A hemocyte-specific integrin required for hemocytic encapsulation in the tobacco hornworm, Manduca sexta

Upon encountering an object recognized as foreign, insect hemocytes aggregate in multiple layers on the surfaces of the object in a process known as encapsulation. For encapsulation to occur, hemocytes must switch from their usual nonadherent state to an adherent state, presumably by regulating the...

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Bibliographic Details
Published in:	Insect biochemistry and molecular biology Vol. 35; no. 5; pp. 369 - 380
Main Authors:	Levin, David M., Breuer, Lisha N., Zhuang, Shufei, Anderson, Sheri A., Nardi, James B., Kanost, Michael R.
Format:	Journal Article
Language:	English
Published:	England Elsevier Ltd 01-05-2005
Subjects:	adhesion receptors Amino Acid Sequence amino acid sequences Animals antigen-antibody reactions Cell adhesion Cell Aggregation - genetics Cell Aggregation - physiology cell-mediated immunity complementary DNA Encapsulation Hemocyte hemocytes Hemocytes - metabolism Hemolymph - physiology immune response Innate immunity Insect immunity Integrin beta Chains - genetics Integrin beta Chains - metabolism integrin beta1 integrins Manduca - genetics Manduca - metabolism Manduca sexta messenger RNA Molecular Sequence Data monoclonal antibodies nucleotide sequences plasmatocyte adhesion RNA interference Encapsulation PBS AC Innate immunity PAGE mAb TEA Hemocyte RT-PCR Cell adhesion RACE NP-40 Insect immunity DOC MSB
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Summary:	Upon encountering an object recognized as foreign, insect hemocytes aggregate in multiple layers on the surfaces of the object in a process known as encapsulation. For encapsulation to occur, hemocytes must switch from their usual nonadherent state to an adherent state, presumably by regulating the activity of adhesion proteins. Although detailed knowledge exists regarding the adhesion receptors for cells of the mammalian immune system, comparable information on adhesion molecules of insect hemocytes and their function in immune responses is extremely limited. We report here the identification of an integrin present exclusively on the surface of hemocytes in the tobacco hornworm, Manduca sexta. Monoclonal antibodies MS13 and MS34, which bind to plasmatocytes and block encapsulation, were used for immunoaffinity chromatography to isolate their corresponding hemocyte antigen, which was revealed to be the same integrin β subunit. A cDNA for this M. sexta integrin β1 was cloned and characterized. Integrin- β1 mRNA was detected by Northern analysis in hemocytes and not in other tissues tested. MS13 and MS34 were demonstrated to bind to a recombinant fragment of integrin β1 consisting of the I-like domain, consistent with their blocking of a ligand-binding site and subsequent disruption of plasmatocyte adhesion. Injection of double stranded integrin- β1 RNA into larvae resulted in decreased integrin β1 expression in plasmatocytes and significantly suppressed encapsulation. These results indicate that activation of ligand-binding by the hemocyte-specific integrin plays a key role in stimulating plasmatocyte adhesion leading to encapsulation.
Bibliography:	ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2
ISSN:	0965-1748 1879-0240
DOI:	10.1016/j.ibmb.2005.01.003