Interleukin 1 and tumor necrosis factor stimulate two novel protein kinases that phosphorylate the heat shock protein hsp27 and beta-casein

Biologic activities of molecular chaperones and pharmacologic chaperone imidazole-containing dipeptide-based compounds: natural skin care help and the ultimate challenge: implication for adaptive responses in the skin

Accumulation of molecular damage and increased molecular heterogeneity are hallmarks of photoaged skin and pathogenesis of human cutaneous disease. Growing evidence demonstrates the ability of molecular chaperone proteins and of pharmacologic chaperones to decrease the environmental stress and ameliorate the oxidation stress-related and glycation disease phenotypes, suggesting that the field of chaperone therapy might hold novel treatments for skin diseases and aging. In this review, we examine the evidence suggesting a role for molecular chaperone proteins in the skin and their inducer and protecting agents: pharmacologic chaperone imidazole dipeptide-based agents (carcinine and related compounds) in cosmetics and dermatology. Furthermore, we discuss the use of chaperone therapy for the treatment of skin photoaging diseases and other skin pathologies that have a component of increased glycation and/or free radical-induced oxidation in their genesis. We examine biologic activities of molecular and pharmacologic chaperones, including strategies for identifying potential chaperone compounds and for experimentally demonstrating chaperone activity in in vitro and in vivo models of human skin disease. This allows the protein to function and traffic to the appropriate location in the skin, thereby increasing protein activity and cellular function and reducing stress on skin cells. The benefits of imidazole dipeptide antioxidants with transglycating activity (such as carcinine) in skin care are that they help protect and repair cell membrane damage and help retain youthful, younger-looking skin. All skin types will benefit from daily, topical application of pharmacologic chaperone antioxidants, anti-irritants, in combination with water-binding protein agents that work to mimic the structure and function of healthy skin. General strategies are presented addressing ground techniques to improve absorption of usually active chaperone proteins and dipeptide compounds, include encapsulation into hydrophobic carriers, a combination with penetration enhancers, active electrical transport, or chemical modification to increase hydrophobicity.

Inhibition of amino acid transport system a by interleukin-1beta in trophoblasts

OBJECTIVE

The current study sought to investigate the influence of interleukin-1beta (IL-1beta) on the function of the amino acid transport system A in trophoblasts.

METHODS

BeWo choriocarcinoma cells were exposed to recombinant human IL-1beta in serum-free medium. Cells incubated with serum-free medium in the absence of IL-1beta were used as control. System A activity was determined in control and treated cells by measuring the uptake of alpha-(methylamino)isobutyric acid. The results obtained were confirmed by measuring system A activity in placental brush border membrane vesicles isolated from pregnant rats injected with IL-1beta.

RESULTS

Treatment of BeWo cells with IL-1beta resulted in a time- and dose- dependent inhibition of system A. Treatment with IL-1beta also inhibited the uptake of arginine, and glutamate but had no significant effect on the uptake of leucine, tryptophan, and ascorbate. The inhibition of system A activity by IL-1beta was abolished in the presence of IL-1beta receptor antagonist. The inhibitory effect was associated with a decrease in the maximal velocity of the transport system with no effect on the substrate affinity. Steady-state levels of both SNAT1 and SNAT2 mRNA were reduced by IL-1beta treatment as evidenced by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. In rat placental brush border membrane vesicles isolated from IL-1beta-treated pregnant rats, system A activity was found to be decreased by approximately 40% compared to activity in control membrane vesicles.

CONCLUSIONS

IL-1beta decreases SNAT1 and SNAT2 mRNA levels in trophoblasts, which is associated with a decrease in system A-mediated transport activity at the functional level. These findings may have important consequences under both physiologic conditions and pathologic conditions during pregnancy that are associated with elevated levels of IL-1beta.

Prospective highlights of functional skin proteomics

Although a wide variety of protein profiles have been extensively constructed via proteomic analysis, the comprehensive proteomic profiling of the skin, which is considered to be the largest organ of the human body, is still far from complete. Our efforts to establish the functional skin proteome, a protein database describing the protein networks that underlie biological processes, has set in motion the identification and characterization of proteins expressed in the epidermis and dermis of the BALB/c mice. In this review, we will highlight various cutaneous proteins we have characterized and discuss their biological functions associated with skin distress, immunity, and cancer. This type of research into functional skin proteomics will provide a critical step toward understanding disease and developing successful therapeutic strategies.

Expression of the small heat‐shock protein Hsp‐16‐2 inCaenorhabditis elegansis suppressed byGinkgo bilobaextract EGb 761

EGb 761, a standardized extract of Ginkgo biloba leaves, has been shown to have antioxidative properties. We have previously demonstrated that EGb 761 increases stress resistance and mean life span in the model organism Caenorhabditis elegans. In this study, the molecular mechanism of EGb 761 on alleviating effects of oxidative stress is further investigated using transgenic C. elegans expressing a jellyfish green fluorescent protein (GFP)-tagged inducible small heat-shock protein gene (hsp-16-2). The expression of hsp-16-2 induced by the pro-oxidant juglone and by heat shock was significantly suppressed by 86% and 33%, respectively, in the transgenic nematode fed with EGb 761. These effects of EGb 761 correlate with its ability to increase mean survival rate of the nematode in response to acute oxidative and thermal stresses, as well as to attenuate the basal levels of hydrogen peroxide in the organism. Thus, we interpret the suppression of hsp-16-2/GFP expression as an indication that EGb 761 decreases cellular stress resulting from exogenous treatments, therefore leading to a decreased transcriptional induction of the reporter transgene. These results support the hypothesis that EGb 761 augments the natural antistress system of C. elegans, thus increasing stress resistance and life span.

Heat shock protein 27 association with the I kappa B kinase complex regulates tumor necrosis factor alpha-induced NF-kappa B activation

Heat shock protein 27 (Hsp27) is a ubiquitously expressed member of the heat shock protein family that has been implicated in various biological functions including the response to heat shock, oxidative stress, and cytokine treatment. Previous studies have demonstrated that heat shock proteins are involved in regulating signal transduction pathways including the NF-kappa B pathway. In this study, we demonstrated that Hsp27 associates with the I kappa B kinase (IKK) complex and that this interaction was stimulated by tumor necrosis factor alpha treatment. Phosphorylation of Hsp27 by the kinase mitogen-activated protein kinase-activated protein kinase 2, a downstream substrate of the mitogen-activated protein kinase p38, enhanced the association of Hsp27 with IKK beta to result in decreased IKK activity. Consistent with these observations, treatment of cells with a p38 inhibitor reduced the association of Hsp27 with IKK beta and thus resulted in increased IKK activity. These studies indicate that Hsp27 plays a negative role in down-regulating IKK signaling by reducing its activity following tumor necrosis factor alpha stimulation.

IRAK-dependent phosphorylation of Stat1 on serine 727 in response to interleukin-1 and effects on gene expression

Interleukin-1 (IL-1) induces the phosphorylation of Stat1 on serine 727 but not on tyrosine 701. Analyses of mutant I1A cells, which lack the IL-1 receptor-associated kinase (IRAK), and of I1A cells reconstituted with deletion mutants of IRAK show that the IL-1-mediated phosphorylation of Stat1 on serine requires the IRAK protein but not its kinase activity and does not involve phosphatidylinositol-3'-kinase (PI3K) or the mitogen-activated protein (MAP) kinases p38 or ERK. IRAK and Stat1 interact in vivo, and this interaction is increased in response to IL-1, suggesting that IRAK may serve to recruit the as yet unknown IL-1-induced Stat1 serine kinase. Chemical inhibitors or dominant-negative forms of signaling components required to activate NF-kappa B, ATF, or AP-1 in response to IL-1 do not affect the phosphorylation of Stat1 on serine. IL-1 and tumor necrosis factor (TNF) enhance the serine phosphorylation of Stat1 that occurs in response to interferon-gamma (IFN-gamma) and potentiate IFN-gamma-mediated, Stat1-driven gene expression, thus contributing to the synergistic activities of these proinflammatory cytokines.

TNF receptor subtype signalling: differences and cellular consequences

Tumour necrosis factor-alpha (TNF alpha) is a multifunctional cytokine belonging to a family of ligands with an associated family of receptor proteins. The pleiotropic actions of TNF range from proliferative responses such as cell growth and differentiation, to inflammatory effects and the mediation of immune responses, to destructive cellular outcomes such as apoptotic and necrotic cell death mechanisms. Activated TNF receptors mediate the association of distinct adaptor proteins that regulate a variety of signalling processes including kinase or phosphatase activation, lipase stimulation, and protease induction. Moreover, the cytokine regulates the activities of transcription factors, heterotrimeric or monomeric G-proteins and calcium ion homeostasis in order to orchestrate its cellular functions. This review addresses the structural basis of TNF signalling, the pathways employed with their cellular consequences, and focuses on the specific role played by each of the two TNF receptor isotypes, TNFR1 and TNFR2.

Purification, cloning, and characterization of Nek8, a novel NIMA-related kinase, and its candidate substrate Bicd2

We describe the isolation, cloning, and characterization of human Nek8, a new mammalian NIMA-related kinase, and its candidate substrate Bicd2. Nek8 was isolated as a beta-casein kinase activity in rabbit lung and has an N-terminal catalytic domain homologous to the Nek family of protein kinases. Nek8 also contains a central domain with homology to RCC1, a guanine nucleotide exchange factor for the GTPase Ran, and a C-terminal coiled-coil domain. Like Nek2, Nek8 prefers beta-casein over other exogenous substrates, has shared biochemical requirements for kinase activity, and is capable of autophosphorylation and oligomerization. Nek8 activity is not cell cycle regulated, but like Nek3, levels are consistently higher in G(0)-arrested cells. During the purification of Nek8 a second protein co-chromatographed with Nek8 activity. This protein, Bicd2, is a human homolog of the Drosophila protein Bicaudal D, a coiled-coil protein. Bicd2 is phosphorylated by Nek8 in vitro, and the endogenous proteins associate in vivo. Bicd2 localizes to cytoskeletal structures, and its subcellular localization is dependent on microtubule morphology. Treatment of cells with nocodazole leads to dramatic reorganization of Bicd2, and correlates with Nek8 phosphorylation. This may be indicative of a role for Nek8 and Bicd2 associated with cell cycle independent microtubule dynamics.

Myocardial hypertrophy in transgenic mice overexpressing human interleukin 1alpha

BACKGROUND

Interleukin (IL)-1 has profound effects on nonimmune cells and organs, including the heart. The effects of IL-1 on transgenic hearts have not yet been described.

METHODS AND RESULTS

We generated transgenic mice overexpressing the human IL-1 gene under control of the cytomegalovirus enhancer/chicken beta-actin promoter. Heart weight-body weight ratio increased 1.4- to 2.2-fold in transgenic mice compared with wild-type mice. Lung weight-body weight ratio also increased in transgenic mice, all of which died within 14 days of birth. Light microscopy revealed concentric hypertrophy with cardiomyocyte hypertrophy in all transgenic mice and pulmonary edema in some of them. Electron microscopy showed myofilament loss and an increased number of giant mitochondria, but no sarcomere disarray. Northern blotting showed that gene expression had been reprogrammed in the left ventricle of transgenic mice. Expression of fetal-type genes such as prepro-atrial natriuretic factor and beta-myosin heavy chain were increased, but voltage-dependent calcium channel messenger RNA expression was decreased in the left ventricle of transgenic mice compared with that of wild-type mice.

CONCLUSIONS

IL-1 may cause structural and functional alterations in cardiac myocytes.

Heat shock proteins in the photobiology of human skin

All organisms respond to sudden environmental changes with the increased transcription of genes belonging to the family of heat shock proteins (hsps). Hsp-inducing stress factors include elevated temperatures, alcohol, heavy metals, oxidants, and agents leading to protein denaturation. The induction of heat shock proteins is followed by a transient state of increased resistance to further stress and the heat shock response is generally thought to represent an evolutionary conserved adaptive mechanism to cope with hostile environmental conditions. Since the skin as a barrier organ has to cope with the potentially harmful consequences of exposure to ultraviolet radiation (UV), it appears reasonable to question whether hsps constitute a natural defence mechanism against UV. Hsps have been detected in resting as well as in stressed epidermal and dermal cells and overexpression of hsps is associated with increased resistance to UV-induced cell death. Furthermore, UV itself is able to induce the expression of specific hsps. Thus, hsps might provide an adaptive cellular response to increasing UV and enhancing the expression of hsps might turn out as a new way to deal with the immediate and long-term consequences of UV exposure. Prerequisite for the utilization of this concept is the development of non-toxic heat shock inducers and their evaluation for clinical efficacy and safety.

Inhibition of p38 Kinase Reveals a TNF-α-Mediated, Caspase-Dependent, Apoptotic Death Pathway in a Human Myelomonocyte Cell Line

TNF-alpha transduces signals of survival or death via its two receptors, R1/p55/p60 and RII/p80/p75. The role of caspases as effectors of cell death is universally accepted, although caspase inhibitors may potentiate TNF cytotoxicity in some instances. In conditions when macromolecular synthesis is blocked, caspases are part of the machinery that executes TNF-triggered apoptotic death in U937, a human myelomonocyte cell line, and in the Jurkat T cell line. However, inhibition of p38 mitogen-activated protein kinase (p38 MAPK) triggered TNF cytotoxicity in U937 cells and murine splenic macrophages, but not the Jurkat cell line. TNF induced expression of the antiapoptotic protein c-IAP2 (cytoplasmic inhibitor of apoptosis protein 2), and was blocked in the presence of a p38 MAPK inhibitor, which also induced caspase-dependent, TNF-mediated apoptosis in U937 cells. Thus, inhibition of p38 MAPK resulted in the activation of caspase 9 and cleavage of the adaptor molecule BH3 interacting domain death agonist, and blocked NF-kappaB-mediated transactivation, without affecting the nuclear translocation of NF-kappaB. Collectively, these data show that activation of p38 MAPK is critical to cell survival by TNF in U937 cells, and demonstrate lineage-specific regulation of TNF-triggered signals of activation or apoptosis.

Two distinct forms of MAPKAP kinase-2 in adult cardiac ventricular myocytes

Hsp27 kinase activities were studied in adult rat ventricular myocytes following sequential chromatography on Mono Q and Mono S. A basal level of activity was present following cell isolation. FPLC on Mono Q revealed three peaks of activity, peaks 'a', 'b', and 'c'. A fourth peak, 'd', was detected upon subsequent chromatography of the Mono Q flow-through on Mono S. Immunoblotting revealed that peaks 'a', 'b', and 'c' contained predominantly a 49 kDa form of MAPKAP kinase-2. Peak 'd' contained a 43 kDa form. 'In-gel' kinase assays using hsp27 indicated both forms of MAPKAP kinase-2 were active. No other bands of hsp27 kinase activity were detected. Both forms of hsp27 kinase immunoprecipitated with a MAPKAP kinase-2 antibody and have therefore been named MAPKAP kinase-2alpha (p49) and MAPKAP kinase-2beta (p43). MAPKAP kinase-2beta chromatographed on Superose 12 as a 60.7 kDa monomer whereas the behavior of MAPKAP kinase-2alpha suggested both a 65.7 kDa monomer and higher molecular mass complexes. Both activities phosphorylated hsp27 on serine residues, and two-dimensional phosphopeptide mapping indicated the same sites were phosphorylated. A tumor-promoting phorbol ester, phorbol 12-myristate 13-acetate (PMA), stimulated both MAPKAP kinase-2alpha and MAPKAP kinase-2beta activity. Inhibition of MEK activation with PD 98059 or p38alpha/beta MAP kinase activity with SB203580 blocked activation by PMA. However, whereas PD 98059 inhibited only the PMA-stimulated activation, SB203580 inhibited both PMA-stimulated and basal hsp27 phosphorylation. These data demonstrate the presence of two forms of MAPKAP kinase-2 in adult ventricular myocytes. Both forms are activated indirectly by the ERK MAP kinase pathway and directly by p38 MAP kinase but independently regulated.

Expression of cytosolic and secreted forms of phospholipase A(2) and cyclooxygenases in human placenta, fetal membranes, and chorionic cell lines

Lipid mediators play a crucial role in human parturition and phospholipase A(2) (PLA(2)) is a key regulator of the production of these compounds. We have investigated by PCR the expression of different groups of PLA(2) and COX enzymes in human fetal membranes (amnion and chorion), placenta and three chorionic cell lines (JEG-3, Jar, BeWo). Our data show that the cytosolic Group IV PLA(2) and COX-1 are expressed in all of them, whereas the secretory forms of PLA(2), (Groups IIA, and V), have a more restricted expression. Group IIA mRNA is most abundant in placenta and chorion, whereas Group V PLA(2) mRNA is most abundant in placenta and amnion. On the other hand, COX-2 is present in placenta, chorion and amnion, but was not detected in any of the chorionic cell lines. These results suggest that both cytosolic and distinct secreted forms of PLA(2) could be involved in arachidonic acid (AA) release preceding prostaglandin production at the fetal/maternal interface.

HSP expression in human leukocytes is modulated by endurance exercise

PURPOSE

Temperature increase, oxidative stress, and inflammatory reactions after endurance exercise were expected to stimulate the synthesis of heat shock proteins (HSP) in peripheral blood leukocytes. Furthermore, it was of interest whether regular endurance training influences HSP expression.

METHODS

The expression of HSP27, HSP60, HSP70, constitutive HSC70, and HSP90 in the cytoplasma and surface of lymphocytes, monocytes, and granulocytes of 12 trained athletes was analyzed by flow cytometry before and after (0, 3, and 24 h) a half marathon. Twelve untrained persons at rest were included as control.

RESULTS

After the race, there was a significantly greater percentage of leukocytes expressing cytoplasmic HSP27, HSP60, and HSP70 (P < 0.01), whereas HSC70 and HSP90 remained unchanged. The fluorescence intensity increased significantly in monocytes for HSP27 (0 and 3 h) and HSP70 (0, 3, and 24 h) and in granulocytes, only 24 h postexercise for HSP70. The percent values of trained athletes at rest were significantly lower compared with untrained persons (P < 0,01).

CONCLUSIONS

Strenuous exercise increased HSP expression in blood immediately after the run, indicating a protective function of HSP in leukocytes of athletes to maintain function after heavy exercise. The downregulation of HSP-positive cells in trained athletes at rest seems to be a result of adaptation mechanisms to regular endurance training.

Role of ERK MAP kinases in responses of cultured human airway smooth muscle cells to IL-1beta

We have previously reported that interleukin (IL)-1beta causes beta-adrenergic hyporesponsiveness in cultured human airway smooth muscle cells by increasing cyclooxygenase-2 (COX-2) expression and prostanoid formation. The purpose of this study was to determine whether extracellular signal-regulated kinases (ERKs) are involved in these events. Levels of phosphorylated ERK (p42 and p44) increased 8.3- and 13-fold, respectively, 15 min after treatment with IL-1beta (20 ng/ml) alone. Pretreating cells with the mitogen-activated protein kinase kinase inhibitor PD-98059 or U-126 (2 h before IL-1beta treatment) decreased ERK phosphorylation. IL-1beta (20 ng/ml for 22 h) alone caused a marked induction of COX-2 and increased basal PGE(2) release 28-fold (P < 0.001). PD-98059 (100 microM) and U-126 (10 microM) each decreased COX-2 expression when administered before IL-1beta treatment. In control cells, PD-98059 and U-126 had no effect on basal or arachidonic acid (AA; 10 microM)-stimulated PGE(2) release, but both inhibitors caused a significant decrease in bradykinin (BK; 1 microM)-stimulated PGE(2) release, consistent with a role for ERK in the activation of phospholipase A(2) by BK. In IL-1beta-treated cells, prior administration of PD-98059 caused 81, 92 and 40% decreases in basal and BK- and AA-stimulated PGE(2) release, respectively (P < 0.01), whereas administration of PD-98059 20 h after IL-1beta resulted in only 38 and 43% decreases in basal and BK-stimulated PGE(2) release, respectively (P < 0.02) and had no effect on AA-stimulated PGE(2) release. IL-1beta attenuated isoproterenol-induced decreases in human airway smooth muscle stiffness as measured by magnetic twisting cytometry, and PD-98059 or U-126 abolished this effect in a concentration-dependent manner. These results are consistent with the hypothesis that ERKs are involved early in the signal transduction pathway through which IL-1beta induces PGE(2) synthesis and beta-adrenergic hyporesponsiveness and that ERKs act by inducing COX-2 and activating phospholipase A(2).

Endogenous substrates of sphingosine-dependent kinases (SDKs) are chaperone proteins: heat shock proteins, glucose-regulated proteins, protein disulfide isomerase, and calreticulin

Protein kinases whose activity is detectable only in the presence of sphingosine (Sph) or N,N'-dimethyl-Sph (DMS), but not in the presence of 15 other sphingolipids, phospholipids, and glycerolipids tested (Megidish, T., et al. (1995) Biochem. Biophys. Res. Commun. 216, 739-747), have been termed "sphingosine-dependent kinases" (SDKs). We showed previously that a purified SDK (termed "SDK1") phosphorylates a specific Ser position of adapter/chaperone protein 14-3-3 isoforms beta, eta, and zeta but not tau or sigma (Megidish, T., et al. (1998) J. Biol. Chem. 273, 21834-45). In this study we found the following: (i) other SDKs with different substrate specificities are present in cytosolic and membrane extracts of mouse Balb/c 3T3 (A31) fibroblasts. (ii) The activation of these SDKs is specific to D-erythro-Sph and its N-methyl derivatives, the effect of L-threo-Sph or its N-methyl derivatives is minimal, and nonspecific cationic amphiphiles have no effect at all. An SDK separated as fractions "TN31-33" phosphorylated a 50 kDa substrate which was identified as calreticulin, as well as two endogenous substrates with molecular mass 58 and 55 kDa, both identified as protein disulfide isomerase (PDI). This SDK, which specifically phosphorylates calreticulin and PDI, both molecular chaperones found at high levels in endoplasmic reticulum, is tentatively termed "SDK2". Another SDK activity was copurified with glucose-regulated protein (GRP) and heat shock proteins (HSP). One GRP substrate had the same amino acid sequence as GRP94 (synonym: endoplasmin); another HSP substrate had the same amino acid sequence as mouse HSP86 or HSP84, the analogues of human HSP90. An SDK activity separated and present in "fraction 42" from Q-Sepharose chromatography specifically phosphorylated GRP105 (or GRP94) and HSP68 but did not phosphorylate PDI or 14-3-3. This SDK is clearly different from other SDKs in its substrate specificity and is tentatively termed "SDK3". Interestingly, substrates of all these SDKs so far identified are molecular chaperones or adapters capable of binding to enzymes and key molecules involved in signal transduction, maintaining tertiary structure of bioactive molecules, or maintaining cellular homeostasis in response to environmental stress. Thus, the essential role of Sph and DMS is to activate molecular chaperones, thereby providing a link to the mechanism by which SDK activity regulates cellular homeostasis and signal transduction.

Binding of interleukin-18 to the interleukin-1 receptor homologous receptor IL-1Rrp1 leads to activation of signaling pathways similar to those used by interleukin-1

Interleukin-18 (IL-18) is an inflammatory cytokine that has been shown to enhance a variety of Th1 type T cell responses. Because IL-18 is homologous to IL-1, we tested binding of IL-18 to the known IL-1R family members. We could show binding of IL-18 to the orphan receptor IL-1Rrp1 but not to other IL-1R homologous proteins. IL-1Rrp1 and IL-1RI share highly conserved domains within their cytoplasmic regions. Comparison of the IL-1 and IL-18 signaling mechanisms showed that they activate identical cytoplasmic messengers. IL-18, like IL-1, induced association of its receptor with IRAK and subsequent recruitment of TRAF6. IL-18 activated p38 MAP kinase, jun kinase, and beta casein kinase (TIP kinase), an apparently novel kinase previously thought to be specifically activated by IL-1 and tumor necrosis factor (TNF). IL-18 activated NF-kappaB in EL4/6.1 thymoma cells but not in COS-7 cells, even though the latter presumably contain all components required for the IL-1 signaling pathway. From our binding and signaling studies, we conclude that the IL-18 receptor complex consists of IL-18, the IL-1Rrp1, and another thus far unidentified receptor molecule.

Stress-activated protein kinase/Jun N-terminal kinase is required for interleukin (IL)-1-induced IL-6 and IL-8 gene expression in the human epidermal carcinoma cell line KB

The cytokine interleukin-1 (IL-1) is a major inflammatory hormone which activates a broad range of genes during inflammation. The signaling mechanisms triggered by IL-1 include activation of several distinct protein kinase systems. The stress-activated protein kinase (SAPK), also termed Jun N-terminal kinase (JNK), is activated particularly strongly by the cytokine. In an attempt to delineate its role in activation of gene expression by IL-1, we inhibited the IL-1-induced SAPK/JNK activity by stable overexpression of either a catalytically inactive mutant of SAPKbeta (SAPKbeta(K-R)) or antisense RNA to SAPKbeta in human epidermal carcinoma cells. A detailed analysis of signal transduction in those cells showed that activation of neither NFkappaB nor p38 mitogen-activated protein kinase was affected, suggesting that we achieved specific blockade of the SAPK/JNK. In untransfected and vector-transfected KB cells, IL-1 induced a strong increase in expression of IL-6 and IL-8 mRNA, along with the synthesis of high amounts of the proteins. In two KB cell clones stably overexpressing the mutant SAPKbeta(K-R), and three clones stably overexpressing antisense RNA to SAPKbeta, expression of IL-6 and IL-8 in response to IL-1 was strongly reduced at both the mRNA and protein level. These data indicate that the SAPK/JNK pathway provides an indispensable signal for IL-1-induced expression of IL-6 and IL-8.

Phosphorylations of alpha A- and alpha B-crystallin

In addition to being refractive proteins in the vertebrate lens, the two alpha-crystallin polypeptides (alpha A and alpha B) are also molecular chaperones that can protect proteins from thermal aggregation. The alpha B-crystallin polypeptide, a functional member of the small heat shock family, is expressed in many tissues in a developmentally regulated fashion, is stress-inducible, and is overexpressed in many degenerative diseases and some tumors indicating that it plays multiple roles. One possible clue to alpha-crystallin functions is the fact that both polypeptides are phosphorylated on serine residues by cAMP-dependent and cAMP-independent mechanisms. The cAMP-independent pathway is an autophosphorylation that has been demonstrated in vitro, depends on magnesium and requires cleavage of ATP. Disaggregation of alpha A-, but not alpha B-crystallin into tetramers results in an appreciable increase in autophosphorylation activity, reminiscent of other heat shock proteins, and suggests the possibility that changes in the aggregation state of alpha A-crystallin are involved in yet undiscovered signal transduction pathways. The alpha-crystallin polypeptides differ with respect to their abilities to undergo cAMP-dependent phosphorylation, with preference given to the alpha B-crystallin chain. These differences and complexities in alpha-crystallin phosphorylations, coupled with the differences in expression patterns of the two alpha-crystallin polypeptides, are consistent with the idea that each polypeptide has distinctive structural and metabolic roles.

MAP kinase-dependent pathways in cell cycle control

Mitogen-activated protein kinases such as Erk1 and Erk2 serve as a paradigm for a growing family of proline-directed protein kinases that mediate entry, progression and exit from the cell cycle in diverse eukaryotic cells. These enzymes function within highly conserved modules of sequentially activating protein kinases that transduce signals from diverse extracellular stimuli. In vertebrates, at least three distinct kinases modules have been characterized. Mitogens induce the sequential activation of the kinases Raf1-->Mek1-->Erk2-->Rsk via the G-protein Ras. Stress factors stimulate c-Jun activation through a related kinase pathway involving Mekk-->Sek-->SAPK c-Jun, and hsp27 phosphorylation via the MKK3-->Hog-->MAPKAPK-2 hsp27 route. Genetic and biochemical studies, for example from budding yeast, imply the existence of several related protein kinase modules that can operate in parallel or within integrated systems.

Overexpression of HSP-70 inhibits the phosphorylation of HSF1 by activating protein phosphatase and inhibiting protein kinase C activity

This laboratory reported previously that overexpressed heat shock protein 70 kDa (HSP-70) inhibited the activation of its transcriptional factor, HSF1. We had conducted experiments to understand the mechanisms whereby HSP-70 down-regulated the activation of HSF1. Genetically overexpressed HSP-70 had no effects on the HSF1 level in cytosol, but significantly inhibited phosphorylation of HSF1 in the nucleus. Transfection of cells with HSF1 cDNA resulted in increases in the unphosphorylated, but not phosphorylated, HSF1 levels in both the cytosol and nucleus. Because serine phosphorylation of various proteins was reduced in HSP-70 cDNA-transfected cells, we measured the activity of enzymes involved in serine phosphorylation. Overexpressed HSP-70 significantly inhibited the enzymatic activities of protein kinase A (PKA by 73 and 62% in the cytosol and membrane-bound fraction, respectively) and protein kinase C (PKC by 61% in membrane-bound fraction), whereas it activated that of protein phosphatase (PP by 33 and 86% in the cytosol and the membrane-bound fraction, respectively). Forskolin (a PKA stimulator), PMA (a PKC stimulator), and okadaic acid (an inhibitor of PP) were used to investigate whether HSP-70-induced changes in PKA, PKC, and PP were responsible for the HSF1 dephosphorylation. Forskolin did not change nuclear HSF1 phosphorylation, suggesting that decreases in PKA activity in HSP-70 overexpressing cells is not associated with HSF1 phosphorylation. PMA and okadaic acid induced an increase in HSF1 phosphorylation in both vector- and HSP-70 cDNA-transfected cells, although levels of phosphorylated HSF1 in HSP-70 cDNA-transfected cells were lower than those in vector-transfected cells. The PMA-induced increase in HSF1 phosphorylation in HSP-70 cDNA-transfected cells was blocked by pretreatment with staurosporine, a PKC inhibitor. These results suggest that overexpression of HSP-70 inhibits phosphorylation of HSF1 at serine residues by activating PP and inhibiting PKC activity.

Tumor necrosis factor-alpha induces interleukin-6 production and integrin ligand expression by distinct transduction pathways

Tumor necrosis factor-alpha (TNF-alpha) is a pleiotropic cytokine that elicits a large number of biological effects. However, the intracellular signaling mechanisms that are responsible for the TNF-alpha effects remain largely unknown. We have previously demonstrated that cultured mouse Sertoli cells, after TNF-alpha treatment, increase the surface expression of adhesion molecules such as intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) and interleukin-6 (IL-6) production (Riccioli, A., Filippini, A., De Cesaris, P., Barbacci, E., Stefanini, M., Starace, G., and Ziparo, E. (1995) Proc. Natl. Acad. Sci. U.S.A. 92, 5808-5812). Here, we show that, in cultured Sertoli cells, TNF-alpha activates the mitogen-activated protein kinase pathway (p38, c-Jun N-terminal protein kinase/stress-activated protein kinase, and the p42/p44 mitogen-activated protein kinases) as revealed by an increased phosphorylation of p38, activating transcription factor-2, c-Jun, and Elk-1. Furthermore, our data indicate that the biological effects induced by TNF-alpha in Sertoli cells (enhancement of ICAM-1, VCAM-1, and IL-6 expression) depend on the activation of different signaling pathways. SB203580, a highly specific p38 inhibitor, does not affect ICAM-1 and VCAM-1 expression, but strongly inhibits IL-6 production. Moreover, interferon-gamma, which up-regulates adhesion molecule expression and reduces IL-6 production, does not induce phosphorylation of p38. Our data strongly support the hypothesis that, in response to TNF-alpha, activation of p38 leads to IL-6 production, whereas ICAM-1 and VCAM-1 expression could be induced by activation of the c-Jun N-terminal protein kinase/stress-activated protein kinase pathway.

Activation of p42mapk in human umbilical vein endothelial cells by interleukin-1 alpha and tumor necrosis factor-alpha

Work from this and other laboratories has identified a role for protein tyrosine kinases in interleukin-1 alpha (IL-1 alpha)- and tumor necrosis factor-alpha (TNF-alpha)-induced responses in endothelial cells. In this study, we show that activation of human umbilical vein endothelial cells (HUVEC) by IL-1 alpha leads to increased tyrosine phosphorylation of several proteins including one with a molecular mass of approximately 42 kDa. This protein was identified as p42mapk by Western blot analysis. Tyrosine phosphorylation and catalytic activation of p42mapk by IL-1 alpha was transient, reaching maximal levels after 30 min and returning to basal levels by 120-300 min. Activation of p42mapk in HUVEC was also observed in response to TNF-alpha or to the protein kinase C (PKC)-activating phorbol ester phorbol 12-myristate 13-acetate (PMA). Pretreatment of HUVEC with IL-1 alpha or TNF-alpha prevented reactivation of p42mapk by either cytokine but did not affect subsequent activation in response to PMA. Activation of p42mapk by PMA was significantly reduced by the PKC inhibitor Ro-31-8220 and completely inhibited by the protein tyrosine kinase inhibitor genistein. Genistein, but not Ro-31-8220, attenuated IL-1 alpha- and TNF-alpha-induced p42mapk activation. Taken together, the results of this study demonstrate 1) that p42mapk is transiently activated in HUVEC by IL-1 alpha and TNF-alpha, 2) that this activation is PKC independent, and 3) that a genistein-inhibitable tyrosine kinase may be an upstream regulator of cytokine-induced p42mapk activation in human endothelium.

Activation of nuclear transcription factor NF-kappaB by interleukin-1 is accompanied by casein kinase II-mediated phosphorylation of the p65 subunit

In fibroblasts and hepatoma cells, interleukin-1 (IL-1) treatment results in the rapid nuclear accumulation of the transcription factor NF-kappaB, present largely as p65 (RelA)/p50 heterodimers. It is well established that this process is dependent in large part upon the phosphorylation and subsequent degradation of the cytosolic inhibitor IkappaB. We looked for other IL-1-induced modifications of NF-kappaB components and found that, in both cell types, IL-1 stimulation led, within minutes, to phosphorylation of both NF-kappaB p65 and p50. Phosphorylation of p65 was sustained for at least 30 min after addition of the cytokine and occurred principally upon serine residues. Immunoprecipitates of NF-kappaB complexes contained an associated protein kinase, the biochemical characteristics of which were indistinguishable from casein kinase II (CKII). Purified CKII efficiently phosphorylated p65 in vitro, apparently on the same major sites that became phosphorylated in intact IL-1-treated cells. Although IL-1 treatment caused little apparent stimulation of total cellular CKII activity, the fraction that was specifically associated with NF-kappaB complexes was markedly elevated by the cytokine. The association of CKII with NF-kappaB occurred in the cytoplasm, suggesting that this phosphorylation might be involved either in control of translocation of the activated complex or in modulation of its DNA binding properties.

Dual specificity of the interleukin 1- and tumor necrosis factor-activated beta casein kinase

Tumor necrosis factor (TNF) and interleukin 1 (IL1) activate a protein kinase, TIP kinase, which phosphorylates beta casein in vitro. We have now identified its main phosphorylation site on beta casein, Ser124 (Km approximately 28 mu M), and a minor phosphorylation site, Ser142 (Km approximately 0.7 mM). The sequence motif that determined the phosphorylation of Ser124 by the kinase was studied with synthetic peptides bearing deletions or substitutions of the neighboring residues. This allowed synthesis of improved substrates (Km approximately 6 mu M) and showed that efficient phosphorylation of Ser124 was favored by the presence of large hydrophobic residues at positions +1, +9, +11, and +13 (counted relative to the position of the phosphoacceptor amino acid) and of a cysteine at position -2. Peptides in which Ser124 was replaced by tyrosine were also phosphorylated by TIP kinase, showing it to have dual specificity. It is unable to phosphorylate the MAP kinases in vitro and is therefore not directly involved in their activation. Its biochemical characteristics indicate that TIP kinase is a novel dual specificity kinase, perhaps related to the mixed lineage kinases. It copurified with a phosphoprotein of about 95 kDa, which could correspond either to the autophosphorylated kinase or to an associated substrate.

Selective activation of JNK/SAPK by interleukin-1 in rabbit liver is mediated by MKK7

Activation of jun N-terminal kinase (JNK)/stress-activated protein kinase (SAPK) by interleukin-1 (IL-1) has been reported in many cells and in rabbit liver. Here we report selective activation of JNK/SAPK, without activation of p38 or p42 mitogen-activated protein kinases (MAPKs), by IL-1 in rabbit liver. We identified an IL-1 regulated JNK/SAPK activator present in rabbit liver using S Sepharose chromatography. It was purified and immunoprecipitated by two antisera to MAP kinase kinase 7 (MKK7). It was not recognised by an antibody to MKK4. We conclude that MKK7 is the activator of JNK/SAPK activated by IL-1 in liver and that JNK/SAPK is the only MAPK activated by IL-1 in liver.

Basolateral membrane-associated 27-kDa heat shock protein and microfilament polymerization

The in vivo activity of the 27-kDa heat shock protein, a barbed-end microfilament capping protein, may be localized to the plasma membrane. To investigate this putative association, bovine endothelial cells expressing the human wild type or a mutant nonphosphorylatable 27-kDa heat shock protein were subjected to subcellular fractionation and immunoblot analysis. The 25-kDa endogenous bovine homolog and both exogenous gene products partitioned with cytosolic or plasma membrane components, indicating that phosphorylation is not required for membrane association. Phorbol ester treatment resulted in phosphorylation of only membrane-associated 25-kDa and wild type 27-kDa heat shock protein and did not induce redistribution. In a second fractionation protocol, streptavidin-agarose precipitation of extracts prepared from cells biotinylated at either the apical or basal surface localized membrane 25- and 27-kDa heat shock protein exclusively to the basolateral surface. Stimulation of transfectants expressing the wild type 27-kDa heat shock protein resulted in its phosphorylation and a doubling in the amount of membrane-associated F-actin precipitated, whereas the mutant protein decreased the amount of F-actin precipitated. These data suggest that membrane-associated 25- and 27-kDa heat shock proteins inhibit the generation of basolateral microfilaments and that phosphorylation releases this inhibition.

The regulation of progesterone and hCG production from placental cells by interleukin-1beta

We have investigated the roles of interleukin-1beta as a regulator of progesterone and chorionic gonadotrophin production from human placental cells. In primary placental cells IL-1beta increased hCG synthesis through a cyclic AMP-independent pathway, and was without effect on progesterone or cyclic AMP production. Since dibutyryl cyclic AMP increased progesterone production, this suggests that there is no coupling between the IL-1beta receptor and the adenylate cyclase enzyme in these cells. Immortalised trophoblast cells responded to IL-1beta by increasing progesterone production through a cyclic AMP-dependent mechanism, but hCG production by these cells was unaffected by IL-1beta or dibutyryl cyclic AMP. Further studies are needed to identify the role of IL-1beta as a possible regulator of progesterone production in primary placental cells. While hCG production in first-trimester trophoblast was increased by dibutyryl cyclic AMP and IL-1beta, both these effects may involve other factors such as IL-6, and their second messenger systems.

Interleukin-1-induced ether-linked diglycerides inhibit calcium-insensitive protein kinase C isotypes. Implications for growth senescence

It is hypothesized that inflammatory cytokines and vasoactive peptides stimulate distinct species of diglycerides that differentially regulate protein kinase C isotypes. In published data, we demonstrated that interleukin-1, in contrast to endothelin, selectively generates ether-linked diglyceride species (alkyl, acyl- and alkenyl, acylglycerols) in rat mesangial cells, a smooth muscle-like pericyte in the glomerulus. We now demonstrate both in intact cell and in cell-free preparations that these interleukin-1 receptor-generated ether-linked diglycerides inhibit immunoprecipitated protein kinase C delta and epsilon but not zeta activity. Neither interleukin-1 nor endothelin affect de novo protein expression of these protein kinase C isotypes. As down-regulation of calcium-insensitive protein kinase C isotypes has been linked to antimitogenic activity, we investigated growth arrest as a functional correlate for IL-1-generated ether-linked diglycerides. Cell-permeable ether-linked diglycerides mimic the effects of interleukin-1 to induce a growth-arrested state in both G-protein-linked receptor- and tyrosine kinase receptor-stimulated mesangial cells. This signaling mechanism implicates cytokine receptor-induced ether-linked diglycerides as second messengers that inhibit the bioactivity of calcium-insensitive protein kinase C isotypes resulting in growth arrest.

Inhibition of protein geranylgeranylation causes a superinduction of nitric-oxide synthase-2 by interleukin-1beta in vascular smooth muscle cells

Recently, we have designed farnesyltransferase and geranylgeranyltransferase I inhibitors (FTI-277 and GGTI-298) that selectively block protein farnesylation and geranylgeranylation, respectively. In this study, we describe the opposing effects of these inhibitors on interleukin-1beta (IL-1beta)-stimulated induction of nitric-oxide synthase-2 (NOS-2) in rat pulmonary artery smooth muscle cells (RPASMC) and rat hepatocytes. Pretreatment of cells with GGTI-298 caused a superinduction of NOS-2 by IL-1beta. RPASMC treated with GGTI-298 (10 microM) prior to IL-1beta (10 ng/ml) expressed levels of NOS-2 protein five times higher than those exposed to IL-1beta alone. This superinduction of NOS-2 protein by pretreatment with GGTI-298 resulted in nitrite concentrations in the medium that were 5-fold higher at 10 ng/ml IL-1beta and 10-fold higher at 1 ng/ml IL-1beta. Furthermore, NOS-2 mRNA levels in RPASMC were also increased 6- and 14-fold (at 10 and 1 ng/ml IL-1beta, respectively) when the cells were pretreated with GGTI-298. In contrast, treatment of cells with the inhibitor of protein farnesylation, FTI-277 (10 microM), blocked IL-1beta-induced NOS-2 expression at mRNA and protein levels. Pretreatment with lovastatin, an inhibitor of protein prenylation, resulted in superinduction of NOS-2. This superinduction was reversed by geranylgeraniol, but not by farnesol, further confirming that inhibition of geranylgeranylation, not farnesylation, is responsible for enhanced NOS-2 expression. The results demonstrate that a farnesylated protein(s) mediates IL-1beta induction of NOS-2, whereas a geranylgeranylated protein(s) represses this induction.

Effect of protein kinase inhibitors on activity of mammalian small heat-shock protein (HSP25) kinase

The aim of this study was to investigate different protein kinase inhibitors (secondary metabolite-derived substances, synthetic compounds, and substrate-based peptides) for their potency to inhibit the mammalian small heat shock protein (HSP25) kinase (E.C. 2.7.1.37) isolated from Ehrlich ascites tumor cells. Among the secondary metabolite-derived inhibitors (staurosporine, K-252a, K-252b, KT5926, KT5720, erbstatin analog, and quercetin) and synthetic compounds (H-9, H-89, HA 1004, KN-62, ML-7, tyrphostin A25, and tyrphostin B42), KT5926, staurosporine, and K-252a inhibited HSP25 kinase most efficiently. Kinetic analysis revealed that inhibition by staurosporine (Ki = 32.4 nM) and K-252a (Ki = 13.7 nM) was competitive with ATP. Inhibition by KT5926 was competitive with the substrate peptide KKKALNRQLSVAA (Ki = 27.2 nM) and noncompetitive with respect to ATP (Ki = 38.8 nM). In comparison with other protein kinases, HSP25 kinase was relatively resistant to most of the inhibitors. KT5926 was the only tested inhibitor with certain preference for HSP25 kinase when compared with protein kinases A, C, and G. Among the tested substrate-based peptides, we identified one peptide (KKKALNRQLGVAA), which preferentially inhibited HSP25 kinase in comparison with protein kinases A and C and mitogen-activated protein kinase. This peptide inhibited HSP25 kinase competitively with the substrate peptide (Ki = 8.1 microM) and noncompetitively with ATP (Ki = 134 microM). A peptide (SRVLKEDKERWEDVK) derived from the putative autoinhibitory domain of the closely related human mitogen-activated protein kinase-activated protein kinase-2 did not inhibit HSP25 kinase activity, suggesting the existence of several species of HSP25 kinases. Furthermore, the data identified structural requirements for inhibitors of HSP25-kinase.

UVB irradiation induces changes in cellular localization and phosphorylation of mouse HSP27

We investigated the induction, cellular localization and phosphorylation of a low-molecular weight stress protein (heat shock protein 27, HSP27) by UVB (290-320 nm, max. 312 nm) irradiation stress using immunoblot and indirect immunofluorescence analysis in in vivo and in vitro experiments. The HSP27 was constitutively expressed and distributed in the cytoplasmic fraction of Pam 212 cells (mouse keratinocyte line) or dorsal skin. The increase in the cytoplasm HSP27 level induced by UVB irradiation was less than two-fold that in nonirradiated controls. On the other hand, the translocation of HSP27 from cytoplasm to the nucleus or perinuclear area was time- and dose-dependently induced by UVB irradiation. After UVB irradiation, three isoforms having different isoelectric points were detected in nucleic HSP27 by two-dimensional immunoblotting. The most basic isoform was the unphosphorylated type and the two acidic isoforms were phosphorylated, suggesting that HSP27 is phosphorylated in response to UVB irradiation and accumulates in or around the nucleus as a phosphorylated isoform. These results suggest that the translocation and phosphorylation of HSP27 are induced in response to UVB-irradiation stress.

Overexpression of the small heat shock protein, hsp27, confers resistance to hyperthermia, but not to oxidative stress and UV-induced cell death, in a stably transfected squamous cell carcinoma cell line

The 27 kD heat shock protein (hsp27) is expressed in human keratinocytes in association with differentiation in vitro and in situ. This study was conducted to investigate whether the expression of hsp27 in keratinocytes is associated with increased resistance to the deleterious effects of heat and UV radiation. A transfection vector carrying the human gene for hsp27, under the control of hsp27 as well as the SV40 promoter (pSG2711, M. Jäättelä et al., EMBO J. 11 (1992) 3507-3512), was introduced together with a neomycin-resistance gene into the squamous cell carcinoma cell line A431. Cells were exposed to either UVA, UVB, head (45 degrees C, 4 h) or hydrogen peroxide (0.025-0.5 mM) and the percentage of surviving cells was determined. Overexpression of hsp27 induced increased resistance to hyperthermia, but not to hydrogen peroxide-mediated oxidative injury. When cells were exposed to increasing amounts of UVA (5-80 J cm-2) and UVB (4-64 mJ cm-2), the percentage of surviving cells was identical for clones overexpressing hsp27 and control clones. From these data, we conclude that hsp27 is a mediator of thermotolerance, but does not protect keratinocytes from UV-induced cell death.

Activation of the HIV-1 long terminal repeat by cytokines and environmental stress requires an active CSBP/p38 MAP kinase

The human immunodeficiency virus, type 1 (HIV-1) promoter is known to be activated by proinflammatory cytokines and UV light. These stimuli also activate various members of the mitogen-activated protein kinase family, including JNK/SAPK and CSBP/p38. In HeLa cells containing an integrated HIV-1 long terminal repeat (LTR) -driven reporter, we now show that the specific p38 inhibitor, SB203580, inhibits activation of the HIV-1 LTR by interleukin-1, tumor necrosis factor, UV light, and osmotic stress. Inhibition was 70-90% in all but the case of tumor necrosis factor stimulation, where inhibition was 50%. Each of these stimuli activated p38, which was inhibited by SB203580 in vitro and in vivo with an IC50 (between 0.1 and 1 microM) similar to that required to inhibit transcription. In contrast, SB203580 had no effect on JNK, which was also activated by these stimuli. The NFkappaB sites in the HIV-1 LTR were required for a response to cytokines but not to UV, and SB203580 remained capable of inhibiting UV activation in the absence of the NFkappaB sites. Studies in which SB203580 was added at different times relative to UV stimulation suggested that the critical p38-mediated phosphorylation event occurred between 2 and 4 h after UV treatment. These data indicate that p38 is required for HIV-1 LTR activation but that the action of p38 is delayed, presumably due to substrate unavailability or inaccessibility.

Tumor necrosis factor receptors (Tnfr) in mouse fibroblasts deficient in Tnfr1 or Tnfr2 are signaling competent and activate the mitogen-activated protein kinase pathway with differential kinetics

To dissect tumor necrosis factor receptor (Tnfr)-1 (CD120a) and Tnfr2 (CD120b)-dependent signal transduction pathways, primary fibroblasts isolated from inguinal adipose tissue of wild type (wt), tnfr1(o), tnfr2(o), and tnfr1(o)/tnfr2(o) mice were studied. The mitogen-activated protein kinases Erk1 and Erk2 were found to be tyrosine-phosphorylated and activated by Tnf treatment in all wt, tnfr1(o), and tnfr2(o) fibroblasts; the activation was down-regulated 60 min after the start of steady state Tnf treatment. Distinct kinetics of Erk1 and Erk2 activation were detected; the Tnfr1-mediated activation of Erk1 and Erk2 started more slowly and persisted for more prolonged times as compared with Tnfr2 activation. Raf-1, Raf-B, Mek-1, Mek kinase, and p90(rsk) kinases were also shown to be activated independently in a distinct time-dependent pattern through the two Tnf receptors. In addition, both Tnfr1 and Tnfr2 mediated independently the activation of the transcription factor Ap-1 albeit with parallel activation kinetics. In contrast, Tnfr1 exclusively mediated activation of NF-kappaB and fibroblast proliferation; however, Tnfr2 enhanced proliferation triggered through Tnfr1. These findings indicate distinct but also overlapping roles of Tnfr1 and Tnfr2 in primary mouse fibroblasts and suggest different regulation mechanisms of signal transduction pathways under the control of both Tnf receptors.

Role of protein kinase activity in apoptosis

The transmission of signals from the plasma membrane to the nucleus involves a number of different pathways all of which have in common protein modification. The modification is primarily in the form of phosphorylation which leads to the activation of a series of protein kinases. It is now evident that these pathways are common to stimuli that lead to mitogenic and apoptotic responses. Even the same stimuli under different physiological conditions can cause either cell proliferation or apoptosis. Activation of specific protein kinases can in some circumstances protect against cell death, while in others it protects the cell against apoptosis. Some of the pathways involved lead to activation of transcription factors and the subsequent induction of genes involved in the process of cell death or proliferation. In other cases, such as for the tumour suppressor gene product p53, activation may be initiated both at the level of gene expression or through pre-existing proteins. Yet in others, while the initial steps in the pathway are ill-defined, it is clear that downstream activation of a series of cystein proteases is instrumental in pushing the cell towards apoptosis. In this report we review the involvement of protein kinases at several different levels in the control of cell behaviour.

Interleukin 1 activates jun N-terminal kinases JNK1 and JNK2 but not extracellular regulated MAP kinase (ERK) in human glomerular mesangial cells

Interleukin 1 (IL-1) potently activates human glomerular mesangial cells (HMC). In cytosolic extracts of IL-1-stimulated HMC or in anion exchange chromatography fractions we could not find any change in phosphorylation of myelin basic protein (MBP), a good substrate for extracellular regulated kinase (ERK). In contrast, IL-1 stimulated GST-jun kinase activity at least 10-fold. The jun kinase activity could be characterised as JNK1 and JNK2 at the protein and mRNA level. IL-1, TNF, UV light and osmotic stress, but not PMA, LPS, IL-3, IL-4, IL-6, IL-8, IL-10, IL-13, GM-CSF, PDGF, bFGF, TGF-beta and interferon-gamma were able to stimulate jun kinase activity in HMC, suggesting that jun kinase is selectively mediating signal transduction of the proinflammatory cytokines IL-1 and TNF as well as of cellular stress in HMC.

Stress proteins in the cellular response to ultraviolet radiation

Virtually all cells-from prokaryotes to highly differentiated mammalian tissues-respond to a sudden increase in temperature with increased production of a limited set of proteins, called heat shock proteins or stress proteins (hsp). Other stress factors such as alcohol, heavy metals, oxidants and agents leading to protein denaturation are equally able to induce a similar response. Induction of hsp is followed by a transient state of increased resistance to further stress. Many hsp function as "molecular chaperones" by binding to partially folded or misfolded proteins thus preventing their irreversible denaturation during stress exposure. The high evolutionary conservation of this reaction suggests its importance for the survival of cells and tissues under hostile environment conditions. Ultraviolet radiation (UV) exerts many potentially harmful effects on prokaryotic and eukaryotic cells and hsp may help the cell to cope with UV-induced damage. This review will focus on the role of hsp in the cellular response of mammalian skin to UV. Hsp have been detected in resting as well as stress exposed epidermal and dermal cells and experimental evidence points to the fact that these proteins mediate protection from UV induced cell death in vitro and in vivo. Experimental studies further indicate that UV itself might be able to induce the expression of specific hsp. Thus, hsp might provide an adaptive cellular response to increasing exposure to UV. Furthermore, UV-activation of hsp synthesis may provide a valuable model for investigation of the transcription regulation of UV-induced gene expression.

Tumor necrosis factor alpha (TNFalpha) induces pro-matrix metalloproteinase 9 production in human uterine cervical fibroblasts but interleukin 1alpha antagonizes the inductive effect of TNFalpha

We have examined the regulation of precursor of matrix metalloproteinase 9 (proMMP-9)/progelatinase B production by tumor necrosis factor alpha (TNFalpha) and interleukin 1alpha (IL-1alpha) using human uterine cervical fibroblasts. TNFalpha, but not IL-1alpha, induces the production of proMMP-9 in the cervical cells. IL-alpha, however, suppresses the TNFalpha-induced proMMP-9 production. 12-0-tetradecanoylphorbol 13-acetate (TPA) also stimulates the cervical cells to produce proMMP-9, and IL-1alpha synergistically enhances its production. TNFalpha-induced proMMP-9 production is not mediated by protein kinase C (PKC), whereas the effect of IL-1alpha is through PKC. By contrast, proMMP-3/prostromelysin 1 is up-regulated by TNFalpha or TPA in the presence of IL-1alpha, whose modulation is PKC-dependent. The suppressive effect of IL-1alpha on the TNFalpha-induced proMMP-9 production is a new biological effect of IL-1 on MMP production.

The casein kinase 1 alpha gene of Drosophila melanogaster is developmentally regulated and the kinase activity of the protein induced by DNA damage

We report the molecular cloning and characterisation of the first CK1(casein kinase) gene of Drosophila melanogaster (dmCK1). The protein sequence (DMCK1) shares significant homology with other mammalian CK1 protein kinases of the alpha sub-class. The dmCK1 gene is expressed only in adult females and during early embryonic development as a single transcript. Western blot analysis of total protein extracts of different stages of development show that the gene product is likewise present during early embryogenesis and in adult females. Kinase activity studies show that DMCK1 is active when in vitro translated but inactive when immunoprecipitated from total early embryo extracts. However, after dephosphorylation treatment the immunoprecipitates show high kinase activity. More significantly, DMCK1 kinase activity present in the immunoprecipitates can be specifically activated by gamma-irradiation of early embryos. Also, when DMCK1 is immunoprecipitated after irradiation it appears to undergo phosphorylation. Immunolocalization of DMCK1 in early embryos shows that the protein is predominantly cytoplasmic but after irradiation there is a significant relocalization to the interphase nucleus. The results suggest a possible requirement of the Drosophila CK1 alpha for mechanisms associated with DNA repair during early embryogenesis.

Interleukin-1 signal transduction

Interleukin-1 (IL-1) is primarily an inflammatory cytokine, although it is capable of mediating a wide variety of effects on many different cell types. Nearly every known signal transduction pathway has been reported to be activated in response to IL-1. However, the significance of many of these signaling events is unclear, due to the use of different and sometimes unique cell lines in studying IL-1-initiated signal transduction. Complicating matters further is the lack of association in many studies between identified IL-1-induced signals and subsequent biological responses. In this article, we review what is known about IL-1 receptor signaling and, whenever possible, correlate signaling events to biological responses.

Identification of stress proteins in endothelial cells

Endothelial cells have been shown to play a major role in the pathophysiology of various diseases including ischemic heart disease and viral infection leading to myocarditis or dilated cardiomyopathy, conditions in which stress proteins (heat shock protein-hsp; glucose-related protein - grp) are likely to be involved. For further characterization of stress proteins and their possible role in these diseases, the major stress proteins in human endothelial cells were separated by two-dimensional polyacrylamide gel electrophoresis with immobilized pH gradients in the first dimension and identified by immunoblotting and either N-terminal or internal amino acid sequencing, respectively. Ubiquitin, hsp27, hsp60, hsp70, heat shock cognate protein 70, grp78 and grp75 were found to be constitutively expressed; hsp72 was found in stressed cells, exclusively, in line with results obtained in other human cell lines. Three additional proteins with molecular masses between 34 and 40 were regularly detected in stressed cells that were found to have identical amino acid sequences with those of members of the hsp70 family.

Interleukin-1 signal transduction

Interleukin 1 (IL1) is a potent pro-inflammatory cytokine which has been implicated in the pathogenesis of chronic inflammatory disease. Despite much effect, the signal transduction pathway activated by IL1 has remained obscure. Recently, much attention has focussed on IL1 receptors and early events triggered by IL1 in cells, including activation of transcription factors and serine/threonine protein kinases. Two main types of IL1 receptors have been described, IL1RI and IL1RII. They appear to belong to a family of proteins which include most notably a Drosophila protein, Toll. Following receptor binding IL1 has been shown to increase protein phosphorylation in cells, and much effort has been made to identify the protein kinases responsible. Novel enzymes have been discovered, including a family of MAP kinase--like enzymes which are also activated by a range of stresses such as hypertonic stress and heat shock. Attention has also been focussed in the activation of the transcription factor NF kappa B, which is rapidly activated by IL1. This review will describe our current understanding of how IL1 activated cells and will particularly describe more recent work on IL1 receptors and early post-receptors events.