An fMLP receptor is involved in activation of phagocytosis by hemocytes from specific insect species

Area of Science:

• Immunology
• Entomology
• Cell Biology

Background:

• The bacterial peptide fMLP (formyl-methionyl-leucyl-phenylalanine) is a known chemoattractant and phagocytosis enhancer in mammalian immune cells.
• Previous studies show fMLP attracts hemocytes in some invertebrates and the insect Manduca sexta, but its effect on insect hemocyte phagocytosis remains unexplored.

Purpose of the Study:

• To investigate the effect of fMLP on phagocytosis in hemocytes from four different insect species.
• To determine if the phagocytic response to fMLP is conserved across insect orders or species-specific.

Main Methods:

• In vitro phagocytosis assays were conducted using hemocytes from Gromphadorhina portentosa (Blattodea), Acheta domesticus (Orthoptera), Zophobas morio (Coleoptera), and Galleria mellonella (Lepidoptera).
• Phagocytosis of various particles (latex, yeast, bacteria) was measured by flow cytometry in the presence of increasing fMLP concentrations.
• The role of the fMLP receptor signaling pathway was assessed using Pertussis toxin, an inhibitor.

Main Results:

• Hemocytes from A. domesticus, Z. morio, and G. mellonella showed enhanced phagocytosis of certain particles (latex, yeast, bacteria) upon fMLP stimulation.
• G. portentosa hemocytes did not exhibit enhanced phagocytosis with fMLP.
• Pertussis toxin treatment reversed fMLP-induced phagocytosis to basal levels, confirming pathway involvement.
• All tested insect species displayed a conserved chemotactic response to fMLP.

Conclusions:

• The chemotactic response of insect hemocytes to fMLP is evolutionarily conserved across diverse insect orders.
• The ability of insect hemocytes to enhance phagocytosis in response to fMLP is not universal but restricted to specific insect species.
• This suggests a divergence in immune signaling pathways related to bacterial peptide recognition among insects.