagy and gut homeostasis in part by stabilizing ATG16L1.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 13/106 / 13/109 / 13/2 / 13/21 / 13/31 / 13/44 / 13/51 / 13/89 / 14 / 14/28 / 14/63 / 631/80/39/2346 / 82/29 / 82/51 / Amino Acid Motifs / Amino acids / Animals / Autophagy / Autophagy (Cytology) / Autophagy - genetics / Autophagy-Related Proteins / Carrier Proteins - chemistry / Carrier Proteins - genetics / Carrier Proteins - metabolism / Caspase 3 - deficiency / Caspase 3 - genetics / Caspase 3 - metabolism / Cell Line / Cells, Cultured / Crohn Disease - genetics / Crohn Disease - pathology / Crohn's disease / Cytokines - immunology / Enzyme Activation / Female / Food Deprivation / Genetic aspects / Genetic research / Genetic susceptibility / Genomes / Humanities and Social Sciences / Humans / Macrophages - immunology / Macrophages - metabolism / Male / Medical research / Medicine, Experimental / Mice / Mice, Inbred C57BL / multidisciplinary / Mutagenesis, Site-Directed / Pathogens / Polymorphism, Single Nucleotide - genetics / Proteins / Proteolysis / Risk factors / Rodents / Science / Small intestine / Stress response / Stress, Physiological / Studies / Yersinia enterocolitica - immunology