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Pan X, Connacher RP, O'Connor MB. Control of the insect metamorphic transition by ecdysteroid production and secretion. CURRENT OPINION IN INSECT SCIENCE 2021; 43:11-20. [PMID: 32950745 PMCID: PMC7965781 DOI: 10.1016/j.cois.2020.09.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 09/02/2020] [Accepted: 09/07/2020] [Indexed: 05/07/2023]
Abstract
Ecdysteroids are a class of steroid hormones that controls molting and metamorphic transitions in Ecdysozoan species including insects, in which ecdysteroid biosynthesis and its regulation have been extensively studied. Insect ecdysteroids are produced from dietary sterols by a series of reduction-oxidation reactions in the prothoracic gland and in Drosophila they are released into the hemolymph via vesicle-mediated secretion at the time of metamorphosis. To initiate precisely controlled ecdysteroid pulses, the prothoracic gland functions as a central node integrating both intrinsic and extrinsic signals to control ecdysteroid biosynthesis and secretion. In this review, we outline recent progress in the characterization of ecdysone biosynthesis and steroid trafficking pathways and the discoveries of novel factors regulating prothoracic gland function.
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Affiliation(s)
- Xueyang Pan
- Department of Genetics, Cell Biology and Development, University of Minnesota, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, USA
| | - Robert P Connacher
- Department Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, USA
| | - Michael B O'Connor
- Department of Genetics, Cell Biology and Development, University of Minnesota, USA.
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Zhao T, Lai D, Zhou Y, Xu H, Zhang Z, Kuang S, Shao X. Azadirachtin A inhibits the growth and development of Bactrocera dorsalis larvae by releasing cathepsin in the midgut. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2019; 183:109512. [PMID: 31398584 DOI: 10.1016/j.ecoenv.2019.109512] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2019] [Revised: 07/13/2019] [Accepted: 07/30/2019] [Indexed: 06/10/2023]
Abstract
Azadirachtin, a botanical insecticide with high potential, has been widely used in pest control. Azadirachtin has shown strong biological activity against Bactrocera dorsalis in toxicological reports, but its mechanism remains unclear. This study finds that azadirachtin A inhibits the growth and development of Bactrocera dorsalis larvae. The larval weights and body sizes of the azadirachtin-treated group were significantly less than those of the control group in a concentration-dependent manner. Further, pathological sections revealed that azadirachtin destroyed the midgut cell structure and intestinal walls, while TUNEL staining showed that azadirachtin could induce apoptosis of midgut cells, and Western blot analysis indicated that Bcl-XL expression was inhibited and cytochrome c (CytC) released into the cytoplasm. The results also imply azadirachtin-induced structural alterations in the Bactrocera dorsalis larvae midgut by activation of apoptosis. RNA-seq analysis of midgut cells found that 482 and 708 unique genes were upregulated and downregulated, respectively. These differentially expressed genes (DEGs) were enriched in apoptotic and lysosomal signaling pathways and included 26 genes of the cathepsin family. qRT-PCR verified the expression patterns of some DEGs, indicating that Cathepsin F was upregulated by 278.47-fold and that Cathepsin L and Cathepsin D were upregulated by 28.06- and 8.97-fold, respectively. Finally, association analysis between DEGs and DEMs (differentially expressed metabolites) revealed that azadirachtin significantly reduced the digestion and absorption of carbohydrates, proteins, fats, vitamins and minerals in the midgut. In conclusion, azadirachtin induces the release of cathepsin from lysosomes, causing apoptosis in the midgut. Ultimately, this leads to reduced digestion and absorption of nutrient metabolites in the midgut and inhibition of the growth and development of Bactrocera dorsalis larvae.
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Affiliation(s)
- Tianyi Zhao
- College of Animal Science and Technology, Shihezi University, Xinjiang, 832003, China
| | - Duo Lai
- Key Laboratory of South Subtropical Fruit Biology and Genetic Resource Utilization (MOA), Guangdong Province Key Laboratory of Tropical and Subtropical Fruit Tree Research, Institute of Fruit Tree Research, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, China
| | - You Zhou
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Key Laboratory of Natural Pesticide and Chemical Biology of the Ministry of Education, South China Agricultural University, Guangzhou, 510642, China
| | - Hanhong Xu
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Key Laboratory of Natural Pesticide and Chemical Biology of the Ministry of Education, South China Agricultural University, Guangzhou, 510642, China
| | - Zhixiang Zhang
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, Key Laboratory of Natural Pesticide and Chemical Biology of the Ministry of Education, South China Agricultural University, Guangzhou, 510642, China.
| | - Shizi Kuang
- Key Laboratory of South Subtropical Fruit Biology and Genetic Resource Utilization (MOA), Guangdong Province Key Laboratory of Tropical and Subtropical Fruit Tree Research, Institute of Fruit Tree Research, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, China.
| | - Xuehua Shao
- Key Laboratory of South Subtropical Fruit Biology and Genetic Resource Utilization (MOA), Guangdong Province Key Laboratory of Tropical and Subtropical Fruit Tree Research, Institute of Fruit Tree Research, Guangdong Academy of Agricultural Sciences, Guangzhou, 510640, China.
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De Loof A, Vandersmissen T, Marchal E, Schoofs L. Initiation of metamorphosis and control of ecdysteroid biosynthesis in insects: The interplay of absence of Juvenile hormone, PTTH, and Ca(2+)-homeostasis. Peptides 2015; 68:120-9. [PMID: 25102449 DOI: 10.1016/j.peptides.2014.07.025] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 07/25/2014] [Accepted: 07/25/2014] [Indexed: 11/24/2022]
Abstract
The paradigm saying that release of the brain neuropeptide big prothoracicotropic hormone (PTTH) initiates metamorphosis by activating the Torso-receptor/ERK pathway in larval prothoracic glands (PGs) is widely accepted nowadays. Upon ligand-receptor interaction Ca(2+) enters the PG cells and acts as a secondary messenger. Ecdysteroidogenesis results, later followed by apoptosis. Yet, some data do not fit in this model. In some species decapitated animals can still molt, even repeatedly, and metamorphose. PTTH does not universally occur in all insect species. PGs may also have other functions; PGs as counterpart of the vertebrate thymus? There are also small PTTHs. Finally, PTTH remains abundantly present in adults and plays a role in control of ecdysteroidogenesis (=sex steroid production) in gonads. This is currently documented only in males. This urges a rethinking of the PTTH-PG paradigm. The key question is: Why does PTTH-induced Ca(2+) entry only result in ecdysteroidogenesis and apoptosis in specific cells/tissues, namely the PGs and gonads? Indeed, numerous other neuropeptides also use Ca(2+) as secondary messenger. The recent rediscovery that in both invertebrates and vertebrates at least some isoforms of Ca(2+)-ATPase need the presence of an endogenous farnesol/juvenile hormone(JH)-like sesquiterpenoid for keeping cytosolic [Ca(2+)]i below the limit of apoptosis-induction, triggered the idea that it is not primarily PTTH, but rather the drop to zero of the JH titer that acts as the primordial initiator of metamorphosis by increasing [Ca(2+)]i. PTTH likely potentiates this effect but only in cells expressing Torso. PTTH: an evolutionarily ancient gonadotropin?
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Affiliation(s)
- Arnold De Loof
- Functional Genomics and Proteomics Group, Department of Biology, KU Leuven-University of Leuven, Belgium.
| | - Tim Vandersmissen
- Department of Teacher Education, Leuven University College, Leuven, Belgium.
| | - Elisabeth Marchal
- Molecular Developmental Physiology and Signal Transduction Group, Department of Biology, KU Leuven-University of Leuven, Belgium.
| | - Liliane Schoofs
- Functional Genomics and Proteomics Group, Department of Biology, KU Leuven-University of Leuven, Belgium.
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Schiesari L, Kyriacou CP, Costa R. The hormonal and circadian basis for insect photoperiodic timing. FEBS Lett 2011; 585:1450-60. [PMID: 21354417 DOI: 10.1016/j.febslet.2011.02.026] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Revised: 02/07/2011] [Accepted: 02/21/2011] [Indexed: 01/17/2023]
Abstract
Daylength perception in temperate zones is a critical feature of insect life histories, and leads to developmental changes for resisting unfavourable seasons. The role of the neuroendocrine axis in the photoperiodic response of insects is discussed in relation to the key organs and molecules that are involved. We also discuss the controversial issue of the possible involvement of the circadian clock in photoperiodicity. Drosophila melanogaster has a shallow photoperiodic response that leads to reproductive arrest in adults, yet the unrivalled molecular genetic toolkit available for this model insect should allow the systematic molecular and neurobiological dissection of this complex phenotype.
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Pérez-Hedo M, Pena RN, Sehnal F, Eizaguirre M. Gene encoding the prothoracicotropic hormone of a moth is expressed in the brain and gut. Gen Comp Endocrinol 2010; 169:203-9. [PMID: 20804759 DOI: 10.1016/j.ygcen.2010.08.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Revised: 08/21/2010] [Accepted: 08/25/2010] [Indexed: 11/25/2022]
Abstract
The molts of lepidopteran insects are typically controlled by the brain-derived prothoracicotropic hormone (PTTH) that stimulates ecdysteroidogenesis in the prothoracic glands (PGs). We report here that the larvae and pupae of the moth Sesamia nonagrioides can molt without brain (PGs must be present), suggesting that there might be a secondary source of PTTH. We addressed this issue by characterizing spatial and temporal expression patterns of the PTTH gene. To this end we identified a major part of the corresponding cDNA. Protein deduced from this cDNA fragment consisted of 128 amino acids and showed 48-85% homology with the matching regions of PTTHs known from other Lepidoptera. Quantification of PTTH expression in major body organs of the last instar larvae revealed high expression in the brain (fading in post-feeding larvae) and considerable expression in the gut (with a maximum in post-feeding larvae). The content of PTTH message in the gut was enhanced after decapitation. It is concluded that the molts of S. nonagrioides larvae are driven by PTTH gene expression in the gut.
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Pérez-Hedo M, Eizaguirre M, Sehnal F. Brain-independent development in the moth Sesamia nonagrioides. JOURNAL OF INSECT PHYSIOLOGY 2010; 56:594-602. [PMID: 20005878 DOI: 10.1016/j.jinsphys.2009.12.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2009] [Revised: 12/01/2009] [Accepted: 12/03/2009] [Indexed: 05/28/2023]
Abstract
The caterpillars of Sesamia nonagrioides developing under long-day (LD) photoperiod pupate in the 5th or 6th instar whereas under short day (SD) conditions they enter diapause and undergo several extra larval molts. The diapause is terminated within 1-3 instars upon transfer of SD larvae to the LD conditions. Brain removal from the 6th instar larvae promotes pupation followed by imaginal development; however, one third of the SD larvae and 12% of the LD larvae debrained at the start of the instar first undergo 1-2 larval molts. The incidence of larval molts is enhanced by the brain implants. Exclusively pupal molts occur in the LD larvae debrained late in the 6th instar. Decapitation elicits pupation in both LD and SD larvae, except for some of the 4th and 5th and rarely 6th instar that are induced to a fast larval molt. The pupation of decapitated larvae is reverted to a larval molt by application of a juvenile hormone (JH) agonist. No molts occur in abdomens isolated from the head and thorax prior to the wandering stage. Abdomens isolated later undergo a larval (SD insects) or a pupal (LD insects) molt. Taken together the data reveal that in S. nonagrioides (1) several larval molts followed by a pupal and imaginal molt can occur without brain; (2) an unknown head factor outside the brain is needed for the pupal-adult molt; (3) brain exerts both stimulatory and inhibitory effect on the corpora allata (CA); (4) larval molts induced in CA absence suggest considerable JH persistence.
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Marchal E, Vandersmissen HP, Badisco L, Van de Velde S, Verlinden H, Iga M, Van Wielendaele P, Huybrechts R, Simonet G, Smagghe G, Vanden Broeck J. Control of ecdysteroidogenesis in prothoracic glands of insects: a review. Peptides 2010; 31:506-19. [PMID: 19723550 DOI: 10.1016/j.peptides.2009.08.020] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/17/2009] [Revised: 08/21/2009] [Accepted: 08/21/2009] [Indexed: 01/13/2023]
Abstract
The very first step in the study of the endocrine control of insect molting was taken in 1922. Stefan Kopec characterized a factor in the brain of the gypsy moth, Lymantria dispar which appeared to be essential for metamorphosis. This factor was later identified as the neuropeptide prothoracicotropic hormone (PTTH), the first discovery of a series of factors involved in the regulation of ecdysteroid biosynthesis in insects. It is now accepted that PTTH is the most important regulator of prothoracic gland (PG) ecdysteroidogenesis. The periodic increases in ecdysteroid titer necessary for insect development can basically be explained by the episodic activation of the PGs by PTTH. However, since the characterization of the prothoracicostatic hormone (PTSH), it has become clear that in addition to 'tropic factors', also 'static factors', which are responsible for the 'fine-tuning' of the hemolymph ecdysteroid titer, are at play. Many of these regulatory factors are peptides originating from the brain, but also other, extracerebral factors both of peptidic and non-peptidic nature are able to affect PG ecdysteroidogenesis, such as the 'classic' insect hormones, juvenile hormone (JH) and the molting hormone (20E) itself. The complex secretory pattern of ecdysteroids as observed in vivo is the result of the delicate balance and interplay between these ecdysiotropic and ecdysiostatic factors.
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Affiliation(s)
- Elisabeth Marchal
- Department of Animal Physiology and Neurobiology, K.U. Leuven, Naamsestraat 59, 3000 Leuven, Belgium
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Gu SH, Lin JL, Lin PL. PTTH-stimulated ERK phosphorylation in prothoracic glands of the silkworm, Bombyx mori: role of Ca(2+)/calmodulin and receptor tyrosine kinase. JOURNAL OF INSECT PHYSIOLOGY 2010; 56:93-101. [PMID: 19800889 DOI: 10.1016/j.jinsphys.2009.09.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2009] [Revised: 08/20/2009] [Accepted: 09/18/2009] [Indexed: 05/28/2023]
Abstract
Our previous studies showed that the prothoracicotropic hormone (PTTH) stimulated extracellular signal-regulated kinase (ERK) phosphorylation in prothoracic glands of Bombyx mori both in vitro and in vivo. In the present study, the signaling pathway by which PTTH activates ERK phosphorylation was further investigated using PTTH, second messenger analogs, and various inhibitors. ERK phosphorylation induced by PTTH was partially reduced in Ca(2+)-free medium. The calmodulin antagonist, calmidazolium, partially inhibited both PTTH-stimulated ERK phosphorylation and ecdysteroidogenesis, indicating the involvement of calmodulin. When the prothoracic glands were treated with agents that directly elevate the intracellular Ca(2+) concentration [either A23187, thapsigargin, or the protein kinase C (PKC) activator, phorbol 12-myristate acetate (PMA)], a great increase in ERK phosphorylation was observed. In addition, it was found that PTTH-stimulated ecdysteroidogenesis was greatly attenuated by treatment with PKC inhibitors (either calphostin C or chelerythrine C). However, PTTH-stimulated ERK phosphorylation was not attenuated by the above PKC inhibitors, indicating that PKC is not involved in PTTH-stimulated ERK phosphorylation. A potent and specific inhibitor of insulin receptor tyrosine kinase, HNMPA-(AM)(3), greatly inhibited the ability of PTTH to activate ERK phosphorylation and stimulate ecdysteroidogenesis. However, genistein, another tyrosine kinase inhibitor, did not inhibit PTTH-stimulated ERK phosphorylation, although it did markedly attenuate the ability of A23187 to activate ERK phosphorylation. From these results, it is suggested that PTTH-stimulated ERK phosphorylation is only partially Ca(2+)- and calmodulin-dependent and that HNMPA-(AM)(3)-sensitive receptor tyrosine kinase is involved in activation of ERK phosphorylation by PTTH.
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Affiliation(s)
- Shi-Hong Gu
- Department of Zoology, National Museum of Natural Science, 1 Kuan-Chien Road, Taichung 404, Taiwan, ROC.
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Gu SH, Lin JL, Lin PL, Chen CH. Insulin stimulates ecdysteroidogenesis by prothoracic glands in the silkworm, Bombyx mori. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2009; 39:171-179. [PMID: 19049871 DOI: 10.1016/j.ibmb.2008.10.012] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2008] [Revised: 10/27/2008] [Accepted: 10/30/2008] [Indexed: 05/27/2023]
Abstract
It is generally accepted that the prothoracicotropic hormone (PTTH) is the stimulator of ecdysteroidogenesis by prothoracic glands in larval insects. In the present study, we investigated activation of ecdysteroidogenesis by bovine insulin in prothoracic glands of the silkworm, Bombyx mori. The results showed that the insulin stimulated ecdysteroidogenesis during a long-term incubation period and in a dose-dependent manner. In addition, insulin also stimulated both DNA synthesis and viability of prothoracic glands. Insulin-stimulated ecdysteroidogenesis was blocked by either LY294002 or wortmannin, indicating involvement of the phosphatidylinositol 3-kinase (PI3K) signaling pathway. Activation of ecdysteroidogenesis by insulin appeared to be developmentally regulated. Moreover, in vitro activation of ecdysteroidogenesis of prothoracic glands by insulin was also verified by in vivo experiments: injection of insulin into day 6 last instar larvae greatly increased both hemolymph ecdysteroid levels and ecdysteroidogenesis 24 h after the injection, indicating its possible in vivo function. Phosphorylation of Akt and the insulin receptor was stimulated by insulin, and stimulation of Akt phosphorylation appeared to be PI3K-dependent and developmentally regulated. Insulin did not stimulate extracellular signal-regulated kinase (ERK) signaling of the prothoracic glands. These results suggest that in silkworm prothoracic glands, in addition to the PTTH and an autocrine factor, ecdysteroidogenesis is also stimulated by insulin during development.
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Affiliation(s)
- Shi-Hong Gu
- Department of Zoology, National Museum of Natural Science, Taichung, Taiwan, ROC.
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Gu SH, Lin JL, Lin PL, Kou R, Smagghe G. Effects of RH-5992 on ecdysteroidogenesis of the prothoracic glands during the fourth larval instar of the silkworm, Bombyx mori. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2008; 68:197-205. [PMID: 18618762 DOI: 10.1002/arch.20262] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Stage-dependent effects of RH-5992 on ecdysteroidogenesis of the prothoracic glands during the fourth larval instar of the silkworm, Bombyx mori, were studied in the present report. When larvae were treated with RH-5992 during the early stages of the fourth larval instar (between day 0 and day 1), initially ecdysteroid levels in the hemolymph were inhibited. However, 24 h after RH-5992 application, ecdysteroid levels were greatly increased as compared with those treated with acetone. The examination of the in vitro prothoracic gland activity upon RH-5992 application during the early stages of the fourth larval instar confirmed a short-term inhibitory effect. When RH-5992 was applied to the later stages of the fourth larval instar, no effects on both hemolymph ecdysteroid levels and prothoracic gland activity were observed. Addition of RH-5992 to incubation medium strongly inhibited ecdysteroid secretion by the prothoracic glands from the early fourth instar, indicating direct action of RH-5992 on ecdysteroidogenesis by prothoracic glands. Four hours after application with RH-5992 on day 1.5, prothoracic glands still showed an activated response to PTTH in both PTTH-cAMP signaling and the extracellular signal-regulated kinase (ERK) signaling. Moreover, addition of RH-5992 to incubation medium did not interfere with the stimulatory effect of the glands to PTTH in ecdysteroidogenesis. These results indicated that both PTTH-cAMP signaling and PTTH-ERK signaling may not be involved in short-term inhibitory regulation by RH-5992.
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Affiliation(s)
- Shi-Hong Gu
- Department of Zoology, National Museum of Natural Science, Taichung, Taiwan, ROC.
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Lin JL, Gu SH. In vitro and in vivo stimulation of extracellular signal-regulated kinase (ERK) by the prothoracicotropic hormone in prothoracic gland cells and its developmental regulation in the silkworm, Bombyx mori. JOURNAL OF INSECT PHYSIOLOGY 2007; 53:622-31. [PMID: 17451740 DOI: 10.1016/j.jinsphys.2007.03.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2007] [Revised: 03/05/2007] [Accepted: 03/05/2007] [Indexed: 05/15/2023]
Abstract
In this study, we investigated activation of the extracellular signal-regulated kinase (ERK) by the prothoracicotropic hormone (PTTH) in prothoracic gland cells of the silkworm, Bombyx mori. The results showed that the PTTH stimulated ERK phosphorylation as this depends on time and dose and ecdysteroidogenic activity. The ERK phosphorylation inhibitors, PD 98059 and U0126, blocked both basal and PTTH-stimulated ERK phosphorylation and ecdysteroidogenesis. In addition, activation of glandular ERK phosphorylation by the PTTH appeared to be developmentally regulated with the refractoriness of gland cells to the PTTH occurring during the latter stages of both the fourth and last larval instars. Moreover, in vitro activation of ERK phosphorylation of prothoracic glands by the PTTH was also verified by in vivo experiments: injection of the PTTH into day 6 last instar larvae greatly increased the activity of glandular ERK phosphorylation and ecdysteroidogenesis. These results suggest that development-specific changes in ERK phosphorylation may play a role in PTTH stimulation of ecdysteroidogenesis.
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Affiliation(s)
- Ju-Ling Lin
- Department of Zoology, National Museum of Natural Science, 1 Kuan Chien Road, Taichung 404, Taiwan, ROC
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