Immunity proteins from mosquito cell lines include three defensin A isoforms from Aedes aegypti and a defensin D from Aedes albopictus.
An Aedes aegypti mosquito cell line, Aag-2, exhibits a response to immune stimulation that is qualitatively similar to that of C7-10 cultured cells from the related mosquito, Aedes albopictus. Using SDS polyacrylamide gels, we found that a small peptide was preferentially induced by the treatment of growing cells with heat-killed, Gram-positive bacteria. By an analogy with other studies, this small peptide was postulated to be a member of the defensin family of insect immunity peptides. A differential display was used to obtain partial polymerase chain reaction products corresponding to mRNAs that were preferentially expressed in induced cells. One of these products, which contained the partial sequence of a defensin gene, was used to screen cDNA libraries from Ae. aegypti and Ae. albopictus cells. From Ae. aegypti cells, we found two previously described isoforms (A1 and A4) of mosquito defensin A, as well as a new isoform which we defined as A5. From Ae. albopictus cells, we found a new mature mosquito defensin, named D, which contains proline and isoleucine as the final amino acids. In both Ae. aegypti and Ae. albopictus cell lines, the expression of defensin mRNA was visible on Northern blots as early as 3 h after exposure to heat-killed bacteria, and defensin mRNA abundance was maximal at 12-36 h after induction.
Gao
Y
Y
Department of Entomology, University of Minnesota, 1980 Folwell Ave., St. Paul, MN 55108, USA.
Hernandez
V P
VP
Fallon
A M
AM
D000330:Aedes / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents; D001483:Base Sequence; D002460:Cell Line; D018076:DNA, Complementary; D023082:Defensins; D019476:Insect Proteins / Q000096:biosynthesis / Q000235:genetics*; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000096:biosynthesis / Q000235:genetics
D000900:Anti-Bacterial Agents; D018076:DNA, Complementary; D023082:Defensins; D019476:Insect Proteins; D020033:Protein Isoforms; C058181:insect defensin A; C400841:insect defensin D