Isolation and identification of a plasmatocyte-spreading peptide from the hemolymph of the lepidopteran insect Pseudoplusia includens

• Published in: The Journal of biological chemistry Vol. 272; no. 37; pp. 23440 - 23447
• Main Authors: Clark, K.D. (University of Wisconsin, Madison.), Pech, L.L, Strand, M.R
• Format: Journal Article
• Language: English
• Published: United States 12-09-1997
• Subjects: ADHESION; Amino Acid Sequence; AMINO ACID SEQUENCES; Animals; Biological Assay; BLOOD CELLS; Cell Adhesion - drug effects; CELL AGGREGATION; Cell Size - drug effects; CELL SPREADING; CELLULE SANGUINE; CELULAS SANGUINEAS; CHEMICAL COMPOSITION; CHRYSODEIXIS; CHRYSODEIXIS INCLUDENS; COMPOSICION QUIMICA; COMPOSITION CHIMIQUE; Dose-Response Relationship, Drug; ESTIMULO; HAEMOLYMPH; HEMOCYTES; Hemocytes - drug effects; Hemocytes - physiology; HEMOLINFA; Hemolymph - chemistry; HEMOLYMPHE; INTERACTIONS; Intercellular Signaling Peptides and Proteins; LARVAE; LARVAS; LARVE; Lepidoptera - chemistry; MECHANICAL PROPERTIES; MOLECULAR SEQUENCE DATA; PEPTIDE; Peptide Biosynthesis; PEPTIDES; Peptides - isolation & purification; Peptides - pharmacology; PEPTIDOS; PROPIEDADES MECANICAS; PROPRIETE MECANIQUE; PSEUDOPLUSIA INCLUDENS; Sequence Analysis; Sequence Homology, Amino Acid; STIMULI; STIMULUS
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.272.37.23440

Insect blood cells (hemocytes) play an essential role in defense against parasites and other pathogenic organisms that infect insects. A key class of hemocytes involved in insect cellular immunity is plasmatocytes. Here we describe the isolation and identification of a peptide from the moth Pseudoplusia includens that mediates the spreading of plasmatocytes to foreign surfaces. This peptide, designated plasmatocyte-spreading peptide (PSP1), contains 23 amino acid residues in the following sequence: H-ENFNGGCLAGYMRTADGRCKPTF-OH. In vitro assays using the synthetic peptide at concentrations >/=2 nM induced plasmatocytes from P. includens to spread on the surface of culture dishes. Injection of this peptide into P. includens larvae caused a transient depletion of plasmatocytes from circulation. Labeling studies indicated that this peptide induced 75% of plasmatocytes that were double-labeled by the monoclonal antibodies 49G3A3 and 43E9A8 to spread, whereas plasma induced significantly more plasmatocytes to spread. This suggests that only a certain subpopulation of plasmatocytes responds to the peptide and that other peptidyl factors mediate plasmatocyte adhesion responses.