题目: A thymosin beta-4 is involved in production of hemocytes and immune defense of Hong Kong oyster, Crassostrea hongkongensis

作者: Jun Li, Yuehuan Zhang, Ying Liu, Yang Zhang*, Zhiming Xiang,Fufa Qu, Ziniu Yu**

刊物: Developmental and Comparative Immunology

年卷期页: 2016,57:1-9

摘要: Thymosin beta-4 (Tb4) is a ubiquitous protein with multiple and diverse intracellular and extracellular functions in vertebrates. In this study, the full-length cDNA of Tb4 was cloned and identified in Crassostrea hongkongensis, designated as ChTb4. The full-length cDNA of ChTb4 consists of 530 bp with an open reading frame of 126 bp encoding a 41 amino acid polypeptide. SMART analysis indicated that there is one thymosin domain and a highly conserved actin-binding motif (18LKKTET23) in ChTb4. In vivo injection of recombinant ChTb4 protein could significantly increase total hemocytes count in oysters, and knockdown of the expression of ChTb4 resulted in a significant decrease in the circulating hemocytes. Tissue distribution analysis revealed a ubiquitous presence of ChTb4, with the highest expression in hemocytes. The upregulated transcripts of ChTb4 in response to bacterial challenge and tissue injury suggest that ChTb4 is involved in both innate immunity against pathogen infection and wound healing. Moreover, bacteria-clearance experiment showed ChTb4 could facilitate the clearance of injected bacteria in oysters. In vivo injection with ChTb4 resulted in reduction of the intracellular ROS in hemocytes, which was associated with increased expression of antioxidant enzymes Cu/Zn superoxide dismutase (SOD), Catalase, and Glutathione Peroxidase (GPX) by pre-treatment with ChTb4. These results suggest that ChTb4 is a thymosin beta-4 homolog and plays a vital role in the immune defense of C. hongkongensis.