KSR2 Is an Essential Regulator of AMP Kinase, Energy Expenditure, and Insulin Sensitivity

Costanzo-Garvey, Diane; Pfluger, Paul T.; Dougherty, M. K.; Stock, Jeffery L.; Boehm, Matthew B.; Chaika, Oleg V.; Fernandez, Mario R.; Fisher, Kurt W.; Kortum, Robert L.; Hong, Eun Gyoung; Jun, John Y.; Ko, Hwi Jin; Schreiner, Aimee; Volle, Deanna J.; Treece, Tina; Swift, Amy L.; Winer, Mike; Chen, Denise; Wu, Min; Leon, Lisa R.; Shaw, Andréy S.; McNeish, John D.; Kim, Jason K.; Morrison, Deborah K.; Tschöp, Matthias H.; Lewis, Robert E.

doi:10.1016/j.cmet.2009.09.010

Cited by 128 publications

(235 citation statements)

References 44 publications

Supporting

Mentioning

226

Contrasting

Order By: Relevance

“…We used KSR1 deficient cells (12) to determine whether KSR was required for the ability of the drugs to induce ERK activation. Whereas mammals have two KSR genes, KSR2 is not expressed in fibroblasts, thus the cell line is deficient for both KSR isoforms (13). Cells transduced with constitutively active RAS(V12) or grown in serum were treated with various doses of each drug.…”

mentioning

confidence: 99%

Mutation that blocks ATP binding creates a pseudokinase stabilizing the scaffolding function of kinase suppressor of Ras, CRAF and BRAF

Yu²,

Kornev

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

117

175

View full text Add to dashboard Cite

Because mutations in RAS and BRAF represent the most common mutations found in human tumors, identification of inhibitors has been a major goal. Surprisingly, new oncogenic BRAF specific inhibitors inhibit cells transformed with mutated BRAF but paradoxically stimulate the growth of cells transformed with RAS. Here, we show that the mechanism for activation is via drug-induced dimer formation between CRAF and kinase suppressor of Ras (KSR)1. To understand the function of KSR1, we generated a KSR1 mutant that cannot bind ATP but stabilizes the closed, active conformation of KSR1. Molecular modeling suggested that the mutant stabilizes the two hydrophobic spines critical for the closed active conformation. We, therefore, could use the mutant to discriminate between the scaffold versus kinase functions of KSR1. The KSR1 mutant bound constitutively to RAF and mitogen-activated protein kinase kinase (MEK) but could not reconstitute activity suggesting that the catalytic activity of KSR1 is required for its function. Analogous mutations in BRAF and CRAF allowed us to test the generality of the model. The mutation induced changes consistent with the active, closed conformation of both kinases and confirmed that BRAF functions distinctly from CRAF in the MAP kinase pathway. Not only does this work suggest that KSR1 may function as a kinase, we anticipate that the mutation that we generated may be broadly applicable to stabilize the closed conformation of other kinases many of which may also form dimers.cancer | protein kinase | signal transduction

show abstract

mentioning

confidence: 99%

Mutation that blocks ATP binding creates a pseudokinase stabilizing the scaffolding function of kinase suppressor of Ras, CRAF and BRAF

Yu²,

Kornev

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

117

175

View full text Add to dashboard Cite

show abstract

“…Although previous reports demonstrated interaction between A-Raf and KSR2 only in response to TNFα, 38 we observe interaction also in quiescent cells and upon stimulation with EGF. KSR2 is also known to bind AMPK mediating its stimulatory effects on glucose uptake and fatty acid oxidation, 39 suggesting that A-Raf may play a direct role in the cross-talk between apoptosis (MST2), energy homeostasis (AMPK), MAPK signaling, and glucose metabolism by binding and inhibiting pyruvate kinase M2 (PKM2). 71,72 In addition to its functional role of regulating MST2-mediated apoptosis in differentiation, A-Raf expression also correlates with the extent of differentiation in the described MCF7 cell model.…”

Section: Discussionmentioning

confidence: 99%

“…38 In addition to MAPK components, KSR2 was shown to interact with AMPK thereby regulating energy intake and fatty acid oxidation. 39,40 In humans, mutations of KSR2 are associated with obesity and insulin resistance. 41 In addition, KSR2 regulates genes controlling adipocyte differentiation in white adipose tissue 39 and is crucial for 1,25-dihydroxyvitamin D 3 -mediated monocytic differentiation of myeloid leukemia HL60 cells.…”

mentioning

confidence: 99%

“…39,40 In humans, mutations of KSR2 are associated with obesity and insulin resistance. 41 In addition, KSR2 regulates genes controlling adipocyte differentiation in white adipose tissue 39 and is crucial for 1,25-dihydroxyvitamin D 3 -mediated monocytic differentiation of myeloid leukemia HL60 cells. 42 Non-keratinized stratified squamous epithelium lines the external surface of tissues such as oral cavity, esophagus, rectum, and cervix, forming a protective barrier.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Differential localization of A-Raf regulates MST2-mediated apoptosis during epithelial differentiation

et al. 2016

View full text Add to dashboard Cite

A-Raf belongs to the family of oncogenic Raf kinases that are involved in mitogenic signaling by activating the MEK-ERK pathway. Low kinase activity of A-Raf toward MEK suggested that A-Raf might have alternative functions. We recently identified A-Raf as a potent inhibitor of the proapoptotic mammalian sterile 20-like kinase (MST2) tumor suppressor pathway in several cancer entities including head and neck, colon, and breast. Independent of kinase activity, A-Raf binds to MST2 thereby efficiently inhibiting apoptosis. Here, we show that the interaction of A-Raf with the MST2 pathway is regulated by subcellular compartmentalization. Although in proliferating normal cells and tumor cells A-Raf localizes to the mitochondria, differentiated non-carcinogenic cells of head and neck epithelia, which express A-Raf at the plasma membrane. The constitutive or induced re-localization of A-Raf to the plasma membrane compromises its ability to efficiently sequester and inactivate MST2, thus rendering cells susceptible to apoptosis. Physiologically, A-Raf re-localizes to the plasma membrane upon epithelial differentiation in vivo. This re-distribution is regulated by the scaffold protein kinase suppressor of Ras 2 (KSR2). Downregulation of KSR2 during mammary epithelial cell differentiation or siRNA-mediated knockdown re-localizes A-Raf to the plasma membrane causing the release of MST2. By using the MCF7 cell differentiation system, we could demonstrate that overexpression of A-Raf in MCF7 cells, which induces differentiation. Our findings offer a new paradigm to understand how differential localization of Raf complexes affects diverse signaling functions in normal cells and carcinomas. A-Raf is a member of the Raf family of serine-threonine protein kinases, which comprises A-Raf, B-Raf, and Raf-1. Raf kinases are at the apex of the three-tiered Raf/MEK/ extracellular signal-regulated kinase (ERK) (mitogen-activated protein kinase (MAPK)) pathway regulating fundamental cellular functions, including differentiation, transformation, apoptosis, proliferation, and metabolism. 1,2 Activation of Ras GTPases at the cell membrane initiates Raf kinase activation and sequential phosphorylation and activation of the serinethreonine kinases MEK1/2 and ERK1/2. 3,4 In comparison to Raf-1 and B-Raf, A-Raf is only weakly activated by oncogenic H-Ras and Src 5 and is a poor MEK kinase, 5-8 which is due to unique non-conserved amino acid substitutions in the N-region. 9 Only recently, the first somatic oncogenic mutations of A-Raf were identified in lung adenocarcinomas 10 and Langerhans cell histiocytosis. 11,12 We recently showed that A-Raf and Raf-1, independent of their kinase activity, bind the proapoptotic mammalian sterile 20-like kinase (MST2) thereby suppressing MST2 activation and MST2-induced apoptosis. 13-17 MST2 employs several mechanisms to induce apoptosis including the transcriptional induction of PUMA, 14 a BH3 domain protein that causes mitochondrial depolarization and subsequent cell death. 18 Although Raf-1 counteracts MS...

show abstract

“…However, novel roles for KSR2 have been reported in metabolic pathways. KSR2 has been shown to regulate AMPK to promote glucose and fatty acid metabolism, and its loss in mouse models leads to obesity and insulin resistance [38].…”

Section: Kinase Suppressor Of Rasmentioning

confidence: 99%

Signal control through Raf: in sickness and in health

2011

View full text Add to dashboard Cite

The extracellular signal-regulated kinase 1/2 (ERK1/2) cascade is the prototype mammalian mitogenactivated protein kinase (MAPK) signaling cascade that regulates a number of processes, including proliferation, differentiation, survival, migration, stress responses and apoptosis. How this seemingly linear cascade is modulated to achieve a specific cellular function has been a main focus of the field. In this review, we describe new as well as old findings in the regulation of the ERK1/2 pathway in normal and disease states via MAP3Ks.

show abstract

KSR2 Is an Essential Regulator of AMP Kinase, Energy Expenditure, and Insulin Sensitivity

Cited by 128 publications

References 44 publications

Mutation that blocks ATP binding creates a pseudokinase stabilizing the scaffolding function of kinase suppressor of Ras, CRAF and BRAF

Mutation that blocks ATP binding creates a pseudokinase stabilizing the scaffolding function of kinase suppressor of Ras, CRAF and BRAF

Differential localization of A-Raf regulates MST2-mediated apoptosis during epithelial differentiation

Signal control through Raf: in sickness and in health

Contact Info

Product

Resources

About