Ras nanoclusters: Versatile lipid-based signaling platforms

Zhou, Yong; Hancock, John F.

doi:10.1016/j.bbamcr.2014.09.008

Cited by 216 publications

(341 citation statements)

References 74 publications

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“…PtdSer is an anionic phospholipid that is actively concentrated in the inner leaflet of the PM and is required for both the localization of K-Ras to the PM and the assembly of K-Ras4B nanoclusters (18,(34)(35)(36). Ras nanoclusters are essential platforms for generating high-fidelity Ras signal transduction (4,37).…”

Section: Resultsmentioning

confidence: 99%

Inhibition of Acid Sphingomyelinase Depletes Cellular Phosphatidylserine and Mislocalizes K-Ras from the Plasma Membrane

Cho

Hoeven

Zhou

et al. 2016

Molecular and Cellular Biology

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143

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e K-Ras must localize to the plasma membrane for biological activity; thus, preventing plasma membrane interaction blocks KRas signal output. Here we show that inhibition of acid sphingomyelinase (ASM) mislocalizes both the K-Ras isoforms K-Ras4A and K-Ras4B from the plasma membrane to the endomembrane and inhibits their nanoclustering. We found that fendiline, a potent ASM inhibitor, reduces the phosphatidylserine (PtdSer) and cholesterol content of the inner plasma membrane. These lipid changes are causative because supplementation of fendiline-treated cells with exogenous PtdSer rapidly restores K-Ras4A and K-Ras4B plasma membrane binding, nanoclustering, and signal output. Conversely, supplementation with exogenous cholesterol restores K-Ras4A but not K-Ras4B nanoclustering. These experiments reveal different operational pools of PtdSer on the plasma membrane. Inhibition of ASM elevates cellular sphingomyelin and reduces cellular ceramide levels. Concordantly, delivery of recombinant ASM or exogenous ceramide to fendiline-treated cells rapidly relocalizes K-Ras4B and PtdSer to the plasma membrane. K-Ras4B mislocalization is also recapitulated in ASM-deficient Neimann-Pick type A and B fibroblasts. This study identifies sphingomyelin metabolism as an indirect regulator of K-Ras4A and K-Ras4B signaling through the control of PtdSer plasma membrane content. It also demonstrates the critical and selective importance of PtdSer to K-Ras4A and K-Ras4B plasma membrane binding and nanoscale spatial organization. Ras proteins are small guanine nucleotide binding proteins that oscillate between active GTP-bound and inactive GDP-bound states. Activated Ras proteins transmit signals for cell proliferation and cell survival. Importantly, ϳ15% of all human tumors express mutant Ras proteins that are locked in the GTP-bound state (1). Of the three ubiquitously expressed Ras isoforms, H-, N-, and K-Ras, oncogenic mutant K-Ras is the most prevalent, being expressed in ϳ95% of pancreatic, ϳ45% of colorectal, and ϳ35% of lung cancers (1). Despite its importance, there are currently no clinically approved drugs that directly target oncogenic K-Ras. To date, Ras drug discovery efforts have focused largely on inhibitors of Ras downstream effectors, including B-Raf, C-Raf, phosphatidylinositol 3-kinase (PI3K), MEK, and extracellular signal-regulated kinase (ERK) (2). For example, B-Raf-specific inhibitors produce excellent albeit often short-lived responses in patients with B-Raf mutant melanoma (3), in part because of a perturbation of complex negative-feedback control loops (2). B-Raf inhibitors also paradoxically activate the mitogen-activated protein kinase (MAPK) cascade in melanoma cells expressing oncogenic mutant N-or K-Ras (4-6). Other highly promising approaches include compounds that covalently modify K-Ras proteins with a G12C mutation to abrogate effector interactions (7,8) and allosteric modulators that directly bind Ras to inhibit guanine nucleotide exchange factor (GEF)-mediated nucleotide exchange (9-11). Chronic i...

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Section: Resultsmentioning

confidence: 99%

Inhibition of Acid Sphingomyelinase Depletes Cellular Phosphatidylserine and Mislocalizes K-Ras from the Plasma Membrane

Cho

Hoeven

Zhou

et al. 2016

Molecular and Cellular Biology

Self Cite

143

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“…It has been demonstrated that changes in the lipid bilayer thickness cause conformational changes that promote changes in the functional activity of several membrane proteins, including those associated with lipid rafts (25). Among the proteins located in lipid rafts that are involved in signal transduction pathways are the small lipid-anchored Ras GTPases (26,27). There are various Ras isoforms that have been implicated in AmB-induced yeast apoptosis and lethal oxidative damage via the cyclic AMP-protein kinase A (cAMP-PKA) and mitogen-activated protein kinase (MAPK) pathway (28)(29)(30).…”

Section: The Molecular Mechanism Of Signal Transduction Induced By Thmentioning

confidence: 99%

The Role of Signaling via Aqueous Pore Formation in Resistance Responses to Amphotericin B

Cohen

2016

Antimicrob Agents Chemother

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Drug resistance studies have played an important role in the validation of antibiotic targets. In the case of the polyene antibiotic amphotericin B (AmB), such studies have demonstrated the essential role that depletion of ergosterol plays in the development of AmB-resistant (AmB-R) organisms. However, AmB-R strains also occur in fungi and parasitic protozoa that maintain a normal level of ergosterol at the plasma membrane. Here, I review evidence that shows not only that there is increased protection against the deleterious consequences of AmB-induced ion leakage across the membrane in these resistant pathogens but also that a set of events are activated that block the cell signaling responses that trigger the oxidative damage produced by the antibiotic. Such signaling events appear to be the consequence of a membrane-thinning effect that is exerted upon lipid-anchored Ras proteins by the aqueous pores formed by AmB. A similar membrane disturbance effect may also explain the activity of AmB on mammalian cells containing Toll-like receptors. These resistance mechanisms expand our current understanding of the role that the formation of AmB aqueous pores plays in triggering signal transduction responses in both pathogens and host immune cells.

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“…Incidentally, H-Ras nanoclusters are enriched in phosphatidylinositols. 57 K-Ras-GTP is similar to H-Ras-GTP in its ability to form nanoclusters on PIP3-rich intact plasma membrane sheets. 57 However, K-Ras-GTP nanoclusters are enriched in phosphatidic acid to a greater extent than either H-Ras-GTP or H-Ras-GDP nanoclusters.…”

Section: Interaction Of Ras Gtpases With Different Membrane Microdomainsmentioning

confidence: 99%

“…57 K-Ras-GTP is similar to H-Ras-GTP in its ability to form nanoclusters on PIP3-rich intact plasma membrane sheets. 57 However, K-Ras-GTP nanoclusters are enriched in phosphatidic acid to a greater extent than either H-Ras-GTP or H-Ras-GDP nanoclusters. 58 Recently, using a phospholipid array binding assay, we found that while GDP-bound full-length wild type K-Ras4B non-specifically interacted with most anionic phospholipids, the GDP-bound oncogenic G12D and G12V mutants preferentially associated with phosphatidylinositol monophosphates and with phosphatidic acid (Banerjee et al, in press).…”

Section: Interaction Of Ras Gtpases With Different Membrane Microdomainsmentioning

confidence: 99%

Plasma membrane regulates Ras signaling networks

et al. 2015

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Ras nanoclusters: Versatile lipid-based signaling platforms

Cited by 216 publications

References 74 publications

Inhibition of Acid Sphingomyelinase Depletes Cellular Phosphatidylserine and Mislocalizes K-Ras from the Plasma Membrane

Inhibition of Acid Sphingomyelinase Depletes Cellular Phosphatidylserine and Mislocalizes K-Ras from the Plasma Membrane

The Role of Signaling via Aqueous Pore Formation in Resistance Responses to Amphotericin B

Plasma membrane regulates Ras signaling networks

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