Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “ERK”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6Linked to original sources
PubMed2003

Activation of extracellular signal-regulated kinases (ERK) during reperfusion of ischemic spinal cord.

The extracellular signal-regulated kinases (ERK) participate in numerous signaling pathways and are abundantly expressed in the CNS. It has been proposed that ERK activation promotes survival in models of neuronal injury. Inhibition of MEK, the upstream kinase that activates ERK, however, leads to neuroprotection in models of cerebral ischemia and trauma, suggesting that in this context ERK activation contributes to cellular damage. The effect of ischemia and reperfusion on activity and expression of ERK was investigated using a reversible model of rabbit spinal cord ischemia. Active ERK was observed in nai;ve animals, which decreased during 15 to 60 min of ischemia. Upon reperfusion, a robust activation of ERK was observed in animals occluded for 60 min that remained permanently paraplegic. Immunohistochemical analyses revealed increased staining of phosphorylated ERK (pERK) in glial cells and faint nuclear staining in motor neurons of animals occluded for 60 min and reperfused for 18 h. In contrast ERK activity did not increase in animals occluded for 15 min that regained motor function. No evidence of increased pERK immunoreactivity in motor neurons or nuclear translocation was noted in these animals. ERK1 was demonstrated to be identical to a p46 c-Jun/ATF-2 kinase previously shown to be activated by reperfusion after a 60-min occlusion. The results suggest that activation of ERK during reperfusion of ischemic spinal cord participates in the cellular pathways leading to neuronal damage.

Activating Transcription Factor 2↗
PubMed2004

Bidirectional signals transduced by DAPK-ERK interaction promote the apoptotic effect of DAPK.

Death-associated protein kinase (DAPK) is a death domain-containing serine/threonine kinase, and participates in various apoptotic paradigms. Here, we identify the extracellular signal-regulated kinase (ERK) as a DAPK-interacting protein. DAPK interacts with ERK through a docking sequence within its death domain and is a substrate of ERK. Phosphorylation of DAPK at Ser 735 by ERK increases the catalytic activity of DAPK both in vitro and in vivo. Conversely, DAPK promotes the cytoplasmic retention of ERK, thereby inhibiting ERK signaling in the nucleus. This reciprocal regulation between DAPK and ERK constitutes a positive feedback loop that ultimately promotes the apoptotic activity of DAPK. In a physiological apoptosis system where ERK-DAPK interplay is reinforced, downregulation of either ERK or DAPK suppresses such apoptosis. These results indicate that bidirectional signalings between DAPK and ERK may contribute to the apoptosis-promoting function of the death domain of DAPK.

Amino Acid Sequence↗
PubMed2005

Quantitative single cell determination of ERK phosphorylation and regulation in relapsed and refractory primary acute myeloid leukemia.

We investigated the constitutive activation of the MEK/ERK pathway in acute myelogenous leukemia (AML) via a flow cytometric technique to quantitate expression of phosphorylated ERK (p-ERK). A total of 42 AML samples (16 newly diagnosed, 26 relapsed/refractory) were analyzed. Normal bone marrow CD34+ cells (n = 10) had little or no expression of p-ERK, while G-CSF-mobilized CD34+ cells exhibited enhanced p-ERK levels. Markedly elevated p-ERK levels were found in 83.3% of the AML samples, with no differences observed between the newly diagnosed and relapsed/refractory samples. Treatment with a MEK inhibitor resulted in significantly decreased p-ERK levels in both the newly diagnosed and relapsed/refractory samples, which was associated with growth arrest, but not apoptosis induction. In summary, we defined conditions for the analysis of MAPK signaling in primary AML samples. Normal CD34+ cells expressed very low levels of p-ERK, and increased p-ERK levels were found in normal G-CSF-stimulated circulating CD34+ cells. Constitutively high p-ERK levels observed in the majority of AML samples suggest deregulation of this pathway that appears to be independent of disease status. The ability of ERK inhibition to promote growth arrest rather than apoptosis suggests that clinical trials of MEK/ERK inhibitors may be more effective when combined with chemotherapy.

Acute Disease↗
PubMed1999

Lysophosphatidic acid-induced proliferation in opossum kidney proximal tubular cells: role of PI 3-kinase and ERK.

UNLABELLED: Lysophosphatidic acid-induced proliferation in opossum kidney proximal tubular cells: Role of PI 3-kinase and ERK. BACKGROUND: Lysophosphatidic acid (LPA) is a mitogenic lipid bound to albumin in the circulation and implicated in the induction of proximal tubular cell (PTC) injury in proteinuric states. In this study, we investigated the effect of LPA on proliferation of opossum kidney (OK) cells and the roles of the p85/p110 phosphatidylinositol 3-kinase (PI 3-kinase) and extracellular signal-regulated kinases (ERKs) ERK-1 and ERK-2 in LPA-induced proliferation. METHODS: [3H]-thymidine incorporation was used as an index of OK cell proliferation. PI 3-kinase and ERK activities were measured by in vitro kinase assays of immunoprecipitates from both wild-type OK cells and OK cells expressing a dominant negative p85 (Deltap85) subunit of PI 3-kinase in an inducible vector. RESULTS: LPA stimulated a marked increase in [3H]-thymidine uptake in wild-type and Deltap85 OK cells. OK cell PI 3-kinase activity was stimulated by LPA and was inhibited by expression of Deltap85. LPA-induced proliferation was inhibited by wortmannin and the induction of Deltap85 expression. These data suggest that LPA stimulates PI 3-kinase activity, which is essential for signaling the induction of proliferation. LPA also stimulated ERK activity (peak at 5 min, return to baseline by 60 min) maximally at a dose of 100 microM LPA. This increase was approximately 600% above basal and was similar to the effects of 10% fetal calf serum. The proliferative effect of LPA was decreased by the ERK-kinase (MEK) inhibitor PD98059 (5 microM), therefore suggesting that ERK as well as PI 3-kinase activation is important for proliferation. ERK activation by LPA was not affected by pretreatment with wortmannin or by the expression of Deltap85. PI 3-kinase activation by LPA was not affected by pretreatment with PD98059. CONCLUSIONS: We conclude that activation of PI 3-kinase is essential for the LPA-induced proliferation of OK cells and that ERK activation is also important. Therefore, they are both vital elements in separate signaling pathways leading to cell proliferation. LPA filtered into the proximal tubule in proteinuric states is likely to have profound effects on PTC growth.

Animals↗
PubMed2005

A requirement for sustained ERK signaling during thymocyte positive selection in vivo.

It is unknown how the contrasting events of positive and negative selection can lead to the distinct biological outcomes of life or death. An increasing body of evidence suggests that the duration of extracellular signal-regulated kinase (ERK) signaling plays a role in thymocyte selection. However, it remains unclear what the kinetics of ERK activation are during positive selection in vivo. In this study, we examined the magnitude and duration of ERK signaling in intact murine thymic tissues cultured under conditions of negative or positive selection. We found that negative selection induced a rapid and robust ERK activation that is associated with death, whereas positive selection stimulated a lower intensity and brief ERK activation that quickly declined and then gradually increased and was sustained over several days. The expression pattern of Egr-1 (early growth response-1), a downstream ERK effector, correlates with the biphasic kinetics of ERK during positive selection. Id3 (inhibitor of differentiation/DNA binding 3) also exhibits biphasic kinetics but appeared to be independent of ERK signaling. Furthermore, inhibitors of T cell receptor ligation and ERK activation block maturation of CD8 single-positive thymocytes even when added after 24 h. These results demonstrate that the in vivo duration of ERK signaling must be sustained to support positive selection.

Animals↗
PubMed2002

Activation of the ERK pathway and atypical protein kinase C isoforms in exercise- and aminoimidazole-4-carboxamide-1-beta-D-riboside (AICAR)-stimulated glucose transport.

Exercise increases glucose transport in muscle by activating 5'-AMP-activated protein kinase (AMPK), but subsequent events are unclear. Presently, we examined the possibility that AMPK increases glucose transport through atypical protein kinase Cs (aPKCs) by activating proline-rich tyrosine kinase-2 (PYK2), ERK pathway components, and phospholipase D (PLD). In mice, treadmill exercise rapidly activated ERK and aPKCs in mouse vastus lateralis muscles. In rat extensor digitorum longus (EDL) muscles, (a) AMPK activator, 5-aminoimidazole-4-carboxamide-1-beta-d-riboside (AICAR), activated PYK2, ERK and aPKCs; (b) effects of AICAR on ERK and aPKCs were blocked by tyrosine kinase inhibitor, genistein, and MEK1 inhibitor, PD98059; and (c) effects of AICAR on aPKCs and 2-deoxyglucose (2-DOG) uptake were inhibited by genistein, PD98059, and PLD-inhibitor, 1-butanol. Similarly, in L6 myotubes, (a) AICAR activated PYK2, ERK, PLD, and aPKCs; (b) effects of AICAR on ERK were inhibited by genistein, PD98059, and expression of dominant-negative PYK2; (c) effects of AICAR on PLD were inhibited by MEK1 inhibitor UO126; (d) effects of AICAR on aPKCs were inhibited by genistein, PD98059, 1-butanol, and expression of dominant-negative forms of PYK2, GRB2, SOS, RAS, RAF, and ERK; and (e) effects of AICAR on 2DOG uptake/GLUT4 translocation were inhibited by genistein, PD98059, UO126, 1-butanol, cell-permeable myristoylated PKC-zeta pseudosubstrate, and expression of kinase-inactive RAF, ERK, and PKC-zeta. AMPK activator dinitrophenol had effects on ERK, aPKCs, and 2-DOG uptake similar to those of AICAR. Our findings suggest that effects of exercise on glucose transport that are dependent on AMPK are mediated via PYK2, the ERK pathway, PLD, and aPKCs.

Aminoimidazole Carboxamide↗
PubMed2003

A novel ERK-dependent signaling process that regulates interleukin-2 expression in a late phase of T cell activation.

Engagement of the T cell antigen receptor (TCR) rapidly induces multiple signal transduction pathways, including ERK activation. Here, we report a critical role for ERK at a late stage of T cell activation. Inhibition of the ERK pathway 2-6 h after the start of TCR stimulation significantly impaired interleukin-2 (IL-2) production, whereas the same treatment during the first 2 h had no effect. ERK inhibition significantly impaired nuclear translocation of c-Rel with a minimum reduction of NF-AT activity. Requirement for sustained ERK activation was also confirmed using primary T cells. To induce sustained activation of ERK, T cells required continuous engagement of TCR. Stimulation of T cells with soluble anti-TCR antibody resulted in activation of ERK lasting for 60 min, but failed to induce IL-2 production. In contrast, plate-bound anti-TCR antibody activated ERK over 4 h and induced IL-2. Furthermore, T cells treated with soluble anti-TCR antibody produced IL-2 when phorbol 12-myristate 13-acetate, which activates ERK, was present in the culture medium 2-6 h after the start of stimulation. Together, the data demonstrate the presence of a novel activation process following TCR stimulation that requires ERK-dependent regulation of c-Rel, a member of the NF-kappaB family.

Active Transport, Cell Nucleus↗
PubMed2003

ERK is regulated by sodium-proton exchanger in rat aortic vascular smooth muscle cells.

The purposes of this study were to test 1) the relationship between two widely studied mitogenic effector pathways, and 2) the hypothesis that sodium-proton exchanger type 1 (NHE-1) is a regulator of extracellular signal-regulated protein kinase (ERK) activation in rat aortic smooth muscle (RASM) cells. Angiotensin II (Ang II) and 5-hydroxytryptamine (5-HT) stimulated both ERK and NHE-1 activities, with activation of NHE-1 preceding that of ERK. The concentration-response curves for 5-HT and Ang II were superimposable for both processes. Inhibition of NHE-1 with pharmacological agents or by isotonic replacement of sodium in the perfusate with choline or tetramethylammonium greatly attenuated ERK activation by 5-HT or Ang II. Similar maneuvers significantly attenuated 5-HT- or Ang II-mediated activation of MEK and Ras but not transphosphorylation of the epidermal growth factor (EGF) receptor. EGF receptor blockade attenuated ERK activation, but not NHE-1 activation by 5-HT and Ang II, suggesting that the EGF receptor and NHE-1 work in parallel to stimulate ERK activity in RASM cells, converging distal to the EGF receptor but at or above the level of Ras in the Ras-MEK-ERK pathway. Receptor-independent activation of NHE-1 by acute acid loading of RASM cells resulted in the rapid phosphorylation of ERK, which could be blocked by pharmacological inhibitors of NHE-1 or by isotonic replacement of sodium, closely linking the proton transport function of NHE-1 to ERK activation. These studies identify NHE as a new regulator of ERK activity in RASM cells.

Angiotensin II↗
PubMed2004

Calcium activation of ERK mediated by calmodulin kinase I.

Elevated intracellular Ca(2+) triggers numerous signaling pathways including protein kinases such as the calmodulin-dependent kinases (CaMKs) and the extracellular signal-regulated kinases (ERKs). In the present study we examined Ca(2+)-dependent "cross-talk" between these two protein kinase families. Using a combination of pharmacological inhibitors and dominant-negative kinases (dnKinase), we identified a requirement for CaMKK acting through CaMKI in the stimulation of ERKs upon depolarization of the neuroblastoma cell line, NG108. Depolarization stimulated prolonged ERK and JNK activation that was blocked by the CaMKK inhibitor, STO-609; this inhibition of ERK activation by STO-609 was rescued by expression of a STO-609-insensitive mutant of CaMKK. However, activation of ERK by epidermal growth factor or carbachol were not suppressed by inhibition of CaMKK, indicating specificity for this "cross-talk." To identify the downstream target of CaMKK that mediated ERK activation upon depolarization, dnKinases were expressed. The dnCaMKI completely suppressed ERK2 activation whereas dnAKT/PKB or nuclear-targeted dnCaMKIV, other substrates for CaMKK, were not inhibitory. ERK activation upon depolarization or transfection with constitutively active (ca) CaMKI was blocked by dnRas. Additionally, depolarization of NG108 cells promoted neurite outgrowth, and this effect was blocked by inhibition of either CaMKK (STO-609) or ERK (UO126). Co-transfection with caCaMKK plus caCaMKI also stimulated neurite outgrowth that was blocked by inhibition of ERK (UO126). These data are the first to suggest that ERK activation and neurite outgrowth in response to depolarization are mediated by CaMKK activation of CaMKI.

Animals↗
PubMed2004

Adhesion stimulates direct PAK1/ERK2 association and leads to ERK-dependent PAK1 Thr212 phosphorylation.

The Rac1/Cdc42 effector p21-activated kinase (PAK) is activated by various signaling cascades including receptor-tyrosine kinases and integrins and regulates a number of processes such as cell proliferation and motility. PAK activity has been shown to be required for maximal activation of the canonical Ras/Raf/MEK/ERK Map kinase signaling cascade, likely because of PAK co-activation of Raf and MEK. Herein, we found that adhesion signaling also stimulates an association between PAK1 and ERK1/2. PAK1 and ERK1/2 co-immunoprecipitated from rat aortic smooth muscle cells (SMC) plated on fibronectin, and the two proteins co-localized in membrane ruffles and adhesion complexes following PDGF-BB or sphingosine 1-phosphate treatment, respectively. Far Western analysis demonstrated a direct association between the two proteins, and peptide mapping identified an ERK2 binding site within the autoinhibitory domain of PAK1. Interestingly, deletion of a major ERK binding site in PAK attenuates activation of an ERK-dependent serum-responsive element (SRE)-luciferase reporter gene, indicating that association between PAK and ERK is required to facilitate ERK signaling. We also show that ERK2 phosphorylates PAK1 on Thr(212) in vitro and that Thr(212) is phosphorylated in smooth muscle cells following PDGF-BB treatment in an adhesion- and MEK/ERK-dependent fashion. Expression of a phosphomimic variant, PAK-T212E, does not alter ERK association, but markedly attenuates downstream ERK signaling. Taken together, these data suggest that PAK1 may facilitate ERK signaling by serving as a scaffold to recruit Raf, MEK, and ERK to adhesion complexes, and that subsequent growth factor-stimulated phosphorylation of PAK-Thr(212) by ERK may serve to provide a negative feedback signal to control coordinate activation of ERK by growth factor- and matrix-induced signals.

Animals↗
PubMed2005

Co-activation of ERK, NF-kappaB, and GADD45beta in response to ionizing radiation.

NF-kappaB has been well documented to play a critical role in signaling cell stress reactions. The extracellular signal-regulated kinase (ERK) regulates cell proliferation and survival. GADD45beta is a primary cell cycle element responsive to NF-kappaB activation in anti-apoptotic responses. The present study provides evidence demonstrating that NK-kappaB, ERK and GADD45beta are co-activated by ionizing radiation (IR) in a pattern of mutually dependence to increase cell survival. Stress conditions generated in human breast cancer MCF-7 cells by the administration of a single exposure of 5 Gy IR resulted in the activation of ERK but not p38 or JNK, along with an enhancement of the NF-kappaB transactivation and GADD45beta expression. Overexpression of dominant negative Erk (DN-Erk) or pre-exposure to ERK inhibitor PD98059 inhibited NF-kappaB. Transfection of dominant negative mutant IkappaB that blocks NF-kappaB nuclear translocation, inhibited ERK activity and GADD45beta expression and increased cell radiosensitivity. Interaction of p65 and ERK was visualized in living MCF-7 cells by bimolecular fluorescence complementation analysis. Antisense inhibition of GADD45beta strikingly blocked IR-induced NF-kappaB and ERK but not p38 and JNK. Overall, these results demonstrate a possibility that NF-kappaB, ERK, and GADD45beta are able to coordinate in a loop-like signaling network to defend cells against the cytotoxicity induced by ionizing radiation.

Active Transport, Cell Nucleus↗
PubMed1998

Tumor necrosis factor receptor-associated factor 6 (TRAF6) stimulates extracellular signal-regulated kinase (ERK) activity in CD40 signaling along a ras-independent pathway.

CD40 activates nuclear factor kappa B (NF kappa B) and the mitogen-activated protein kinase (MAPK) subfamily, including extracellular signal-regulated kinase (ERK). The CD40 cytoplasmic tail interacts with tumor necrosis factor receptor-associated factor (TRAF)2, TRAF3, TRAF5, and TRAF6. These TRAF proteins, with the exception of TRAF3, are required for NF kappa B activation. Here we report that transient expression of TRAF6 stimulated both ERK and NF kappa B activity in the 293 cell line. Coexpression of the dominant-negative H-Ras did not affect TRAF6-mediated ERK activity, suggesting that TRAF6 may activate ERK along a Ras-independent pathway. The deletion mutant of TRAF6 lacking the NH2-terminal domain acted as a dominant-negative mutant to suppress ERK activation by full-length CD40 and suppress prominently ERK activation by a deletion mutant of CD40 only containing the binding site for TRAF6 in the cytoplasmic tail (CD40 delta 246). Transient expression of the dominant-negative H-Ras significantly suppressed ERK activation by full-length CD40, but marginally suppressed ERK activation by CD40 delta 246, compatible with the possibility that TRAF6 is a major transducer of ERK activation by CD40 delta 246, whose activity is mediated by a Ras-independent pathway. These results suggest that CD40 activates ERK by both a Ras-dependent pathway and a Ras-independent pathway in which TRAF6 could be involved.

CD40 Antigens↗
PubMed2006

Opposing role of synaptic and extrasynaptic NMDA receptors in regulation of the extracellular signal-regulated kinases (ERK) activity in cultured rat hippocampal neurons.

The extracellular signal-regulated kinases (ERK) signalling cascade is a key pathway that mediates the NMDA receptor (NMDAR)-dependent neuronal plasticity and survival. However, it is not clear yet how NMDARs regulate ERK activity. Stimulation of the NMDARs induces a complex modification of ERK that includes both ERK activation and inactivation and depends on particular experimental conditions. Here we show that there exists a differential restriction in the regulation of ERK activity that depends on the pool of NMDAR that was activated. The synaptic pool of NMDARs activates ERK whereas the extrasynaptic pool does not; on the contrary, it triggers a signalling pathway that results in the inactivation of ERK. As a result, simultaneous activation of both extrasynaptic and synaptic NMDAR using bath application of NMDA or glutamate (a typical protocol explored in the majority of studies) produced ERK activation that depended on the concentration of agonists and was always significantly weaker than those mediated by synaptic NMDARs. Since the activation of the extrasynaptic NMDA is attributed mainly to global release of glutamate occurring at pathological conditions including hypoxic/ischaemic insults, traumas and epileptic brain damage, the reported differential regulation of ERK cascade by NMDARs provides a unique mechanism for an early identification of the physiological and/or pathophysiological consequences of NMDAR activation. The negative regulation of the ERK activity might be one of the first signalling events determining brain injury and constitutes a putative target of new pharmacological applications.

Action Potentials↗
PubMed2001

Zap-70-independent Ca(2+) mobilization and Erk activation in Jurkat T cells in response to T-cell antigen receptor ligation.

The tyrosine kinase ZAP-70 has been implicated as a critical intermediary between T-cell antigen receptor (TCR) stimulation and Erk activation on the basis of the ability of dominant negative ZAP-70 to inhibit TCR-stimulated Erk activation, and the reported inability of anti-CD3 antibodies to activate Erk in ZAP-70-negative Jurkat cells. However, Erk is activated in T cells receiving a partial agonist signal, despite failing to activate ZAP-70. This discrepancy led us to reanalyze the ZAP-70-negative Jurkat T-cell line P116 for its ability to support Erk activation in response to TCR/CD3 stimulation. Erk was activated by CD3 cross-linking in P116 cells. However, this response required a higher concentration of anti-CD3 antibody and was delayed and transient compared to that in Jurkat T cells. Activation of Raf-1 and MEK-1 was coincident with Erk activation. Remarkably, the time course of Ras activation was comparable in the two cell lines, despite proceeding in the absence of LAT tyrosine phosphorylation in the P116 cells. CD3 stimulation of P116 cells also induced tyrosine phosphorylation of phospholipase C-gamma1 (PLCgamma1) and increased the intracellular Ca(2+) concentration. Protein kinase C (PKC) inhibitors blocked CD3-stimulated Erk activation in P116 cells, while parental Jurkat cells were refractory to PKC inhibition. The physiologic relevance of these signaling events is further supported by the finding of PLCgamma1 tyrosine phosphorylation, Erk activation, and CD69 upregulation in P116 cells on stimulation with superantigen and antigen-presenting cells. These results demonstrate the existence of two pathways leading to TCR-stimulated Erk activation in Jurkat T cells: a ZAP-70-independent pathway requiring PKC and a ZAP-70-dependent pathway that is PKC independent.

CD3 Complex↗
PubMed2002

Molecular psychology: roles for the ERK MAP kinase cascade in memory.

In this review we describe an emerging understanding of the roles of the Extracellular-signal regulated kinase/mitogen-activated protein kinase (ERK/MAPK) cascade in learning and memory. We begin by describing several behavioral memory paradigms and review data implicating ERK as an essential component of the signal transduction mechanisms subserving these processes. We then describe evidence implicating ERK as a critical player in synaptic and neuronal plasticity-a cellular role likely to underlie ERK's behavioral role in the animal. We then proceed to parsing the complexities of biochemical regulation of ERK in neurons and to a description of a few likely cellular targets of ERK. This is in order to begin discussing the possible molecular basis of ERK-mediated behavioral change. We close our review with speculations concerning how the complexities and idiosyncrasies of ERK regulation may allow for sophisticated information processing at the biochemical level in neurons-attributes that may make the ERK cascade well-suited for triggering complex and long-lasting behavioral change. Our goal in this review is not so much to portray ERK as unique regarding its role as a signal transducter in memory, but rather to use ERK as one specific example of recent studies beginning to address the molecules and signal transduction pathways subserving cognition.

Animals↗
PubMed2003

Collagen IV regulates Caco-2 migration and ERK activation via alpha1beta1- and alpha2beta1-integrin-dependent Src kinase activation.

Our previous work indicates intestinal epithelial cell ERK activation by collagen IV, a major component of the intestinal epithelial basement membrane, requires focal adhesion kinase (FAK) and suggests FAK and ERK may have important roles in regulating intestinal epithelial cell migration. We therefore sought to identify FAK downstream targets regulating intestinal epithelial cell spreading, migration, and ERK activation on collagen IV and the integrins involved. Both dominant-negative Src and Src inhibitor PP2 strongly inhibited collagen IV ERK activation in Caco-2 intestinal epithelial cells. Collagen IV stimulated Grb2 binding site FAK Y925 phosphorylation, which was inhibited by PP2 and required FAK Y397 autophosphorylation. Additionally, FAK Y925F expression blocked collagen IV ERK activation. alpha(1)beta(1)- Or alpha(2)beta(1)-integrin blockade with alpha(1)- or alpha(2)-integrin subunit antibodies indicated that either integrin can mediate adhesion, cell spreading, and FAK, Src, and ERK activation on collagen IV. Both dominant-negative Src and PP2 inhibited Caco-2 spreading on collagen IV. PP2 inhibited p130(Cas) tyrosine phosphorylation, but dominant-negative p130(Cas) did not inhibit cell spreading. PP2 inhibited Caco-2 migration on collagen IV much more strongly than the mitogen-activated protein kinase kinase inhibitor PD-98059, which completely inhibited collagen IV ERK activation. These results suggest a pathway for collagen IV ERK activation requiring Src phosphorylation of FAK Y925 not previously described for this matrix protein and suggest either alpha(1)beta(1)- or alpha(2)beta(1)-integrins can regulate Caco-2 spreading and ERK activation on collagen IV via Src. Additionally, these results suggest Src regulates Caco-2 migration on collagen IV primarily through ERK-independent pathways.

Antibodies, Blocking↗
PubMed2005

In vivo adenosine receptor preconditioning reduces myocardial infarct size via subcellular ERK signaling.

The protective effects of adenosine receptor acute preconditioning (PC) are well known; however, the signaling mechanism mediating this effect has not been determined in in vivo models. The purpose of this study was to determine the role of the extracellular signal-regulated kinase (ERK) pathway in mediating adenosine PC in in vivo rat myocardium. Open-chest rats were submitted to 25 min of coronary artery occlusion and 2 h of reperfusion. ERK activation was assessed by measuring total and dually phosphorylated p44/42 ERK isoforms in nuclear and/or myofilament, mitochondrial, cytosolic, and membrane fractions. Adenosine receptor PC with the A1/A2a agonist 1S-[1a,2b,3b,4a(S*)]-4-[7-[[2-(3-chloro-2-thienyl)-1-methylpropyl]amino]-3H-imidazo[4,5-b]pyridyl-3-yl]cyclopentane carboxamide (AMP-579) reduced infarct size from 49 +/- 3% to 29 +/- 3%, an effect that was blocked by the mitogen-activated protein kinase-ERK inhibitor U-0126. ERK isoforms were present in all fractions, with the greatest expression in the cytosolic fraction and the least in the mitochondrial fraction. AMP-579 treatment increased preischemic p44/42 ERK phosphorylation in all fractions 2.7- to 6.9-fold. Reperfusion increased ERK isoform activation in all fractions, but there were no differences between control and AMP-579 hearts. Preischemic increases in phospo-p44/p42 ERK with AMP-579 were blunted by U-0126, although only in mitochondrial and membrane compartments. The PC effects of AMP-579 on infarct size and ERK were blunted by both the A1 antagonist 8-cyclopentyl-1,3-dipropylxanthine and, surprisingly, the A2a antagonist ZM-241385. These results indicate that the unique adenosine receptor agonist AMP-579 exerts its beneficial effects in vivo via both A1 and A2a receptor modulation of subcellular ERK isoform signaling.

Animals↗
PubMed2006

Activation of MAPK ERK in peripheral nerve after injury.

BACKGROUND: Activation of extracellular signal-regulated protein kinase (ERK), a member of mitogen-activated protein kinase (MAPK) family, has been proposed to mediate neurite outgrowth-promoting effects of several neurotrophic factors in vitro. However, the precise activity of ERK during axonal regeneration in vivo remains unclear. Peripheral axotomy has been shown to activate ERK in the cell bodies of primary afferent neurons and associated satellite cells. Nevertheless, whether ERK is also activated in the axons and surrounded Schwann cells which also play a key role in the regeneration process has not been clarified. RESULTS: Phosphorylation of ERK in the sciatic nerve in several time-points after crush injury has been examined. Higher phosphorylation of ERK was observed in the proximal and distal nerve stumps compared to the contralateral intact nerve from one day to one month after crush. The activation of ERK was mainly localized in the axons of the proximal segments. In the distal segments, however, active ERK was predominantly found in Schwann cells forming Bungner's bands. CONCLUSION: The findings indicate that ERK is activated in both the proximal and distal nerve stumps following nerve injury. The role of activated ERK in Wallerian degeneration and subsequent regeneration in vivo remains to be elucidated.

Analysis of Variance↗