The MEK Kinase Activity of the Catalytic Domain of RAF-1 Is Regulated Independently of Ras Binding in T Cells

Whitehurst, Charles E.; Owaki, Hajime; Bruder, Joseph T.; Rapp, Ulf R.; Geppert, Thomas D.

doi:10.1074/jbc.270.10.5594

Cited by 55 publications

(40 citation statements)

References 64 publications

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“…This would satisfactorily explain why serine-621 mutants cannot be activated. However, this mutation also almost completely abolishes basal catalytic activity when introduced into the isolated Raf-1 kinase domain [9,82,84]. This phenotype is consistent with an essential structural role of serine-621, or a strict requirement for 14-3-3 to attract factors that allow Raf-1 activity.…”

Section: Making Connections : 14-3-3 Is At the Hubsupporting

confidence: 59%

“…Both sites are phosphorylated in resting cells [80], but can be hyperinduced by activation of PKA [81]. Replacing serine-621 with a number of other amino acids almost completely destroys the catalytic activity of Raf-1 and limits the usefulness of these mutants for activity studies [80,[82][83][84]. Although this indicates an essential function of serine-621, in itro biochemical experiments with the isolated Raf kinase domain, BXB, suggest an inhibitory influence of serine-621 phosphorylation.…”

Section: Making Connections : 14-3-3 Is At the Hubmentioning

confidence: 99%

“…The same holds true for the oncogenic deletion mutants that lack the whole N-terminal regulatory domain. These mutants are constitutively active, but are susceptible to further activation [82,84]. The phenotype of the serine-621 mutant is more difficult to rationalize.…”

Section: Making Connections : 14-3-3 Is At the Hubmentioning

confidence: 99%

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Meaningful relationships: the regulation of the Ras/Raf/MEK/ERK pathway by protein interactions

Kölch

2000

Biochemical Journal

1,057

118

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The Ras\Raf\MEK (mitogen-activated protein kinase\ERK kinase)\ERK (extracellular-signal-regulated kinase) pathway is at the heart of signalling networks that govern proliferation, differentiation and cell survival. Although the basic regulatory steps have been elucidated, many features of this pathway are only beginning to emerge. This review focuses on the role of protein-protein interactions in the regulation of this pathway, INTRODUCTIONThe mitogen-activated protein kinase (MAPK) pathway is one of the primordial signalling systems that Nature has used in several permutations to accomplish an amazing variety of tasks. It exists in all eukaryotes, and controls such fundamental cellular processes as proliferation, differentiation, survival and apoptosis. The basic arrangement includes a G-protein working upstream of a core module consisting of three kinases : a MAPK kinase kinase (MAPKKK) that phosphorylates and activates a MAPK kinase (MAPKK), which in turn activates MAPK ( Figure 1). This set-up provides not only for signal amplification, but, maybe even more importantly, for additional regulatory interfaces that allow the kinetics, duration and amplitude of the activity to be precisely tuned. At present we can distinguish six MAPK modules, which share structurally related components, but seem to mediate specific biological responses. For recent reviews on MAPK pathways, the reader is referred to references [1][2][3]. Here we will focus on the regulation of the ERK (extracellular-signal-regulated kinase) pathway, which features Ras as G-protein, Raf as MAPKKK, MEK (MAPK\ERK kinase) as MAPKK and ERK as MAPK.Despite enjoying a decade in the limelight of scientific interest and revealing a plethora of new insights into the circuitry of signalling pathways in general, this pathway still holds many secrets. These pertain mainly to the regulation of Raf, and to a deeper understanding of how specific biological responses are encoded by spatial and temporal changes in the activity and subcellular distribution of the pathway components, and how these fluctuations are orchestrated at the molecular level. Work from many laboratories has highlighted protein-protein interactions as powerful means of co-ordinating signalling processes, most strikingly exemplified by the assembly of multi-protein signalling complexes on activated receptors, or of transcriptionfactor complexes on gene promoters. However, it is becoming Abbreviations used : Bcr, Breakpoint cluster region ; BXB, isolated Raf-1 kinase domain ; CNK, connector-enhancer of KSR ; CK2, casein kinase 2 ; CRD, cysteine-rich domain ; DEF, docking site for ERK, FxFP ; DLK, dual leucine-zipper-bearing kinase ; ERK, extracellular-signal-regulated kinase ; Hsp, heat-shock protein ; KIM, kinase interaction motif ; IκB, inhibitor of NF-κB ; JNK, c-Jun N-terminal kinase ; KSR, kinase suppressor of Ras ; MAPK, mitogen-activated protein kinase ; MAPKK, MAPK kinase ; MAPKKK, MAPK kinase kinase ; MEK, MAPK/ERK kinase ; MEKK, MEK kinase ; MP1, MEK partner 1 ; MUK, MAPK upstream kin...

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Section: Making Connections : 14-3-3 Is At the Hubsupporting

confidence: 59%

Section: Making Connections : 14-3-3 Is At the Hubmentioning

confidence: 99%

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Meaningful relationships: the regulation of the Ras/Raf/MEK/ERK pathway by protein interactions

Kölch

2000

Biochemical Journal

1,057

118

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“…Mechanisms have been proposed for Ras-independent activation of MAP kinase (59,60). MAP kinase has a number of substrates including transcription factors that may be involved in regulation of gene expression (54,61,62).…”

Section: Discussionmentioning

confidence: 99%

Insulin Regulation of Glucose-6-phosphate Dehydrogenase Gene Expression Is Rapamycin-sensitive and Requires Phosphatidylinositol 3-Kinase

Wagle¹,

Jivraj²,

Garlock³

et al. 1998

Journal of Biological Chemistry

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Glucose-6-phosphate dehydrogenase (G6PDH) controls the flow of carbon through the pentose phosphate pathway and also produces NADPH needed for maintenance of reduced glutathione and reductive biosynthesis. Hepatic expression of G6PDH is known to respond to several dietary and hormonal factors, but the mechanism behind regulation of this expression has not been characterized. We show that insulin similarly induces expression of endogenous hepatic G6PDH and a reporter construct containing 935 base pairs of the G6PDH promoter linked to luciferase in transient transfection assays. Using well tested and structurally distinct inhibitors of Ras farnesylation, lovastatin and B581, and a specific inhibitor of mitogen-activated protein kinase kinase activation, PD 98059, we show that the Ras/Raf/ mitogen-activated protein kinase pathway is not utilized for the insulin-induced stimulation of G6PDH gene expression in primary rat hepatocytes. Similarly, using well characterized inhibitors of phosphatidylinositol 3-kinase, wortmannin and LY 294002, we show that PI 3-kinase activity is necessary for the induction of G6PDH expression by insulin. Rapamycin, an inhibitor of FRAP protein, which is involved in the activation of pp70 S6 kinase, blocks the insulin induction of G6PDH, suggesting that S6 kinase is also necessary for the insulin induction of G6PDH expression.

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“…Mitogen-activated protein (MAP) kinase activity was measured as described following phosphorylation of myelin basic protein (MBP) in MAP kinase immunoprecipitates (Whitehurst et al, 1995). Brie¯y, frozen tissue samples were extracted as described for immunoprecipitating Ras and a rabbit polyclonal anti-MAP kinase antibody (Santa Cruz Biotechnology, Santa Cruz, CA, USA) was added to the cell lysates along with protein G agarose beads.…”

Section: Measurement Of Map Kinase Activitymentioning

confidence: 99%

Amplification of Ki-ras and elevation of MAP kinase activity during mammary tumor progression in C3(1)/SV40 Tag transgenic mice

et al. 1998

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We have previously documented that transgenic mice expressing SV40 Tag regulated by the rat prostatic steroid-binding protein C3(1) 5'-¯anking region display multistage mammary tumorigenesis. To delineate genetic changes associated with mammary tumor progression, comparative genomic hybridization (CGH) was performed. CGH revealed a consistent gain of the telomeric region of chromosome 6. This region contains the Ki-ras proto-oncogene. Analyses of genomic DNA by Southern blot demonstrated up to 40-fold ampli®cation of the Kiras gene. Ki-ras ampli®cation was detected in 12, 46 and 68% of tumors from 4, 5 and 6 month old mice, respectively, whereas no ampli®cations were found in any preneoplastic mammary tissues. Tumors bearing Ki-ras gene ampli®cation exhibited high levels of Ki-ras RNA and protein. The over-expressed Ki-Ras protein in these tumors appeared functionally active as indicated by the elevated MAP kinase activity. These data demonstrate that while Ki-ras ampli®cation might not be an early event, there is a strong association between Ki-ras ampli®cation and over-expression and mammary tumor progression in this model. This study also shows that CGH is a powerful and useful technique for identifying chromosomal copy number changes during tumor progression, and that this model may provide a predictable in vivo system for studying gene ampli®ca-tion.

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The MEK Kinase Activity of the Catalytic Domain of RAF-1 Is Regulated Independently of Ras Binding in T Cells

Cited by 55 publications

References 64 publications

Meaningful relationships: the regulation of the Ras/Raf/MEK/ERK pathway by protein interactions

Meaningful relationships: the regulation of the Ras/Raf/MEK/ERK pathway by protein interactions

Insulin Regulation of Glucose-6-phosphate Dehydrogenase Gene Expression Is Rapamycin-sensitive and Requires Phosphatidylinositol 3-Kinase

Amplification of Ki-ras and elevation of MAP kinase activity during mammary tumor progression in C3(1)/SV40 Tag transgenic mice

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