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.

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 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 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 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 Developing Nanodisc-ID for label-free characterizations of membrane proteins

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Huan Bao
Keyword(s):  
Membrane Proteins ◽  
Protein Interactions ◽  
Gel Electrophoresis ◽  
Low Cost ◽  
Label Free ◽  
Protein Protein Interactions ◽  
Peripheral Membrane Proteins ◽  
Wide Range ◽  
Neural Transmission

AbstractMembrane proteins (MPs) influence all aspects of life, such as tumorigenesis, immune response, and neural transmission. However, characterization of MPs is challenging, as it often needs highly specialized techniques inaccessible to many labs. We herein introduce nanodisc-ID that enables quantitative analysis of membrane proteins using a gel electrophoresis readout. By leveraging the power of nanodiscs and proximity labeling, nanodisc-ID serves both as scaffolds for encasing biochemical reactions and as sensitive reagents for detecting membrane protein-lipid and protein-protein interactions. We demonstrate this label-free and low-cost tool by characterizing a wide range of integral and peripheral membrane proteins from prokaryotes and eukaryotes.

scholarly journals Trafficking of Stretch-Regulated TRPV2 and TRPV4 Channels Inferred Through Interactomics

Biomolecules ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 791
Author(s):  
Pau Doñate-Macián ◽  
Jennifer Enrich-Bengoa ◽  
Irene R. Dégano ◽  
David G. Quintana ◽  
Alex Perálvarez-Marín
Keyword(s):  
Protein Interactions ◽  
Transient Receptor Potential ◽  
Cell Structure ◽  
Receptor Potential ◽  
Transient Receptor Potential Vanilloid ◽  
Protein Protein Interactions ◽  
Phosphoinositide Signaling ◽  
Transient Receptor ◽  
Cellular Compartments ◽  
Structure And Activity

Transient receptor potential cation channels are emerging as important physiological and therapeutic targets. Within the vanilloid subfamily, transient receptor potential vanilloid 2 (TRPV2) and 4 (TRPV4) are osmo- and mechanosensors becoming critical determinants in cell structure and activity. However, knowledge is scarce regarding how TRPV2 and TRPV4 are trafficked to the plasma membrane or specific organelles to undergo quality controls through processes such as biosynthesis, anterograde/retrograde trafficking, and recycling. This revision lists and reviews a subset of protein–protein interactions from the TRPV2 and TRPV4 interactomes, which is related to trafficking processes such as lipid metabolism, phosphoinositide signaling, vesicle-mediated transport, and synaptic-related exocytosis. Identifying the protein and lipid players involved in trafficking will improve the knowledge on how these stretch-related channels reach specific cellular compartments.

Structure, Function, Involvement in Diseases and Targeting of 14-3-3 Proteins: An Update

2018 ◽  
Vol 25 (1) ◽  
pp. 5-21 ◽  
Author(s):  
Ylenia Cau ◽  
Daniela Valensin ◽  
Mattia Mori ◽  
Sara Draghi ◽  
Maurizio Botta
Keyword(s):  
Protein Interactions ◽  
Molecular Mechanisms ◽  
Physiological Role ◽  
Specific Protein ◽  
Protein Protein Interactions ◽  
Cellular Processes ◽  
Protein Partners ◽  
High Sequence Homology ◽  
Small Molecule Modulators

14-3-3 is a class of proteins able to interact with a multitude of targets by establishing protein-protein interactions (PPIs). They are usually found in all eukaryotes with a conserved secondary structure and high sequence homology among species. 14-3-3 proteins are involved in many physiological and pathological cellular processes either by triggering or interfering with the activity of specific protein partners. In the last years, the scientific community has collected many evidences on the role played by seven human 14-3-3 isoforms in cancer or neurodegenerative diseases. Indeed, these proteins regulate the molecular mechanisms associated to these diseases by interacting with (i) oncogenic and (ii) pro-apoptotic proteins and (iii) with proteins involved in Parkinson and Alzheimer diseases. The discovery of small molecule modulators of 14-3-3 PPIs could facilitate complete understanding of the physiological role of these proteins, and might offer valuable therapeutic approaches for these critical pathological states.

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