The Sp185/333 Proteins from the California Purple Sea Urchin Opsonize Bacteria, Retard Bacterial Growth, and Augment Phagocytosis.
Open AccessThe purple sea urchin has a complex immune response mediated by a number of multi-gene families including the Sp185/333 gene family, which is an important component of innate immunity. In response to immune challenge from bacteria and various pathogen-associated molecular patterns, the Sp185/333 genes are up-regulated. Sea urchin phagocytes express the large family of Sp185/333 genes (50±10) which encode an abundant array of Sp185/333 proteins (up to 260 variants/animal). The diversity in size and sequence of the Sp185/333 proteins suggests that different variants may have different immune effector functions. I show that Sp185/333 proteins, once thought to be strictly membrane-associated, are secreted from the phagocytes and bind to bacteria in culture. Vibrio diazotrophicus becomes coated with Sp185/333 proteins after 24 hours of incubation with phagocytes. Nickel-isolated native Sp185/333 proteins isolated from the coelomocytes (cNi-Sp185/333) bind to both Gram-positive and Gram-negative bacteria and Baker's yeast with saturable kinetics and specificity. A recombinant Sp185/333 protein, rSp0032, also shows saturable binding to Vibrio. Microbial binding is the first step in anti-microbial processes, and cNi-Sp185/333 proteins significantly retard growth rates of multiple species of bacteria whereas rSp0032 does not. Additionally, while the rSp0032 variant does not appear to augment phagocytosis, cNi-Sp185/333 proteins moderately augment phagocytosis. This suggests that some Sp185/333 proteins have a moderate ability to retard bacterial growth and augment phagocytosis. Our results demonstrate the first antimicrobial functions identified for the Sp185/333 proteins, which suggests variable functions among the Sp185/333 variants, and that they may function synergistically to detect pathogens and promote their removal from the host.
- All rights reserved
Notice to Authors
If you are the author of this work and you have any questions about the information on this page, please use the Contact form to get in touch with us.