Estrogen and resveratrol regulate Rac and Cdc42 signaling to the actin cytoskeleton of metastatic breast cancer cells.
ABSTRACT Estrogen and structurally related molecules play critical roles in breast cancer. We reported that resveratrol (50 microM), an estrogen-like phytosterol from grapes, acts in an antiestrogenic manner in breast cancer cells to reduce cell migration and to induce a global and sustained extension of actin structures called filopodia. Herein, we report that resveratrol-induced filopodia formation is time-dependent and concentration-dependent. In contrast to resveratrol at 50 microM, resveratrol at 5 microM acts in a manner similar to estrogen by increasing lamellipodia, as well as cell migration and invasion. Because Rho GTPases regulate the extension of actin structures, we investigated a role for Rac and Cdc42 in estrogen and resveratrol signaling. Our results demonstrate that 50 microM resveratrol decreases Rac and Cdc42 activity, whereas estrogen and 5 microM resveratrol increase Rac activity in breast cancer cells. MDA-MB-231 cells expressing dominant-negative Cdc42 or dominant-negative Rac retain filopodia response to 50 microM resveratrol. Lamellipodia response to 5 microM resveratrol, estrogen, or epidermal growth factor is inhibited in cells expressing dominant-negative Rac, indicating that Rac regulates estrogen and resveratrol (5 microM) signaling to the actin cytoskeleton. These results indicate that signaling to the actin cytoskeleton by low and high concentrations of resveratrol may be differentially regulated by Rac and Cdc42.
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ABSTRACT: Rho family GTPases are GDP/GTP-regulated molecular switches that regulate signaling pathways controlling diverse cellular processes. Wrch-1 was identified as a Wnt-1 regulated Cdc42 homolog, upregulated by Wnt1 signaling in Wnt1-transformed mouse mammary cells, and was able to promote formation of filopodia and activate the PAK serine/threonine kinase. Wrch-1 shares significant sequence and functional similarity with the Cdc42 small GTPase. However, Wrch-1 possesses a unique N-terminal 46 amino acid sequence extension that contains putative Src homology 3 (SH3) domain-interacting motifs. We determined the contribution of the N terminus to Wrch-1 regulation and activity. We observed that Wrch-1 possesses properties that distinguish it from Cdc42 and other Rho family GTPases. Unlike Cdc42, Wrch-1 possesses an extremely rapid, intrinsic guanine nucleotide exchange activity. Although the N terminus did not influence GTPase or GDP/GTP cycling activity in vitro, N-terminal truncation of Wrch-1 enhanced its ability to interact with and activate PAK and to cause growth transformation. The N terminus associated with the Grb2 SH3 domain-containing adaptor protein, and this association increased the levels of active Wrch-1 in cells. We propose that Grb2 overcomes N-terminal negative regulation to promote Wrch-1 effector interaction. Thus, Wrch-1 exhibits an atypical model of regulation not seen in other Rho family GTPases.Current Biology 12/2004; 14(22):2052-6. · 9.65 Impact Factor
Article: Resveratrol induces FasL-related apoptosis through Cdc42 activation of ASK1/JNK-dependent signaling pathway in human leukemia HL-60 cells.[show abstract] [hide abstract]
ABSTRACT: Trans-resveratrol, a phytoalexin found at high levels in grapes and in grape products such as red wine, has been shown to prevent carcinogenesis or antitumor growth in murine models. Here we dissect the detailed signaling pathway involved in resveratrol-induced apoptosis. Our data showed that treatment with resveratrol-induced activation of apoptosis signal-regulating kinase 1, a mitogen-activated protein kinase kinase kinase, in turn, activated the downstream kinases c-Jun N-terminal kinase and p38 mitogen-activated protein kinase, but not extracellular signal-regulated kinase. Transfection with a dominant-negative c-Jun N-terminal kinase expression vector reduced FasL expression and DNA fragmentation induced by resveratrol. However, inhibition of p38 mitogen-activated protein kinase activity by treatment with SB203580 (p38 mitogen-activated protein kinase specific inhibitor) or expression of mutant p38 mitogen-activated protein kinase expression vector did not alter the apoptosis and FasL expression in response to resveratrol. Furthermore, genetic inhibition of apoptosis signal-regulating kinase 1 signaling inhibited not only the activation of c-Jun N-terminal kinase, but also the expression of FasL and apoptosis. Similarly, over-expression of wild-type apoptosis signal-regulating kinase 1 strengthened the resveratrol-induced c-Jun N-terminal kinase activation, FasL expression and subsequent apoptosis. These results suggest the possible involvement of apoptosis signal-regulating kinase 1/c-Jun N-terminal kinase signaling in the regulation of FasL expression and subsequent apoptosis induced by resveratrol in HL-60 cells. Resveratrol also activated the small GTP-binding protein Cdc42, rather than other members such as RhoA or Rac1. Expression of a mutant Cdc42 (N17 Cdc42) dramatically reduced resveratrol-induced c-Jun N-terminal kinase activity, FasL expression and apoptotic cell death. These results showed that resveratrol induced apoptosis through the Cdc42/apoptosis signal-regulating kinase 1/c-Jun N-terminal kinase/FasL signaling cascade in HL-60 cells.Carcinogenesis 02/2005; 26(1):1-10. · 5.70 Impact Factor
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ABSTRACT: Many cell types can generate thin actin-based protrusive structures, which are often classified under the general term of 'filopodia'. However, a range of filopodia-like structures exists that differ both morphologically and functionally. In this brief review, we discuss the different types of filopodial structures, together with the actin-binding proteins and signalling pathways involved in their formation. Specifically, we highlight the differences between the filopodial extensions induced by the Rho GTPases Cdc42 and Rif.Biochemical Society Transactions 01/2005; 32(Pt 6):1115-7. · 3.71 Impact Factor