The Nimrod transmembrane receptor Eater is required for hemocyte attachment to the sessile compartment in Drosophila melanogaster.

Andrew J Bretscher,Olivier Burri,Bruno Lemaitre,Mickael Poidevin,Olivier Binggeli,István Andó,Éva Kurucz,Viktor Honti,János Zsámboki

doi:10.1242/bio.201410595

Abstract

ABSTRACTEater is an EGF-like repeat transmembrane receptor of the Nimrod family and is expressed in Drosophila hemocytes. Eater was initially identified for its role in phagocytosis of both Gram-positive and Gram-negative bacteria. We have deleted eater and show that it appears to be required for efficient phagocytosis of Gram-positive but not Gram-negative bacteria. However, the most striking phenotype of eater deficient larvae is the near absence of sessile hemocytes, both plasmatocyte and crystal cell types. The eater deletion is the first loss of function mutation identified that causes absence of the sessile hemocyte state. Our study shows that Eater is required cell-autonomously in plasmatocytes for sessility. However, the presence of crystal cells in the sessile compartment requires Eater in plasmatocytes. We also show that eater deficient hemocytes exhibit a cell adhesion defect. Collectively, our data uncovers a new requirement of Eater in enabling hemocyte attachment at the sessile compartment and points to a possible role of Nimrod family members in hemocyte adhesion.

Highlights

Circulating immune cells express many cell surface receptors, following their specialized role in host defense
We extended our analysis to other Gram-positive and Gram-negative bacteria. eater1 null hemocytes phagocytosed the Gram-negative Serratia marcescens to wild type levels, but were deficient in phagocytosis of the Grampositive Staphylococcus epidermidis and Micrococcus luteus (Fig. 2E)
Together these data indicate that phagocytosis of the Gram-positive bacteria S. aureus, S. epidermidis and M. luteus, but not the Gram-negative bacteria E. coli and S. marcescens by plasmatocytes, the major macrophage-like cell type in Drosophila, is defective in eater1 null larvae

Summary

Introduction

Circulating immune cells express many cell surface receptors, following their specialized role in host defense. These roles include cell adhesion, cell-cell recognition, phagocytosis, chemokine-binding and others (Alberts et al, 2002). Drosophila hemocytes express many surface receptors, some of whose functions are not well understood or have not been studied. We re-visit the function of Eater, an EGF-like repeat Nimrod receptor that is expressed in Drosophila hemocytes (Kocks et al, 2005; Kurucz et al, 2007)

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Conclusion