Arp2/3: Structural Insights into a Primary Engine of Cell Motility

Background: A diverse set of transcripts called 185/333 is strongly expressed in sea urchins responding to immune challenge. Optimal alignments of full-length 185/333 cDNAs requires the insertion of large gaps that define 25 blocks of sequence called elements. The presence or absence of individual elements also defines a specific element pattern for each message. Individual sea urchins were challenged with pathogen associated molecular patterns (PAMPs) (lipopolysaccharide, β-1,3glucan, or double stranded RNA), and changes in the 185/333 message repertoire were followed over time. Results: Each animal expressed a diverse set of 185/333 messages prior to challenge and a 0.96 kb message was the predominant size after challenge. Sequence analysis of the cloned messages indicated that the major element pattern expressed in immunoquiescent sea urchins was either C1 or E2.1. In contrast, most animals responding to lipopolysaccharide, β-1,3-glucan or injury, predominantly expressed messages of the E2 pattern. In addition to the major patterns, extensive element pattern diversity was observed among the different animals before and after challenge. Nucleotide sequence diversity of the transcripts increased in response to β-1,3-glucan, double stranded RNA and injury, whereas diversity decreased in response to LPS. Conclusion: These results illustrate that sea urchins appear to be able to differentiate among different PAMPs by inducing the transcription of different sets of 185/333 genes. Furthermore, animals may share a suite of 185/333 genes that are expressed in response to common pathogens, while also maintaining a large number of unique genes within the population. Background Recent advances in invertebrate immunology have led to a paradigm shift in our understanding of the ways in which animals respond to immunological challenges. Previously, it was assumed that invertebrate immune response proteins were germ-line encoded and were selected over evolutionary time scales for broad recognition of conserved pathogen-associated molecular patterns Published: 1 March 2007 BMC Molecular Biology 2007, 8:16 doi:10.1186/1471-2199-8-16 Received: 9 November 2006 Accepted: 1 March 2007 This article is available from: http://www.biomedcentral.com/1471-2199/8/16 © 2007 Terwilliger et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.