Regulation of cytochrome P450, CYP4C1, gene expression by hypertrehalosemic hormone in the fat body of the neotropical cockroach, Blaberus discoidalis /
The hypertrehalosemic hormone (Bld-HrTH) up-regulates expression of a cytochrome P450 family 4 gene, CYP4C], in the fat body of adult Blaberus discoidalis cockroaches. Bld-HrTH elevates CYP4CI-mRNA levels rapidly in a dose-dependent manner with a maximum response at 8 h. Gene expression reached its...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1995.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742744531&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The hypertrehalosemic hormone (Bld-HrTH) up-regulates expression of a cytochrome P450 family 4 gene, CYP4C], in the fat body of adult Blaberus discoidalis cockroaches. Bld-HrTH elevates CYP4CI-mRNA levels rapidly in a dose-dependent manner with a maximum response at 8 h. Gene expression reached its upper limit regardless of whether the hormone was administered in a single large or repeated small doses. Bld- HrTH appears to influence CYP4C] transcription or stability without involvement by intervening regulatory genes. Age-related profiles of the CYP4C I transcript differed between males and females. In males, CYP4Cl-mRNA declined only slightly with age and was elevated by starvation. Refeeding eliminated this starvation effect indicating that the increase in CYP4C] expression is due to nutrient shortage. Decapitation prevented the increase by starvation, and cardiacectomized, starving animals failed to maintain their over-expression of CYP4C]. This suggested that the starvation effect was mediated by the secretion of Bld-HrTH from the corpora cardiaca (CC). Despite a starvation effect, as in adult males, in adult females CYP4C I transcript nearly disappeared after day 4. Application of methoprene, a juvenile hormone (JH) analog, to decapitated (JH-deficient) or allatectornized females decreased the fat body CYP4Cl transcript. This result suggested that JH suppresses CYP4Cl expression in females. Administration of Bld-HrTH elevated CYP4C] expression in intact females when transcript levels were naturally minimal; thus, Bld-HrTH appeared to override the JH inhibition. These results indicate the existence of a dual hormonal regulation of CYP4CI expression in adult female B. discoidalis. This phenomenon is sex-specific because CYP4Cl expression in males was not sensitive to JH suppression. The intracellular signal transduction cascade for Bld-HrTH-regulated CYP4C] expression did not indicate the involvement of either CAMP or CGMP; however, it was Ca - the involvement of either CAMP or CGMP; however, it was Ca - dependent. Therefore, Ca 2+ is a likely component of the second messenger system for Bld-HrTH-regulated CYP4Cl expression. Moreover, CYP4CI expression may be facilitated by the activation of a calcium/calmodulin-dependent protein kinase. Finally, the up-regulation of CYP4Cl expression by Bld-HrTH and the importance of Ca 2+ were demonstrated using fat body in vitro, indicating that the elevation of CYP4Cl expression was a direct result of Bld-HrTH actions on the fat body. These studies demonstrate that regulation of CYP4C1 expression is influenced by gender, age, Bld-HrTH, JH, and the nutritional state of the animal. |
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| Item Description: | Vita. "Major Subject: Entomology". In title, numerals are used. |
| Physical Description: | ix, 106 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |