Plasmatocyte spreading peptide (PSP1) and growth blocking peptide (GBP) are multifunctional homologs

Strand, Michael R.; Hayakawa, Yoichi; Clark, Kevin D.

doi:10.1016/s0022-1910(99)00171-7

Cited by 119 publications

(114 citation statements)

References 26 publications

Supporting

Mentioning

111

Contrasting

Order By: Relevance

“…Both purified and synthetic PSP1 peptide induce plasmatocytes to rapidly adhere and spread across foreign surfaces at concentrations greater than 1 nmol l -1 (Clark et al, 1998;Wang et al, 1999). PSP1 homologs have been identified from other Lepidoptera and, based on the consensus sequence of their N termini, these molecules are collectively referred to as the ENF peptide family (Strand et al, 2000). ENF family members have very similar sequences (>70% identity) but their reported functions are diverse: these include growth-inhibiting and mitogenic activities (growth-blocking peptide, GBP), induction of paralysis (paralytic peptides, PP) and regulation of hemocyte behavior (plasmatocyte-spreading peptide) (reviewed by Matsumoto et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

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

Eleftherianos

Yadi

et al. 2009

Journal of Experimental Biology

View full text Add to dashboard Cite

SUMMARYInsect hemocytes (blood cells) are a central part of the insect's cellular response to bacterial pathogens, and these specialist cells can both recognize and engulf bacteria. During this process, hemocytes undergo poorly characterized changes in adhesiveness. Previously, a peptide termed plasmatocyte-spreading peptide (PSP), which induces the adhesion and spreading of plasmatocytes on foreign surfaces, has been identified in lepidopteran insects. Here, we investigate the function of this peptide in the moth Manduca sexta using RNA interference (RNAi) to prevent expression of the precursor protein proPSP. We show that infection with the insect-specific bacterial pathogen Photorhabdus luminescens and non-pathogenic Escherichia coli induces proPSP mRNA transcription in the insect fat body but not in hemocytes; subsequently, proPSP protein can be detected in cell-free hemolymph. We used RNAi to silence this upregulation of proPSP and found that the knock-down insects succumbed faster to infection with P. luminescens, but not E. coli. RNAi-treated insects infected with E. coli showed a reduction in the number of circulating hemocytes and higher bacterial growth in hemolymph as well as a reduction in overall cellular immune function compared with infected controls. Interestingly, RNAi-mediated depletion of proPSP adversely affected the formation of melanotic nodules but had no additional effect on other cellular responses when insects were infected with P. luminescens, indicating that this pathogen employs mechanisms that suppress key cellular immune functions in M. sexta. Our results provide evidence for the central role of PSP in M. sexta cellular defenses against bacterial infections. Supplementary material available online at

show abstract

Section: Introductionmentioning

confidence: 99%

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

Eleftherianos

Yadi

et al. 2009

Journal of Experimental Biology

View full text Add to dashboard Cite

show abstract

“…Binding Constants of Representative Peptides-Prior analysis indicated that several residues are invariant among ENF peptide family members (8,16). These include Cys 7 and Cys 19 , Thr 14 and Thr 22 , all of the charged amino acids in the structured C terminus (Arg 13 , Asp 16 , Arg 18 , and Lys 20 ), and the three N-terminal residues Glu 1 , Asn 2 , and Phe 3 .…”

Section: Resultsmentioning

confidence: 99%

“…This biologically inactive precursor is then cleaved by an unknown protease to release the mature 23-amino acid peptide (ENFNGGCLAGYMRTADGRCKPTF). PSP homologs have been identified from a number of other moth species, and based on the consensus sequence of their N termini (Glu-Asn-Phe-X-X-Gly), these molecules are collectively referred to as the ENF peptide family (8). Other ENF peptides besides PSP also function as plasmatocyte activators, suggesting these molecules may be of widespread importance as regulators of the cellular immune response in Lepidoptera (8 -10).…”

mentioning

confidence: 99%

Specific Residues in Plasmatocyte-spreading Peptide Are Required for Receptor Binding and Functional Antagonism of Insect Immune Cells

Clark

Garczynski

Arora

et al. 2004

Journal of Biological Chemistry

View full text Add to dashboard Cite

Plasmatocyte-spreading peptide (PSP) is a 23-amino acid cytokine that activates a class of insect immune cells called plasmatocytes. PSP consists of two regions:an unstructured N terminus (1-6) and a highly structured core (7-23). Prior studies identified specific residues in both the structured and unstructured regions required for biological activity. Most important for function were Arg 13 , Phe 3 , Cys 7 , Cys 19 , and the N-terminal amine of Glu 1 . Here we have built on these results by conducting cell binding and functional antagonism studies. Alanine replacement of Met 12 (M12A) resulted in a peptide with biological activity indistinguishable from PSP. Competitive binding experiments using unlabeled and 125 I-M12A generated an IC 50 of 0.71 nM and indicated that unlabeled M12A, at concentrations >100 nM, completely blocked binding of label to hemocytes. We then tested the ability of other peptide mutants to displace 125 I-M12A at a concentration of 100 nM. In the structured core, we found that Cys 7 and Cys 19 were essential for cell binding and functional antagonism, but these effects were likely because of the importance of these residues for maintaining the tertiary structure of PSP. Arg 13 , in contrast, was also essential for binding and activity but is not required for maintenance of structure. In the unstructured N-terminal region, deletion of the phenyl group from Phe 3 yielded a peptide that reduced binding of 125 I-M12A 326-fold. This and all other mutants of Phe 3 we bioassayed were unable to antagonize PSP. Deletion of Glu 1 in contrast had almost no effect on binding and was a strong functional antagonist. Experiments using a photoaffinity analog indicated that PSP binds to a single 190-kDa protein.

show abstract

“…Activation of the prophenoloxidase cascade in locusts presumably involves activation of the haemocytes, which could then release other signalling molecules such as cytokines or effector molecules such as reactive oxygen species. There is evidence for the presence of cytokines in insects, most notably plasmatocyte-spreading peptide and growth-blocking peptide in Lepidoptera (Strand et al, 2000;Wang et al, 1999). If cytokines are indeed released from the haemocytes in response to immunogens in locusts, these could be the effector molecules that bring about the hyperlipaemia observed after immune challenge.…”

Section: Discussionmentioning

confidence: 99%

Induced hyperlipaemia and immune challenge in locusts

Mullen

Lightfoot

Goldsworthy

2004

Journal of Insect Physiology

View full text Add to dashboard Cite

Injections of immunogens, such as β-1,3-glucan or lipopolysaccharide (LPS), bring about a marked hyperlipaemia with associated changes in lipophorins and apolipophorin-III in the haemolymph of Locusta migratoria. These changes are similar to those observed after injection of adipokinetic hormone (AKH). The possibility that endogenous AKH is released as part of the response to these immunogens is investigated using passive immunisation against AKH-I, and measurement of AKH-I titre in the haemolymph after injection of immunogens. The data presented show that, despite the similarity of the changes brought about by the presence of immunogens in the haemolymph to those brought about by AKH, there is no release of endogenous AKH after injection of laminarin or LPS. A direct effect of the immunogens on release of neutral lipids by the fat body cannot be demonstrated in vitro, and the mechanism by which hyperlipaemia is induced during immune challenge remains uncertain.

show abstract

Plasmatocyte spreading peptide (PSP1) and growth blocking peptide (GBP) are multifunctional homologs

Cited by 119 publications

References 26 publications

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

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

Specific Residues in Plasmatocyte-spreading Peptide Are Required for Receptor Binding and Functional Antagonism of Insect Immune Cells

Induced hyperlipaemia and immune challenge in locusts

Contact Info

Product

Resources

About