Bacteria-induced protein P4 (hemolin) from Manduca sexta: a member of the immunoglobulin superfamily which can inhibit hemocyte aggregation.
The synthesis of a number of hemolymph proteins is induced in insects in response to bacterial infections. The major induced hemolymph protein in larvae of Manduca sexta is a glycoprotein of Mr = 48,000 known as P4. We have isolated a clone for P4 from a fat body cDNA library constructed from RNA isolated from larvae injected with bacteria. The cDNA has an open reading frame encoding a 411 residue polypeptide with a hydrophobic NH2-terminal sequence, which appears to be a signal peptide. Analysis of the deduced amino acid sequence shows that P4 is a member of the immunoglobulin (Ig) gene superfamily, and is composed largely of four C2 type Ig domains. The M. sexta P4 amino acid sequence is 60% identical with hemolin (P4) from Hyalophora cecropia. The name "hemolin" has also been adopted for the M. sexta P4 protein. Hemolin mRNA levels in fat body begin to increase within 1 h after injection of bacteria into fifth instar larvae and within 4 h after injection of adults. Hemolin associates with the surface of hemocytes and inhibits hemocyte aggregation responses, suggesting a role for the protein in modulating hemocyte adhesion during recognition and response to bacterial infections in insects.
Ladendorff
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NE
Department of Biochemistry, University of Arizona, Tucson.
Kanost
M R
MR
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002449:Cell Aggregation / Q000276:immunology; D004247:DNA / Q000235:genetics; D004926:Escherichia coli / Q000276:immunology; D006434:Hemocytes / Q000276:immunology; D007136:Immunoglobulins / Q000235:genetics; D019476:Insect Proteins; D008969:Molecular Sequence Data; D009036:Moths / Q000235:genetics / Q000276:immunology*; D005810:Multigene Family; D011506:Proteins / Q000235:genetics / Q000276:immunology*
D007136:Immunoglobulins; D019476:Insect Proteins; D011506:Proteins; C066846:hemolin; D004247:DNA