Actin redistribution in mosquito Malpighian tubules after a blood meal and cyclic AMP stimulation

• Published in: Journal of insect physiology Vol. 51; no. 9; pp. 1041 - 1054
• Main Authors: Karas, Katherine, Brauer, Philip, Petzel, David
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.09.2005
• Subjects: Actin; actin fibrils; Actins - metabolism; Aedes - cytology; Aedes - drug effects; Aedes - metabolism; Aedes aegypti; Animals; Blood; Bucladesine - pharmacology; Culicidae; cyclic AMP; Cyclic AMP - pharmacology; Cytochalasin D; cytoskeleton; Cytoskeleton - metabolism; Dose-Response Relationship, Drug; Eating - physiology; Female; Fluid secretion; fluorescent dyes; hematophagy; immunohistochemistry; intracellular distribution; Malpighian tubules; Malpighian Tubules - cytology; Malpighian Tubules - drug effects; Malpighian Tubules - metabolism; Mosquito development; Phalloidin; Phalloidine - pharmacology; secretion; Water-Electrolyte Balance; Cytochalasin D; Phalloidin; Fluid secretion; Actin; Mosquito development
• ISSN: 0022-1910; 1879-1611
• DOI: 10.1016/j.jinsphys.2005.05.002

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, β-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 β-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) β-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 β-actin is required for db-cAMP-stimulated secretion.