Three isoforms of the Atg16L1 protein contribute different autophagic properties

Abstract

The mammalian Atg16L1 protein consists of a coiled-coil domain and a tryptophan-aspartic acid (WD) repeat domain and is involved in the process of autophagy. However, the mechanisms underlying the effect of the Atg16L1 isoforms on autophagy remain to be elucidated in humans. In the present study, we successfully cloned three isoforms: Atg16L1-1, which contains the complete sequence; Atg16L1-2, which lacks all of exon 8; and Atg16L1-3, which lacks the coiled-coil domain. Subsequent experiments showed that the three isoforms of Atg16L1 were colocalised with MDC within the cells. Quantitative analysis of fluorescence showed that the average number of dots of Atg16L1-1 that colocalised with MDC was higher than those of Atg16L1-2 and Atg16L1-3. The three isoforms of Atg16L1 also colocalised with the lysosome within the cells. The average number of dots of Atg16L1-1 that colocalised with the lysosome was higher than those of Atg16L1-2 and Atg16L1-3. However, although Atg16L1-1 and Atg16L1-3 colocalised with the mitochondria, Atg16L1-2 did not. Functional analysis showed that overexpression of the three isoforms of Atg16L1 had a stimulative effect on autophagy. Significant increase in the number of positive LC3-II dots per cell was observed in Atg16L1-1 (70.2 ± 2.39 dots); this number was greater than those of the other two isoforms. Atg16L1-2 appeared to have an average of 59.25 ± 2.22 LC3-II dots per cell. Atg16L1-3 appeared to have the least number of LC3-II dots per cell (48.25 ± 2.22 dots) (P < 0.001). Our results indicated that the degree of autophagy varied with different Atg16L1 isoforms. The different domains of Atg16L1 played different roles in the process of autophagy. The coiled-coil domain of Atg16L1 was involved in the process of autophagy.

Intestinal Epithelium and Autophagy: Partners in Gut Homeostasis

“…However, Thachil and colleagues reported that neither the common ATG16L1 nor IRGM polymorphisms associated with CD, appeared to be responsible for the increased numbers of autophagosomes in Paneth cells (77). It is possible that other ATG16L1 variants exist, in the coiled-coil domain region for example, which would prevent efficient autophagosome degradation (80). Further characterization of the CD-associated ATG16L1 mutant proteins will likely explain the conflicting data.…”

Regulation of autophagy, NF-κB signaling, and cell viability by miR-124 in KRAS mutant mesenchymal-like NSCLC cells

“…5A) (27). In addition, miR-124 caused robust suppression of the selective autophagy adaptor protein p62.…”

The Role of ATG16 in Autophagy and The Ubiquitin Proteasome System

“…Human ATG16L1 was identified by large-scale sequencing analysis of a human fetal brain cDNA library [22]. Database searching revealed that there exist at least four splice variants [22] and Jiang et al suggested the presence of seven splice variants of ATG16L1 in H. sapiens [23]. Functional analysis of three isoforms revealed different autophagic properties because of the absence of some regions of ATG16L1 which impaired their localization on autophagosomes [23].…”

“…Database searching revealed that there exist at least four splice variants [22] and Jiang et al suggested the presence of seven splice variants of ATG16L1 in H. sapiens [23]. Functional analysis of three isoforms revealed different autophagic properties because of the absence of some regions of ATG16L1 which impaired their localization on autophagosomes [23]. For ATG16L2 it was shown that mRNA and protein levels decreased in Multiple Sclerosis (MS) patients.…”