Molluscan Beclin-1 is involved in the innate immune response by regulating the autophagosomes formation in Crassostrea hongkongensis

• Published in: Aquaculture reports 2020-11, Vol.18, p.100541, Article 100541
• Main Authors: Zhou, Yinyin, Liu, Kunna, Li, Xingyou, Qin, Yanpin, Zhang, Yuehuan, Zhang, Yang, Xiang, Zhiming, Ma, Haitao, Li, Jun, Yu, Ziniu
• Format: Article
• Language: English
• Subjects: Autophagy pathway; Beclin-1; Crassostrea hongkongensis; Innate immune
• ISSN: 2352-5134; 2352-5134
• DOI: 10.1016/j.aqrep.2020.100541

•ChBeclin-1 was involved in the immune reaction in response to pathogen infection.•Knockdown of ChBeclin-1 gene impeded the formation of autophagosomes.•Overexpression of ChBeclin-1 suppressed the transcriptional activity of NF-κB. Beclin-1 plays a central role in autophagy, which is well documented in mammals. However, the identity and function of Beclin-1 remain largely unclear in mollusks. In this study, a Beclin-1 gene (ChBeclin-1) was identified and characterized from Crassostrea hongkongensis. The full length of ChBeclin-1 cDNA encoded a predicted 442-amino acid protein with a deduced molecular weight of 51.11 kDa and a theoretical isoelectric point of 4.71. The putative amino acid sequence of ChBeclin-1 contained a typical Bcl-2 homology domain 3 (BH3), a coiled-coil domain (CCD), and an Atg6 domain. Phylogenetic analysis showed that ChBeclin-1 was clustered with Beclin-1 from other mollusks such as Crassostrea gigas, Crassostrea virginica, and Mizuhopecten yessoensis. ChBeclin-1 mRNA was constitutively expressed in all detected tissues, with the highest relative expression in the gills. Additionally, significant inductions in the mRNA level of ChBeclin-1 were observed after bacterial stimulations, indicating its involvement in the innate immune response. The knockdown of ChBeclin-1 via RNA interference impeded the formation of autophagosomes, denoting ChBeclin-1 plays a role in autophagy. Moreover, in subcellular localization and dual-luciferase reporter assays, ChBeclin-1 protein was found to be localized mainly in the endoplasmic reticulum, and its overexpression suppressed the transcriptional activity of an NF-κB reporter gene in a dose-dependent manner in HEK 293T cells. Collectively, these findings provide experimental evidence of a functional Beclin-1 in autophagy and demonstrate its involvement in the innate immunity of C. hongkongensis.