The role of scaffold proteins in MEK/ERK signalling

2006 ◽  
Vol 34 (5) ◽  
pp. 833-836 ◽  
Author(s):  
D.B. Sacks
Keyword(s):  
Mammalian Cells ◽  
Phorbol Esters ◽  
Biological Response ◽  
Adaptor Proteins ◽  
Scaffold Proteins ◽  
Mitogen Activated Protein Kinase ◽  
Cellular Functions ◽  
Extracellular Signal ◽  
Kinase Suppressor Of Ras ◽  
Mitogen Activated Protein

Signal transduction networks allow cells to recognize and respond to changes in the extracellular environment. All eukaryotic cells have MAPK (mitogen-activated protein kinase) pathways that participate in diverse cellular functions, including differentiation, survival, transformation and movement. Five distinct groups of MAPKs have been characterized in mammals, the most extensively studied of which is the Ras/Raf/MEK [MAPK/ERK (extracellular-signal-regulated kinase) kinase]/ERK cascade. Numerous stimuli, including growth factors and phorbol esters, activate MEK/ERK signalling. How disparate extracellular signals are translated by MEK/ERK into different cellular functions remains obscure. Originally identified in yeast, scaffold proteins are now recognized to contribute to the specificity of MEK/ERK pathways in mammalian cells. These scaffolds include KSR (kinase suppressor of Ras), β-arrestin, MEK partner-1, Sef and IQGAP1. Scaffolds organize multiprotein signalling complexes. This targets MEK/ERK to specific substrates and facilitates communication with other pathways, thereby mediating diverse functions. The adaptor proteins regulate the kinetics, amplitude and localization of MEK/ERK signalling, providing an efficient mechanism that enables an individual extracellular stimulus to promote a specific biological response.

Identification of the autophosphorylation sites and characterization of their effects in the protein kinase DYRK1A

2001 ◽  
Vol 359 (3) ◽  
pp. 497-505 ◽  
Author(s):  
Sunke HIMPEL ◽  
Pascal PANZER ◽  
Klaus EIRMBTER ◽  
Hanna CZAJKOWSKA ◽  
Muhammed SAYED ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Map Kinase ◽  
Mammalian Cells ◽  
Catalytic Domain ◽  
Molecular Model ◽  
Enzymic Activity ◽  
Mitogen Activated Protein Kinase ◽  
Kinase Family ◽  
Extracellular Signal ◽  
Mitogen Activated Protein

Protein kinases of the DYRK (‘dual-specificity tyrosine-regulated kinase’) family are characterized by a conserved Tyr-Xaa-Tyr motif (Tyr-319–Tyr-321) in a position exactly corresponding to the activation motif of the mitogen-activated protein kinase (MAP kinase) family (Thr-Xaa-Tyr). In a molecular model of the catalytic domain of DYRK1A, the orientation of phosphorylated Tyr-321 is strikingly similar to that of Tyr-185 in the known structure of the activated MAP kinase, extracellular-signal-regulated kinase 2. Consistent with our model, substitution of Tyr-321 but not of Tyr-319 by phenylalanine markedly reduced the enzymic activity of recombinant DYRK1A expressed in either Escherichia coli or mammalian cells. Direct identification of phosphorylated residues by tandem MS confirmed that Tyr-321, but not Tyr-319, was phosphorylated. When expressed in COS-7 cells, DYRK1A was found to be fully phosphorylated on Tyr-321. A catalytically inactive mutant of DYRK1A contained no detectable phosphotyrosine, indicating that Tyr-321 is autophosphorylated by DYRK1A. MS identified Tyr-111 and Ser-97 as additional autophosphorylation sites in the non-catalytic N-terminal domain of bacterially expressed DYRK1A. Enzymic activity was not affected in the DYRK1A-Y111F mutant. The present experimental data and the molecular model indicate that the activity of DYRK1A is dependent on the autophosphorylation of a conserved tyrosine residue in the activation loop.

scholarly journals IQGAP1 Is a Scaffold for Mitogen-Activated Protein Kinase Signaling

2005 ◽  
Vol 25 (18) ◽  
pp. 7940-7952 ◽  
Author(s):  
Monideepa Roy ◽  
Zhigang Li ◽  
David B. Sacks
Keyword(s):  
Growth Factor ◽  
Map Kinase ◽  
Mitogen Activated Protein Kinase ◽  
Kinase Signaling ◽  
Cellular Functions ◽  
Molecular Scaffold ◽  
Extracellular Signal ◽  
Mitogen Activated Protein ◽  
Erk Activity

ABSTRACT IQGAP1 modulates many cellular functions such as cell-cell adhesion, transcription, cytoskeletal architecture, and selected signaling pathways. We previously documented that IQGAP1 binds extracellular signal-regulated kinase (ERK) 2 and regulates growth factor-stimulated ERK activity. Here we show that MEK, the molecule immediately upstream of ERK in the Ras/mitogen-activated protein (MAP) kinase signaling cascade, also interacts directly with IQGAP1. Both MEK1 and MEK2 bound IQGAP1 in vitro and coimmunoprecipitated with IQGAP1. The addition of ERK2 enhanced by fourfold the in vitro interaction of MEK2 with IQGAP1 without altering binding of MEK1. Similarly, ERK1 promoted MEK binding to IQGAP1, but either MEK protein altered the association between IQGAP1 and ERK. Epidermal growth factor (EGF) differentially regulated binding, enhancing MEK1 interaction while reducing MEK2 binding to IQGAP1. In addition, both knockdown and overexpression of IQGAP1 reduced EGF-stimulated activation of MEK and ERK. Analyses with selective IQGAP1 mutant constructs indicated that MEK binding is crucial for IQGAP1 to modulate EGF activation of ERK. Our data strongly suggest that IQGAP1 functions as a molecular scaffold in the Ras/MAP kinase pathway.

scholarly journals Extracellular Signal-Regulated Kinase 2 Interacts with and Is Negatively Regulated by the LIM-Only Protein FHL2 in Cardiomyocytes

2004 ◽  
Vol 24 (3) ◽  
pp. 1081-1095 ◽  
Author(s):  
Nicole H. Purcell ◽  
Dina Darwis ◽  
Orlando F. Bueno ◽  
Judith M. Müller ◽  
Roland Schüle ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Mapk Pathway ◽  
Mapk Signaling ◽  
Mitogen Activated Protein Kinase ◽  
Erk Signaling ◽  
Interacting Protein ◽  
Hypertrophic Response ◽  
Extracellular Signal ◽  
Mitogen Activated Protein

ABSTRACT The mitogen-activated protein kinase (MAPK) signaling pathway regulates diverse biologic functions including cell growth, differentiation, proliferation, and apoptosis. The extracellular signal-regulated kinases (ERKs) constitute one branch of the MAPK pathway that has been implicated in the regulation of cardiac differentiated growth, although the downstream mechanisms whereby ERK signaling affects this process are not well characterized. Here we performed a yeast two-hybrid screen with ERK2 bait and a cardiac cDNA library to identify novel proteins involved in regulating ERK signaling in cardiomyocytes. This screen identified the LIM-only factor FHL2 as an ERK interacting protein in both yeast and mammalian cells. In vivo, FHL2 and ERK2 colocalized in the cytoplasm at the level of the Z-line, and interestingly, FHL2 interacted more efficiently with the activated form of ERK2 than with the dephosphorylated form. ERK2 also interacted with FHL1 and FHL3 but not with the muscle LIM protein. Moreover, at least two LIM domains in FHL2 were required to mediate efficient interaction with ERK2. The interaction between ERK2 and FHL2 did not influence ERK1/2 activation, nor was FHL2 directly phosphorylated by ERK2. However, FHL2 inhibited the ability of activated ERK2 to reside within the nucleus, thus blocking ERK-dependent transcriptional responsiveness of ELK-1, GATA4, and the atrial natriuretic factor promoter. Finally, FHL2 partially antagonized the cardiac hypertrophic response induced by activated MEK-1, GATA4, and phenylephrine agonist stimulation. Collectively, these results suggest that FHL2 serves a repressor function in cardiomyocytes through its ability to inhibit ERK1/2 transcriptional coupling.

Hautalterung: Über die Rolle von Fibroblasten-Wachstumsfaktoren

2020 ◽  
Vol 8 (2) ◽  
pp. 65-67
Author(s):  
Andrea Schulz
Keyword(s):  
Map Kinases ◽  
Skin Resistance ◽  
Skin Aging ◽  
Mitogen Activated Protein Kinase ◽  
Cellular Functions ◽  
Molecular Alterations ◽  
Extracellular Signal ◽  
Mitogen Activated Protein ◽  
Relevant Role ◽  
Dermal Cells

Cutaneous aging is a complex and continuous biological process characterized by cellular and molecular alterations, with progressive reduction of the bodyʼs capacity to maintain the homeostasis, senescence, and/or apoptosis of the dermal cells. Fibroblast growth factors (FGF) have elicited studies to evaluate their role of repair and remodeling of the dermis during the skin anti-aging process, since they are regulatory proteins that mediate important signaling pathways and act on cell regeneration and repair processes. FGF acts primarily through binding to tyrosine kinase receptors through the autophosphorylation of their residues, promoting the phosphorylation of serine, threonine, and tyrosine residues of specific target proteins such as Raf-1, MAPK/Erk kinase, and extracellular signal-regulated kinase-1, which are part of the cascade of MAP kinases (mitogen-activated protein kinase). Then, FGF initiate signaling cascades inside the cell, where each kinase activates the following by phosphorylation, resulting in alterations of cellular functions. In addition, the FGF has a relevant role in anti-aging therapy because it is related to collagen and elastin synthesis activation responsible for skin resistance and elasticity, characteristics that are diminished with skin aging. Thus, the present article aims to review several scientific studies that demonstrated the cell signaling involved with the action of FGF on skin aging.

scholarly journals Extracellular Signal-regulated Kinase Regulates Clathrin-independent Endosomal Trafficking

2006 ◽  
Vol 17 (2) ◽  
pp. 645-657 ◽  
Author(s):  
Sarah E. Robertson ◽  
Subba Rao Gangi Setty ◽  
Anand Sitaram ◽  
Michael S. Marks ◽  
Robert E. Lewis ◽  
...  
Keyword(s):  
Surface Expression ◽  
Mek Inhibitor ◽  
Endocytic Pathway ◽  
Mitogen Activated Protein Kinase ◽  
Erk Signaling ◽  
Endosomal Trafficking ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal ◽  
Kinase Suppressor Of Ras ◽  
Mitogen Activated Protein

Extracellular signal-regulated kinase (Erk) is widely recognized for its central role in cell proliferation and motility. Although previous work has shown that Erk is localized at endosomal compartments, no role for Erk in regulating endosomal trafficking has been demonstrated. Here, we report that Erk signaling regulates trafficking through the clathrin-independent, ADP-ribosylation factor 6 (Arf6) GTPase-regulated endosomal pathway. Inactivation of Erk induced by a variety of methods leads to a dramatic expansion of the Arf6 endosomal recycling compartment, and intracellular accumulation of cargo, such as class I major histocompatibility complex, within the expanded endosome. Treatment of cells with the mitogen-activated protein kinase kinase (MEK) inhibitor U0126 reduces surface expression of MHCI without affecting its rate of endocytosis, suggesting that inactivation of Erk perturbs recycling. Furthermore, under conditions where Erk activity is inhibited, a large cohort of Erk, MEK, and the Erk scaffold kinase suppressor of Ras 1 accumulates at the Arf6 recycling compartment. The requirement for Erk was highly specific for this endocytic pathway, because its inhibition had no effect on trafficking of cargo of the classical clathrin-dependent pathway. These studies reveal a previously unappreciated link of Erk signaling to organelle dynamics and endosomal trafficking.

scholarly journals p63α and γ Induce TAU Phosphorylation in Cultured Mammalian Cells

2010 ◽  
Vol 4 ◽  
pp. JEN.S6295
Author(s):  
Claudie Hooper ◽  
Reem Soliman ◽  
Simon Lovestone ◽  
Richard Killick
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Protein Kinase ◽  
Mammalian Cells ◽  
Neuronal Development ◽  
Glycogen Synthase ◽  
Tau Phosphorylation ◽  
Mitogen Activated Protein Kinase ◽  
Extracellular Signal ◽  
Mitogen Activated Protein

Here we show by western blotting that transcriptionally active isoforms of p63 (p63α and p63γ) induce the phosphorylation of human 2N4R tau at the tau-1/AT8 epitope in HEK293a cells; a phospho-epitope increased in Alzheimer's disease. Confocal microscopy shows that tau and p63α are spatially separated intracellularly. Tau was found in the cytoskeletal compartment, whilst p63α was located in the nucleus, indicating that the effects of p63 on tau phosphorylation are indirectly mediated. Tau phosphorylation occurred independently of the known tau kinases, protein kinase C delta (PKCδ), c-Jun N-terminal kinase (JNK), extracellular-signal-regulated kinase (ERK), p38 mitogen-activated protein kinase (p38), glycogen synthase kinase 3 (GSK3), v-akt murine thymoma viral oncogene homolog (AKT) and cyclin-dependent kinase 5 (Cdk5) and the tau protein phosphatases (PP), PP1 and PP2A-Aα/β. Considering that p63 and tau are both associated with developmental processes, these findings have ramifications for neuronal development and synaptic plasticity and also neurodegenerative diseases such as Alzheimer's disease and other tauopathies.

scholarly journals Alternative splicing results in RET isoforms with distinct trafficking properties

2012 ◽  
Vol 23 (19) ◽  
pp. 3838-3850 ◽  
Author(s):  
Douglas S. Richardson ◽  
David M. Rodrigues ◽  
Brandy D. Hyndman ◽  
Mathieu J. F. Crupi ◽  
Adrian C. Nicolescu ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Expression Patterns ◽  
Adaptor Proteins ◽  
Mitogen Activated Protein Kinase ◽  
Functional Differences ◽  
Midbrain Dopaminergic Neurons ◽  
Extracellular Signal ◽  
Mitogen Activated Protein ◽  
Alternatively Spliced

RET encodes a receptor tyrosine kinase that is essential for spermatogenesis, development of the sensory, sympathetic, parasympathetic, and enteric nervous systems and the kidneys, as well as for maintenance of adult midbrain dopaminergic neurons. RET is alternatively spliced to encode multiple isoforms that differ in their C-terminal amino acids. The RET9 and RET51 isoforms display unique levels of autophosphorylation and have differential interactions with adaptor proteins. They induce distinct gene expression patterns, promote different levels of cell differentiation and transformation, and play unique roles in development. Here we present a comprehensive study of the subcellular localization and trafficking of RET isoforms. We show that immature RET9 accumulates intracellularly in the Golgi, whereas RET51 is efficiently matured and present in relatively higher amounts on the plasma membrane. RET51 is internalized faster after ligand binding and undergoes recycling back to the plasma membrane. This differential trafficking of RET isoforms produces a more rapid and longer duration of signaling through the extracellular-signal regulated kinase/mitogen-activated protein kinase pathway downstream of RET51 relative to RET9. Together these differences in trafficking properties contribute to some of the functional differences previously observed between RET9 and RET51 and establish the important role of intracellular trafficking in modulating and maintaining RET signaling.

scholarly journals MAPK and PKC activity are not required for H2O2-induced arterial muscle contraction

2000 ◽  
Vol 279 (3) ◽  
pp. H1194-H1200 ◽  
Author(s):  
N. J. Pelaez ◽  
S. L. Osterhaus ◽  
A. S. Mak ◽  
Y. Zhao ◽  
H. W. Davis ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Phorbol Esters ◽  
Isometric Tension ◽  
Mitogen Activated Protein Kinase ◽  
Tension Development ◽  
Extracellular Signal ◽  
High K ◽  
Mitogen Activated Protein ◽  
Pulmonary Arterial ◽  
Time Courses

H2O2-induced pulmonary arterial smooth muscle (PASM) contractions are independent of Ca2+and myosin light chain phosphorylation. The purpose of this study was to determine whether mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK) 1 and ERK2, or protein kinase C (PKC) activation is required for H2O2-induced contraction. Porcine PASM strips were stimulated with 1 mM H2O2, 120 mM KCl, or 10 μM phorbol myristic acetate and freeze clamped at various times during the contractions. Changes in relative amounts of tyrosine/threonine phosphorylated MAPK compared with total MAPK were measured. MAPK tyrosine phosphorylation levels increased in correlation with tension development. However, 50 μM PD-98059, a MAPK/ERK kinase-MAPK kinase blocker, reduced MAPK phosphorylation below resting levels, even though the magnitude of the isometric tension development was unaltered. Freeze-clamped PASM strips were placed in a PKC activity assay buffer containing 32P and CaCl2 to measure the total myelin basic protein phosphorylation. The data show that: 1) the time courses of PKC activity and force produced in response to H2O2 do not correlate, and 2) MAPK activation may be a concurrent event with, or a consequence of, tension development in response to a variety of agonists but is not responsible for contractions to H2O2, high K+, or phorbol esters.

scholarly journals Sequential Activation of the MEK-Extracellular Signal-Regulated Kinase and MKK3/6-p38 Mitogen-Activated Protein Kinase Pathways Mediates Oncogenic ras-Induced Premature Senescence

2002 ◽  
Vol 22 (10) ◽  
pp. 3389-3403 ◽  
Author(s):  
Weiping Wang ◽  
Joan X. Chen ◽  
Rong Liao ◽  
Qingdong Deng ◽  
Jennifer J. Zhou ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Mammalian Cells ◽  
Human Fibroblasts ◽  
Mitogen Activated Protein Kinase ◽  
Premature Senescence ◽  
Erk Pathway ◽  
Primary Cells ◽  
Extracellular Signal Regulated Kinase ◽  
Extracellular Signal ◽  
Mitogen Activated Protein

ABSTRACT In primary mammalian cells, oncogenic ras induces premature senescence, depending on an active MEK-extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) pathway. It has been unclear how activation of the mitogenic MEK-ERK pathway by ras can confer growth inhibition. In this study, we have found that the stress-activated MAPK, p38, is also activated during the onset of ras-induced senescence in primary human fibroblasts. Constitutive activation of p38 by active MKK3 or MKK6 induces senescence. Oncogenic ras fails to provoke senescence when p38 activity is inhibited, suggesting that p38 activation is essential for ras-induced senescence. Furthermore, we have demonstrated that p38 activity is stimulated by ras as a result of an activated MEK-ERK pathway. Following activation of MEK and ERK, expression of oncogenic ras leads to the accumulation of active MKK3/6 and p38 activation in a MEK-dependent fashion and subsequently induces senescence. Active MEK1 induces the same set of changes and provokes senescence relying on active p38. Therefore, oncogenic ras provokes premature senescence by sequentially activating the MEK-ERK and MKK3/6-p38 pathways in normal, primary cells. These studies have defined the molecular events within the ras signaling cascade that lead to premature senescence and, thus, have provided new insights into how ras confers oncogenic transformation in primary cells.

scholarly journals Targeting of FAK Ser910 by ERK5 and PP1δ in non-stimulated and phorbol ester-stimulated cells

2007 ◽  
Vol 408 (1) ◽  
pp. 7-18 ◽  
Author(s):  
Emma Villa-Moruzzi
Keyword(s):  
Gene Silencing ◽  
Focal Adhesion ◽  
Phorbol Ester ◽  
Kinase Inhibitors ◽  
Phorbol Esters ◽  
Morphological Changes ◽  
Mitogen Activated Protein Kinase ◽  
Extracellular Signal ◽  
Mitogen Activated Protein ◽  
In Cells

Ser910 of FAK (focal adhesion kinase) was phosphorylated in fibroblasts treated with the phorbol ester PMA and dephosphorylated by PP1δ (protein phosphatase 1δ), as indicated by shRNA (small-hairpin RNA) gene silencing. Ser910 of FAK was reported previously to be an ERK (extracellular-signal-regulated kinase) 1/2 target in cells treated with phorbol esters. In contrast, various approaches, including the use of the MEK (mitogen-activated protein kinase/ERK kinase) inhibitors UO126 and CI-1040 to inhibit ERK1/2 pointed to the involvement of ERK5. This hypothesis was confirmed by: (i) shRNA ERK5 gene silencing, which resulted in complete pSer910 loss in non-stimulated and PMA-stimulated cells; (ii) direct phosphorylation of recombinant FAK by ERK5; and (iii) ERK5 activation by PMA. PMA stimulation and ERK5 silencing in MDA-MB 231 and MDA-MB 361 breast cancer cells indicated Ser910 targeting by ERK5 also in these cells. Given the proximity of Ser910 to the FAT (focal adhesion targeting) regulatory domain of FAK, cell proliferation and morphology were investigated in FAK−/− cells expressing S910A mutant FAK. The cell growth rate decreased and exposure to PMA induced peculiar morphological changes in cells expressing S910A, with respect to wild-type FAK, suggesting a role for Ser910 in these processes. The present study indicates, for the first time, the phosphorylation of Ser910 of FAK by ERK5 and its dephosphorylation by PP1δ, and suggested a role for Ser910 in the control of cell shape and proliferation.

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