Extracellular signal-regulated kinases

Erk-1 Research advances

A previous study suggested that p38 can be a serine kinase for Stat-1 (23), and it’s widely recognized that phosphorylation on Ser727 is needed for its full transcriptional activity (5) without modifying its ability to bind to DNA (33).

Our results imply that in macrophages, Ser727 phosphorylation occurs independently of activation of p38, in comparison to reports generated by other authors (34); their studies demonstrated a role for this particular MAPK at Stat-1 phosphorylation just in reaction to stress signaling. Some reports show that members of the MAPK family could be triggered by IFN-γ in a number of cellular versions (8, 7 ). MAPKs are evolutionarily conserved serine/threonine kinases involved in the transduction of derived signals that regulate cell growth, differentiation, and apoptosis (9). All these kinases include JNK-1 and -2, ERK-1 and -2, and p38. Activation of the ERK-1/2 signaling pathway is essential for HGF-induced cell motility/morphogenesis, whereas ERK-5 appears to be required for EGF-dependent morphogenesis (16). Another example of pathway-specific morphogenic programming involves the EpH4 mammary epithelial cells (27). They form branched tubules but form alveolar structures in the presence of neuregulin, a ligand of c-erbB tyrosine kinase receptors when cultured in Matrigel.
Specific nucleoporin levels seemingly govern cell cycle progression and phase-specific gene expression 44, and expression of human pore and transportation factor proteins may differ between tissues and developmental phases 24, 35, 45, and also in several disease states, where over-expression of importin-alpha and -beta are reported in colon, breast, and lung cancers 24, 35 Our findings of improved NPC discoloration in ovarian and adrenal glands substantiate this, and expression profiling confirmed an early observation that mRNA for Nup88 has been over-expressed in a panel of ovarian carcinoma cell lines 46 A lowered degree of importin 7 and in particular important B would be called to decrease the efficacy of MAPK nuclear import in the most important cells, as it’s been found in Drosophila and other cell types 8, 47, 48 Moreover, the number of usable pores is known to vary depending on the growth state of the cell, increasing in proliferating versus quiescent BALB/c 3T3 cells 45. These gaps could be reconciled by comparing the staining patterns seen with the MAPK antibody versus staining using an antibody recognizing both unphosphorylated and phosphorylated ERK. Growth and differentiation factors govern the mitogen-activated protein (MAP) 1 extracellular signal-regulated protein kinases 1 and 2 (ERK1 and ERK2) through pathways with receptor tyrosine kinases, cytokine receptors, and heterotrimeric G protein- coupled receptors (Lewis et al., 1998; Robinson and Cobb, 1997). Activation occurs by coupling receptors to Ras, Raf-1, and MAP kinase kinase-1 or -2 (MKK 1 or 2), the latter of that activates ERK straight through phosphorylation.
Estrogens have profound effects on hippocampal structure and physiology (1 – 4) and on hippocampal-dependent memory and learning (5, 6). Specifically, estrogens have been shown to raise the density of dendritic spines on CA1 pyramidal neurons (7). In hippocampal slices, 17β-estradiol increases electrophysiological responses elicited by activation of the two α-amino-3-hydroxy-5-methylisoxazole propionic acid and N-methyl-d-aspartate (NMDA) receptors as well as the magnitude of chronic potentiation (LTP) in area CA1 (8, 9). At the cellular level, numerous laboratories have shown that, in addition to direct genetic effects, 17β-estradiol activates the extracellular regulated kinase/mitogen-activated protein (ERK/MAP) kinase pathway (10 – 12), an effect associated with the neurotrophic/neuroprotective actions of estrogen (13, 14). We recently reported that estrogen-mediated activation of this ERK/MAP kinase pathway in the hippocampus was included in the rapid effects of estrogen on NMDA receptors and LTP through tyrosine phosphorylation of NR2 subunits of NMDA receptors (15).

There was little expression of phosphorylated ERK and JNK in the normal retina, and minimal staining for p38 was detected from the GCL (Table 1) ERK phosphorylation was evident from the INL, inner plexiform layer (IPL), also GCL at 1 hour following ischemia, apparently in Müller cell bodies and in astrocytic processes.

A strong nuclear localization signal inserted to MAPK disrupts this cytoplasmic retention, and effectively upsets the differentiation pattern of their eye 7 We have also demonstrated that in response to retinoic acid, mouse embryonic carcinoma and stem cells undergo differentiation to embryonic primitive endoderm cells, and differentiation is accompanied by a decrease in both cell proliferation and nuclear entry of activated MAPK 10 Cytoplasmic retention of active MAPK also occurs in senescence of human fibroblasts 11, and during cytoskeleton changes related to motility in cultured cells 12 – 14 This evidence from several systems demonstrates that cytoplasmic activity of ERK/MAPK can clearly occur independently of its nuclear transcriptional function 9, 15 – 17, and atomic restriction of phospho-ERK after cell stimulation with growth factors might be the physiologically normal circumstance in either differentiating or normal differentiated cells. Spindle pole immunostaining was formerly reported during meiotic metaphase in mouse oocytes and mitosis in Xenopus tadpole cells (Verlhac et al., 1993; Wang et al., 1997). ERK staining of microtubules has also been detected in NIH 3T3 cells, even though it’s somewhat dependent on the antibody used (Rezka et al., 1995), and association of inactive and active ERK pools with tubulin and MAPs has been demonstrated biochemically (Morishima-Kawashima and Kosik, 1996; Mandelkow et al., 1992). Furthermore, adding active MAPK into interphase frog embryo extracts leads to microtubule shortening and association, which resemble a mitotic array (Gotoh et al., 1991). Potential mediators of microtubule depolymerization include MAPs such as tau, which, upon phosphorylation by ERK enhances the probability of microtubule depolymerization (Shiina et al., 1992; Hoshi et al., 1992; Dreschsel et al., 1992). Consistent with results from early Xenopus embryos, preceding reports in somatic mammalian cells have demonstrated that no activation of ERK during mitosis, as quantified by SDS-PAGE gel mobility retardation or in-gel phosphorylation assays (Tamemoto et al., 1992; Edelmann et al., 1996). Ras also seems to stay inactive during mitosis (Taylor and Shalloway, 1996). These statistics indicate the existence of mitotic mechanisms for activating ERK.

ERK1 and ERK 2 are activated by dual phosphorylation by the upstream kinases MEK1/2 at a conserved threonine-glutamate-tyrosine (TEY) theme (Thr 202 and Tyr 204 in human ERK1, Thr 185 and Tyr 187 in human ERK2) two, 11 While phosphorylation at both, Tyr and Thr are required for full enzyme activation, also the monophosphorylated forms of ERK2 were shown to have appreciable kinase activities in vitro in 1 mM ATP 12, which is in the range of physiological intracellular ATP levels in cells 13 Thus, monophosphorylated forms of ERK2 were proposed to possibly represent intermediate action states which may have different biological functions in vivo 12 Tyrosine-monophosphorylated ERK2 was reported to transiently associate with the Golgi complex in HELA cells during cell cycle G2 and M phases, suggesting a function in the regulation of Golgi structure 14. Many domain names of dp-ERK correspond to areas of known or speculated FGF signaling in mouse, and dp-ERK staining was abolished or attenuated in the majority of domain names by FGFR-specific inhibitor (Figs 4, 5). Though RAS-ERK was described originally as a universal signaling cascade downstream of all RTKs, some RTKs elicit only feeble RAS-ERK responses preferentially use other pathways or even inhibit the RAS-ERK cascade (Elowe et al., 2001; Schlessinger, 2000). Not all domains of RTK signaling are scored in this assay. This, in turn, contributes to the activation of a range of intracellular signaling cascades, including the RAS-MAPK pathway (Marshall, 1995; Schlessinger, 2000). RTK activation leads to RAS activation, which, in turn, induces sequential phosphorylation of this protein kinases RAF, MEK and ERK (MAPK).
4B, E) suggested FGF signaling may play a part in heart induction in mouse as it can in zebrafish and poultry (Alsan and Schultheiss, 2002; Reifers et al., 2000). In the EPC, dp-ERK staining began after the initial formation of the tissue and persisted for several days in the central diploid cells (Fig. SB203580 is a putatively specific inhibitor of the activity of p38 kinases (not of the phosphorylation), that can be parallel members of the MAPK superfamily and are activated by cellular stressors (Cuenda et al., 1995). We tested three different levels of SB203580 for effects on p-ERK amounts (Fig. Consistently, down-regulation of Nup153 decreased c-Fos expression in transfected cells without lowering phospho-ERK levels (Figure 4), showing that uncoupling of MAPK stimulation and c-Fos expression occurs in the level of nuclear import machinery.
MAP kinases are omnipresent serine-threonine protein kinases expressed in all eukaryotic cells , 5 and can be divided into five classes: The Erk1/2, p38, Jnk, Erk3/4, and Erk5 subfamilies 5 They are activated by MAP kinase kinase-mediated double phosphorylation on two different amino acids, Threonine and Tyrosine, in a T-X-Y motif of the regeneration loop 6 Phosphorylation induces a rotation involving the N- and C-terminal domains that activate the kinase 7 Activation is accompanied with a partial translocation to the nucleus 8, 9 for phosphorylation of atomic goals which mostly consist of transcription factors 5 MAP kinase inactivation on the other hand is achieved by MAP kinase phosphatases that specifically recognise and take out the double phosphorylation 10. Immunoblots of whole-cell extracts using the anti-ACTIVE MAPK antibody revealed elevated reactivity using ERKs 1 and 2 after stimulation of NIH 3T3, CHO, or PtK1 cells with 10% serum/phorbol ester, consistent with the anticipated protein kinase activation (Fig. MAP kinase signaling is likewise triggered during development in a wide array of organisms (13, 17, 35). In Caenorhabditis elegans, by way of instance, the ERK-1/two homolog MPK-1 phosphorylates the winged-helix transcription factor Lin-31, which disrupts the Lin-1 (Ets transcription factor) /Lin-31 inhibitory complex to define vulval cell fate (35). In Drosophila, antibodies into the activated form of ERK detected dynamic expression patterns which correlated with famous RTK pathways (13). These studies imply this law is conserved and that ERK-1 / 2 signaling is regulated during development.
Our observation that inhibition of MEK/ERK indicating with U-0126 results in caspase-dependent apoptosis indicates that diminished ERK-1/2 signaling induces apoptosis and is consistent with other studies (2, 22, 31). In HeLa cells, inhibition of ERK signaling together with the MEK inhibitor PD-98059 led to caspase-dependent apoptosis and induced p38 activity, whilst JNK activities remained unchanged, as in the current study (two ). Inhibition of ERK-1/two with U-0126 blocked proliferation of neural progenitor cells while increasing the population of cells undergoing apoptosis (22). Additionally, U-0126-mediated dose-dependent activation of caspase-3, cleavage of 116-kDa poly(ADP-ribose) polymerase, and morphological signs of apoptosis were observed in human chondrocytes (31), implying MEK/ERK inhibition may lead to increased apoptosis in a broad range of cell types. Evidence for the role of ERK-1/2 signaling in lung development is circumstantial and is founded on the effects of receptor tyrosine kinase (RTK) stimulation, such as hepatocyte growth factor (HGF), epidermal growth factor (EGF), platelet-derived growth factor (PDGF), fibroblast growth factor (FGF), insulin-like growth factor (IGF) (25, 26, 28, 29, 33), and G protein activation (19). However, the signaling pathways that lead or markers which differentiation have yet to be elucidated. Both ERK-1 and -2 are thought to be involved primarily in proliferation and differentiation, whereas JNK and p38 are thought to be involved in stress responses and apoptosis (10). ERK-1 and -2 are 44- and 42-kDa proteins, respectively, which become activated when phosphorylated on either the tyrosine and threonine residues within the TEY motif by ERK MAP kinase (MEK) -1 and -2 (10). MEK-specific inhibitors PD-98059 and 1,4-diamino-2,3-dicyano-1,4-bis(2-aminophenylthio) butadiene (U-0126) have been shown to decrease ERK-1/two signaling, together with the latter having a lower IC50 than the former (8, 11). U-0126 is an organic compound that noncompetitively inhibits the catalytic activity of the active enzyme (7).
The procedures of lung growth and development are extremely complex, involving plenty of effects including growth factors, extracellular matrix interactions, and hormones (9, 38). A number of these effectors activate signaling pathways which converge to the mitogen-activated protein (MAP) kinases. In the model organism C. elegans, the hormonal trigger for oocyte maturation and MAP kinase activation is MSP, a cytoskeletal protein secreted from sperm 28 In addition, recent evidence indicates that MSP action on somatic gonadal sheath cells regulates the production, growth and meiotic maturation of oocytes 31, 68 Oocyte meiotic development and ovulation hence strictly be based on the existence of semen in C. elegans. Besides its functions in sperm structure and motility 25 – 27, Greenstein and colleagues have revealed that MSP has a range of extracellular signaling properties 28 In oocytes, MSP signaling triggers through the receptor tyrosine kinase VAB-1 the activation of MAP kinase and then meiotic maturation and cell cycle progression 28, 29 It boosts muscle contractions in somatic gonadal sheath cells to facilitate ovulation 28 In parallel, MSP signaling antagonises inhibitory signals from both, gonadal sheath cells and oocytes, that prevent meiotic maturation in the absence of semen 29, 30 Gonadal sheath cells consequently seem to be the significant initial sensor of MSP and control all MSP-dependent meiotic maturation occasions, possibly via multiple classes of G-protein-coupled receptors and communication through gap junctions 31.