Post-feeding induction of trypsin in the midgut of Aedes aegypti L. (Diptera: Culicidae) is separable into two cellular phases |
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| Institution: | 1. Center for Applied Life Science, Hanbat National University, Taejon, 305-719, Republic of Korea;2. Genome Research Center for Hematopoietic Diseases, Chonnam National University Hwasun Hospital, Hwasun, 519-763, Republic of Korea;3. Medical Genomics Research Center, Korea Research Institute of Bioscience and Biotechnology, 125 Gwahangno, Yuseong-gu, Daejeon, 305-806, Republic of Korea;4. New Drug Development Center, Daegu-Gyeongbuk Medical Innovation Foundation, Daegu, 41061, Republic of Korea;5. Department of Biology, Chonnam National University, Gwangju, 500-757, Republic of Korea;1. Divisions of Biostatistics and Epidemiology, School of Public Health, University of California, Berkeley, CA, USA;2. Global Health Group, University of California, San Francisco, CA, USA;3. Environmental Health and Ecological Sciences Thematic Group, Ifakara Health Institute, Dar es Salaam, Tanzania;1. British Columbia Ministry of Forests, Lands, Natural Resource Operations, 727 Fisgard Street, Victoria, BC V8W1N1, Canada;2. Environmental Science and Engineering Programs, Natural Resources and Environmental Studies Institute, University of Northern British Columbia, 3333 University Way Prince George, BC V2N 4Z9, Canada;1. Department of Life Sciences, University of Modena and Reggio Emilia, Italy;2. Department of Medical and Surgical Sciences, University of Modena and Reggio Emilia, Hematology Unit, AOU Policlinico, Modena, Italy;1. Research Group of Insect Physiology and Molecular Ethology, KU Leuven, Naamsestraat 59, B-3000, Belgium;2. Research Group of Functional Genomics and Proteomics, KU Leuven, Naamsestraat 59, B-3000, Belgium |
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| Abstract: | The induction of trypsin activity in the midgut of the mosquito, Aedes aegypti, was studied following meals of chicken blood, and several protein and peptide diets. Various concentrations of bovine serum albumin (BSA) in 0.15 M NaCl stimulated trypsin activity, in a similar fashion to the initial increase observed after a normal blood meal. Trypsin synthesis was also initiated when Ae. aegypti were fed on glutaraldehyde cross-linked BSA and on BSA fragments prepared by both pepsin and cyanogen bromide cleavage. Non-soluble proteins, in the form of glutaraldehyde-fixed erythrocyte ghosts, induced a delayed and reduced trypsin response, whilst small peptides from neutralized liver digests did not induce trypsin activity until 8–10 h after feeding. Metabolic inhibitors had varying effects on the post-feeding activity of trypsin stimulated by BSA feeding. Cycloheximide, a peptidyl transferase inhibitor prevented expression of all activity in vivo, whereas α-amanitin (RNA-polymerase inhibitor) did not affect trypsin activity in the first 10 h after feeding. At 20 μg/ml concentration in the diet, actinomycin D (RNA synthesis inhibitor) caused temporary superinduction followed by inhibition of trypsin activity, but at lower concentrations, the later phase of trypsin activity was inhibited. The results suggest that post-feeding induction of trypsin activity in Ae. aegypti is a two-phase process regulated at the midgut cellular level. The first phase of trypsin synthesis is stimulated by soluble proteins of variable molecular weights, and only involves translation of messenger RNA already available within the midgut cells. The second phase is stimulated by small peptides and requires complete synthesis of new mRNA from DNA. |
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