Small GTP-binding proteins in the brain-corpus cardiacum-corpus allatum complex of the silkworm, Bombyx mori: involvement in the secretion of prothoracicotropic hormone.
At least three GTP-binding proteins (G-proteins), 28, 25, and 21 kDa, were found in the brain-corpus cardiacum-corpus allatum complex (BR-CC-CA) of the silkworm, Bombyx mori. They bound to GTP and GDP specifically among nucleotides tested, indicating that these proteins are small G-proteins. The 25 kDa G-protein showed a cross-reactivity to anti-rab3A antibody, while it did not cross-react with anti-rhoA, rab3B, and anti-ras antibodies. On the other hand, the 28 and 21 kDa G-proteins showed no cross-reactivity to any of those antibodies tested. Immunoblot analysis using the anti-rab3A antibody demonstrated that the 25 kDa G-protein was detected preferentially in the BR-CC-CA, and to some extent in the suboesophageal ganglion, but not in the salivary gland, fat body, prothoracic gland, and oesophagus. These results suggested that the 25 kDa G-protein was a member of the rab family of G-proteins. Furthermore, 1 mM GTP gamma S capable of activating G-proteins induced BR-CC-CA to release PTTH under the conditions that stimulation of the PTTH release with hetero-trimeric G-protein was suppressed. These results indicated that the small G-proteins may possibly contribute to PTTH release in Bombyx mori.
Shirai
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Laboratory of Molecular Pharmacology, Kobe University, Hyogo, Japan. shirai@kobe-u.ac.jp
Uno
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T
Aizono
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D000818:Animals; D000906:Antibodies / Q000276:immunology; D015139:Blotting, Southern; D015153:Blotting, Western; D012831:Bombyx / Q000737:chemistry / Q000378:metabolism*; D001923:Brain Chemistry / Q000502:physiology*; D003335:Corpora Allata / Q000737:chemistry / Q000378:metabolism*; D003429:Cross Reactions; D004591:Electrophoresis, Polyacrylamide Gel; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism; D006023:Glycoproteins / Q000096:biosynthesis / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000737:chemistry; D006153:Guanosine Diphosphate / Q000737:chemistry; D006160:Guanosine Triphosphate / Q000737:chemistry; D007301:Insect Hormones / Q000096:biosynthesis / Q000378:metabolism*; D008297:Male; D051379:Mice; D009479:Neuropeptides / Q000096:biosynthesis / Q000378:metabolism*; D011817:Rabbits; D014018:Tissue Distribution
D000906:Antibodies; D006023:Glycoproteins; D007301:Insect Hormones; D009479:Neuropeptides; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C009089:prothoracicotropic hormone; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins