Abstract
Antimicrobial peptides (AMPs) play a crucial role in innate immunity. We have previously reported the isolation and characterization of the AMPs, strongylocins 1 and 2, and centrocin 1, from coelomocyte extracts of Strongylocentrotus droebachiensis. Here we show that these AMPs were expressed in phagocytes. In addition, transcripts of strongylocin 1 were detected in vibratile cells and/or colorless spherule cells, while transcripts of strongylocin 2 were found in red spherule cells. Results from immunoblotting and immunocytochemistry studies showed that centrocin 1 was produced by phagocytes and stored in granular vesicles. Co-localization of centrocin 1 and phagocytosed bacteria suggests that the granular vesicles containing centrocin 1 may be involved in the formation of phagolysosomes. We also analyzed the temporal and spatial expression of AMPs throughout larval development. Strongylocins were expressed in the early pluteus stage, while centrocin 1 was expressed in the mid pluteus stage. The spatial expression pattern showed that centrocin 1 was mainly located in blastocoelar cells (BCs) around the stomach and the esophagus. In addition, a few patrolling BCs were detected in some larval arms. Together, these results suggest that AMPs are expressed in different types of coelomocytes and that centrocin 1 is involved in response against bacteria. Furthermore, the expression of AMPs in larval pluteus stage, especially in BCs, indicates that AMPs and BCs are engaged in the larval immune system.
Highlights
Antimicrobial peptides (AMPs) are commonly found in the animal and plant kingdoms where they serve as the first line of host defense against pathogens
We show that centrocin 1 was localized in blastocoelar cells (BCs) around the digestive tract and some of them were able to migrate to the arms
Coelomocytes, consisting of several cell types, are considered to mediate defense functions in sea urchins (Smith et al, 2006). Their predominant cell type is phagocytes that are involved in phagocytosis, graft rejection, encapsulation and clotting reactions reviewed by Gross et al (1999) and Smith et al (2006)
Summary
AMPs are commonly found in the animal and plant kingdoms where they serve as the first line of host defense against pathogens. There are more than 2200 AMPs recorded (Wang et al, 2009). AMPs are characterized by a short amino acid sequence (
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