scholarly journals Kinase Suppressor of Ras Forms a Multiprotein Signaling Complex and Modulates MEK Localization

1999 ◽  
Vol 19 (8) ◽  
pp. 5523-5534 ◽  
Author(s):  
Scott Stewart ◽  
Meera Sundaram ◽  
Yanping Zhang ◽  
Jeeyong Lee ◽  
Min Han ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Mitogen Activated Protein Kinase ◽  
Scaffolding Protein ◽  
Ras Signaling ◽  
Loss Of Function ◽  
C Elegans ◽  
Signaling Complex ◽  
Independent Functions ◽  
Kinase Suppressor Of Ras ◽  
Mitogen Activated Protein

ABSTRACT Genetic screens for modifiers of activated Ras phenotypes have identified a novel protein, kinase suppressor of Ras (KSR), which shares significant sequence homology with Raf family protein kinases. Studies using Drosophila melanogaster andCaenorhabditis elegans predict that KSR positively regulates Ras signaling; however, the function of mammalian KSR is not well understood. We show here that two predicted kinase-dead mutants of KSR retain the ability to complement ksr-1 loss-of-function alleles in C. elegans, suggesting that KSR may have physiological, kinase-independent functions. Furthermore, we observe that murine KSR forms a multimolecular signaling complex in human embryonic kidney 293T cells composed of HSP90, HSP70, HSP68, p50CDC37, MEK1, MEK2, 14-3-3, and several other, unidentified proteins. Treatment of cells with geldanamycin, an inhibitor of HSP90, decreases the half-life of KSR, suggesting that HSPs may serve to stabilize KSR. Both nematode and mammalian KSRs are capable of binding to MEKs, and three-point mutants of KSR, corresponding to C. elegans loss-of-function alleles, are specifically compromised in MEK binding. KSR did not alter MEK activity or activation. However, KSR-MEK binding shifts the apparent molecular mass of MEK from 44 to >700 kDa, and this results in the appearance of MEK in membrane-associated fractions. Together, these results suggest that KSR may act as a scaffolding protein for the Ras-mitogen-activated protein kinase pathway.

scholarly journals APPL1 mediates adiponectin-stimulated p38 MAPK activation by scaffolding the TAK1-MKK3-p38 MAPK pathway

2011 ◽  
Vol 300 (1) ◽  
pp. E103-E110 ◽  
Author(s):  
Xiaoban Xin ◽  
Lijun Zhou ◽  
Caleb M. Reyes ◽  
Feng Liu ◽  
Lily Q. Dong
Keyword(s):  
Protein Kinase ◽  
P38 Mapk ◽  
Mapk Pathway ◽  
Adaptor Protein ◽  
Mapk Signaling ◽  
Mitogen Activated Protein Kinase ◽  
Scaffolding Protein ◽  
Mapk Activation ◽  
P38 Mapk Pathway ◽  
Mitogen Activated Protein

The adaptor protein APPL1 mediates the stimulatory effect of adiponectin on p38 mitogen-activated protein kinase (MAPK) signaling, yet the underlying mechanism remains unclear. Here we show that, in C2C12 cells, overexpression or suppression of APPL1 enhanced or suppressed, respectively, adiponectin-stimulated p38 MAPK upstream kinase cascade, consisting of transforming growth factor-β-activated kinase 1 (TAK1) and mitogen-activated protein kinase kinase 3 (MKK3). In vitro affinity binding and coimmunoprecipitation experiments revealed that TAK1 and MKK3 bind to different regions of APPL1, suggesting that APPL1 functions as a scaffolding protein to facilitate adiponectin-stimulated p38 MAPK activation. Interestingly, suppressing APPL1 had no effect on TNFα-stimulated p38 MAPK phosphorylation in C2C12 myotubes, indicating that the stimulatory effect of APPL1 on p38 MAPK activation is selective. Taken together, our study demonstrated that the TAK1-MKK3 cascade mediates adiponectin signaling and uncovers a scaffolding role of APPL1 in regulating the TAK1-MKK3-p38 MAPK pathway, specifically in response to adiponectin stimulation.

scholarly journals Radioiodine-Refractory Thyroid Cancer: Molecular Basis of Redifferentiation Therapies, Management, and Novel Therapies

Cancers ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1382 ◽  
Author(s):  
Mohamed Aashiq ◽  
Deborah A. Silverman ◽  
Shorook Na’ara ◽  
Hideaki Takahashi ◽  
Moran Amit
Keyword(s):  
Thyroid Cancer ◽  
Protein Kinase ◽  
Tyrosine Kinase ◽  
Mitogen Activated Protein Kinase ◽  
Sodium Iodide Symporter ◽  
Tumor Resistance ◽  
Loss Of Function ◽  
Iodide Uptake ◽  
Mitogen Activated Protein ◽  
Recurrent Thyroid Cancer

Recurrent, metastatic disease represents the most frequent cause of death for patients with thyroid cancer, and radioactive iodine (RAI) remains a mainstay of therapy for these patients. Unfortunately, many thyroid cancer patients have tumors that no longer trap iodine, and hence are refractory to RAI, heralding a poor prognosis. RAI-refractory (RAI-R) cancer cells result from the loss of thyroid differentiation features, such as iodide uptake and organification. This loss of differentiation features correlates with the degree of mitogen-activated protein kinase (MAPK) activation, which is higher in tumors with BRAF (B-Raf proto-oncogene) mutations than in those with RTK (receptor tyrosine kinase) or RAS (rat sarcoma) mutations. Hence, inhibition of the mitogen-activated protein kinase kinase-1 and -2 (MEK-1 and -2) downstream of RAF (rapidly accelerated fibrosarcoma) could sensitize RAI refractivity in thyroid cancer. However, a significant hurdle is the development of secondary tumor resistance (escape mechanisms) to these drugs through upregulation of tyrosine kinase receptors or another alternative signaling pathway. The sodium iodide symporter (NIS) is a plasma membrane glycoprotein, a member of solute carrier family 5A (SLC5A5), located on the basolateral surfaces of the thyroid follicular epithelial cells, which mediates active iodide transport into thyroid follicular cells. The mechanisms responsible for NIS loss of function in RAI-R thyroid cancer remains unclear. In a study of patients with recurrent thyroid cancer, expression levels of specific ribosomal machinery—namely PIGU (phosphatidylinositol glycan anchor biosynthesis class U), a subunit of the GPI (glycosylphosphatidylinositol transamidase complex—correlated with RAI avidity in radioiodine scanning, NIS levels, and biochemical response to RAI treatment. Here, we review the proposed mechanisms for RAI refractivity and the management of RAI-refractive metastatic, recurrent thyroid cancer. We also describe novel targeted systemic agents that are in use or under investigation for RAI-refractory disease, their mechanisms of action, and their adverse events.

scholarly journals MKP-3 Has Essential Roles as a Negative Regulator of the Ras/Mitogen-Activated Protein Kinase Pathway during Drosophila Development

2004 ◽  
Vol 24 (2) ◽  
pp. 573-583 ◽  
Author(s):  
Myungjin Kim ◽  
Guang-Ho Cha ◽  
Sunhong Kim ◽  
Jun Hee Lee ◽  
Jeehye Park ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Cell Fate ◽  
Photoreceptor Cells ◽  
Mapk Signaling ◽  
Negative Regulator ◽  
Mitogen Activated Protein Kinase ◽  
Loss Of Function ◽  
Wing Vein ◽  
Mitogen Activated Protein

ABSTRACT Mitogen-activated protein kinase (MAPK) phosphatase 3 (MKP-3) is a well-known negative regulator in the Ras/extracellular signal-regulated kinase (ERK)-MAPK signaling pathway responsible for cell fate determination and proliferation during development. However, the physiological roles of MKP-3 and the mechanism by which MKP-3 regulates Ras/Drosophila ERK (DERK) signaling in vivo have not been determined. Here, we demonstrated that Drosophila MKP-3 (DMKP-3) is critically involved in cell differentiation, proliferation, and gene expression by suppressing the Ras/DERK pathway, specifically binding to DERK via the N-terminal ERK-binding domain of DMKP-3. Overexpression of DMKP-3 reduced the number of photoreceptor cells and inhibited wing vein differentiation. Conversely, DMKP-3 hypomorphic mutants exhibited extra photoreceptor cells and wing veins, and its null mutants showed striking phenotypes, such as embryonic lethality and severe defects in oogenesis. All of these phenotypes were highly similar to those of the gain-of-function mutants of DERK/rl. The functional interaction between DMKP-3 and the Ras/DERK pathway was further confirmed by genetic interactions between DMKP-3 loss-of-function mutants or overexpressing transgenic flies and various mutants of the Ras/DERK pathway. Collectively, these data provide the direct evidences that DMKP-3 is indispensable to the regulation of DERK signaling activity during Drosophila development.

scholarly journals Transcriptional Repressor ERF Is a Ras/Mitogen-Activated Protein Kinase Target That Regulates Cellular Proliferation

1999 ◽  
Vol 19 (6) ◽  
pp. 4121-4133 ◽  
Author(s):  
Lionel le Gallic ◽  
Dionyssios Sgouras ◽  
Gregory Beal ◽  
George Mavrothalassitis
Keyword(s):  
Protein Kinase ◽  
Signaling Pathway ◽  
Cellular Proliferation ◽  
Transcriptional Repressor ◽  
Mitogen Activated Protein Kinase ◽  
Ras Signaling ◽  
Mitogen Activated Protein ◽  
Ets Family

ABSTRACT A limited number of transcription factors have been suggested to be regulated directly by Erks within the Ras/mitogen-activated protein kinase signaling pathway. In this paper we demonstrate that ERF, a ubiquitously expressed transcriptional repressor that belongs to the Ets family, is physically associated with and phosphorylated in vitro and in vivo by Erks. This phosphorylation determines the ERF subcellular localization. Upon mitogenic stimulation, ERF is immediately phosphorylated and exported to the cytoplasm. The export is blocked by specific Erk inhibitors and is abolished when residues undergoing phosphorylation are mutated to alanine. Upon growth factor deprivation, ERF is rapidly dephosphorylated and transported back into the nucleus. Phosphorylation-defective ERF mutations suppress Ras-induced tumorigenicity and arrest the cells at the G0/G1 phase of the cell cycle. Our findings strongly suggest that ERF may be important in the control of cellular proliferation during the G0/G1 transition and that it may be one of the effectors in the mammalian Ras signaling pathway.

Extracellular signal regulated kinase (ERK)/mitogen activated protein kinase (MAPK)-independent functions of Raf kinases

2002 ◽  
Vol 115 (8) ◽  
pp. 1575-1581 ◽  
Author(s):  
Alison Hindley ◽  
Walter Kolch
Keyword(s):  
Protein Kinase ◽  
Gene Knockout ◽  
Scaffold Protein ◽  
Mitogen Activated Protein Kinase ◽  
Current Evidence ◽  
Extracellular Signal Regulated Kinase ◽  
Recent Advances ◽  
Extracellular Signal ◽  
Independent Functions ◽  
Mitogen Activated Protein

Raf comprises a family of three kinases, A-Raf, B-Raf and Raf-1, which are best known as key regulators of the MEK—MAPK/ERK cascade. This module is often perceived as a linear pathway in which ERK is the effector. However,recent advances have unveiled a role for Raf outside this established signalling unit. Current evidence, including gene-knockout studies in mice,suggests that there are ERK-independent functions of Raf kinases. Regulation of apoptosis is one area in which Raf may function independently of ERK,although its substrates remain to be identified. Other studies have suggested that Raf has kinase-independent functions and may act as a scaffold protein.

scholarly journals Identification of B-KSR1, a Novel Brain-Specific Isoform of KSR1 That Functions in Neuronal Signaling

2000 ◽  
Vol 20 (15) ◽  
pp. 5529-5539 ◽  
Author(s):  
Jürgen Müller ◽  
Angela M. Cacace ◽  
W. Ernest Lyons ◽  
Carolyn B. McGill ◽  
Deborah K. Morrison
Keyword(s):  
Growth Factor ◽  
Neurite Outgrowth ◽  
Neuronal Differentiation ◽  
Catalytic Domain ◽  
Mek Inhibitor ◽  
Mitogen Activated Protein Kinase ◽  
Loss Of Function ◽  
Mapk Activity ◽  
Kinase Suppressor Of Ras ◽  
Mitogen Activated Protein

ABSTRACT Kinase suppressor of Ras (KSR) is an evolutionarily conserved component of Ras-dependent signaling pathways. Here, we report the identification of B-KSR1, a novel splice variant of murine KSR1 that is highly expressed in brain-derived tissues. B-KSR1 protein is detectable in mouse brain throughout embryogenesis, is most abundant in adult forebrain neurons, and is complexed with activated mitogen-activated protein kinase (MAPK) and MEK in brain tissues. Expression of B-KSR1 in PC12 cells resulted in accelerated nerve growth factor (NGF)-induced neuronal differentiation and detectable epidermal growth factor (EGF)-induced neurite outgrowth. Sustained MAPK activity was observed in cells stimulated with either NGF or EGF, and all effects on neurite outgrowth could be blocked by the MEK inhibitor PD98059. In B-KSR1-expressing cells, the MAPK–B-KSR1 interaction was inducible and correlated with MAPK activation, while the MEK–B-KSR1 interaction was constitutive. Further examination of the MEK–B-KSR1 interaction revealed that all genetically identified loss-of-function mutations in the catalytic domain severely diminished MEK binding. Moreover, B-KSR1 mutants defective in MEK binding were unable to augment neurite outgrowth. Together, these findings demonstrate the functional importance of MEK binding and indicate that B-KSR1 may function to transduce Ras-dependent signals that are required for neuronal differentiation or that are involved in the normal functioning of the mature central nervous system.

scholarly journals A Novel 14-Kilodalton Protein Interacts with the Mitogen-Activated Protein Kinase Scaffold Mp1 on a Late Endosomal/Lysosomal Compartment

2001 ◽  
Vol 152 (4) ◽  
pp. 765-776 ◽  
Author(s):  
Winfried Wunderlich ◽  
Irene Fialka ◽  
David Teis ◽  
Arno Alpi ◽  
Andrea Pfeifer ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Protein Complexes ◽  
Cell Types ◽  
Mapk Signaling ◽  
Mitogen Activated Protein Kinase ◽  
Scaffolding Protein ◽  
Interacting Protein ◽  
Late Endosomes ◽  
Mitogen Activated Protein

We have identified a novel, highly conserved protein of 14 kD copurifying with late endosomes/lysosomes on density gradients. The protein, now termed p14, is peripherally associated with the cytoplasmic face of late endosomes/lysosomes in a variety of different cell types. In a two-hybrid screen with p14 as a bait, we identified the mitogen-activated protein kinase (MAPK) scaffolding protein MAPK/extracellular signal–regulated kinase (ERK) kinase (MEK) partner 1 (MP1) as an interacting protein. We confirmed the specificity of this interaction in vitro by glutathione S-transferase pull-down assays and by coimmunoprecipitation, cosedimentation on glycerol gradients, and colocalization. Moreover, expression of a plasma membrane–targeted p14 causes mislocalization of coexpressed MP1. In addition, we could reconstitute protein complexes containing the p14–MP1 complex associated with ERK and MEK in vitro. The interaction between p14 and MP1 suggests a MAPK scaffolding activity localized to the cytoplasmic surface of late endosomes/lysosomes, thereby combining catalytic scaffolding and subcellular compartmentalization as means to modulate MAPK signaling within a cell.

Mitogen-activated protein kinase pathways in C. elegans

2002 ◽  
Vol 1246 ◽  
pp. 91-99 ◽  
Author(s):  
Naoki Hisamoto ◽  
Rie Sakamoto ◽  
Kunihiro Matsumoto
Keyword(s):  
Protein Kinase ◽  
Mitogen Activated Protein Kinase ◽  
C Elegans ◽  
Mitogen Activated Protein
Sign in / Sign up

Export Citation Format

Share Document