Effects of silkworm paralytic peptide on in vitro hematopoiesis and plasmatocyte spreading

Abstract

Bombyx mori paralytic peptide (BmPP), a multifunctional cytokine-like molecule, is expressed in the hematopoietic organ-wing imaginal disc complex, suggesting that BmPP is involved in both immune response and the hematopoietic process. We studied the effects of BmPP on plasmatocytes and hematopoietic organs of the silkworm. BmPP (1 microM) stimulated spreading of circulating plasmatocytes, but the percentage of spread plasmatocytes was only 20%. Over 10 nM of BmPP, however, elicited prominent spreading in 70% of young plasmatocytes discharged from cultured hematopoietic organs. Cells in hematopoietic organs that were enzymatically dispersed did not spread even after adding 100 nM of BmPP, indicating that plasmatocytes acquired BmPP-sensitivity immediately after discharge. When cultured in a medium containing larval plasma, hematopoietic organs grew markedly and discharged a large number of hemocytes, over 95% of which were morphologically plasmatocytes. The hemocyte discharge was blocked in the medium containing BmPP dose-dependently, although hematopoietic organ growth was not suppressed. These results suggest that BmPP plays important roles both in hematopoietic regulation and in the hemocyte immune reaction of the silkworm.

Plasmatocyte-spreading peptide (PSP) plays a central role in insect cellular immune defenses against bacterial infection

“…The most potent known activator of plasmatocytes is the plasmatocyte-spreading peptide (PSP) (Clark et al, 1997), homologs of which have been identified from a number of other moth species, including M. sexta (Clark et al, 2004). PSP and related homologs are the only molecules identified to date that activate plasmatocytes (Clark et al, 1997;Strand et al, 2000;Miura et al, 2002;Nakahara et al, 2003), although circumstantial evidence suggests that several other molecules besides PSP mediate plasmatocyte function (Lackie, 1988;Gillespie et al, 1997;Lavine and Strand, 2002). However, there has been no detailed investigation of the participation and role of PSP in hemocytic reactions responsible for bacterial clearance in vivo.…”

Crustacean hematopoiesis

“…Among insects, apart from Drosophila, hematopoiesis has been primarily studied in Orthoptera (Hoffmann et al, 1974;Hoffmann and Porte, 1973;Hoffmann, 1970) and Lepidoptera (Nakahara et al, 2010(Nakahara et al, , 2006(Nakahara et al, , 2003Nardi et al, 2003).Two extracellular peptides have been identified in Bombyx mori that have some impact on hematopoiesis. The paralytic peptide BmPP (NP_001036883.1), showing inhibitory activity, whereas the insulin-like peptide Bombyxin (BAA00246.1) stimulates the proliferation of hematopoietic cells (Nakahara et al, 2006(Nakahara et al, , 2003.…”

“…The paralytic peptide BmPP (NP_001036883.1), showing inhibitory activity, whereas the insulin-like peptide Bombyxin (BAA00246.1) stimulates the proliferation of hematopoietic cells (Nakahara et al, 2006(Nakahara et al, , 2003. None of these peptides were detected in the P. leniusculus transcriptome, again showing differences between species in extracellular hematopoietic growth factors and cytokines.…”

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).…”