Insect Cytokine Growth-blocking Peptide Triggers a Termination System of Cellular Immunity by Inducing Its Binding Protein

Abstract

Growth-blocking peptide (GBP) is a 25-amino acid cytokine found in lepidopteran insects that possesses diverse biological activities such as stimulation of immune cells (plasmatocytes), cell proliferation, and larval growth regulation. We found another novel function of GBP that induces a hemolysis of another class of blood cells (oenocytoids). In the lysate of oenocytoids we identified a GBP-binding protein that shows a specific affinity for GBP. The characterization of purified GBP-binding protein and its cDNA demonstrated it as a 49.5-kDa novel protein with a C-terminal region displaying limited homology to several insect lipoproteins. Results of Northern and Western blotting indicated that the GBPbinding protein should be synthesized only in blood cells. Immunoelectron microscopic analyses confirmed that indirect immunoreactive signals were mostly localized in oenocytoids. Kinetic and biological analyses of interaction between GBP and the binding protein showed their strong binding was followed by clearance of GBP from hemolymph, thus indicating that this protein might function as an inhibitory factor against GBP. Based on these results, we propose that insect cytokine GBP shows multifunctions even in cellular immunity: it serves to stimulate immune cells and afterward silences its own action by inducing the binding protein through specific hemolysis.

Identification of a Novel Gene, Anorexia, Regulating Feeding Activity via Insulin Signaling in Drosophila melanogaster

“…Each purified protein was emulsified by Titer Max Gold (CytRx Co.) and injected into a rabbit to generate a specific polyclonal antibody. The antibodies were precipitated by adding ammonium sulfate to 40% saturation and further purified by an affinity column of protein G-Sepharose (GE Healthcare) (20). Proteins of Drosophila larval brains were separated by SDS-PAGE and electrically transferred to a polyvinylidene difluoride membrane filter.…”

An Ancient Role for a Prokineticin Domain in Invertebrate Hematopoiesis

“…A cytokine-like molecule (coelomic cytolytic factor) found in the earthworm, Eisenia foetida, with lectinlike activities similar to TNF instead suggests a convergent evolution of cytokines (9). Similarly, the ENF peptides found in some lepidopteran insects have cytokine-like activity, but they lack any sequence homology to vertebrate proteins (10,11).…”

Paralytic Peptide Binding Protein (PP-BP) Gene Expression During Egg Diapause and Its Multi-Gene Organization in the Silkworm Bombyx mori

“…Excessive amount of PPs cause serious damage to insect self organization. Paralytic peptide binding proteins are also up-regulated during the diapause period, which suggests that PP-BP act as active regulators of the paralytic peptide (Matsumoto et al, 2003), as even the over expression of the paralytic peptide might cause damage to the cells.…”

“…The C-terminal amino acid sequence (190th-430th amino acids) of B. mori paralytic peptide binding proteins is homologous to 30KPs (Hu et al, 2006). Growth-blocking peptide binding protein was reported to function for silencing the GBP action (Matsumoto et al, 2003) In a recent study by Zhang et al, (2012), 73 genes of Lipoprotein_11 family were retrieved from 12 lepidopteran species and the structural analysis showed that these genes could be divided into three distinct subfamilies according to their differential N-terminal domain. A novel subfamily of Lipoprotein_11 was reported for the first time in the study and named serine/threonine-rich 30KP according to its exclusive domain.…”

“…Ten 30KP genes have been identified in the silkworm (Sun et al, 2007), and more genes show sequence homologous to 30KPs like B. mori larvae serum protein (LSP) and LSP-T protein that are homologs of 30KPs (Fujiwara and Yamashita, 1992;Miyagawa et al, 2004). Microvitellogenin of Manduca sexta and the C terminus (170th-430th amino acids) of growth-blocking peptide binding protein (GBP-BP) of Pseudaletia separata also show some similarity to 30KPs (Matsumoto et al, 2003;Wang et al, 1989). Both Growth blocking peptide (GBP) and PP belong to ENF peptide family in view of the consensus N-terminal sequence (Glu-AsnPhe).…”