AUTHOR=Huang Ying , Wu Lei , Jin Min , Hui Kaimin , Ren Qian 

TITLE=A C1qDC Protein (HcC1qDC6) with Three Tandem C1q Domains Is Involved in Immune Response of Triangle-Shell Pearl Mussel (Hyriopsis cumingii)

JOURNAL=Frontiers in Physiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2017.00521

DOI=10.3389/fphys.2017.00521

ISSN=1664-042X

ABSTRACT=<p>C1q-domain-containing (C1qDC) proteins are a family of proteins with a globular C1q (gC1q) domain and participate in several immune responses. In this study, a <italic>C1qDC</italic> gene was identified from the triangle-shell pearl mussel <italic>Hyriopsis cumingii</italic> (designated as <italic>HcC1qDC6</italic>). This gene has a full-length cDNA of 1782 bp and an open reading frame of 1,335 bp that encodes a 444-amino acid polypeptide containing three gC1q domains. <italic>HcC1qDC6</italic> contains at least five exons and four introns. The mRNA transcripts of <italic>HcC1qDC6</italic> were found to have the highest expression levels in the mantle tissue. The expression levels in the mantle and hepatopancreas were significantly upregulated by <italic>Staphylococcus aureus</italic> and <italic>Vibrio parahaemolyticus</italic> challenges. Moreover, knockdown of <italic>HcC1qDC6</italic> inhibits the expression of two immune-related genes (<italic>tumor necrosis factor</italic> and <italic>whey acidic protein</italic>). The recombinant proteins of C1q1, C1q2, and C1q3 all exhibit a binding activity against seven bacterial species and directly bind to peptidoglycan and lipopolysaccharide. The results indicate that HcC1qDC6 is involved in the innate immunity of <italic>H. cumingii</italic>.</p>