Journal
JOURNAL OF INSECT PHYSIOLOGY
Volume 51, Issue 9, Pages 1041-1054Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jinsphys.2005.05.002
Keywords
fluid secretion; actin; cytochalasin D; phalloidin; mosquito development
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Funding
- NIDDK NIH HHS [R01-DK59922] Funding Source: Medline
- NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES [R01DK059922] Funding Source: NIH RePORTER
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Fluid secretion by mosquito Malpighian tubules is critical to maintaining fluid and electrolyte balance after a blood meal. Endogenous cAMP levels increase in Malpighian tubules after a blood meal. Here, we determined if corresponding changes in intracellular actin distribution occur after a blood meal or dibutyryl-cAMP (db-cAMP) stimulation and whether altering actin turnover inhibits secretion. In untreated Malpighian tubules, beta-actin immunostaining was more intense in the apical region of adult Malpighian tubules than in the cytoplasm. Stimulation by a blood meal or db-cAMP significantly decreased beta-actin immunostaining in the non-apical region of the cell. Db-cAMP had similar effects in larvae and pupae Malpighian tubules. In contrast, no detectable shift in F-actin distribution was detected; however, F-actin bundles within the cytoplasm increased in size after treatment with db-cAMP. Pretreatment of Malpighian tubules with agents perturbing actin fiber assembly and disassembly decreased basal secretion rates and inhibited the stimulatory effects of db-cAMP. Our results show (1) beta-actin redistributes toward the apical membrane after a blood meal and this correlates temporally with increase urine flow rate and intracellular cAMP levels, (2) Malpighian tubules from all developmental stages exhibit this same response to db-cAMP-stimulation, and (3) dynamic assembly and disassembly of beta-actin is required for db-cAMP-stimulated secretion. (c) 2005 Elsevier Ltd. All rights reserved.
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