Mutations within the WNK1 (with-no-K[Lys] kinase-1) gene cause Gordon's hypertension syndrome. Little is known about how WNK1 is regulated. We demonstrate that WNK1 is rapidly activated and phosphorylated at multiple residues after exposure of cells to hyperosmotic conditions and that activation is mediated by the phosphorylation of its T-loop Ser382 residue, possibly triggered by a transautophosphorylation reaction. Activation of WNK1 coincides with the phosphorylation and activation of two WNK1 substrates, namely, the protein kinases STE20/SPS1-related proline alanine–rich kinase (SPAK) and oxidative stress response kinase-1 (OSR1). Small interfering RNA depletion of WNK1 impairs SPAK/OSR1 activity and phosphorylation of residues targeted by WNK1. Hyperosmotic stress induces rapid redistribution of WNK1 from the cytosol to vesicular structures that may comprise trans-Golgi network (TGN)/recycling endosomes, as they display rapid movement, colocalize with clathrin, adaptor protein complex 1 (AP-1), and TGN46, but not the AP-2 plasma membrane–coated pit marker nor the endosomal markers EEA1, Hrs, and LAMP1. Mutational analysis suggests that the WNK1 C-terminal noncatalytic domain mediates vesicle localization. Our observations shed light on the mechanism by which WNK1 is regulated by hyperosmotic stress.

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Resveratrol (RES), a chemopreventive molecule, inhibits the proliferation of tumor cells of different etiologies. We previously showed that RES alters the cell cycle and induces apoptosis in MCF-7 breast tumor cells by interfering with the estrogen receptor (ERa)-dependent phosphoinositide 3-kinase (PI3K) pathway. Here, we analyzed signaling downstream of PI3K, to understand the mechanisms of RES-induced apoptosis. Apoptotic death by RES in MCF-7 was mediated by Bcl-2 downregulation since overexpression of this protein abolished apoptosis. Decreased Bcl-2 levels were not related to cytochrome c release, activation of caspases 3/8 or poly(ADP-ribose) polymerase proteolysis. However, RES decreased mitochondrial membrane potential and increased reactive oxygen species and nitric oxide production. NF-kB, a regulator of Bcl-2 expression, and calpain protease activity, a regulator of NF-kB, were both inhibited by RES. The patterns for NFkB and calpain activities followed that of PI3K and were inhibited by LY294002. NF-kB inhibition coincided with diminished MMP-9 activity and cell migration. These data suggest that RES-induced apoptosis in MCF-7 could involve an oxidative, caspase-independent mechanism, whereby inhibition of PI3K signaling converges to Bcl-2 through NF-kB and calpain protease activity. Therefore, Bcl-2 and NF-kB could be considered potential targets for the chemopreventive activity of RES in estrogen-responsive tumor cells. ' 2005 Wiley-Liss, Inc.Key words: resveratrol; caspase; Bcl-2; NF-kB; apoptosis Among natural compounds with beneficial effects on human health, RES (3,4 0 ,5-trihydroxystilbene) has attracted considerable interest. This molecule, present at relevant concentrations in red wine, 1 has been associated with a lower incidence of cardiovascular disease. Different studies have also suggested a beneficial effect of RES in cancer since it inhibits proliferation and promotes death in tumor cell lines of different origins, 2-4 and, in vivo, suppresses the formation of skin 5 and mammary gland 6 tumors in rodent models of carcinogenesis.We, as well as other laboratories, have found that the ability of RES to inhibit cell viability and proliferation in the human breast cancer cell lines MCF-7 and MDA-MB-231 was unrelated to ERa status. 7,8 However, apoptotic cell death was present only in ERapositive MCF-7 and involved cell-specific regulation of the G 1 /S and G 2 /M transitions of the cell cycle. 2,8 RES properties are related to ERa since this compound has estrogenic or antiestrogenic activities depending on its concentration and the phenotype of the target cell. 9,10 ERa, in addition to its nuclear role as a transcription factor, is involved in regulating the PI3K pathway, which controls cell growth, proliferation and apoptosis. [11][12][13] In MCF-7 cells, RES induced a biphasic pattern of PI3K activity that increased at low concentrations and decreased at high concentrations. Activation of downstream PI3K effectors PKB/AKT and GSK-3 closely followed the pattern of PI3K activity. 14 The ...

SummaryStore-operated calcium entry (SOCE) is an important Ca 2+ entry pathway that regulates many cell functions. Upon store depletion, STIM1, a transmembrane protein located in the endoplasmic reticulum (ER), aggregates and relocates close to the plasma membrane (PM) where it activates store-operated calcium channels (SOCs). Although STIM1 was early defined as a phosphoprotein, the contribution of the phosphorylation has been elusive. In the present work, STIM1 was found to be a target of extracellular-signalregulated kinases 1 and 2 (ERK1/2) in vitro, and we have defined the ERK1/2-phosphorylated sites on the STIM1 sequence. Using HEK293 cells stably transfected for the expression of tagged STIM1, we found that alanine substitution mutants of ERK1/2 target sites reduced SOCE significantly, suggesting that phosphorylation of these residues are required to fully accomplish SOCE. Indeed, the ERK1/2 inhibitors PD184352 and PD0325901 decreased SOCE in transfected cells. Conversely, 12-O-tetradecanoylphorbol-13-acetate, which activates ERK1/2, enhanced SOCE in cells expressing wild-type tagged STIM1, but did not potentiate Ca 2+ influx in cells expressing serine to alanine mutations in ERK1/2 target sites of STIM1. Alanine substitution mutations decreased Ca 2+ influx without disturbing the aggregation of STIM1 upon store depletion and without affecting the relocalization in ER-PM punctae. However, our results suggest that STIM1 phosphorylation at ERK1/2 target sites can modulate SOCE by altering STIM1 binding to SOCs, because a significant decrease in FRET efficiency was observed between alanine substitution mutants of STIM1-GFP and ORAI1-CFP.

Mutations in the WNK [with no lysine (K) kinase] family instigate hypertension and pain perception disorders. Of the four WNK isoforms, much of the focus has been on WNK1, which is activated in response to osmotic stress by phosphorylation of its T-loop residue (Ser382). WNK isoforms phosphorylate and activate the related SPAK (SPS1-related proline/alanine-rich kinase) and OSR1 (oxidative stress-responsive kinase 1) protein kinases. In the present study, we first describe the generation of double-knockin ES (embryonic stem) cells, where SPAK and OSR1 cannot be activated by WNK1. We establish that NKCC1 (Na+/K+/2Cl− co-transporter 1), a proposed target of the WNK pathway, is not phosphorylated or activated in a knockin that is deficient in SPAK/OSR1 activity. We also observe that activity of WNK1 and WNK3 are markedly elevated in the knockin cells, demonstrating that SPAK/OSR1 significantly influences WNK activity. Phosphorylation of another regulatory serine residue, Ser1261, in WNK1 is unaffected in knockin cells, indicating that this is not phosphorylated by SPAK/OSR1. We show that WNK isoforms interact via a C-terminal CCD (coiled-coil domain) and identify point mutations of conserved residues within this domain that ablate the ability of WNK isoforms to interact. Employing these mutants, we demonstrate that interaction of WNK isoforms is not essential for their T-loop phosphorylation and activation, at least for overexpressed WNK isoforms. Moreover, we finally establish that full-length WNK1, WNK2 and WNK3, but not WNK4, are capable of directly phosphorylating Ser382 of WNK1 in vitro. This supports the notion that T-loop phosphorylation of WNK isoforms is controlled by trans-autophosphorylation. These results provide novel insights into the WNK signal transduction pathway and provide genetic evidence confirming the essential role that SPAK/OSR1 play in controlling NKCC1 function. They also reveal a role in which the downstream SPAK/OSR1 enzymes markedly influence the activity of the upstream WNK activators. The knockin ES cells lacking SPAK/OSR1 activity will be useful in validating new targets of the WNK signalling pathway.

Resveratrol is a polyphenol found at high concentrations in grapes and red wine with reported anticarcinogenic effects. We studied the molecular mechanism of resveratrol-induced apoptosis and proliferation arrest in prostate derived cells PZ-HPV-7 (nontumorigenic line), LNCaP (androgen-sensitive cancer line), and PC-3 (androgen-insensitive cancer line). Apoptosis and cell cycle distribution were evaluated by flow cytometry and proliferation by MTT assay and direct cell counting. Caspases, bax, bcl-2, cyclins, Cdks, p53, p21, and p27 were measured by Western blot and kinase activities of cyclin/Cdk complexes by immunoprecipitation followed by kinase assays with appropriate substrates. Resveratrol induced a decrease in proliferation rates and an increase in apoptosis in cancer cell lines in a dose-and time-dependent manner. These effects were coincident with cell accumulation at the G0/G1 phase. In LNCaP and PC-3, the apoptosis induced by resveratrol was mediated by activation of caspases 9 and 3 and a change in the ratio of bax/bcl-2. Expressions of cyclin D1, E, and Cdk4 as well as cyclin D1/Cdk4 kinase activity were reduced by resveratrol only in LNCaP cells. In contrast, cyclin B and Cdk1 expression and cyclin B/ Cdk1 kinase activity were decreased in both cell lines in the presence of resveratrol. However, modulator proteins p53, p21, and p27 were increased by resveratrol only in LNCaP cells. These effects probably result in the observed proliferation arrest and disruption of cell cycle control. In addition, the specific differences found between LNCaP and PC-3 suggest that resveratrol acts through different mechanisms upon the androgen or estrogen receptor cell status.

Summary STIM1 (stromal interaction molecule 1) is a key regulator of store-operated calcium entry (SOCE). Upon depletion of Ca 2+concentration within the endoplasmic reticulum (ER), STIM1 relocalizes at ER-plasma membrane junctions, activating store-operated calcium channels (SOCs). Although the molecular details for STIM1-SOC binding is known, the regulation of SOCE remains largely unknown. A detailed list of phosphorylated residues within the STIM1 sequence has been reported. However, the molecular pathways controlling this phosphorylation and its function are still under study. Using phosphospecific antibodies, we demonstrate that ERK1/2 mediates STIM1 phosphorylation at Ser575, Ser608 and Ser621 during Ca 2+ store depletion, and that Ca 2+ entry and store refilling restore phosphorylation to basal levels. This phosphorylation occurs in parallel to the dissociation from end-binding protein 1 (EB1), a regulator of growing microtubule ends. Although Ser to Ala mutation of residues 575, 608 and 621 showed a constitutive binding to EB1 even after Ca 2+ store depletion, Ser to Glu mutation of these residues (to mimic the phosphorylation profile attained after store depletion) triggered full dissociation from EB1. Given that wild-type STIM1 and STIM1 S575E/S608E/S621E activate SOCE similarly, a model is proposed to explain how ERK1/2-mediated phosphorylation of STIM1 regulates SOCE. This regulation is based on the phosphorylation of STIM1 to trigger dissociation from EB1 during Ca 2+ store depletion, an event that is fully reversed by Ca 2+ entry and store refilling.

Resveratrol (RES), a natural phytoalexin, has antiproliferative activity in human-derived cancer cells and in rodent models of tumor development. We have previously shown that RES induced apoptotic death in estrogen-responsive MCF-7 human breast cancer cells. Recent data have indicated that the estrogen receptor-␣ (ER␣), through interaction with p85, regulates phosphoinositide 3-kinase (PI3K) activity, revealing a physiologic, nonnuclear function of the ER␣ potentially relevant in cell proliferation and apoptosis. In our study, using MCF-7, we have analyzed the ability of RES to modulate the ER␣-dependent PI3K pathway. Immunoprecipitation and kinase activity assays showed that RES increased the ER␣-associated PI3K activity with a maximum stimulatory effect at concentrations close to 10 M; concentrations >50 M decreased PI3K activity. Stimulation of PI3K activity by RES was ER␣-dependent since it could be blocked by the antiestrogen ICI 182,780. RES did not affect p85 protein expression but induced the proteasome-dependent degradation of the ER␣. Nevertheless, the amount of PI3K immunoprecipitated by the ER␣ remained unchanged in presence of RES, indicating that ER␣ availability was not limiting PI3K activity. Phosphoprotein kinase B (pPKB/AKT) followed the pattern of PI3K activity, whereas RES did not affect total PKB/AKT expression. PKB/AKT downstream target glycogen synthase kinase 3 (GSK3) also showed a phosphorylation pattern that followed PI3K activity. We propose a mechanism through which RES could inhibit survival and proliferation of estrogen-responsive cells by interfering with an ER␣-associated PI3K pathway, following a process that could be independent of the nuclear functions of the ER␣. © 2003 Wiley-Liss, Inc. Key words: resveratrol; PI3K; PKB/AKT; GSK-3; proliferationTrans-RES (3,4Ј,5-trihydroxystilbene) is a natural phytoalexin found in grapes and red wine. 1 RES has potential beneficial effects in human health by inhibiting polymorphonuclear leukocyte function and platelet aggregation, 2,3 by decreasing oxidative stress 4 and by antagonizing the actions of estrogens. 5,6 Interestingly, RES has also estrogenic activity, being able to function as an ER␣ agonistic ligand. 7-9 Recent reports have analyzed the antiproliferative activity of RES in human cancer cell lines of diverse origin. 10 -12 Experiments using rodent models of carcinogenesis have shown that RES also suppresses the formation of skin 13 and mammary gland 14 tumors in mice and rats, respectively.We, and others, have reported that RES inhibited cell viability and proliferation in the human breast cancer cell lines MCF-7 and MDA-MB-231, regardless of their estrogen receptor-␣ (ER␣) status. 6,12,15 However, we found that whereas the ER␣-positive MCF-7 cells exhibited apoptotic cell death, the ER␣-negative MDA-MB-231 did not, 15 suggesting that apoptosis induction by RES in human breast cancer cells could be ER␣ mediated. From studies analyzing the effects of RES on ER␣ activity, it was suggested that this molecule could be either an ag...