scholarly journals Compartmentalization of Ras proteins

2001 ◽  
Vol 114 (9) ◽  
pp. 1603-1608 ◽  
Author(s):  
I.A. Prior ◽  
J.F. Hancock
Keyword(s):  
Plasma Membrane ◽  
Protein Interactions ◽  
Ras Proteins ◽  
Protein Protein Interactions ◽  
Diverse Range ◽  
Ras Gtpases ◽  
Extracellular Stimuli ◽  
Ras Isoforms ◽  
Complex Signaling ◽  
Exocytic Pathway

The Ras GTPases operate as molecular switches that link extracellular stimuli with a diverse range of biological outcomes. Although many studies have concentrated on the protein-protein interactions within the complex signaling cascades regulated by Ras, it is becoming clear that the spatial orientation of different Ras isoforms within the plasma membrane is also critical for their function. H-Ras, N-Ras and K-Ras use different membrane anchors to attach to the plasma membrane. Recently it has been shown that these anchors also act as trafficking signals that direct palmitoylated H-Ras and N-Ras through the exocytic pathway to the cell surface but divert polybasic K-Ras around the Golgi to the plasma membrane via an as yet-unidentified-route. Once at the plasma membrane, H-Ras and K-Ras operate in different microdomains. K-Ras is localized predominantly to the disordered plasma membrane, whereas H-Ras exists in a GTP-regulated equilibrium between disordered plasma membrane and cholesterol-rich lipid rafts. These observations provide a likely explanation for the increasing number of biological differences being identified between the otherwise highly homologous Ras isoforms and raise interesting questions about the role membrane microlocalization plays in determining the interactions of Ras with its effectors and exchange factors.

scholarly journals Signal Integration by Lipid-Mediated Spatial Cross Talk between Ras Nanoclusters

2013 ◽  
Vol 34 (5) ◽  
pp. 862-876 ◽  
Author(s):  
Yong Zhou ◽  
Hong Liang ◽  
Travis Rodkey ◽  
Nicholas Ariotti ◽  
Robert G. Parton ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Spatial Organization ◽  
Signal Transmission ◽  
Signal Integration ◽  
Ras Proteins ◽  
Cortical Actin ◽  
Mediated Communication ◽  
Ras Gtpases ◽  
Ras Isoforms ◽  
Lipid Assemblies

Lipid-anchored Ras GTPases form transient, spatially segregated nanoclusters on the plasma membrane that are essential for high-fidelity signal transmission. The lipid composition of Ras nanoclusters, however, has not previously been investigated. High-resolution spatial mapping shows that different Ras nanoclusters have distinct lipid compositions, indicating that Ras proteins engage in isoform-selective lipid sorting and accounting for different signal outputs from different Ras isoforms. Phosphatidylserine is a common constituent of all Ras nanoclusters but is only an obligate structural component of K-Ras nanoclusters. Segregation of K-Ras and H-Ras into spatially and compositionally distinct lipid assemblies is exquisitely sensitive to plasma membrane phosphatidylserine levels. Phosphatidylserine spatial organization is also modified by Ras nanocluster formation. In consequence, Ras nanoclusters engage in remote lipid-mediated communication, whereby activated H-Ras disrupts the assembly and operation of spatially segregated K-Ras nanoclusters. Computational modeling and experimentation reveal that complex effects of caveolin and cortical actin on Ras nanoclustering are similarly mediated through regulation of phosphatidylserine spatiotemporal dynamics. We conclude that phosphatidylserine maintains the lateral segregation of diverse lipid-based assemblies on the plasma membrane and that lateral connectivity between spatially remote lipid assemblies offers important previously unexplored opportunities for signal integration and signal processing.

scholarly journals Spatial diversity: Ras trafficking and signalling

2003 ◽  
Vol 25 (3) ◽  
pp. 22-24 ◽  
Author(s):  
Ian A. Prior
Keyword(s):  
Cell Proliferation ◽  
Plasma Membrane ◽  
G Proteins ◽  
Spatial Diversity ◽  
Ras Proteins ◽  
Cell Proliferation And Differentiation ◽  
Proliferation And Differentiation ◽  
Extracellular Stimuli ◽  
New Research ◽  
Ras Isoforms

Ras proteins are small monomeric G-proteins that play a central role in linking extracellular stimuli with the internal kinase cascades that are primarily involved in modulating cell proliferation and differentiation. Constitutively activated mutants of these proteins are found in many human cancers. Differences in the trafficking and plasma membrane localization of Ras isoforms play critical roles in regulating their function. New research is trying to understand the mechanisms behind, and consequences of, these differences.

scholarly journals The Hypervariable Region of K-Ras4B Governs Molecular Recognition and Function

2019 ◽  
Vol 20 (22) ◽  
pp. 5718 ◽  
Author(s):  
Abdelkarim ◽  
Banerjee ◽  
Grudzien ◽  
Leschinsky ◽  
Abushaer ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Protein Interactions ◽  
Membrane Lipids ◽  
Hypervariable Region ◽  
Specific Protein ◽  
Protein Protein Interactions ◽  
Post Translational Modification ◽  
Gtpase Domain ◽  
Ras Gtpases ◽  
And Function

The flexible C-terminal hypervariable region distinguishes K-Ras4B, an important proto-oncogenic GTPase, from other Ras GTPases. This unique lysine-rich portion of the protein harbors sites for post-translational modification, including cysteine prenylation, carboxymethylation, phosphorylation, and likely many others. The functions of the hypervariable region are diverse, ranging from anchoring K-Ras4B at the plasma membrane to sampling potentially auto-inhibitory binding sites in its GTPase domain and participating in isoform-specific protein–protein interactions and signaling. Despite much research, there are still many questions about the hypervariable region of K-Ras4B. For example, mechanistic details of its interaction with plasma membrane lipids and with the GTPase domain require further clarification. The roles of the hypervariable region in K-Ras4B-specific protein–protein interactions and signaling are incompletely defined. It is also unclear why post-translational modifications frequently found in protein polylysine domains, such as acetylation, glycation, and carbamoylation, have not been observed in K-Ras4B. Expanding knowledge of the hypervariable region will likely drive the development of novel highly-efficient and selective inhibitors of K-Ras4B that are urgently needed by cancer patients.

scholarly journals The NHR1 Domain of Neuralized Binds Delta and Mediates Delta Trafficking and Notch Signaling

2007 ◽  
Vol 18 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Cosimo Commisso ◽  
Gabrielle L. Boulianne
Keyword(s):  
Plasma Membrane ◽  
Notch Signaling ◽  
Ubiquitin Ligase ◽  
Protein Interactions ◽  
Neural Development ◽  
Ring Domain ◽  
Protein Protein Interactions ◽  
Necessary And Sufficient ◽  
Conserved Residue ◽  
Notch Ligands

Notch signaling, which is crucial to metazoan development, requires endocytosis of Notch ligands, such as Delta and Serrate. Neuralized is a plasma membrane-associated ubiquitin ligase that is required for neural development and Delta internalization. Neuralized is comprised of three domains that include a C-terminal RING domain and two neuralized homology repeat (NHR) domains. All three domains are conserved between organisms, suggesting that these regions of Neuralized are functionally important. Although the Neuralized RING domain has been shown to be required for Delta ubiquitination, the function of the NHR domains remains elusive. Here we show that neuralized1, a well-characterized neurogenic allele, exhibits a mutation in a conserved residue of the NHR1 domain that results in mislocalization of Neuralized and defects in Delta binding and internalization. Furthermore, we describe a novel isoform of Neuralized and show that it is recruited to the plasma membrane by Delta and that this is mediated by the NHR1 domain. Finally, we show that the NHR1 domain of Neuralized is both necessary and sufficient to bind Delta. Altogether, our data demonstrate that NHR domains can function in facilitating protein–protein interactions and in the case of Neuralized, mediate binding to its ubiquitination target, Delta.

scholarly journals Analysis of RAS protein interactions in living cells reveals a mechanism for pan-RAS depletion by membrane-targeted RAS binders

2020 ◽  
Vol 117 (22) ◽  
pp. 12121-12130
Author(s):  
Yao-Cheng Li ◽  
Nikki K. Lytle ◽  
Seth T. Gammon ◽  
Luke Wang ◽  
Tikvah K. Hayes ◽  
...  
Keyword(s):  
Protein Interactions ◽  
Developmental Disorders ◽  
Degradation Pathway ◽  
Small Gtpases ◽  
Small Gtpase ◽  
Ras Proteins ◽  
Ras Protein ◽  
Protein Levels ◽  
Ras Family ◽  
Ras Isoforms

HRAS, NRAS, and KRAS4A/KRAS4B comprise the RAS family of small GTPases that regulate signaling pathways controlling cell proliferation, differentiation, and survival. RAS pathway abnormalities cause developmental disorders and cancers. We found that KRAS4B colocalizes on the cell membrane with other RAS isoforms and a subset of prenylated small GTPase family members using a live-cell quantitative split luciferase complementation assay. RAS protein coclustering is mainly mediated by membrane association-facilitated interactions (MAFIs). Using the RAS–RBD (CRAF RAS binding domain) interaction as a model system, we showed that MAFI alone is not sufficient to induce RBD-mediated RAS inhibition. Surprisingly, we discovered that high-affinity membrane-targeted RAS binding proteins inhibit RAS activity and deplete RAS proteins through an autophagosome–lysosome-mediated degradation pathway. Our results provide a mechanism for regulating RAS activity and protein levels, a more detailed understanding of which should lead to therapeutic strategies for inhibiting and depleting oncogenic RAS proteins.

scholarly journals The Lipid Raft Component Stomatin Interacts with the Na+ Taurocholate Cotransporting Polypeptide (NTCP) and Modulates Bile Salt Uptake

Cells ◽  
2020 ◽  
Vol 9 (4) ◽  
pp. 986
Author(s):  
Monique D. Appelman ◽  
Marion J.D. Robin ◽  
Esther W.M. Vogels ◽  
Christie Wolzak ◽  
Winnie G. Vos ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Bile Salt ◽  
Protein Interactions ◽  
Basolateral Membrane ◽  
Sodium Taurocholate ◽  
Salt Transport ◽  
Protein Protein Interactions ◽  
Cell Surface Biotinylation ◽  
Detergent Resistant Membranes ◽  
Entry Receptor

The sodium taurocholate cotransporting polypeptide (NTCP) is expressed at the basolateral membrane of hepatocytes, where it mediates the uptake of conjugated bile acids and forms the hepatocyte entry receptor for the hepatitis B and D virus. Here, we aimed to identify novel protein–protein interactions that could play a role in the regulation of NTCP. To this end, NTCP was precipitated from HA-tagged hNTCP-expressing HepG2 cells, and chloride channel CLIC-like 1 (CLCC1) and stomatin were identified as interacting proteins by mass spectrometry. Interaction was confirmed by co-immunoprecipitation. NTCP, CLCC1 and stomatin were found at the plasma membrane in lipid rafts, as demonstrated by a combination of immunofluorescence, cell surface biotinylation and isolation of detergent-resistant membranes. Neither CLCC1 overexpression nor its knockdown had an effect on NTCP function. However, both stomatin overexpression and knockdown increased NTCP-mediated taurocholate uptake while NTCP abundance at the plasma membrane was only increased in stomatin depleted cells. These findings identify stomatin as an interactor of NTCP and show that the interaction modulates bile salt transport.

One Hippo and many masters: differential regulation of the Hippo pathway in cancer

2014 ◽  
Vol 42 (4) ◽  
pp. 816-821 ◽  
Author(s):  
David Romano ◽  
David Matallanas ◽  
Dennie T. Frederick ◽  
Keith T. Flaherty ◽  
Walter Kolch
Keyword(s):  
Protein Interactions ◽  
Hippo Pathway ◽  
Promoter Hypermethylation ◽  
Protein Protein Interactions ◽  
Evolutionarily Conserved ◽  
Or Gene ◽  
Phosphoinositide 3 Kinase ◽  
Ras Isoforms ◽  
The Hippo Pathway

The Hippo/MST2 (mammalian sterile 20-like kinase 2) pathway is a signalling cascade evolutionarily conserved in its structure. Originally described in Drosophila melanogaster as a regulator of organ size, this pathway has greater functions in mammals. Disturbance of mammalian MST2 pathway is associated with tumorigenesis by affecting apoptosis, cell cycle and polarity. In addition, this pathway has been shown to cross-talk with mitogenic pathways at multiple levels. In the present mini-review, we discuss our contribution highlighting the regulation of MST2 signalling by frequently observed oncogenic perturbations affecting mitogenic pathways. In particular, we review the role of RAS isoforms and PI3K (phosphoinositide 3-kinase)/Akt in the regulation of MST2 activity by phosphorylation. We also put the emphasis on RAF-induced control of MST2 signalling by protein–protein interactions. Finally, we recapitulate some of the direct mechanisms, such as ubiquitin-dependent degradation or gene silencing by promoter hypermethylation, involved in MST2 pathway component down-regulation in cancers.

scholarly journals Membrane Binding of HIV-1 Matrix Protein: Dependence on Bilayer Composition and Protein Lipidation

2016 ◽  
Vol 90 (9) ◽  
pp. 4544-4555 ◽  
Author(s):  
Marilia Barros ◽  
Frank Heinrich ◽  
Siddhartha A. K. Datta ◽  
Alan Rein ◽  
Ioannis Karageorgos ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Protein Interactions ◽  
Matrix Protein ◽  
Full Length ◽  
Protein Protein Interactions ◽  
Binding Studies ◽  
Protein Protein Interaction ◽  
Gag Polyprotein ◽  
Protein Lipidation ◽  
Hiv 1

ABSTRACTBy assembling in a protein lattice on the host's plasma membrane, the retroviral Gag polyprotein triggers formation of the viral protein/membrane shell. The MA domain of Gag employs multiple signals—electrostatic, hydrophobic, and lipid-specific—to bring the protein to the plasma membrane, thereby complementing protein-protein interactions, located in full-length Gag, in lattice formation. We report the interaction of myristoylated and unmyristoylated HIV-1 Gag MA domains with bilayers composed of purified lipid components to dissect these complex membrane signals and quantify their contributions to the overall interaction. Surface plasmon resonance on well-defined planar membrane models is used to quantify binding affinities and amounts of protein and yields free binding energy contributions, ΔG, of the various signals. Charge-charge interactions in the absence of the phosphatidylinositide PI(4,5)P2attract the protein to acidic membrane surfaces, and myristoylation increases the affinity by a factor of 10; thus, our data do not provide evidence for a PI(4,5)P2trigger of myristate exposure. Lipid-specific interactions with PI(4,5)P2, the major signal lipid in the inner plasma membrane, increase membrane attraction at a level similar to that of protein lipidation. While cholesterol does not directly engage in interactions, it augments protein affinity strongly by facilitating efficient myristate insertion and PI(4,5)P2binding. We thus observe that the isolated MA protein, in the absence of protein-protein interaction conferred by the full-length Gag, binds the membrane with submicromolar affinities.IMPORTANCELike other retroviral species, the Gag polyprotein of HIV-1 contains three major domains: the N-terminal, myristoylated MA domain that targets the protein to the plasma membrane of the host; a central capsid-forming domain; and the C-terminal, genome-binding nucleocapsid domain. These domains act in concert to condense Gag into a membrane-bounded protein lattice that recruits genomic RNA into the virus and forms the shell of a budding immature viral capsid. In binding studies of HIV-1 Gag MA to model membranes with well-controlled lipid composition, we dissect the multiple interactions of the MA domain with its target membrane. This results in a detailed understanding of the thermodynamic aspects that determine membrane association, preferential lipid recruitment to the viral shell, and those aspects of Gag assembly into the membrane-bound protein lattice that are determined by MA.

scholarly journals Latest update on chemokine receptors as therapeutic targets

2021 ◽  
Author(s):  
Wing Yee Lai ◽  
Anja Mueller
Keyword(s):  
Protein Interactions ◽  
Chemokine Receptors ◽  
Inflammatory Diseases ◽  
Specific Binding ◽  
Therapeutic Targets ◽  
Cell Types ◽  
Fine Tuning ◽  
Protein Protein Interactions ◽  
Diverse Range ◽  
Chemokine Ligand

The chemokine system plays a fundamental role in a diverse range of physiological processes, such as homeostasis and immune responses. Dysregulation in the chemokine system has been linked to inflammatory diseases and cancer, which renders chemokine receptors to be considered as therapeutic targets. In the past two decades, around 45 drugs targeting chemokine receptors have been developed, yet only three are clinically approved. The challenging factors include the limited understanding of aberrant chemokine signalling in malignant diseases, high redundancy of the chemokine system, differences between cell types and non-specific binding of the chemokine receptor antagonists due to the broad ligand-binding pockets. In recent years, emerging studies attempt to characterise the chemokine ligand–receptor interactions and the downstream signalling protein–protein interactions, aiming to fine tuning to the promiscuous interplay of the chemokine system for the development of precision medicine. This review will outline the updates on the mechanistic insights in the chemokine system and propose some potential strategies in the future development of targeted therapy.

scholarly journals The structural basis of the oncogenic mutant K-Ras4B homodimers

2020 ◽  
Author(s):  
Kayra Kosoglu ◽  
Meltem Eda Omur ◽  
Hyunbum Jang ◽  
Ruth Nussinov ◽  
Ozlem Keskin ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Structural Basis ◽  
Ras Proteins ◽  
Oncogenic Ras ◽  
Extracellular Stimuli ◽  
Prediction Server ◽  
Physical Interactions ◽  
Multiple Conformations ◽  
Dynamics Simulations ◽  
Membrane Signaling

AbstractRas proteins activate their effectors through physical interactions in response to the various extracellular stimuli at the plasma membrane. Oncogenic Ras forms dimer and nanoclusters at the plasma membrane, boosting the downstream MAPK signal. It was reported that K-Ras4B can dimerize through two major interfaces: (i) the effector lobe interface, mapped to Switch I and effector binding regions; (ii) the allosteric lobe interface involving α3 and α4 helices. Recent experiments showed that constitutively active, oncogenic mutant K-Ras4BG12D dimers are enriched in the plasma membrane. Here, we perform molecular dynamics simulations of K-Ras4BG12D homodimers aiming to quantify the two major interfaces in atomic level. To examine the effect of mutations on dimerization, two double mutations, K101D/R102E on the allosteric lobe and R41E/K42D on the effector lobe interfaces were added to the K-Ras4BG12D dimer simulations. We observed that the effector lobe K-Ras4BG12D dimer is stable, while the allosteric lobe dimer alters its helical interface during the simulations, presenting multiple conformations. The K101D/R102E mutations slightly weakens the allosteric lobe interface. However, the R41E/K42D mutations disrupt the effector lobe interface. Using the homo-oligomers prediction server, we obtained trimeric, tetrameric, and pentameric complexes with the allosteric lobe K-Ras4BG12D dimers. However, the allosteric lobe dimer with the K101D/R102E mutations is not capable of generating multiple higher order structures. Our detailed interface analysis may help to develop inhibitor design targeting functional Ras dimerization and high order oligomerization at the membrane signaling platform.

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