Structure and Function of New Neurotransmitters in Brains in the Silkworm Bombyx Mori

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1) In the case of the silkworm, an intrinsic diapause hormone secreted from subesophageal ganglion in the maternal-pupal stage, acts on ovaries and embryonic development arrests in oviposited eggs. AnyParP (a paralytic peptide isolated from the wild silkmoth, Antheraea yamamai, named as AnyParP) had the same function with this diapause hormone. Even if the sequence of amino acids between AnyParP (23 residues and C-terminal is carboxylic acid) and diapause hormone (24 residues and C-terminal is amide) is entirely different, both peptides can elicit the same function in embryonic diapause. This is the first report of a functional mimicry of the silkworm diapasue hormone by an unrelated insect peptide2) This study isolated a protein from pupal brain extract of the silkworm, Bomby mori using two chromatographic steps, and identified its N-terminal amino acid sequence. Based on the amino acid sequence, degenerate oligodeoxynucleotide was synthesized and used as a hybridization probe to screen a pupal brain cDNA library. The sequence analysis of the identified cDNA clones indicated that a 603 bp open reading frame encodes a 201-amino-acid protein containing a 15-amino-acid leader peptide. This protein has high similarity to the Galleria mellonella Gallerin as a member of the lipocalin family. We named this novel protein from the Bombyx central nervous system as Bombyrin. The immunohistochemistry and Western blot analysis indicated that Bombyrin is only expressed in the central nervous system (CNS) of Bombyx mori.3) The immunoactivity of P2X_1-like receptor was first found in the central nervous system of insects, using P2X_1 antibody against the peptide of mammalian P2X_1 receptor 382-399. Six pairs of immunoreactive somata were distributed in brains of 5th instar larvae and pupae of Bombyx mori, and they showed a relationship between developmental stages and a specific P2 X_1-like protein.