An Integrin-Tetraspanin Interaction Required for Cellular Innate Immune Responses of an Insect, Manduca sexta

Abstract

In their encounters with foreign intruders, the cells of the insect innate immune system, like those of the mammalian immune system, exhibit both humoral and cell-mediated responses. Some intruders can be dispatched by the humoral immune system alone, but many must be phagocytosed by individual hemocytes or encapsulated by interacting hemocytes. Surface proteins of hemocytes control the abrupt transition of hemocytes from resting, nonadherent cells to activated, adherent cells during these cell-mediated responses. Two of these surface proteins, an integrin and a tetraspanin, interact during this adhesive transition. As demonstrated with a hemocyte adhesion assay and a surface plasmon resonance assay, the large extracellular loop of tetraspanin D76 binds to a hemocyte-specific integrin of Manduca sexta. The interaction between the large extracellular loop domain and hemocyte-specific integrin is interrupted not only by a monoclonal antibody (MS13) that binds to a domain of ␤-integrin known to be a ligand-binding site for cell adhesion but also by double-stranded ␤-integrin RNA. Transfected S2 cells expressing tetraspanin mediate adhesion of hemocytes. A monoclonal antibody to tetraspanin D76 perturbs the cell-mediated immune response of encapsulation. These studies involving antibody blocking, RNA interference, and binding assays imply a trans interaction of integrin and tetraspanin on hemocyte surfaces.

A target‐specific feeding toxicity of β1 integrin dsRNA against diamondback moth, Plutella xylostella

“…Therefore, RNAi of bPx1 inhibited de novo synthesis of the subunit and disrupted formation of functional integrins to be involved in nodule formation. Neuroglian, a cell adhesion molecule (CAM), is expressed on cell surfaces of granulocytes and a subset of large plasmatocytes of M. sexta (Zhuang et al, 2007a). Neuroglian-positive hemocytes act as aggregation foci against foreign surface (Nardi et al, 2006).…”

Insect Cytokine Paralytic Peptide (PP) Induces Cellular and Humoral Immune Responses in the Silkworm Bombyx mori

“…Microarray and quantitative RT-PCR indicated that PP induces the expression of tetraspanin E and ced-6 in silkworm hemocytes. The gene families of tetraspanin and ced encode proteins necessary for the phagocytosis of bacteria in Manduca sexta (22) and D. melanogaster (23), respectively. Based on these previous findings, we considered that PP might stimulate the phagocytotic activity of silkworm hemocytes.…”

TM9SF4 is required forDrosophilacellular immunity via cell adhesion and phagocytosis

“…These large cells attach to the plasmatocyte layer and form a hermetic capsule around the invader (Russo et al, 1996;Williams et al, 2005). In insects, plasmatocyte adhesion to wasp eggs is a crucial step for encapsulation and strongly depends on cell surface molecules such as integrins (Irving et al, 2005;Zhuang et al, 2007). Besides the cellular immune response, Drosophila possesses a sophisticated humoral response, which includes the synthesis of antimicrobial peptides by fat body cells under the control of the two conserved NF-κB signalling pathways Toll and Imd (immune deficiency) (Lemaitre and Hoffmann, 2007;Ferradon et al, 2007).…”