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Increased Src activity, often associated with tumorigenesis, leads to the formation of invasive adhesions termed podosomes. Podosome formation requires the function of Rho family guanosine triphosphatases and reorganization of the actin cytoskeleton. In addition, Src induces changes in gene expression required for transformation, in part by activating mitogen-activated protein kinase (MAPK) signaling pathways. We sought to determine whether MAPK signaling regulates podosome formation. Unlike extracellular signal--regulated kinase 1/2 (ERK1/2), ERK5 is constitutively activated in Src-transformed fibroblasts. ERK5-deficient cells expressing v-Src exhibited increased RhoA activation and signaling, which lead to cellular retraction and an inability to form podosomes or induce invasion. Addition of the Rho-kinase inhibitor Y27632 to ERK5-deficient cells expressing v-Src led to cellular extension and restored podosome formation. In Src-transformed cells, ERK5 induced the expression of a Rho GTPase-activating protein (RhoGAP), RhoGAP7/DLC-1, via activation of the transcription factor myocyte enhancing factor 2C, and RhoGAP7 expression restored podosome formation in ERK5-deficient cells. We conclude that ERK5 promotes Src-induced podosome formation by inducing RhoGAP7 and thereby limiting Rho activation.

Signaling mucins are cell adhesion molecules that activate RAS/RHO guanosine triphosphatases and their effector mitogen-activated protein kinase (MAPK) pathways. We found that the Saccharomyces cerevisiae mucin Msb2p, which functions at the head of the Cdc42p-dependent MAPK pathway that controls filamentous growth, is processed into secreted and cell-associated forms. Cleavage of the extracellular inhibitory domain of Msb2p by the aspartyl protease Yps1p generated the active form of the protein by a mechanism incorporating cellular nutritional status. Activated Msb2p functioned through the tetraspan protein Sho1p to induce MAPK activation as well as cell polarization, which involved the Cdc42p guanine nucleotide exchange factor Cdc24p. We postulate that cleavage-dependent activation is a general feature of signaling mucins, which brings to light a novel regulatory aspect of this class of signaling adhesion molecule.

The geographical mosaic theory of coevolution predicts that different local species interactions will shape population traits, but little is known about the molecular factors involved in mediating the specificity of these interactions. Pristionchus nematodes associate with different scarab beetles around the world, with Pristionchus pacificus isolated primarily from the oriental beetle in Japan. In particular, the constituent populations of P. pacificus represent a rare opportunity to study multiple specialized interactions and the mechanisms that influence population traits at the genetic level. We identified a component of the cGMP signaling pathway to be involved in the natural variation for sensing the insect pheromone ETDA, using targeted introgression lines, exogenous cGMP treatment, and a null egl-4 allele. Our data strongly implicate egl-4 as one of several loci involved in behavioral variation in P. pacificus populations. That EGL-4 homologs have been independently implicated for behavioral variations in other invertebrate models suggests that EGL-4 may act as a modulator for interspecies behavioral repertoires across large phylogenetic distances. chemosensation | nematode | near-isogenic lines

The metabolic actions of the antidiabetic agent metformin reportedly occur via the activation of the AMP-activated protein kinase (AMPK) in the heart and other tissues in the presence or absence of changes in cellular energy status. In this study, we tested the hypothesis that mefformin has AMPK-independent effects on metabolism in heart muscle. Fatty acid oxidation and glucose utilization (glycolysis and glucose uptake) were measured in isolated working hearts from halothanebanesthetized male Sprague-Dawley rats and in cultured heart-derived H9c2 cells in the absence or in the presence of metformin (2 mM). Fatty acid oxidation and glucose utilization were significantly altered by metformin in hearts and H9c2 cells. AMPK activity was not measurably altered by metformin in either model system, and no impairment of energetic state was observed in the intact hearts. Furthermore, the inhibition of AMPK by 6-[4-(2-pipefidin-1-ylethoxy)-phenyl]-3-pyridin-4-yl-pyyrazolo[1,5-a] pyrimidine (Compound C), a well-recognized pharmacological inhibitor of AMPK, or the overexpression of a dominant-negative form of AMPK failed to prevent the metabolic actions of metformin in H9c2 cells. The exposure of H9c2 cells to inhibitors of p38 mitogen-activated protein kinase (p38 MAPK) or protein kinase C (PKC) partially or completely abrogated metformin-induced alterations in metabolism in these cells, respectively. Thus the metabolic actions of metformin in the heart muscle can occur independent of changes in AMPK activity and may be mediated by p38 MAPK- and PKC-dependent mechanisms. AMP-activated protein kinase; energy metabolism

First published April 11, 2008; doi:10.1152/ajpheart.91476.2007.--We have previously described a PKC-[epsilon] interaction with cytochrome oxidase subunit IV (COIV) that correlates with enhanced CO activity and cardiac ischemic preconditioning (PC). We therefore investigated the effects of PC and ischemia-reperfusion (I/R) injury on CO subunit levels in an anesthetized rat coronary ligation model. Homogenates prepared from the left ventricular regions at risk (RAR) and not at risk (RNAR) for I/R injury were fractionated into cell-soluble (S), 600 g low-speed centrifugation (L), gradient-purified mitochondrial (M), and 100,000 g particulate (P) fractions. In RAR tissue, PC (2 cycles of 5-rain ischemia and 5-min reperfusion) decreased the COI in the P fraction (~29% of total cellular COI), suggesting changes in interfibrillar mitochondria. After 30 min of ischemia and 120 rain of reperfusion, total COI levels decreased in the RAR by 72%. Subunit Va was also downregulated by 42% following prolonged I/R in the RAR. PC administered before I/R reduced the loss of COI in the M and P fractions ~30% and prevented COVa losses completely. We observed no losses in subunits Vb and VIIa following I/R alone; however, significant losses occurred when PC was administered before prolonged I/R. Delivery of a cell-permeable PKC-[epsilon] translocation inhibitor ([epsilon]V1-2) to isolated rat hearts before prolonged I/R dramatically increased COI loss, suggesting that PKC-[epsilon] protects COI levels. We propose that additional measures to protect CO subunits when coadministered with PC may improve its cardioprotection against I/R injury. preconditioning; protein kinase C; cytochrome oxidase subunit; coronary ligation; mitochondria

Epidemiological data suggest that hyperglycemia abrogates the gender-based cardiovascular protection possibly associated with estrogens. This study was designed to investigate 1) whether rabbit aortic rings show gender differences in the development of abnormal endothelium-dependent vasodilation (EDV) under acute hyperglycemic conditions, 2) the potential role of PKC isoforms and superoxide ([O.sup-.sub.2]) in acute hyperglycemia-induced vascular dysfunction, and 3) the effect of acute estrogen administration on hyperglycemia-induced endothelial dysfunction in male and female rabbits. EDV to ACh was determined before and after 3 h of treatment with high glucose (HG) in phenylephrine-precontracted aortic rings from male and female New Zealand White rabbits. Similar experiments were conducted in the presence of inhibitors of PKC-[alpha], PKC-[beta], and PKC-[delta] or an [O.sup-.sub.2] scavenger. The effect of acute estrogen administration was evaluated in the presence and absence of HG. Finally, mRNA expression of PKC isoforms was measured by real-time PCR. We found that 1) 3 h of incubation with HG impairs EDV to a greater extent in female than male aorta, 2) inhibition of PKC-[beta] or [O.sup-.sub.2] prevents HG-induced impairment of EDV in female aorta, 3) acute 17[beta]-estradiol aggravates HG-induced endothelial dysfunction in female, but not male, aorta, and 4) PKC-[alpha] and PKC-[beta] expression are significantly higher in female than male aorta. This study reveals the predisposition of female rabbit aorta to vascular injury under hyperglycemic conditions, possibly via activation of PKC-[beta] and [O.sup-.sub.2] production. Furthermore, it suggests that, under hyperglycemic conditions, acute estrogen treatment is detrimental to endothelial function in female rabbits. cardiovascular disease; superoxide; diabetes; protein kinase C

The neuropeptide substance P (SP), as a major mediator of neuroimmunomodulatory activity, modulates diverse functions of immune cells, including macrophages. In the current study, we focused on the yet uncertain role of SP in enhancing the inducible/inflammatory chemokine response of macrophages and the signaling mechanism involved. We studied the effect on the murine monocyte/macrophage cell line RAW 264.7 as well as isolated primary macrophages. Our data show that SP, at nanomolar concentrations, elicited selective chemokine production from murine macrophages. Among the chemokines examined, macrophage inflammatory protein-2 and monocyte chemoattractant protein-1 are two major chemokines that were synthesized by macrophages in response to SP. Furthermore, SP treatment strongly induced the classic pathway of I[kappa]B-dependent NF-[kappa]B activation and enhanced DNA binding as well as transactivation activity of the transcription factor. SP-evoked transcriptional induction of chemokines was specific, since it was blocked by treatment with selective neurokinin-1 receptor antagonists. Moreover, SP stimulation of macrophages activated the ERK 1/2 and p38 MAPK but not JNKs. Blockade of these two MAPK pathways with specific inhibitors abolished SP-elicited nuclear translocation of phosphorylated NF-[kappa]B p65 and NF-[kappa]B-driven chemokine production, suggesting that the two MAPKs lie in the signaling pathways leading to the chemokine response. Collectively, our data demonstrate that SP enhances selective inflammatory chemokine production by murine macrophages via ERK/p38 MAPK-mediated NF-[kappa]B activation. neuropeptides; monocytes/macrophages; protein kinases; transcription factors; chemokines

The role of PKC in the regulation of store-operated [Ca.sup.2+] entry (SOCE) is rather controversial. Here, we used [Ca.sup.2+]-imaging, biochemical, pharmacological, and molecular techniques to test if [Ca.sup.2+]-independent [PLA.sub.2][beta] ([iPLA.sub.2][beta]), one of the transducers of the signal from depleted stores to plasma membrane channels, may be a target for the complex regulation of SOCE by PKC and diacylglycerol (DAG) in rabbit aortic smooth muscle cells (SMCs). We found that the inhibition of PKC with chelerythrine resulted in significant inhibition of thapsigargin (TG)-induced SOCE in proliferating SMCs. Activation of PKC by the diacylglycerol analog 1-oleoyl-2-acetyl-sn-glycerol (OAG) caused a significant depletion of intracellular [Ca.sup.2+] stores and triggered [Ca.sup.2+] influx that was similar to TG-induced SOCE. OAG and TG both produced a PKC-dependent activation of [iPLA.sub.2][beta] and [Ca.sup.2+] entry that were absent in SMCs in which [iPLA.sub.2][beta] was inhibited by a specific chiral enantiomer of bromoenol lactone (S-BEL). Moreover, we found that PKC regulates TG- and OAG-induced [Ca.sup.2+] entry only in proliferating SMCs, which correlates with the expression of the specific PKC-[epsilon] isoform. Molecular downregulation of PKC-[epsilon] impaired TG- and OAG-induced [Ca.sup.2+] influx in proliferating SMCs but had no effect in confluent SMCs. Our results demonstrate that DAG (or OAG) can affect SOCE via multiple mechanisms, which may involve the depletion of [Ca.sup.2+] stores as well as direct PKC-[epsilon]-dependent activation of [iPLA.sub.2][beta], resulting in a complex regulation of SOCE in proliferating and confluent SMCs. protein kinase C-[epsilon]; [Ca.sup.2+]-independent phospholipase [A.sub.2]; diacylglycerol; smooth muscle cells

Previous studies indicate involvement of the multifunctional [Ca.sup.2+]/calmodulin-dependent protein kinase II (CaMKII) in vascular smooth muscle (VSM) cell migration. In the present study, molecular loss-of-function studies were used specifically to assess the role of the predominant CaMKII[[delta].sub.2] isoform on VSM cell migration using a scratch wound healing assay. Targeted CaMKII[[delta].sub.2] knockdown using siRNA or inhibition of activity by overexpressing a kinase-negative mutant resulted in attenuation of VSM cell migration. Temporal and spatial assessments of kinase autophosphorylation indicated rapid and transient activation in response to wounding, in addition to a sustained activation in the leading edge of migrating and spreading cells. Furthermore, siRNA-mediated suppression of CaMKII[[delta].sub.2] resulted in the inhibition of wound-induced Rac activation and Golgi reorganization, and disruption of leading edge morphology, indicating an important function for CaMKII[[delta].sub.2] in regulating VSM cell polarization. Numerous previous reports link activation of CaMKII to ERK 1/2 signaling in VSM. Wound-induced ERK 1/2 activation was also found to be dependent on CaMKII; however, ERK activity did not account for effects of CaMKII in regulating Golgi polarization, indicating alternative mechanisms by which CaMKII affects the complex events involved in cell migration. Wounding a VSM cell monolayer results in CaMKII[[delta].sub.2] activation, which positively regulates VSM cell polarization and downstream signaling, including Rac and ERK 1/2 activation, leading to cell migration. [Ca.sup.2+]/calmodulin-dependent protein kinase II; CaMKII; Golgi; calcium signaling; Rac; ERK 1/2

Cholinergic-muscarinic receptor agonists are used to alleviate mouth dryness, although the cellular signals mediating the actions of these agents on salivary glands have not been identified. We examined the activation of ERK 1/2 by two muscarinic agonists, pilocarpine and carbachol, in a human salivary cell line (HSY). Immunoblot analysis revealed that both agonists induced transient activation of ERK 1/2. Whereas pilocarpine induced phosphorylation of the epidermal growth factor (EGF) receptor, carbachol did not. Moreover, ERK activation by pilocarpine, but not carbachol, was abolished by the EGF receptor inhibitor AG-1478. Downregulation of PKC by prolonged treatment of cells with the phorbol ester PMA diminished carbachol-induced ERK phosphorylation but had no effect on pilocarpine responsiveness. Depletion of intracellular [Ca.sup.2+] ([[Ca.sup.2+].sub.i]) by EGTA did not affect ERK activation by either agent. In contrast to carbachol, pilocarpine did not elicit [[Ca.sup.2+].sub.i] mobilization in HSY cells. Treatment of cells with the muscarinic receptor subtype 3 (M3) antagonist N-(3-chloropropyl)-4-piperidnyl diphenylacetate decreased ERK responsiveness to both agents, whereas the subtype 1 ([M.sub.1]) antagonist pirenzepine reduced only the carbachol response. Stimulation of ERKs by pilocarpine was also decreased by [M.sub.3], but not [M.sub.1], receptor small interfering RNA. The Src inhibitor PP2 blocked pilocarpine-induced ERK activation and EGF receptor phosphorylation, without affecting ERK activation by carbachol. Our results demonstrate that the actions of pilocarpine and carbachol in salivary cells are mediated through two distinct signaling mechanisms--pilocarpine acting via M3 receptors and Src-dependent transactivation of EGF receptors, and carbachol via [M.sub.1]/[M.sub.3] receptors and PKC--converging on the ERK pathway. muscarinic receptor; epidermal growth factor receptor; protein kinase C

Nitric oxide (NO) donors decrease intraocular pressure (IOP) by increasing aqueous outflow facility in the trabecular meshwork (TM) and/or Schlemm's canal. However, the cellular mechanisms are unknown. Cellular mechanisms known to regulate outflow facility include changes in cell volume and cellular contractility. In this study, we investigated the effects of NO donors on outflow facility and NO-induced effects on TM cell volume. We tested the involvement of soluble guanylate cyclase (sGC), cGMP, PKG, and the large-conductance [Ca.sup.2+]-activated [K.sup.+] (B[K.sub.Ca]) channel using inhibitors and activators. Cell volume was measured using calcein AM fluorescent dye, detected by confocal microscopy, and quantified using NIH ImageJ software. An anterior segment organ perfusion system measured outflow facility. NO increased outflow facility in porcine eye anterior segments (0.4884-1.3956 [micro]l x [min.sup.-1] x mm[Hg.sup.-1]) over baseline (0.2373-0.5220 [micro]l x [min.sup.-1] x mm[Hg.sup.-1]) within 10 min of drug application. These NO-induced increases in outflow facility were inhibited by the the B[K.sub.Ca] channel inhibitor IBTX. Exposure of TM cells to NO resulted in a 10% decrease in cell volume, and these decreases were abolished by the sGC inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one and IBTX, suggesting the involvement of sGC and [K.sup.+] eflux, respectively. NO-induced decreases in cell volume were mimicked by 8-Br-cGMP and abolished by the PKG inhibitor (RP)-8-Br-PET-cGMP-S, suggesting the involvement cGMP and PKG. Additionally, the time course for NO-induced decreases in TM cell volume correlated with NO-induced increases in outflow facility, suggesting that the NO-induced alterations in cell volume may influence outflow facility. eye; signal transduction; cGMP; protein kinase G; soluble guanylate cyclase

Marbling, or i.m. fat, is an important factor determining beef quality. Both adipogenesis and hypertrophy of existing adipocytes contribute to enhanced marbling. We hypothesized that the fetal stage is important for the formation of i.m. adipocytes and that AMP-activated protein kinase (AMPK) has a key role in adipogenesis during this stage. The objective of this study was to assess the role of AMPK in adipogenesis in fetal sheep muscle and 3T3-L1 cells. Nonpregnant ewes were randomly assigned to a control (Con, 100% of NRC recommendations, n = 7) or overfed (OF, 150% of NRC, n = 7) diet from 60 d before to 75 d after conception, when the ewes were killed. The fetal LM was collected at necropsy for biochemical analyses. The activity of AMPK was less in the fetal muscle of OF sheep. The expression of peroxisome proliferator-activated receptor (PPAR)[gamma], a marker of adipogenesis, was greater in OF fetal muscle compared with Con fetal muscle. To further show the role of AMPK in adipogenesis, we used 3T3-L1 cells. The 3T3-L1 cells were incubated in a standard adipogenic medium for 24 h and 10 d. Activation of AMPK by 5-aminoimidazole-4-carboxamide-1-[beta]-d-ribonucleoside dramatically inhibited the expression of PPAR[gamma] and reduced the presence of adipocytes after 10 d of differentiation. Inhibition of AMPK by compound C enhanced the expression of PPAR[gamma]. In conclusion, these data show that AMPK activity is inversely related to adipogenesis in fetal sheep muscle and 3T3-L1 cells. Key words: 3T3-L1 cells, adipogenesis, AMP-activated protein kinase, fetus, sheep, skeletal muscle

The protein tyrosine phosphatase Shp2 is a positive regulator of growth factor signaling. Gain-of-function mutations in several types of leukemia define Shp2 as a bona fide oncogene. We performed a high-throughput in silico screen for small-molecular-weight compounds that bind the catalytic site of Shp2. We have identified the phenylhydrazonopyrazolone sulfonate PHPS1 as a potent and cell-permeable inhibitor, which is specific for Shp2 over the closely related tyrosine phosphatases Shpl and PTP1B. PHPS1 inhibits Shp2-dependent cellular events such as hepatocyte growth factor/scatter factor (HGF/SF)-induced epithelial cell scattering and branching morphogenesis. PHPS1 also blocks Shp2-dependent downstream signaling, namely HGF/SF-induced sustained phosphorylation of the Erk1/2 MAP kinases and dephosphorylation of paxillin. Furthermore, PHPS1 efficiently inhibits activation of Erk1/2 by the leukemia-associated Shp2 mutant, Shp2-E76K, and blocks the anchorage-independent growth of a variety of human tumor cell lines. The PHPS compound class is therefore suitable for further development of therapeutics for the treatment of Shp2-dependent diseases. chemical biology | growth factor signaling | phosphatase inhibition | virtual drug screening

Plakophilins (PKPs) are armadillo family members related to the classical cadherin-associated protein [p120.sup.ctn]. PKPs localize to the cytoplasmic plaque of intercellular junctions and participate in linking the intermediate filament (IF)-binding protein desmoplakin (DP) to desmosomal cadherins. In response to cell-cell contact, PKP2 associates with DP in plaque precursors that form in the cytoplasm and translocate to nascent desmosomes. Here, we provide evidence that PKP2 governs DP assembly dynamics by scaffolding a DP-PKP2-protein kinase C[alpha] (PKC[alpha]) complex, which is disrupted by PKP2 knockdown. The behavior of a phosphorylation-deficient DP mutant that associates more tightly with IF is mimicked by PKP2 and PKC[alpha] knockdown and PKC pharmacological inhibition, all of which impair junction assembly. PKP2 knockdown is accompanied by increased phosphorylation of PKC substrates, raising the possibility that global alterations in PKC signaling may contribute to pathogenesis of congenital defects caused by PKP2 deficiency.

Endothelin- 1 (ET- 1) plays an important role in the regulation of salt and water excretion in the kidney. Considerable in vitro evidence suggests that the renal medullary [ET.sub.B] receptor mediates ET-l-induced inhibition of electrolyte reabsorption by stimulating nitric oxide (NO) production. The present study was conducted to test the hypothesis that NO synthase 1 (NOS 1) and protein kinase G (PKG) mediate the diuretic and natriuretic effects of [ET.sub.B] receptor stimulation in vivo. Infusion of the [ET.sub.B] receptor agonist sarafotoxin $6c ($6c: 0.45 [micro] g*[kg.sup.-1]* [h.sup.-1]) in the renal medulla of anesthetized, male Sprague-Dawley rats markedly increased the urine flow (UV) and urinary sodium excretion (UNaV) by 67 and 120%, respectively. This was associated with an increase in medullary cGMP content but did not affect blood pressure. In addition, S6c-induced diuretic and natriuretic responses were absent in [ET.sub.B] receptor-deficient rats. Coinfusion of [N.sup.G]-propyl-L-arginine (10 [micro]g*[kg.sup.-1]*[h.sup.-1]), a selective NOS1 inhibitor, suppressed S6c-induced increases in UV, UNaV, and medullary cGMP concentrations. Rp-8-Br-PET-cGMPS (10 [micro]g* [kg.sup.-1]*[h.sup.-1]) or [RQIKIWFQNRRMKWKKLRK.sub.5]H-amide (18 [micro]g*[kg.sup.-1]*[h.sup.-1]), a PKG inhibitor, also inhibited S6c-induced increases in UV and UNaV. These results demonstrate that renal medullary [ET.sub.B] receptor activation induces diuretic and natriuretic responses through a NOS1, cGMP, and PKG pathway. sodium excretion; nitric oxide synthase 1; guanosine 3',5'-cyclic monophosphate; protein kinase G

Transient receptor potential vanilloid 5 (TRPV5) constitutes the apical entry pathway for transepithelial [Ca.sup.2+] reabsorption in kidney. Many hormones alter renal [Ca.sup.2+] reabsorption at least partly by regulating TRPV5. The mechanism for acute regulation of TRPV5 by phospholipase C-coupled hormones is largely unknown. Here, we found that protein kinase C (PKC) activator 1-oleoyl-acetyl-sn-glycerol (OAG) increased TRPV5 current density and surface abundance in cultured cells. The OAG-mediated increase of TRPV5 was prevented by preincubation with specific PKC inhibitors. Coexpression with a dominant-negative dynamin increased the basal TRPV5 current density and prevented the increase by OAG. Knockdown of caveolin-1 by small interference RNA (siRNA) prevented the increase of TRPV5 by OAG. In contrast, knockdown of clathrin heavy chain had no effects. OAG had no effect on TRPV5 expressed in caveolin-1 null cells derived from caveolin-1 knockout mice. Forced expression of recombinant caveolin-1 restored the regulation of TRPV5 by OAG in caveolin-1 knockout cells. Mutations of serine-299 and/or serine-654 of TRPV5 (consensus residues for phosphorylation by PKC) abolished the regulation by OAG. Parathyroid hormone (PTH) increased TRPV5 current density in cells coexpressing TRPV5 and type 1 PTH receptor. The increase caused by PTH was prevented by PKC inhibitor, mutation of serine-299/serine-654, or by knockdown of caveolin-1. Thus, TRPV5 undergoes constitutive caveolae-mediated endocytosis. Activation of PKC increases cell surface abundance of TRPV5 by inhibiting the endocytosis. This mechanism of regulation by PKC may contribute to the acute stimulation of TRPV5 and renal [Ca.sup.2+] reabsorption by PTH. dynamin; caveolin; parathyroid hormone; phospholipase C; Madin-Darby canine kidney cells

Statins have been shown to be cardioprotective; however, their interaction with endogenous cardioprotection by ischemic preconditioning and postconditioning is not known. In the present study, we examined if acute and chronic administration of the 3-hydroxy-3-methylglutaryl CoA reductase inhibitor lovastatin affected the infarct size-limiting effect of ischemic preconditioning and postconditioning in rat hearts. Wistar rats were randomly assigned to the following three groups: 1) vehicle (1% methylcellulose per os for 12 days), 2) chronic lovastatin (15 mg.[kg.sup.-1].[day.sup.-1] per os for 12 days), and 3) acute lovastatin (1% methylcellulose per os for 12 days and 50 [micro]mol/1 lovastatin in the perfusate). Hearts isolated from the three groups were either subjected to a nonconditioning (aerobic perfusion followed by 30-min coronary occlusion and 120-min reperfusion, i.e., test ischemia-reperfusion), preconditioning (three intermittent periods of 5-min ischemia-reperfusion cycles before test ischemia-reperfusion), or postconditioning (six cycles of 10-s ischemia-reperfusion after test ischemia) perfusion protocol. Preconditioning and postconditioning significantly decreased infarct size in vehicle-treated hearts. However, preconditioning failed to decrease infarct size in acute lovastatin-treated hearts, but the effect of postconditioning remained unchanged. Chronic lovastatin treatment abolished postconditioning but not preconditioning; however, it decreased infarct size in the nonconditioned group. Myocardial levels of coenzyme Q9 were decreased in both acute and chronic lovastatin-treated rats. Western blot analysis revealed that both acute and chronic lovastatin treatment attenuated the phoshorylation of Akt; however, acute but not chronic lovastatin treatment increased the phosphorylation of p42 MAPK/ERK. We conclude that, although lovastatin may lead to cardioprotection, it interferes with the mechanisms of cardiac adaptation to ischemic stress. coronary occlusion; coenzyme Q9; Akt; p42 mitogen-activated protein kinase/extracellular signal-regulated kinase; statin

Shear stress is a pathophysiologically relevant mechanical signal in cartilage biology and tissue engineering. Cyclooxygenase-2 (COX-2) is a pivotal proinflammatory enzyme, which is induced by mechanical loading-derived shear stress in chondrocytes. In the present study, we investigated the transcriptional machinery and signaling pathway regulating shear-induced COX-2 expression in human chondrocytic cells. Deletion and mutation analyses of the human cox-2 promoter reveal that the CCAAT/enhancer-binding protein (C/EBP) and activator protein-1 (AP-1) predominantly contribute to the shear-induced cox-2 promoter activity. Supershift assays disclose that C/EBP[beta], but not C/EBP[alpha] or C/EBP[delta], binds to the C/EBP site, whereas c-Jun binds to AP-1. Individual gene knockdown experiments demonstrate the direct regulation of C/EBP[beta] expression by c-Jun, and the critical roles of both c-Jun and C/EBP[beta] in shear-induced COX-2 synthesis. Our studies also indicate that Rac and, to a lesser extent, Cdc42 transactivate MEKK1, which is, in turn, responsible for activation of mitogen-activated protein kinase kinase 7 (MKK7). MKK7 regulates c-Jun N[H.sub.2]-terminal kinase 2 activation, which, in turn, triggers the phosphorylation of c-Jun that controls shear-mediated COX-2 upregulation in chondrocytes. Reconstructing the signaling network regulating shear-induced COX-2 expression and inflammation may provide insights to optimize conditions for culturing artificial cartilage in bioreactors and for developing therapeutic interventions for arthritic disorders. mechanobiology; signal transduction; shear stress; cyclooxygenase; enhancer-binding protein; mitogen-activated protein kinase kinase; c-Jun N[H.sub.2]-terminal kinase

Cigarette smoke is a major environmental air pollutant that injures airway epithelium and incites subsequent diseases including chronic obstructive pulmonary disease. The lesion that smoke induces in airway epithelium is still incompletely understood. Using a LIVE/DEAD cytotoxicity assay, we observed that subconfluent cultures of bronchial epithelial cells derived from both human and monkey airway tissues and an immortalized normal human bronchial epithelial cell line (HBEI) were more susceptible to injury by cigarette smoke extract (CSE) and by direct cigarette smoke exposure than cells in confluent cultures. Scraping confluent cultures also caused an enhanced cell injury predominately in the leading edge of the scraped confluent cultures by CSE. Cellular ATP levels in both subconfluent and confluent cultures were drastically reduced after CSE exposure. In contrast, GSH levels were significantly reduced only in subconfluent cultures exposed to smoke and not in confluent cultures. Western blot analysis demonstrated ERK activation in both confluent and subconfluent cultures after CSE. However, activation of apoptosis signal-regulating kinase I (ASKI), JNK, and p38 were demonstrated only in subconfluent cultures and not in confluent cultures after CSE. Using short interfering RNA (siRNA) to JNK1 and JNK2 and a JNK inhibitor, we attenuated CSE-mediated cell death in subconfluent cultures but not with an inhibitor of the p38 pathway. Using the tetracycline (Tet)-on inducible approach, overexpression of thioredoxin (TRX) attenuated CSE-mediated cell death and JNK activation in subconfluent cultures. These results suggest that the TRX-ASKI-JNK pathway may play a critical role in mediating cell density-dependent CSE cytotoxicity. airway epithelial cells; injury; thioredoxin; mitogen-activated protein kinase

Tachykinins, acting through N[K.sub.3] receptors (N[K.sub.3]R), contribute to excitatory transmission to intrinsic primary afferent neurons (IPANs) of the small intestine. Although this transmission is dependent on protein kinase C (PKC), its maintenance could depend on protein kinase D (PKD), a downstream target of PKC. Here we show that PKD1/2-immunoreactivity occurred exclusively in IPANs of the guinea pig ileum, demonstrated by double staining with the IPAN marker NeuN. PKC[epsilon] was also colocalized with PKD1/2 in IPANs. PKC[epsilon] and PKD1/2 trafficking was studied in enteric neurons within whole mounts of the ileal wall. In untreated preparations, PKC[epsilon] and PKD1/2 were cytosolic and no signal for activated (phosphorylated) PKD was detected. The N[K.sub.3]R agonist senktide evoked a transient translocation of PKC[epsilon] and PKD1/2 from the cytosol to the plasma membrane and induced PKD1/2 phosphorylation at the plasma membrane. PKC[epsilon] translocation was maximal at 10 s and returned to the cytosol within 2 min. Phosphorylated-PKD 1/2 was detected at the plasma membrane within 15 s and translocated to the cytosol by 2 min, where it remained active up to 30 min after N[K.sub.3]R stimulation. PKD1/2 activation was reduced by a PKC[epsilon] inhibitor and prevented by N[K.sub.3]R inhibition. N[K.sub.3]Rmediated PKC[epsilon] and PKD activation was confirmed in HEK293 cells transiently expressing N[K.sub.3]R and green fluorescent protein-tagged PKC[epsilon], PKD1, PKD2, or PKD3. Senktide caused membrane translocation and activation of kinases within 30 s. After 15 min, phosphorylated PKD had returned to the cytosol. PKD activation was confirmed through Western blotting. Thus stimulation of N[K.sub.3]R activates PKC[epsilon] and PKD in sequence, and sequential activation of these kinases may account for rapid and prolonged modulation of IPAN function. tachykinins; primary afferent neurons

We have shown earlier that platelet-activating factor (PAF) causes apoptosis in enterocytes via a mechanism that involves Bax translocation to mitochondria, followed by caspase activation and DNA fragmentation. Herein we report that, in rat small intestinal epithelial cells (IEC-6), these downstream apoptotic effects are mediated by a PAF-induced inhibition of the phosphatidylinositol 3-kinase (PI 3-kinase)/protein kinase B (Akt) signaling pathway. Treatment with PAF results in rapid dephosphorylation of Akt, phosphoinositide-dependent kinase-1, and the YXXM p85 binding motif of several proteins and redistribution of Akt-pleckstrin homology domain-green fluorescent protein, i.e., an in vivo phosphatidylinositol (3,4,5)-trisphosphate sensor, from membrane to cytosol. The proapoptotic effects of PAF were inhibited by both n-3 and n-6 polyunsaturated fatty acids but not by a saturated fatty acid palmitate. Indomethacin, an inhibitor of prostaglandin biosynthesis, did not influence the baseline or PAF-induced apoptosis, but 2-bromopalmitate, an inhibitor of protein palmitoylation, inhibited all of the proapoptotic effects of PAF. Our data strongly suggest that an inhibition of the PI 3-kinase/Akt signaling pathway is the main mechanism of PAF-induced apoptosis in enterocytes and that polyunsaturated fatty acids block this mechanism very early in the signaling cascade independently of any effect on prostaglandin synthesis, and probably directly via an effect on protein palmitoylation. platelet-activating factor; protein kinase B

Epithelial-mesenchymal interactions are essential for growth, differentiation, and regeneration of exocrine and endocrine cells in the pancreas. The keratinocyte growth factor (KGF) is derived from mesenchyme and has been shown to promote epithelial cell differentiation and proliferation in a paracrine fashion. Here, we have examined the effect of ectopic expression of KGF on pancreatic differentiation and proliferation in transgenic mice by using the proximal elastase promoter. KGF transgenic mice were generated following standard procedures and analyzed by histology, morphometry, immunohistochemistry, Western blot analysis, and glucose tolerance testing. In KGF transgenic mice, the number of islets, the average size of islets, and the relation of endocrine to exocrine tissue are increased compared with littermate controls. An expansion of the [beta]-cell population is responsible for the increase in the endocrine compartment. Ectopic expression of KGF results in proliferation of [beta]-cells and pancreatic duct cells most likely through activation of the protein kinase B (PKB)/Akt signaling pathway. Glucose tolerance and insulin secretion are impaired in transgenic animals. These results provide evidence that ectopic expression of KGF in acinar cells promotes the expansion of the [beta]-cell lineage in vivo through activation of the PKB/Akt pathway. Furthermore, the observed phenotype demonstrates that an increase in the [beta]-cell compartment does not necessarily result in an improved glucose tolerance in vivo. [beta]-cell proliferation; protein kinase B; glucose tolerance

Obese conditions increase the expression of adipocytokine monocyte chemoattractant protein-1 (MCP-1) in adipose tissue as well as MCP-1 plasma levels. To investigate the mechanism behind increased MCP-1, we used a model in which 3T3-L1 adipocytes were artificially hypertrophied by preloading with palmitate in vitro. As observed in obesity, under our model conditions, palmitate-preloaded ceils showed significantly increased oxidative stress and increased MCP-1 expression relative to control cells. This increased MCP-1 expression was enhanced by adding exogenous tumor necrosis factor-[alpha] (TNF-[alpha]; 17.8-fold vs. control cells, P < 0.01 ) rather than interleukin-1[beta] (IL-1[beta]; 2.6-fold vs. control cells, P < 0.01). However, endogenous TNF-[alpha] and IL-1[beta] release was not affected in hypertrophied cells, suggesting that these endogenous cytokines do not mediate hypertrophy-induced increase in MCP-1. MCP-1 secretion from hypertrophied cells was significantly decreased by treatment with antioxidant N-acetyl-cysteine, JNK inhibitors SP600125 and JIP-1 peptide, and I[kappa]B phosphorylation inhibitors BAY 11-7085 and BMS-345541 (P < 0.01). MCP-1 secretion was not affected by peroxisome proliferator-activated receptor-[gamma] (PPAR[gamma]) antagonists assayed. Adiponectin, another adipocytokine studied in parallel, also showed increased release in hypertrophy relative to control cells. But in contrast to MCP-1, adiponectin release was significantly suppressed by both exogenous TNF-[alpha] and IL-1[beta] as well as by PPAR[gamma] antagonists bisphenol A diglycidyl ether and T0070907 (P < 0.01). JNK inhibitors and I[kappa]B phosphorylation inhibitors showed no significant effect on adiponectin. We conclude that adipocyte hypertrophy through palmitate loading causes oxidative stress, which in turn increases MCP-1 expression and secretion through JNK and I[kappa]B signaling. In contrast, the parallel increase in adiponectin expression appears to be related to the PPAR[gamma] ligand properties of palmitate. c-Jun N[H.sub.2]-terminal kinase; monocyte chemoattractant protein-1; tumor necrosis factor-[alpha]; interleukin-1[beta]

We determined the acute effects of oxidative stress on glucose uptake and intracellular signaling in skeletal muscle by incubating muscles with reactive oxygen species (ROS). Xanthine oxidase (XO) is a superoxide-generating enzyme that increases ROS. Exposure of isolated rat extensor digitorum long us (EDL) muscles to Hx/XO (Hx/XO) for 20 min resulted in a dose-dependent increase in glucose uptake. To determine whether the mechanism leading to Hx/XO-stimulated glucose uptake is associated with the production of [H.sub.2][O.sub.2], EDL muscles from rats were preincubated with the [H.sub.2][O.sub.2] scavenger catalase or the superoxide scavenger superoxide dismutase (SOD) prior to incubation with Hx/XO. Catalase treatment, but not SOD, completely inhibited the increase in Hx/XO-stimulated 2-deoxyglucose (2-DG) uptake, suggesting that [H.sub.2][O.sub.2] is an intermediary leading to Hx/XO-stimulated glucose uptake with incubation. Direct [H.sub.2][O.sub.2] also resulted in a dose-dependent increase in 2-DG uptake in isolated EDL muscles, and the maximal increase was threefold over basal levels at a concentration of 600 [micro]mol/l [H.sub.2][O.sub.2]. [H.sub.2][O.sub.2]-stimulated 2-DG uptake was completely inhibited by the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin, but not the nitric oxide inhibitor [N.sup.G]-monomethyl-L-arginine. [H.sub.2][O.sub.2] stimulated the phosphorylation of Akt [Set.sup.473] (7-fold) and [Thr.sup.308] (2-fold) in isolated EDL muscles. [H.sub.2][O.sub.2] at 600 [micro]mol/l had no effect on ATP concentrations and did not increase the activities of either the [alpha]1 or [alpha]2 catalytic isoforms of AMP-activated protein kinase. These results demonstrate that acute exposure of muscle to ROS is a potent stimulator of skeletal muscle glucose uptake and that this occurs through a PI3K-dependent mechanism. hydrogen peroxide; Akt phosphorylation; adenosine monophosphate-activated protein kinase

High-glucose/low-dose insulin-mediated insulin resistance of glucose transport was studied in 3T3-L1 adipocytes. In this model, proximal insulin signaling, including insulin receptor substrate (IRS)-1-bound phosphatidylinositol 3-kinase (PI 3-kinase) activation, is preserved, but insulin-stimulated protein kinase B (Akt) activation is markedly impaired. To assess a difference in acute insulin-stimulated production of phosphatidylinositol 3,4,5-trisphosphate [PtdIns(3,4,5)[P.sub.3]], cells were labeled with [[sup.32]P]orthophosphate, and glycerophosphoinositides were quantified by HPLC. Although basal PtdIns(3,4,5)[P.sub.3] was similar, insulin stimulated its production 33.6% more in controls (P < 0.03) than in insulin-resistant cells. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) protein, a lipid phosphatase that dephosphorylates PtdIns(3,4,5)[P.sub.3] in the 3-position, was significantly and specifically increased in insulin-resistant cells. Treatment with rapamycin [a specific inhibitor of mammalian target of rapamycin complex 1 (mTORC1)] inhibited the increased PTEN expression and partially restored insulin-stimulated glucose transport and Akt activation to insulin-resistant cells. Acute insulin markedly stimulated [Ser.sup.636/639] phosphorylation of IRS-1; this was rapamycin inhibited but was significantly decreased in cells that had been preexposed to insulin, whereas total IRS-1 was unaffected. These findings were essentially paralleled by changes in the activation of p70 S6 kinase and S6ribosomal protein. Overexpression of uncoupling protein-1 or manganese superoxide dismutase did not prevent the development of insulin-resistant glucose transport and impaired Akt activation in high-glucose/low-insulin-pretreated cells. The insulin resistance associated with glucotoxicity in our model reflects in part decreased availability of PtdIns(3,4,5)[P.sub.3], which correlates with increased PTEN protein expression. Chronic activation of mTORC1 plays a role in stimulating PTEN expression and possibly in activation or induction of a phosphoprotein phosphatase. No evidence was found for a role for increased mitochondrial superoxide production in this model. phosphatidylinositol 3,4,5-trisphosphate; phosphatase and tensin homolog deleted on chromosome 10; mammalian target of rapamycin complex 1; rapamycin; protein kinase B

FGF-16 has been reported to be preferentially expressed in the adult rat heart. We have investigated the expression of FGF-16 in the perinatal and postnatal heart and its functional significance in neonatal rat cardiac myocytes. FGF-16 mRNA accumulation was observed by quantitative RT-PCR between neonatal days 1 and 7, with this increased expression persisting into adulthood. FGF-2 has been shown to increase neonatal rat cardiac myocyte proliferative potential via PKC activation. Gene array analysis revealed that FGF-16 inhibited the upregulation by FGF-2 of cell cycle promoting genes including cyclin F and Ki67. Furthermore, the CDK4/6 inhibitor gene Arf/INK4A was upregulated with the combination of FGF- 16 and FGF-2 but not with either factor on its own. The effect on Ki67 was validated by protein immunodetection, which also showed that FGF-16 significantly decreased FGF-2-induced Ki67 labeling of cardiac myocytes, although it alone had no effect on Ki67 labeling. Inhibition of p38 MAPK potentiated cardiac myocyte proliferation induced by FGF-2 but did not alter the inhibitory action of FGF-16. Receptor binding assay showed that FGF-16 can compete with FGF-2 for binding sites including FGF receptor 1. FGF-16 had no effect on activated p38, ERK1/2, or JNK/SAPK after FGF-2 treatment. However, FGF-16 inhibited PKC-[alpha] and PKC-[member of] activation induced by FGF-2 and, importantly, IGF-1. Collectively, these data suggest that expression and release of FGF-16 in the neonatal myocardium interfere with cardiac myocyte proliferative potential by altering the local signaling environment via modulation of PKC activation and cell cycle-related gene expression. fibroblast growth factor; protein kinase C; Ki67

Prolactin (PRL) was previously demonstrated to rapidly enhance calcium absorption in rat duodenum and the intestine-like Caco-2 monolayer. However, its mechanism was not completely understood. Here, we investigated nongenomic effects of PRL on the transepithelial calcium transport and paracellular permselectivity in the Caco-2 monolayer by Ussing chamber technique. PRL increased the transcellular and paracellular calcium luxes and paracellular calcium permeability within 60 min after exposure but decreased the transepithelial resistance of the monolayer. The effects of PRL could not be inhibited by RNA polymerase II inhibitor (5,6-dichloro-1-[beta]-D-ribobenzimidazole), confirming that PRL actions were nongenomic. Exposure to protein kinase C (PKC) or RhoA-associated coiled-coil forming kinase (ROCK) inhibitors (GF-109203X and Y-27632, respectively) abolished the stimulatory effect of PRL on transcellular calcium transport, whereas ROCK inhibitor, but not PKC inhibitor, diminished the PRL effect on paracellular calcium transport. Knockdown of the long isoform of PRL receptor (PRLR-L) also prevented the enhancement of calcium transport by PRL. In addition, PRL markedly increased paracellular sodium permeability and the permeability ratio of sodium to chloride, which are indicators of the paracellular charge-selective property and are known to be associated with the enhanced paracellular calcium transport. The permeability of other cations in the alkali metal series was also increased by PRL, and such increases were abolished by ROCK inhibitor. It could be concluded that PRL stimulated transepithelial calcium transport through PRLR-L and increased paracellular permeability to cations in the Caco-2 monolayer. These nongenomic actions of PRL were mediated by the PKC and ROCK signaling pathways. charge selectivity; dilution potential; paracellular transport; phosphoinositide 3-kinase; protein kinase C; long form of prolactin receptor; RhoA; short interference RNA; transcellular transport

Scar formation occurs during the late stages of the inflammatory response but, when excessive, produces fibrosis that can lead to functional and structural damage of tissues. Here, we show that the profibrogenic agonist, transforming growth factor [beta]1, transcriptionally decreases expression of Exchange protein activated by cAMP 1 (Epac1) in fibroblasts/fibroblast-like cells from multiple tissues (i.e., cardiac, lung, and skin fibroblasts and hepatic stellate cells). Overexpression of Epac1 inhibits transforming growth factor [beta]1-induced collagen synthesis, indicating that a decrease of Epac1 expression appears to be necessary for the fibrogenic phenotype, an idea supported by evidence that Epac1 expression in cardiac fibroblasts is inhibited after myocardial infarction. Epac and protein kinase A, a second mediator of cAMP action, have opposite effects on migration but both inhibit synthesis of collagen and DNA by fibroblasts. Epac is preferentially activated by low concentrations of cAMP and stimulates migration via the small G protein Rap1 but inhibits collagen synthesis in a Rap1-independent manner. The regulation of Epac expression and activation thus appear to be critical for the integration of pro- and anti-fibrotic signals and for the regulation of fibroblast function. exchange protein activated by cyclic AMP | fibrosis | protein kinase A | tissue remodeling

we develop a probabilistic method for analyzing global features of a cellular network under intrinsic statistical fluctuations, which is important when there are finite numbers of molecules. By making a self-consistent mean field approximation of splitting the variables in order to reduce the large number of degrees of freedom, which is reasonable for a not very strongly interacting network, we discovered that the underlying energy landscape of the mitogen-activated protein kinases (MAPKs) signal transduction network (with experimentally measured of inferred parameters such as chemical reaction rate coefficients in the network) is funneled toward a global minimum characterized by the nonequilibrium steady-state fixed point of the system at the end of the signal transduction process. For this system, we also show that the energy landscape is robust against intrinsic fluctuations and random perturbation to the inherent chemical reaction rates. The ratio of the slope versus the roughness of the energy landscape becomes a quantitative measure of robustness and stability of the network. Furthermore, we quantify the dissipation cost of this nonequilibrium system through entropy production, caused by the nonequilibrium flux in the system. We found that a lower dissipation cost corresponds to a more robust network. This least dissipation property might provide a design principle for robust and functional networks. Finally, we find the possibility of bistable and oscillatory-like solutions, which are important for cell fate decisions, upon perturbations. The method described here can be used in a variety of biological networks. funnel | stability | potential landscape | function

Translation initiation factors have complex functions in cells that are not yet understood. We show that depletion of initiation factor elF4GI only modestly reduces overall protein synthesis in cells, but phenocopies nutrient starvation or inhibition of protein kinase mTOR, a key nutrient sensor, elF4GI depletion impairs cell proliferation, bioenergetics, and mitochondrial activity, thereby promoting autophagy. Translation of mRNAs involved in cell growth, proliferation, and bioenergetics were selectively inhibited by reduction of elF4GI, as was the mRNA encoding Skp2 that inhibits p27, whereas catabolic pathway factors were increased. Depletion or overexpression of other elF4G family members did not recapitulate these results. The majority of mRNAs that were translationally impaired with elF4GI depletion were excluded from polyribosomes due to the presence of multiple upstream open reading frames and low mRNA abundance. These results suggest that the high levels of elF4GI observed in many breast cancers might act to specifically increase proliferation, prevent autophagy, and release tumor cells from control by nutrient sensing.

Protein kinase CK2 (also known as casein kinase 2) is present in the cytoplasm, nuclei, and several other organelles. In addition, this enzyme has been found bound to the external side of the cell membrane where it acts as an ectokinase phosphorylating several extracellular proteins. Previous experiments with transfection of HEK-293T cells demonstrated that expression of both subunits, CK2[alpha] (catalytic) and CK2[beta] (regulatory), was necessary for the appearance of the ectopic enzyme as an ectokinase. In this work, using deletion and point mutations of CK2[beta], it was possible to demonstrate that the region between amino acids 20 and 33 was necessary for the export of the enzyme as an ectokinase. Phenylalanines 21 and 22 and acidic residues in positions 26-28 are involved in the structural aspects that are required for export. However, the region encompassing amino acids 20-33 of CK2[beta] is not sufficient to make the carboxyl half of this subunit functional in bringing CK2 to the ectokinase locus. In cells transfected with only CK2[beta], it was demonstrated that 3-4% of the subunit is exported to the cell medium, but the subunit is not bound to the external membrane. casein kinase 2 | export of proteins | shedding

Plant recognition of pathogens leads to rapid activation of MPK3 and MPK6, two Arabidopsis mitogen-activated protein kinases (MAPKs), and their orthologs in other species. Here, we report that synthesis of camalexin, the major phytoalexin in Arabidopsis, is regulated by the MPK3/MPK6 cascade. Activation of MPK3/MPK6 by expression of active upstream MAPK kinase (MAPKK) or MAPKK kinase (MAPKKK) was sufficient to induce camalexin synthesis in the absence of pathogen attack. Induction of camalexin by Botrytis cinerea was preceded by MPK3/MPK6 activation, and compromised in mpk3 and mpk6 mutants. Genetic analysis placed the MPK3/MPK6 cascade upstream of PHYTOALEXIN DEFICIENT 2 (PAD2) and PAD3, but independent or downstream of PAD1 and PAD4. Camalexin induction after MPK3/MPK6 activation was preceded by rapid and coordinated up-regulation of multiple genes encoding enzymes in the tryptophan (Trp) biosynthetic pathway, in the conversion of Trp to indole-3-acetaldoxime (IAOx, a branch point between primary and secondary metabolism), and in the camalexin biosynthetic pathway downstream of IAOx. These results indicate that the MPK3/MPK6 cascade regulates camalexin synthesis through transcriptional regulation of the biosynthetic genes after pathogen infection. defense signaling | fungal resistance | camalexin biosynthesis | Botrytis cinerea

MYt1 was originally identified as an inhibitory kinase for Cdc2 (Cdk1), the master engine of mitosis, and has been thought to function, together with Wee1, as a negative regulator of mitotic entry. In this study, we report an unexpected finding that Myt1 is essential for Golgi and endoplasmic reticulum (ER) assembly during telophase in mammalian cells. Our analyses reveal that both cyclin B1 and cyclin B2 serve as targets of Myt1 for proper Golgi and ER assembly to occur. Thus, our results show that Myt1 -mediated suppression of Cdc2 activity is not indispensable for the regulation of a broad range of mitotic events but is specifically required for the control of intracellular membrane dynamics during mitosis.

Focal adhesion kinase (FAK) plays a critical role during vascular development because knockout of FAK in endothelial cells (ECs) is embryonic lethal. Surprisingly, tamoxifen-inducible conditional knockout of FAK in adult blood vessels (inducible EC-specific FAK knockout [i-EC-FAK-KO]) produces no vascular phenotype, and these animals are capable of developing a robust growth factor-induced angiogenic response. Although angiogenesis in wild-type mice is suppressed by pharmacological inhibition of FAK, i-EC-FAK-KO mice are refractory to this treatment, which suggests that adult i-EC-FAK-KO mice develop a compensatory mechanism to bypass the requirement for FAK. Indeed, expression of the FAK-related proline-rich tyrosine kinase 2 (Pyk2) is elevated and phosphorylated in i-EC-FAK-KO blood vessels. In cultured ECs, FAK knockdown leads to increased Pyk2 expression and, surprisingly, FAK kinase inhibition leads to increased Pyk2 phosphorylation. Pyk2 can functionally compensate for the loss of FAK because knockdown or pharmacological inhibition of Pyk2 disrupts angiogenesis in i-EC-FAK-KO mice. These studies reveal the adaptive capacity of ECs to switch to Pyk2-dependent signaling after deletion or kinase inhibition of FAK.

The I[kappa]B kinases (IKKs) IKK-[alpha] and IKK-[beta], and the IKK-related kinases TBK1 and IKK-[epsilon], have essential roles in innate immunity through signal-induced activation of NF-[kappa]B, IRF3 and IRF7, respectively. Although the signaling events within these pathways have been extensively studied, the mechanisms of IKK and IKK-related complex assembly and activation remain poorly defined. Recent data provide insight into the requirement for scaffold proteins in complex assembly; NF-[kappa]B essential modulator coordinates some IKK complexes, whereas TANK, NF-[kappa]B-activating kinase-associated protein 1 (NAP1) or similar to NAP1 TBK1 adaptor (SINTBAD) assemble TBK1 and IKK-[epsilon] complexes. The different scaffold proteins undergo similar post-translational modifications, including phosphorylation and non-degradative polyubiquitylation. Moreover, increasing evidence indicates that distinct scaffold proteins assemble IKK, and potentially TBK1 and IKK-[epsilon] subcomplexes, in a stimulus-specific manner, which might be a mechanism to achieve specificity.

Multiple signaling pathways are engaged by the type I and II IFN receptors, but their specific roles and possible coordination in the generation of IFN-mediated biological responses remain unknown. We provide evidence that activation of Akt kinases is required for IFN-inducible engagement of the mTOR/p70 S6 kinase pathway. Our data establish that Akt activity is essential for up-regulation of key IFN-[alpha]- and IFN-[gamma]-inducible proteins, which have important functional consequences in the induction of IFN responses. Such effects of the Akt pathway are unrelated to regulatory activities on IFN-dependent STAT phosphorylation/activation or transcriptional regulation. By contrast, they reflect regulatory activities on mRNA translation via direct control of the mTOR pathway. In studies using Aktl and Akt2 double knockout cells, we found that the absence of Akt kinases results in dramatic reduction in IFN-induced antiviral responses, establishing a critical role of the Akt pathway in IFN signaling. Thus, activation of the Akt pathway by the IFN receptors complements the function of IFN-activated JAK--STAT pathways, by allowing mRNA translation of IFN-stimulated genes and, ultimately, the induction of the biological effects of IFNs.

A hallmark of the pathology of Alzheimer's disease is the accumulation of the microtubule-associated protein tau into fibrillar aggregates. Recent studies suggest that they accumulate because cytosolic chaperones fail to clear abnormally phosphorylated tau, preserving a pool of toxic tau intermediates within the neuron. We describe a mechanism for tau clearance involving a major cellular kinase, Akt. During stress, Akt is ubiquitinated and degraded by the tau ubiquitin ligase CHIP, and this largely depends on the Hsp90 complex. Akt also prevents CHIP-induced tau ubiquitination and its subsequent degradation, either by regulating the Hsp90/CHIP complex directly or by competing as a client protein with tau for binding. Akt levels tightly regulate the expression of CHIP, such that, as Akt levels are suppressed, CHIP levels also decrease, suggesting a potential stress response feedback mechanism between ligase and kinase activity. We also show that Akt and the microtubule affinity-regulating kinase 2 (PARI/MARK2), a known tau kinase, interact directly. Akt enhances the activity of PAR1 to promote tau hyperphosphorylation at S262/S356, a tau species that is not recognized by the CHIP/Hsp90 complex. Moreover, Akt1 knockout mice have reduced levels of tau phosphorylated at PAR1/MARK2 consensus sites. Hence, Akt serves as a major regulator of tau biology by manipulating both tau kinases and protein quality control, providing a link to several common pathways that have demonstrated dysfunction in Alzheimer's disease. Alzheimer's disease | cell signaling | chaperone | MARK2/PAR1

Articles in recent years have described two separate and distinct NF-[kappa]B activation pathways that result in the differential activation of p50- or p52-containing NF-[kappa]B complexes. Studies examining tumor-necrosis factor receptor-associated factors (TRAFs) have identified positive roles for TRAF2, TRAF5, and TRAF6, but not TRAF3, in canonical (p50-dependent) NF-[kappa]B activation. Conversely, it recently was reported that TRAF3 functions as an essential negative regulator of the noncanonical (p52-dependent) NF-[kappa]B pathway. In this article, we provide evidence that TRAF3 potently suppresses canonical NF-[kappa]B activation and gene expression in vitro and in vivo. We also demonstrate that deregulation of the canonical NF-[kappa]B pathway in TRAF3-deficient cells results from accumulation of NF-[kappa]B-inducing kinase (NIK), the essential kinase mediating noncanonical NF-[kappa]B activation. Thus, our data demonstrate that inhibition of TRAF3 results in coordinated activation of both NF-[kappa]B activation pathways. lymphotoxin-[beta] receptor | p50 | tumor-necrosis factor receptor-associated factor 3 (TRAF3)

It is now recognized that significant tubular reabsorption of albumin occurs under physiological conditions that may play an important role in maintaining proximal tubular integrity and function. Therefore, this study examined the effect of bovine serum albumin (BSA) on DNA synthesis and its related signal molecules in primary cultured rabbit renal proximal tubule cells (PTCs). BSA increased the level of [[sup.3]H]thymidine incorporation in a dose ([greater than or equal to] 3 mg/ml)--and time ([greater than or equal to] 3 h)-dependent manner, intracellular [Ca.sup.2+] concentration, and the level of protein kinase C (PKC) phosphorylation and stimulated the phosphorylation of the epidermal growth factor receptor (EGFR), which was inhibited by EGTA (extracellular [Ca.sup.2+] chelator), 1,2-bis(2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester (BAPTA-AM, intracellular [Ca.sup.2+] chelator), or PKC inhibitors (staurosporine or bisindolylmaleimide I). In addition, the PKC inhibitors or an EGFR inhibitor (AG-1478) blocked the BSA-induced phosphorylation of p44/42 mitogen-activated protein kinases (MAPKs). BSA also increased the level of nuclear factor-[kappa]B (NF-[kappa]B) and inhibitor of NF-[kappa]B (I[kappa]B) phosphorylation, which was blocked by staurosporine, AG-1478, or PD-98059 (p44/42 MAPK inhibitor). Inhibition of [[Ca].sup.2+], PKC, EGFR, p44/42 MAPK, or NF-[kappa]B signal pathways blocked the BSA-induced incorporation of [[sup.3]H]thymidine. Consequently, the inhibition of [Ca.sup.2+], PKC, EGFR, p44/42 MAPKs, or NF-KB blocked the BSA-induced increases in cyclin DI, cyclin-dependent kinase (CDK)4, cyclin E, or CDK2 and restored the BSA-induced inhibition of [p21.sup.WAF/Cip1] and [p27.sup.Kipl] expression. In conclusion, BSA stimulates DNA synthesis that is mediated by [[Ca].sup.2+] /PKC as well as the EGFR-dependent p44/42 MAPK and NF-[kappa]B signal pathways in PTCs. kidney; cyclins; cyclin-dependent kinases; [p21.sup.WAF/Cip1]; [p27.sup.Kip1]

The rate of glucose phosphorylation in hepatocytes is determined by the subcellular location of glucokinase and by its association with its regulatory protein (GKRP) in the nucleus. Elevated glucose concentrations and precursors of fructose 1-phosphate (e.g., sorbitol) cause dissociation of glucokinase from GKRP and translocation to the cytoplasm. In this study, we investigated the counter-regulation of substrate-induced translocation by AICAR (5-aminoimidazole-4-carboxamide-1-[beta]-D-ribofuranoside), which is metabolized by hepatocytes to an AMP analog, and causes activation of AMP-activated protein kinase (AMPK) and depletion of ATP. During incubation of hepatocytes with 25 mM glucose, AICAR concentrations below 200 [micro]M activated AMPK without depleting ATP and inhibited glucose phosphorylation and glucokinase translocation with half-maximal effect at 100-140 [micro]M. Glucose phosphorylation and glucokinase translocation correlated inversely with AMPK activity. AICAR also counteracted translocation induced by a glucokinase activator and partially counteracted translocation by sorbitol. However, AICAR did not block the reversal of translocation (from cytoplasm to nucleus) after substrate withdrawal. Inhibition of glucose-induced translocation by AICAR was greater than inhibition by glucagon and was associated with phosphorylation of both GKRP and the cytoplasmic glucokinase binding protein, 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFK2) on ser-32. Expression of a kinase-active PFK2 variant lacking set-32 partially reversed the inhibition of translocation by AICAR. Phosphorylation of GKRP by AMPK partially counteracted its inhibitory effect on glucokinase activity, suggesting altered interaction of glucokinase and GKRP. In summary, mechanisms downstream of AMPK activation, involving phosphorylation of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase and GKRP are involved in the ATP-independent inhibition of glucose-induced glucokinase translocation by AICAR in hepatocytes. liver; 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase AMP-activated protein kinase; glucose metabolism

Although splenic dendritic cell (DC) functions are markedly altered following trauma-hemorrhage, the mechanism(s) responsible for the altered DC functions remains unknown. We hypothesized that trauma-hemorrhage inhibits DC function via suppressing toll-like receptor 4 (TLR4) expression and mitogen-activated protein kinases (MAPKs). To examine this, male C3H/HeN (6-8 wk) mice were randomly assigned to sham operation or trauma-hemorrhage. Trauma-hemorrhage was induced by midline laparotomy and ~90 min of hypotension [blood pressure (BP) 35 mmHg], followed by fluid resuscitation (4x the shed blood volume in the form of Ringer lactate). Two hours later, mice were euthanized, splenic DCs were isolated, and the changes in their MAPK activation, TLR4-MD-2 expression, and ability to produce cytokines were measured. The results indicate that trauma-hemorrhage downregulated the lipopolysaccharide (LPS)-induced MAPK activation in splenic DCs. In addition to the decrease in MAPK activation, surface expression of TLR4-MD-2 was suppressed following trauma-hemorrhage. Furthermore, LPS-induced cytokine production from splenic DCs was also suppressed following trauma-hemorrhage. These findings thus suggest that the decrease in TLR4-MD-2 and MAPK activation may contribute to the LPS hyporesponsiveness of splenic DCs following trauma-hemorrhage. Hyporesponsiveness of splenic DCs was also found alter stimulation with the TLR2 agonist zymosan. Our results may thus explain the profound immunosuppression that is known to occur under those conditions. toll-like receptor 4 expression; splenic dendritic cell; toll-like receptors; lipopolysaccharide

Sjogren's syndrome and therapeutic radiation for head and neck cancers result in irreversible changes in the parenchyma of salivary glands, loss of acinar cells, prominence of duct cells, and fibrosis. To clarify mechanisms of salivary gland dysfunction, we identified a signaling pathway involved in the dedifferentiation of primary cultures of parotid acinar cells. We reported previously that the expression pattern of claudins changes during culture, is related to the three-dimensional organization of the cells, and reflects their ability to function as acinar cells. In this study, we found that this change of claudin expression is a process of dedifferentiation, because expression of other differentiation markers also changes during culture. The expression levels of claudins-4 and -6, cytokeratin 14, and vimentin are increased, and those of claudin-10, aquaporin 5, and amylase are decreased. Inhibitors of Src and p38 MAP kinases suppress these changes and increase the expression of acinar marker proteins. Differences in extracellular matrix components have no effect. Activation of p38 MAP kinase occurs during cell isolation from the parotid glands and is retained up to 6 h after the isolation. In contrast, activation of Src kinases does not increase during the cell isolation. The Src inhibitor PP1 suppresses the activation of p38 MAP kinase. Therefore, cellular stresses induced during cell isolation cause dedifferentiation and transition to duct-like cells through activation of p38 MAP kinase and constitutively active Src kinases. salivary gland; exocrine gland; epithelium; tight junction

We used Western blot analysis to examine the effect of dietary K intake on the expression of serine/ threonine protein phosphatase in the kidney. K restriction significantly decreased the expression of catalytic subunit of protein phosphatase (PP)2B but increased the expression of PP2B regulatory subunit in both rat and mouse kidney. However, K depletion did not affect the expression of PP1 and PP2A. Treatment of M-1 cells, mouse cortical collecting duct (CCD) cells, or 293T cells with glucose oxidase (GO), which generates superoxide anions through glucose metabolism, mimicked the effect of K restriction on PP2B expression and significantly decreased expression of PP2B catalytic subunits. However, GO treatment increased expression of regulatory subunit of PP2B and had no effect on expression of PP1, PP2A, and protein tyrosine phosphatase 1D. Moreover, deletion of gp91-containing NADPH oxidase abolished the effect of K depletion on PP2B. Thus superoxide anions or related products may mediate the inhibitory effect of K restriction on the expression of PP2B catalytic subunit. We also used patch-clamp technique to study the effect of inhibiting PP2B on renal outer medullary K (ROMK) channels in the CCD. Application of cyclosporin A or FK506, inhibitors of PP2B, significantly decreased ROMK channels, and the effect of PP2B inhibitors was abolished by blocking p38 mitogen-activated protein kinase (MAPK) and ERK. Furthermore, Western blot demonstrated that inhibition of PP2B with cyclosporin A or small interfering RNA increased the phosphorylation of ERK and p38 MAPK. We conclude that K restriction suppresses the expression of PP2B catalytic subunits and that inhibition of PP2B decreases ROMK channel activity through stimulation of MAPK in the CCD. potassium depletion; p38 mitogen-activated protein kinase; extracellular signal-regulated kinase 1/2; potassium secretion

[BRAF.sub.v600E] is the most frequent oncogenic protein kinase mutation known. Furthermore, inhibitors targeting 'active' protein kinases have demonstrated significant utility in the therapeutic repertoire against cancer. Therefore, we pursued the development of specific kinase inhibitors targeting B-Raf, and the V600E allele in particular. By using a structure-guided discovery approach, a potent and selective inhibitor of active B-Raf has been discovered. PLX4720, a 7-azaindole derivative that inhibits B-[Raf.sup.v600E] with an I[C.sub.50] of 13 nM, defines a class of kinase inhibitor with marked selectivity in both biochemical and cellular assays. PLX4720 preferentially inhibits the active B-[Raf.sup.v600E] kinase compared with a broad spectrum of other kinases, and potent cytotoxic effects are also exclusive to cells bearing the V600E allele. Consistent with the high degree of selectivity, ERK phosphorylation is potently inhibited by PLX4720 in B-[Raf.sup.v600E]-bearing tumor cell lines but not in cells lacking oncogenic B-Raf. In melanoma models, PLX4720 induces cell cycle arrest and apoptosis exclusively in B-[Raf.sup.v600E]-positive cells. In B-[Raf.sup.v600E]-dependent tumor xenograft models, orally dosed PLX4720 causes significant tumor growth delays, including tumor regressions, without evidence of toxicity. The work described here represents the entire discovery process, from initial identification through structural and biological studies in animal models to a promising therapeutic for testing in cancer patients bearing B-[Raf.sup.v600E]-driven tumors. cancer | cell signaling | melanoma | phosphorylation | protein kinases

The adult heart responds to biomechanical stress and neurohormonal signaling by hypertrophic growth, accompanied by fibrosis, diminished pump function, and activation of a fetal gene program. Class II histone deacetylases (HDACs) suppress stress-dependent remodeling of the heart via their association with the MEF2 transcription factor, an activator of heart disease. Protein kinase D (PKD) is a stress-responsive kinase that phosphorylates class II HDACs, resulting in their dissociation from MEF2 with consequent activation of MEF2 target genes. To test whether PKD1 is required for pathological cardiac remodeling in vivo, we generated mice with a conditional PKD1-null allele. Mice with cardiac-specific deletion of PKD1 were viable and showed diminished hypertrophy, fibrosis, and fetal gene activation as well as improved cardiac function in response to pressure overload or chronic adrenergic and angiotensin II signaling. We conclude that PKD1 functions as a key transducer of stress stimuli involved in pathological cardiac remodeling in vivo. cardiac hypertrophy | histone deacetylase | stress-responsive kinase

Interaction of the activating receptor NKG2D with its ligands is a major stimulatory pathway for cytotoxicity of natural killer (NK) cells. Here, the signaling pathway involved after NKG2D ligation is examined. Either incubation of the NKG2D-bearing human NKL tumor cell line with K562 target cells or cross-linking with NKG2D mAb induced strong activation of the mitogen-activated protein (MAP) kinases. Selective inhibition of JNK MAP kinase with four different means of inhibition greatly reduced NKG2D-mediated cytotoxicity toward target cells and furthermore, blocked the movement of the microtubule organizing center (MTOC), granzyme B (a component of cytotoxic granules), and paxillin (a scaffold protein) to the immune synapse. NKG2D-induced activation of JNK kinase was also blocked by inhibitors of Src protein tyrosine kinases and phospholipase PL[C.sub.[gamma]], upstream of JNK. Similarly, a second MAP kinase pathway through ERK was previously shown to be required for NK cell cytotoxicity. Thus, activation of two MAP kinase pathways is required for cytotoxic granule and MTOC polarization and for cytotoxicity of human NK cells when NKG2D is ligated. D-JNK-1 | ERK | paxillin | siRNA | synapse

The protein kinase encoded by the Tpl2 protooncogene plays an obligatory role in the transduction of Toll-like receptor and death receptor signals in macrophages, B cells, mouse embryo fibroblasts, and epithelial cells in culture and promotes inflammatory responses in animals. To address its role in T cell activation, we crossed the T cell receptor (TCR) transgene 2C, which recognizes class I MHC presented peptides, into the Tpl[2.sup.-/-] genetic background. Surprisingly, the TCR2[C.sup.tg/tg]/Tpl[2.sup.-/-] mice developed T cell lymphomas with a latency of 4-6 months. The tumor cells were consistently TCR2[C.sup.+]CD[8.sup.+]CD[4.sup.-], suggesting that they were derived either from chronically stimulated mature T cells or from immature single positive (ISP) cells. Further studies showed that the population of CD[8.sup.+] ISP cells was not expanded in the thymus of TCR2[C.sup.tg/tg]/Tpl[2.sup.-/-] mice, making the latter hypothesis unlikely. Mature peripheral T cells of Tpl[2.sup.-/-] mice were defective in ERK activation and exhibited enhanced proliferation after TCR stimulation. The same cells were defective in the induction of CTLA4, a negative regulator of the T cell response, which is induced by TCR signals via ERK. These findings suggest that Tpl2 functions normally in a feedback loop that switches off the T cell response to TCR stimulation. As a result, Tpl2, a potent oncogene, functions as a tumor suppressor gene in chronically stimulated T cells. CTLA4 | cancer | lymphoma | T cell receptor transgene 2C (TCR2C) | CD8