Actin redistribution in mosquito malpighian tubules after a blood meal and cyclic AMP stimulation.
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.
Department of Biomedical Sciences, Creighton University School of Medicine, Omaha, NE 68178, USA.
Katherine
K
Karas
Philip
P
Brauer
David
D
Petzel
D000199:Actins / Q000378:metabolism*; D000330:Aedes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D000818:Animals; D001769:Blood; D003994:Bucladesine / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology*; D003599:Cytoskeleton / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004435:Eating / Q000502:physiology*; D005260:Female; D008317:Malpighian Tubules / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010590:Phalloidine / Q000494:pharmacology; D014882:Water-Electrolyte Balance
D000199:Actins; D010590:Phalloidine; D003994:Bucladesine; D000242:Cyclic AMP