The bacterium Xenorhabdus nematophila inhibits phospholipases A2 from insect, prokaryote, and vertebrate sources

Abstract

The bacterium Xenorhabdus nematophila is a virulent insect pathogen. Part of its pathogenicity is due to impairing cellular immunity by blocking biosynthesis of eicosanoids, the major recognized signal transduction system in insect cellular immunity. X. nematophila inhibits the first step in eicosanoid biosynthesis, phospholipase A2 (PLA2). Here we report that the bacterium inhibits PLA2 from two insect immune tissues, hemocytes and fat body, as well as PLA2s selected to represent a wide range of organisms, including prokaryotes, insects, reptiles, and mammals. Our finding on a bacterial inhibitor of PLA2 activity contributes new insight into the chemical ecology of microbe-host interactions, which usually involve actions rather than inhibitors of PLA2s.

Phospholipase A 2 Inhibitors Synthesized by Two Entomopathogenic Bacteria, Xenorhabdus nematophila and Photorhabdus temperata subsp. temperata

“…These suggested that both bacterial cultures might have similar metabolites possessing PLA 2 -inhibitory effects. A previous study predicted that a novel PLA 2 -inhibitory compound(s) originated from the entomopathogenic bacteria because an organic extract of X. nematophila culture broth inhibited various PLA 2 s derived from a wide range of organisms, including prokaryotes, insects, reptiles, and mammals (24). Later, chemical fractionation of the X. nematophila culture broth led to identification of three PLA 2 -inhibitory compounds, including BZA, PY, and Ac-FGV (11,35).…”

Physiological trade-off between cellular immunity and flight capability in the wing-dimorphic sand cricket, Gryllus firmus

“…Four points stress the biological significance of PG signaling in insect immunity. First, insect pathogenic bacteria in the genera Xenorhabdus and Photorhabdus suppress insect immunity by generating and secreting compounds that inhibit secretory PLA 2 s (Park and Kim, 2000;Park et al, 2004;Kim et al, 2005). Second, silencing genes encoding PLA 2 s with dsRNA constructs inhibited insect nodulation reactions to bacterial infection (Shrestha et al, 2010).…”

A secretory PLA2 associated with tobacco hornworm hemocyte membrane preparations acts in cellular immune reactions

“…Hence, it is reasonable to propose that the immunity-impairing influence of X. nematophila is exerted through its inhibitory action on sPLA 2 . This proposal was strongly bolstered by another inquiry in which we found the X. nematophila factors inhibit sPLA 2 s from vertebrate and invertebrate sources (Park et al, 2004b).…”