Abstract
Growth factors induce massive actin cytoskeletal remodeling in cells. These reorganization events underlie various cellular responses such as cell migration and morphological changes. One major form of actin reorganization is the formation and disassembly of dorsal ruffles (also named waves, dorsal rings, or circular ruffles). Dorsal ruffles are involved in physiological functions including cell migration, invasion, macropinocytosis, plasma membrane recycling, and others. Growth factors initiate rapid formation (within 5 min) of circular membrane ruffles, and these ruffles move along the dorsal side of the cells, constrict, close, and eventually disassemble ( approximately 20 min). Considerable attention has been devoted to the mechanism by which growth factors induce the formation of dorsal ruffles. However, little is known of the mechanism by which these ruffles are disassembled. Here we have shown that G proteins G(12) and G(13) control the rate of disassembly of dorsal ruffles. In Galpha(12)(-/-)Galpha(13)(-/-) fibroblast cells, dorsal ruffles induced by growth factor treatment remain visible substantially longer ( approximately 60 min) than in wild-type cells, whereas the rate of formation of these ruffles was the same with or without Galpha(12) and Galpha(13). Thus, Galpha(12)/Galpha(13) critically regulate dorsal ruffle turnover.
Highlights
In serum-starved fibroblasts, platelet-derived growth factor (PDGF)2 induces at least two types of membrane ruffles, peripheral membrane ruffles and dorsal ruffles [12]
In addition to fibroblast cells, dorsal ruffle formation in response to growth factors has been reported in glial cells, endothelial cells, hippocampal neurons, kidney epithelial cells, and tumor cells [1, 2, 11, 13, 14]
After expression for 1–2 h, we treated the cells with PDGF-BB (20 ng/ml) and monitored the subcellular distribution of actin polymers
Summary
In serum-starved fibroblasts, platelet-derived growth factor (PDGF)2 induces at least two types of membrane ruffles, peripheral membrane ruffles (or lamellipodia) and dorsal ruffles [12]. In G␣12Ϫ/ϪG␣13Ϫ/Ϫ cells, dorsal ruffles formed within 5 min (4.86 Ϯ 3.88 min, n ϭ 51) after PDGF-BB treatment Formation of dorsal ruffles in G␣12Ϫ/ϪG␣13Ϫ/Ϫ cells was dependent on PDGF treatment (Fig. 1D and supplemental Movie S4).
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