Display Settings:

Format

Send to:

Choose Destination
See comment in PubMed Commons below
Insect Biochem Mol Biol. 2005 Dec;35(12):1356-66. Epub 2005 Sep 21.

Prophenoloxidase binds to the surface of hemocytes and is involved in hemocyte melanization in Manduca sexta.

Author information

  • 1Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri-Kansas City, 64110, USA.

Abstract

In insects, melanotic encapsulation is an important innate immune response against large pathogens or parasites, and phenoloxidase (PO) is a key enzyme in this process. Activation of prophenoloxidase (proPO) to PO is mediated by a serine proteinase cascade. PO has a tendency to adhere to foreign surfaces including hemocyte surfaces. In this study, we showed that in the naïve larvae of the tobacco hornworm Manduca sexta, hemolymph proPO bound to the surface of granulocytes and spherule cells but not to oenocytoids, and about 10% hemocytes had proPO on their surfaces. When larvae were injected with water (injury) or microsphere beads (immune-challenge), hemolymph proPO was activated, and the number of hemocytes with surface proPO/PO increased at 12 h post-injection, but dropped to the normal level at 24 h. Hemocyte surface proPO can be activated in vitro, leading to melanization of these hemocytes. The number of melanized hemocytes from the larvae injected with water or microsphere beads significantly increased. We also showed that neither hemocytes nor cell-free plasma alone triggered melanization of immulectin-2-coated agarose beads in vitro. However, agarose beads were effectively melanized by isolated hemocytes in the presence of cell-free plasma. Our results suggest that activation of hemocyte surface proPO may initiate melanization, leading to the systemic melanization of hemocyte capsules.

PMID:
16291091
[PubMed - indexed for MEDLINE]
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Elsevier Science
    Loading ...
    Write to the Help Desk