Toll/IMD signal pathways mediate cellular immune responses via induction of intracellular PLA₂ expression

Abstract

Phospholipase A 2 (PLA 2 ) hydrolyzes fatty acids from phospholipids at the sn-2 position. Two intracellular PLA 2 s, iPLA 2 A and iPLA 2 B, have been found in Spodoptera exigua.

Molecular Characterization of Two Genes Encoding Novel Ca2+-Independent Phospholipase A2s from the Silkworm, Bombyx mori

“…sPLA2s have been described in a variety of insect species [10][11][12]14,16]. However, only a few iPLA2s have been identified among insects, such as Spodoptera exigua [7][8][9] and Drosophila melanogaster [10]. The present study reports two novel iPLA2s from B. mori, and their expression patterns.…”

“…BmiPLA2A (GTSTG) differs from BmiPLA2B (GVSTG) in that it has a distinct lipase motif. Likewise, Spodoptera exigua, SeiPLA2A, and SeiPLA2B have the same protein sequence differences [9]. Due to the greatest degree of similarity between the protein sequence features of iPLA2s in B. mori to SeiPLA2A and SeiPLA2B in Spodoptera exigua, they have been classified as BmiPLA2A and BmiPLA2B.…”

“…In addition, BmiPLA2s were found to be expressed at various developmental stages in the three immune-related tissues of B. mori. The broad tissue and temporal distribution of BmiPLA2s indicate that they may be involved in various biological functions [9].…”

“…Interestingly, viral infection increased the mRNA levels of BmiPLA2s in the fat body in the early infection while suppressing their transcription levels in the fat body at certain times during infection. Previous studies have shown that the expression of Se-iPLA2A and Se-iPLA2B in Spodoptera exigua are induced upon bacterial challenge [9].…”

“…Insect iPLA2s, such as SeiPLA2A and SeiPLA2B, were first discovered in Spodoptera exigua, and have been demonstrated to play crucial physiological roles in insect immunity and larval growth [7,8]. IMD/Toll pathways have been shown to regulate these two iPLA2s, and immune challenges with different types of pathogens significantly increased their transcription [9]. Otherwise, PLA2-VIA mutation in Drosophila caused increased sensitivity to oxidative stress, progressive neurodegeneration, and a severely reduced lifespan [10].…”