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

Levin, David Michael; Breuer, Lisha N.; Zhuang, Shufei; Anderson, Sheri; Nardi, James B.; Kanost, Michael R.

doi:10.1016/j.ibmb.2005.01.003

Cited by 107 publications

(72 citation statements)

References 33 publications

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“…Opsonin-dependent pathways are regulated by binding of complement-like or other humoral pattern recognition molecules prior to uptake by hemocytes, while opsonin-independent pathways involve direct binding of the target to cell surface receptors like integrins and scavenger receptors (27,34,45,46). Integrin expression by hemocytes is also implicated in the encapsulation of foreign targets, including parasitoids (27,32,35,62). Integrin-mediated adhesion and signaling by mammalian immune cells require tyrosine phosphorylation of the PTK Fak or Pyk2, as well as other proteins, including p130…”

Section: Discussionmentioning

confidence: 99%

PTP-H2 and PTP-H3 from Microplitis demolitor Bracovirus Localize to Focal Adhesions and Are Antiphagocytic in Insect Immune Cells

Pruijssers

Strand

2007

J Virol

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Viruses in the family Polydnaviridae are symbiotically associated with parasitoid wasps. Wasps inject polydnaviruses (PDVs) when laying an egg into their insect host, and expression of viral gene products causes several physiological alterations, including immunosuppression, that allow the wasp's progeny to develop. As with other PDVs, most Microplitis demolitor bracovirus (MdBV) genes are related variants that form gene families. The largest MdBV gene family includes 13 members that encode predicted proteins related to protein tyrosine phosphatases (PTPs). Sequence analysis during the present study indicated that five PTP family members (PTP-H2, -H3, -N1, and -N2) have fully conserved catalytic domains, whereas other family members exhibited replacements, deletions, or rearrangements of amino acids considered essential for tyrosine phosphatase activity. Expression studies indicated that most MdBV PTP genes are expressed in virus-infected host insects, with transcript abundance usually being highest in hemocytes. MdBV-infected hemocytes also exhibited higher levels of tyrosine phosphatase activity than noninfected hemocytes. We produced expression constructs for four of the most abundantly expressed PTP family members and conducted functional studies with hemocyte-like Drosophila S2 cells. These experiments suggested that recombinant PTP-H2 and PTP-H3 are functional tyrosine phosphatases whereas PTP-H1 and PTP-J1 are not. PTP-H2 and -H3 localized to focal adhesions in S2 cells, and coexpression with another MdBV gene product, Glc1.8, resulted in complete inhibition of phagocytosis.

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Section: Discussionmentioning

confidence: 99%

PTP-H2 and PTP-H3 from Microplitis demolitor Bracovirus Localize to Focal Adhesions and Are Antiphagocytic in Insect Immune Cells

Pruijssers

Strand

2007

J Virol

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“…The PCR product was used as template for preparation of dsRNA using MEGAscript RNAi kit (Ambion), following its isolation and extraction after agarose gel electrophoresis. Double-stranded RNA of the M. sexta ␤1-integrin subunit was prepared as described previously (7). Green fluorescent protein (GFP) dsRNA that was used as a control was purchased from Dharmacon.…”

Section: Methodsmentioning

confidence: 99%

“…We previously demonstrated that an integrin containing a ␤ subunit expressed specifically in hemocytes (M. sexta integrin-␤1) functions in plasmatocyte adhesion and encapsulation (7,27). At that time, the ␣ subunit of this HS-integrin was not known; in fact, no ␣-integrins from M. sexta had been characterized.…”

Section: Identification Of the ␣1 Chain Of Hs-integrin-mentioning

confidence: 99%

“…Drosophila integrins are expressed in a variety of cells during embryonic and larval development and bind to ligands of extracellular matrices such as laminin and tiggrin (16), but the function of integrins in hemocytes is not well understood. Among the arthropods, integrins are known to be expressed by hemocytes of crayfish (17) and by hemocytes of a few insects that include Drosophila melanogaster (9), the mosquito Anopheles gambiae (8), and two lepidopteran species, Pseudoplusia includens (6) and Manduca sexta (7).…”

mentioning

confidence: 99%

“…The nucleotide sequence (s) cell-mediated responses of insects include sealing of wounds, hemolymph clotting, phagocytosis, nodulation of bacteria, and encapsulation of parasitoids, all of which involve regulated hemocyte adhesion (25,26). An integrin ␤ subunit that is expressed specifically in M. sexta hemocytes functions in hemocyte adhesion and encapsulation (7,27). We describe here an ␣ subunit that pairs with this ␤ subunit to form a hemocytespecific integrin (HS-integrin) 2 and provide results indicating that a tetraspanin of M. sexta (D76) that is expressed mainly on hemocytes (24) is a ligand for this integrin and likewise functions in the cell-mediated responses of the immune cells.…”

mentioning

confidence: 99%

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

Zhuang

Kelo

Nardi

et al. 2007

Journal of Biological Chemistry

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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.

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Host refractoriness of the tobacco hornworm, Manduca sexta, to the braconid endoparasitoid Cotesia flavipes

Rodríguez‐Pérez

Dumpit

Lenz

et al. 2005

Arch Insect Biochem Physiol

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Cotesia flavipes (Hymenoptera:Braconidae) is a gregarious endoparasitoid of several pyralid stemborer larvae of economic significance including the sugarcane borer, Diatraea saccharalis. In this study, the ability of this parasitoid to develop in a sphingid host, Manduca sexta, was tested. First, second, third, fourth, and even pharate fifth instar host tobacco hornworm larvae were readily parasitized by the female C. flavipes parasitoids but no wasp larvae hatched from the eggs in this refractory host. Instead, the parasitoid eggs were invariably encapsulated by the host's hemocytes and, ultimately, no parasitoids emerged from tobacco hornworm hosts. The first stages of encapsulation were evident at 2 h post-parasitization of the host M. sexta larvae, when the beginning stages of capsule formation were seen. The developmental fate of the host larvae with encapsulated parasitoids was variable. Most succumbed as abnormally small fifth instars or as post-wandering prepupal animals, while a few developed normally to the pupal stage. Dissection of all the larvae or pupae with encapsulated wasp eggs showed evidence of hemocytic encapsulation and melanization of the C. flavipes eggs. This report describes the association between C. flavipes and M. sexta, which appears to be an excellent model system for studying the physiological processes accompanying wasp egg encapsulation that result in death of the host as well as the parasitoid. Since the parasitoid egg never hatches, the system offers an excellent opportunity to identify and study the effects of parasitoid-injected polydnavirus and venom on host physiology.

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

Cited by 107 publications

References 33 publications

PTP-H2 and PTP-H3 from Microplitis demolitor Bracovirus Localize to Focal Adhesions and Are Antiphagocytic in Insect Immune Cells

PTP-H2 and PTP-H3 from Microplitis demolitor Bracovirus Localize to Focal Adhesions and Are Antiphagocytic in Insect Immune Cells

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

Host refractoriness of the tobacco hornworm, Manduca sexta, to the braconid endoparasitoid Cotesia flavipes

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