A Crohn's disease variant in Atgl6l1 enhances its degradation by caspase 3

摘要

M.K. (mackillo.kira@physik.uni-marburg.de). 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.%自噬基ATG16L1因中的Thr300-to-Ala(T300A)多态性已被发现是克罗恩氏病（一种慢性肠道炎症，目前正成为工业化国家一个较大的健康问题）的一个显著的易感因子。这项研究显示，Thr300位于人ATG16L内一个"半胱天冬酶解理点"的P1'位置，在那里它能提高ATG16L1对由''半胱天冬酶-3"介导的解理的敏感性。这会降低对响应于代谢应激或死亡受体刺激而发生的自噬作用的诱导，导致炎性细胞因子分泌的增加。这些发现提出这样一个可能性："半胱天冬酶-3"激活通道的治疗性抑制也许能恢复自噬作用和肠道动态平衡——部分是通过稳定ATG16L1来发挥这种作用。