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 S-Acylation of plant immune receptors mediates immune signaling in plasma membrane nanodomains

2019 ◽  
Author(s):  
Dongqin Chen ◽  
Nagib Ahsan ◽  
Jay J. Thelen ◽  
Gary Stacey
Keyword(s):  
Plasma Membrane ◽  
Protein Interactions ◽  
Critical Role ◽  
Specific Protein ◽  
Protein Protein Interactions ◽  
Post Translational Modification ◽  
Immune Signaling ◽  
Immune Receptors ◽  
Similar Phenotype ◽  
External Stimuli

SUMMARYS-Acylation is a reversible protein post-translational modification mediated by Protein S-acyltransferases (PATs). Here, we demonstrate that three plant immune receptors P2K1 (DORN1), FLS2 and CERK1, representing three distinct families of receptor like-kinases, are S-acylated by Arabidopsis PAT5 and PAT9 on the plasma membrane (PM). Mutations in Atpat5 and Atpat9 resulted in an elevated plant immune response, increased phosphorylation and decreased degradation of FLS2, P2K1 and CERK1 during immune signaling. Mutation of key cysteine residues S-acylated in these receptors resulted in a similar phenotype as exhibited by Atpat5/Atpat9 mutant plants. The data indicate that S-acylation also controls localization of the receptors in distinct PM nanodomains and, thereby, controls the formation of specific protein-protein interactions. Our study reveals that S-acylation plays a critical role in mediating spatiotemporal dynamics of plant receptors within PM nanodomains, suggesting a key role for this modification in regulating the ability of plants in respond to external stimuli.

scholarly journals A proline-rich sequence unique to MEK1 and MEK2 is required for raf binding and regulates MEK function.

1995 ◽  
Vol 15 (10) ◽  
pp. 5214-5225 ◽  
Author(s):  
A D Catling ◽  
H J Schaeffer ◽  
C W Reuter ◽  
G R Reddy ◽  
M J Weber
Keyword(s):  
Protein Interactions ◽  
Critical Role ◽  
Phosphorylation Site ◽  
Specific Protein ◽  
Protein Protein Interactions ◽  
Serum Stimulation ◽  
And Function

Mammalian MEK1 and MEK2 contain a proline-rich (PR) sequence that is absent both from the yeast homologs Ste7 and Byr1 and from a recently cloned activator of the JNK/stress-activated protein kinases, SEK1/MKK4. Since this PR sequence occurs in MEKs that are regulated by Raf family enzymes but is missing from MEKs and SEKs activated independently of Raf, we sought to investigate the role of this sequence in MEK1 and MEK2 regulation and function. Deletion of the PR sequence from MEK1 blocked the ability of MEK1 to associate with members of the Raf family and markedly attenuated activation of the protein in vivo following growth factor stimulation. In addition, this sequence was necessary for efficient activation of MEK1 in vitro by B-Raf but dispensable for activation by a novel MEK1 activator which we have previously detected in fractionated fibroblast extracts. Furthermore, we found that a phosphorylation site within the PR sequence of MEK1 was required for sustained MEK1 activity in response to serum stimulation of quiescent fibroblasts. Consistent with this observation, we observed that MEK2, which lacks a phosphorylation site at the corresponding position, was activated only transiently following serum stimulation. Finally, we found that deletion of the PR sequence from a constitutively activated MEK1 mutant rendered the protein nontransforming in Rat1 fibroblasts. These observations indicate a critical role for the PR sequence in directing specific protein-protein interactions important for the activation, inactivation, and downstream functioning of the MEKs.

scholarly journals Insights into the Role of Membrane Lipids in the Structure, Function and Regulation of Integral Membrane Proteins

2021 ◽  
Vol 22 (16) ◽  
pp. 9026
Author(s):  
Kenta Renard ◽  
Bernadette Byrne
Keyword(s):  
Membrane Proteins ◽  
Membrane Protein ◽  
Conformational Changes ◽  
Protein Interactions ◽  
Membrane Lipids ◽  
Protein Protein Interactions ◽  
Technological Advances ◽  
Highly Hydrophobic ◽  
Dynamics Simulations ◽  
And Function

Membrane proteins exist within the highly hydrophobic membranes surrounding cells and organelles, playing key roles in cellular function. It is becoming increasingly clear that the membrane does not just act as an appropriate environment for these proteins, but that the lipids that make up these membranes are essential for membrane protein structure and function. Recent technological advances in cryogenic electron microscopy and in advanced mass spectrometry methods, as well as the development of alternative membrane mimetic systems, have allowed experimental study of membrane protein–lipid complexes. These have been complemented by computational approaches, exploiting the ability of Molecular Dynamics simulations to allow exploration of membrane protein conformational changes in membranes with a defined lipid content. These studies have revealed the importance of lipids in stabilising the oligomeric forms of membrane proteins, mediating protein–protein interactions, maintaining a specific conformational state of a membrane protein and activity. Here we review some of the key recent advances in the field of membrane protein–lipid studies, with major emphasis on respiratory complexes, transporters, channels and G-protein coupled receptors.

scholarly journals Formation of functional cell membrane domains: the interplay of lipid– and protein–mediated interactions

2003 ◽  
Vol 358 (1433) ◽  
pp. 863-868 ◽  
Author(s):  
Thomas Harder
Keyword(s):  
Cell Membrane ◽  
Protein Interactions ◽  
Membrane Lipids ◽  
Phase Behaviour ◽  
Coat Proteins ◽  
Membrane Domains ◽  
Protein Protein Interactions ◽  
Numerous Cell ◽  
Functional Membrane ◽  
And Function

Numerous cell membrane associated processes, including signal transduction, membrane sorting, protein processing and virus trafficking take place in membrane subdomains. Protein–protein interactions provide the frameworks necessary to generate biologically functional membrane domains. For example, coat proteins define membrane areas destined for sorting processes, viral proteins self–assemble to generate a budding virus, and adapter molecules organize multimolecular signalling assemblies, which catalyse downstream reactions. The concept of raft lipid–based membrane domains provides a different principle for compartmentalization and segregation of membrane constituents. Accordingly, rafts are defined by the physical properties of the lipid bilayer and function by selective partitioning of membrane lipids and proteins into membrane domains of specific phase behaviour and lipid packing. Here, I will discuss the interplay of these independent principles of protein scaffolds and raft lipid microdomains leading to the generation of biologically functional membrane domains.

scholarly journals CD63 interacts with the carboxy terminus of the colonic H+-K+-ATPase to increase plasma membrane localization and86Rb+uptake

2005 ◽  
Vol 288 (6) ◽  
pp. C1279-C1286 ◽  
Author(s):  
Juan Codina ◽  
Jian Li ◽  
Thomas D. DuBose
Keyword(s):  
Plasma Membrane ◽  
Protein Interactions ◽  
Surface Expression ◽  
Cell Surface Expression ◽  
Carboxy Terminus ◽  
Protein Protein Interactions ◽  
Α Subunit ◽  
Hek 293 ◽  
And Function

The carboxy terminus (CT) of the colonic H+-K+-ATPase is required for stable assembly with the β-subunit, translocation to the plasma membrane, and efficient function of the transporter. To identify protein-protein interactions involved in the localization and function of HKα2, we selected 84 amino acids in the CT of the α-subunit of mouse colonic H+-K+-ATPase (CT-HKα2) as the bait in a yeast two-hybrid screen of a mouse kidney cDNA library. The longest identified clone was CD63. To characterize the interaction of CT-HKα2with CD63, recombinant CT-HKα2and CD63 were synthesized in vitro and incubated, and complexes were immunoprecipitated. CT-HKα2protein (but not CT-HKα1) coprecipitated with CD63, confirming stable assembly of HKα2with CD63. In HEK-293 transfected with HKα2plus β1-Na+-K+-ATPase, suppression of CD63 by RNA interference increased cell surface expression of HKα2/NKβ1and86Rb+uptake. These studies demonstrate that CD63 participates in the regulation of the abundance of the HKα2-NKβ1complex in the cell membrane.

scholarly journals Direct interaction of PIWI and DEPS-1 is essential for piRNA function and condensate ultrastructure inCaenorhabditis elegans

2019 ◽  
Author(s):  
KM Suen ◽  
F Braukmann ◽  
R Butler ◽  
D Bensaddek ◽  
A Akay ◽  
...  
Keyword(s):  
Protein Interactions ◽  
Direct Interaction ◽  
Specific Protein ◽  
Protein Protein Interactions ◽  
Piwi Domain ◽  
Small Ncrnas ◽  
Complex Forms ◽  
Rna Pathways ◽  
And Function

SummaryMembraneless organelles are platforms for many aspects of RNA biology including small non-coding RNA (ncRNA) mediated gene silencing. How small ncRNAs utilise phase separated environments for their function is unclear. To address this question, we investigated how the PIWI-interacting RNA (piRNA) pathway engages with the membraneless organelle P granule inCaenorhabditis elegans. Proteomic analysis of the PIWI protein PRG-1 revealed an interaction with the constitutive P granule protein DEPS-1. Furthermore we identified a novel motif on DEPS-1, PBS, which interacts directly with the Piwi domain of PRG-1. This protein complex forms intertwining ultrastructures to build elongated condensatesin vivo. These sub-organelle ultrastructures depend on the Piwi-interacting motif of DEPS-1 and mediate piRNA function. Additionally, we identify a novel interactor of DEPS-1, EDG-1, which is required for DEPS-1 condensates to form correctly. We show that DEPS-1 is not required for piRNA biogenesis but piRNA function:deps-1mutants fail to produce the secondary endo-siRNAs required for the silencing of piRNA targets. Our study reveals how specific protein-protein interactions drive the spatial organisation and function of small RNA pathways within membraneless organelles.

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 p53 Forms Redox-Dependent Protein–Protein Interactions through Cysteine 277

Antioxidants ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 1578
Author(s):  
Tao Shi ◽  
Paulien E. Polderman ◽  
Marc Pagès-Gallego ◽  
Robert M. van Es ◽  
Harmjan R. Vos ◽  
...  
Keyword(s):  
Protein Interactions ◽  
Fine Tuning ◽  
Protein Protein Interactions ◽  
Post Translational Modification ◽  
Cysteine Oxidation ◽  
Interaction Partners ◽  
Dependent Protein ◽  
And Function

Reversible cysteine oxidation plays an essential role in redox signaling by reversibly altering protein structure and function. Cysteine oxidation may lead to intra- and intermolecular disulfide formation, and the latter can drastically stabilize protein–protein interactions in a more oxidizing milieu. The activity of the tumor suppressor p53 is regulated at multiple levels, including various post-translational modification (PTM) and protein–protein interactions. In the past few decades, p53 has been shown to be a redox-sensitive protein, and undergoes reversible cysteine oxidation both in vitro and in vivo. It is not clear, however, whether p53 also forms intermolecular disulfides with interacting proteins and whether these redox-dependent interactions contribute to the regulation of p53. In the present study, by combining (co-)immunoprecipitation, quantitative mass spectrometry and Western blot we found that p53 forms disulfide-dependent interactions with several proteins under oxidizing conditions. Cysteine 277 is required for most of the disulfide-dependent interactions of p53, including those with 14-3-3q and 53BP1. These interaction partners may play a role in fine-tuning p53 activity under oxidizing conditions.

scholarly journals Sinner or Saint?: Nck Adaptor Proteins in Vascular Biology

2021 ◽  
Vol 9 ◽  
Author(s):  
Mabruka Alfaidi ◽  
Matthew L. Scott ◽  
Anthony Wayne Orr
Keyword(s):  
Protein Interactions ◽  
Vascular Biology ◽  
Adaptor Proteins ◽  
Specific Protein ◽  
Sh2 Domain ◽  
Cell Phenotype ◽  
Protein Protein Interactions ◽  
Cytoskeletal Dynamics ◽  
Phosphotyrosine Signaling ◽  
And Function

The Nck family of modular adaptor proteins, including Nck1 and Nck2, link phosphotyrosine signaling to changes in cytoskeletal dynamics and gene expression that critically modulate cellular phenotype. The Nck SH2 domain interacts with phosphotyrosine at dynamic signaling hubs, such as activated growth factor receptors and sites of cell adhesion. The Nck SH3 domains interact with signaling effectors containing proline-rich regions that mediate their activation by upstream kinases. In vascular biology, Nck1 and Nck2 play redundant roles in vascular development and postnatal angiogenesis. However, recent studies suggest that Nck1 and Nck2 differentially regulate cell phenotype in the adult vasculature. Domain-specific interactions likely mediate these isoform-selective effects, and these isolated domains may serve as therapeutic targets to limit specific protein-protein interactions. In this review, we highlight the function of the Nck adaptor proteins, the known differences in domain-selective interactions, and discuss the role of individual Nck isoforms in vascular remodeling and function.

scholarly journals Fractionation of the Epithelial Apical Junctional Complex: Reassessment of Protein Distributions in Different Substructures

2005 ◽  
Vol 16 (2) ◽  
pp. 701-716 ◽  
Author(s):  
Roger Vogelmann ◽  
W. James Nelson
Keyword(s):  
Membrane Proteins ◽  
Protein Interactions ◽  
Cell Structure ◽  
Specific Protein ◽  
Junctional Complex ◽  
Protein Protein Interactions ◽  
Peripheral Membrane Proteins ◽  
Apical Junctional Complex ◽  
Important Regulator ◽  
And Function

The epithelial apical junctional complex (AJC) is an important regulator of cell structure and function. The AJC is compartmentalized into substructures comprising the tight and adherens junctions, and other membrane complexes containing the membrane proteins nectin, junctional adhesion molecule, and crumbs. In addition, many peripheral membrane proteins localize to the AJC. Studies of isolated proteins indicate a complex map of potential binding partners in which there is extensive overlap in the interactions between proteins in different AJC substructures. As an alternative to a direct search for specific protein-protein interactions, we sought to separate membrane substructures of the AJC in iodixanol density gradients and define their protein constituents. Results show that the AJC can be fractured into membrane substructures that contain specific membrane and peripheral membrane proteins. The composition of each substructure reveals a more limited overlap in common proteins than predicted from the inventory of potential interactions; some of the overlapping proteins may be involved in stepwise recruitment and assembly of AJC substructures.

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