Disassembly of Subplasmalemmal Actin Filaments Induces Cytosolic Ca2+ Increases in Astropecten aranciacus Eggs

Cellular Physiology and Biochemistry

Filip Vasilev¹ 

关键词: Actin;    Calcium;    Fertilization;    Phospholipase C;    Inositol trisphosphate;    Latrunculin;   

DOI  :  10.1159/000492523

学科分类：分子生物学，细胞生物学和基因

来源: S Karger AG

【 摘 要 】

Background/Aims Eggs of all animal species display intense cytoplasmic Ca2+ increases at fertilization. Previously, we reported that unfertilized eggs of Astropecten aranciacus exposed to an actin drug latrunculin A (LAT-A) exhibit similar Ca2+ waves and cortical flashes after 5-10 min time lag. Here, we have explored the molecular mechanisms underlying this unique phenomenon. Methods Starfish eggs were pretreated with various agents such as other actin drugs or inhibitors of phospholipase C (PLC), and the changes of the intracellular Ca2+ levels were monitored by use of Calcium Green in the presence or absence of LAT-A. The concomitant changes of the actin cytoskeleton were visualized with fluorescent F-actin probes in confocal microscopy. Results We have shown that the LAT-A-induced Ca2+ increases are related to the disassembly of actin flaments i) not only LAT-A but also other agents depolymerizing F-actin (i.e. cytochalasin B and mycalolide B) induced similar Ca2+ increases, albeit with slightly lower efficiency; ii) drugs stabilizing F-actin (i.e. phalloidin and jasplakinolide) either blocked or significantly delayed the LAT-A-induced Ca2+ increases. Further studies utilizing pharmacological inhibitors of PLC (U-73122 and neomycin), dominant negative mutant of PLC-ɣ, specific sequestration of PIP2 (RFP-PH), InsP3 uncaging, and quantitation of endogenous InsP3 all indicated that LAT-A induces Ca2+ increases by stimulating PLC rather than sensitizing InsP3 receptors. In support of the idea, it bears emphasis that LAT-A timely increased intracellular contents of InsP3 with concomitant decrease of PIP2 levels in the plasma membrane. Conclusion Taken together, our results suggest that suboolemmal actin filaments may serve as a scaffold for cell signaling and modulate the activity of the key enzyme involved in intracellular Ca2+ signaling.

【 授权许可】

CC BY-NC-ND