Multidomain Adaptor Protein Research Articles

Role of an adaptor protein human germinal center-associated lymphoma (HGAL) in cell signaling and lymphomagenesis

Human germinal center (GC)-associated lymphoma (HGAL) is a multi-domain adaptor protein expressed in GC B lymphocytes, T follicular helper (Tfh) cells and lymphomas derived from these cells. HGAL expression is an independent predictor of longer survival of diffuse large B-cell lymphoma (DLBCL) and classical Hodgkin’s lymphoma (HL) patients. HGAL regulates B cell receptor (BCR) signaling and immunological synapse formation by binding to either the downstream effectors [e.g., spleen tyrosine kinase (Syk)] or other signaling regulators [e.g., growth factor receptor-bound protein 2 (Grb2)]. HGAL regulates the cytoskeleton that reshapes B cell morphology during BCR signaling and cell motility by at least two molecular mechanisms: enhanced Ras homolog gene family member A (RhoA) signaling and inhibition of myosin-actin translocation. These effects on the cytoskeleton decrease lymphoma dissemination in animal models and contribute to decreased lymphoma dissemination in patients. The latter may contribute to the association of HGAL protein expression with longer survival of patients with DLBCL and HL tumors. The ability to regulate multiple and distinct functions simultaneously in B cells implies that the HGAL protein level is tightly regulated. It was demonstrated that HGAL can be regulated by PR/SET domain 1 (PRDM1)/B lymphocyte-induced maturation protein-1 (BLIMP1) and interleukin-4 (IL-4) at the transcription level, by microRNA-155 (miR-155) at the post-transcriptional level, and by F-box protein 10 (FBXO10) at the post-translational level. Constitutive enforced expression of HGAL at physiological levels leads to lymphoid hyperplasia and DLBCL in mice. Future studies need to focus on identifying HGAL interactome, dissecting its interaction network, and understanding HGAL spatiotemporal signaling in live cells in physiological conditions. Further, the recent demonstration of HGAL expression in Tfh cells requires the determination of its function in these cells. These studies will contribute to new insights into the biology of these cellular subsets and how immune dysregulation contributes to lymphomagenesis.

The phospho-regulated amphiphysin/endophilin interaction is required for synaptic vesicle endocytosis.

The multidomain adaptor protein amphiphysin-1 (Amph1) is an important coordinator of clathrin-mediated endocytosis in non-neuronal cells and synaptic vesicle (SV) endocytosis at central nerve terminals. Amph1 contains a lipid-binding N-BAR (Bin/Amphiphysin/Rvs) domain, central proline-rich (PRD) and clathrin/AP2 (CLAP) domains, and a C-terminal SH3 domain. Amph1 interacts with both lipids and proteins, with all of these interactions required for SV endocytosis, with the exception of the Amph1 PRD. The Amph1 PRD associates with the endocytosis protein endophilin A1, however, the role of this interaction in SV endocytosis has not been investigated. In this study, we set out to determine whether the Amph1 PRD and its interaction with endophilin A1 was essential for efficient SV endocytosis at typical small central synapses. To achieve this, domain-specific interactions of Amph1 were validated using in vitro GST pull-down assays, with the role of these interactions in SV endocytosis determined in molecular replacement experiments in primary neuronal culture. Using this approach, we confirmed important roles for CLAP and SH3 domain interactions of Amph1 in the control of SV endocytosis. Importantly, we identified the interaction site for endophilin A1 within the Amph1 PRD and exploited specific binding mutants to reveal a key role for this interaction in SV endocytosis. Finally, we determined that the formation of the Amph1-endophilin A1 complex is dependent on the phosphorylation status of Amph1-S293 within the PRD and that the phosphorylation status of this residue is essential for efficient SV regeneration. This work, therefore, reveals a key role for the dephosphorylation-dependent Amph1-endophilin A1 interaction in efficient SV endocytosis.

The Role of Paxillin Aberrant Expression in Cancer and Its Potential as a Target for Cancer Therapy

Paxillin is a multi-domain adaptor protein. As an important member of focal adhesion (FA) and a participant in regulating cell movement, paxillin plays an important role in physiological processes such as nervous system development, embryonic development, and vascular development. However, increasing evidence suggests that paxillin is aberrantly expressed in many cancers. Many scholars have also recognized that the abnormal expression of paxillin is related to the prognosis, metastases, invasion, survival, angiogenesis, and other aspects of malignant tumors, suggesting that paxillin may be a potential cancer therapeutic target. Therefore, the study of how aberrant paxillin expression affects the process of tumorigenesis and metastasis will help to develop more efficacious antitumor drugs. Herein, we review the structure of paxillin and its function and expression in tumors, paying special attention to the multifaceted effects of paxillin on tumors, the mechanism of tumorigenesis and progression, and its potential role in tumor therapy. We also hope to provide a reference for the clinical prognosis and development of new tumor therapeutic targets.

Loss of ASAP1 in the MMTV-PyMT model of luminal breast cancer activates AKT, accelerates tumorigenesis, and promotes metastasis

ASAP1 is a multi-domain adaptor protein that regulates cytoskeletal dynamics, receptor recycling and intracellular vesicle trafficking. Its expression is associated with poor prognosis in a variety of cancers, and can promote cell migration, invasion and metastasis. Although amplification and expression of ASAP1 has been associated with poor survival in breast cancer, we found that in the autochthonous MMTV-PyMT model of luminal breast cancer, ablation of ASAP1 resulted in an earlier onset of tumor initiation and increased metastasis. This was due to tumor cell-intrinsic effects of ASAP1 deletion, as ASAP1 deficiency in tumor, but not in stromal cells was sufficient to replicate the enhanced tumorigenicity and metastasis observed in the ASAP1-null MMTV-PyMT mice. Loss of ASAP1 in MMTV-PyMT mice had no effect on proliferation, apoptosis, angiogenesis or immune cell infiltration, but enhanced mammary gland hyperplasia and tumor cell invasion, indicating that ASAP1 can accelerate tumor initiation and promote dissemination. Mechanistically, these effects were associated with a potent activation of AKT. Importantly, lower ASAP1 levels correlated with poor prognosis and enhanced AKT activation in human ER+/luminal breast tumors, validating our findings in the MMTV-PyMT mouse model for this subtype of breast cancer. Taken together, our findings reveal that ASAP1 can have distinct functions in different tumor types and demonstrate a tumor suppressive activity for ASAP1 in luminal breast cancer.

The Diarylheptanoid Curcumin Induces MYC Inhibition and Cross-Links This Oncoprotein to the Coactivator TRRAP.

The c-Myc protein (MYC) is a transcription factor with strong oncogenic potential controlling fundamental cellular processes. In most human tumors, MYC is overexpressed by enhanced transcriptional activation, gene amplification, chromosomal rearrangements, or increased protein stabilization. To pharmacologically suppress oncogenic MYC functions, multiple approaches have been applied either to inhibit transcriptional activation of the endogenous MYC gene, or to interfere with biochemical functions of aberrantly activated MYC. Other critical points of attack are targeted protein modification, or destabilization leading to a non-functional MYC oncoprotein. It has been claimed that the natural compound curcumin representing the principal curcumoid of turmeric (Curcuma longa) has anticancer properties although its specificity, efficacy, and the underlying molecular mechanisms have been controversially discussed. Here, we have tested curcumin’s effect on MYC-dependent cell transformation and transcriptional activation, and found that this natural compound interferes with both of these MYC activities. Furthermore, in curcumin-treated cells, the endogenous 60-kDa MYC protein is covalently and specifically cross-linked to one of its transcriptional interaction partners, namely the 434-kDa transformation/transcription domain associated protein (TRRAP). Thereby, endogenous MYC levels are strongly reduced and cells stop to proliferate. TRRAP is a multidomain adaptor protein of the phosphoinositide 3-kinase-related kinases (PIKK) family and represents an important component of many histone acetyltransferase (HAT) complexes. TRRAP is important to mediate transcriptional activation executed by the MYC oncoprotein, but on the other hand TRRAP also negatively regulates protein stability of the tumor suppressor p53 (TP53). Curcumin-mediated covalent binding of MYC to TRRAP reduces the protein amounts of both interaction partners but does not downregulate TP53, so that the growth-arresting effect of wild type TP53 could prevail. Our results elucidate a molecular mechanism of curcumin action that specifically and irreversibly targets two crucial multifunctional cellular players. With regard to their broad impact in cancer, our findings contribute to explain the pleiotropic functions of curcumin, and suggest that this natural spice, or more bioavailable derivatives thereof, may constitute useful adjuvants in the therapy of MYC-dependent and TRRAP-associated human tumors.

Fyn Tyrosine Kinase Elicits Amyloid Precursor Protein Tyr682 Phosphorylation in Neurons from Alzheimer's Disease Patients.

Alzheimer’s disease (AD) is an incurable neurodegenerative disorder with a few early detection strategies. We previously proposed the amyloid precursor protein (APP) tyrosine 682 (Tyr682) residue as a valuable target for the development of new innovative pharmacologic or diagnostic interventions in AD. Indeed, when APP is phosphorylated at Tyr682, it is forced into acidic neuronal compartments where it is processed to generate neurotoxic amyloid β peptides. Of interest, Fyn tyrosine kinase (TK) interaction with APP Tyr682 residue increases in AD neurons. Here we proved that when Fyn TK was overexpressed it elicited APP Tyr682 phosphorylation in neurons from healthy donors and promoted the amyloidogenic APP processing with Aβ peptides accumulation and neuronal death. Phosphorylation of APP at Tyr (pAPP-Tyr) increased in neurons of AD patients and AD neurons that exhibited high pAPP-Tyr also had higher Fyn TK activity. Fyn TK inhibition abolished the pAPP-Tyr and reduced Aβ42 secretion in AD neurons. In addition, the multidomain adaptor protein Fe65 controlled the Fyn-mediated pAPP-Tyr, warranting the possibility of targeting the Fe65-APP-Fyn pathway to develop innovative strategies in AD. Altogether, these results strongly emphasize the relevance of focusing on pAPP Tyr682 either for diagnostic purposes, as an early biomarker of the disease, or for pharmacological targeting, using Fyn TKI.

Crystal structure of the FYCO1 RUN domain suggests possible interfaces with small GTPases.

FYCO1 is a multidomain adaptor protein that plays an important role in autophagy by mediating the kinesin-dependent microtubule plus-end-directed transport of autophagosomes. FYCO1 contains a RUN domain, which is hypothesized to function as a specific effector for members of the Ras superfamily of small GTPases, but its role has not been well characterized and its interaction partner(s) have not been identified. Here, the crystal structure of the FYCO1 RUN domain was determined at 1.3 Å resolution. The overall structure of the FYCO1 RUN domain was similar to those of previously reported RUN domains. Detailed structural comparisons with other RUN domains and docking studies suggested a possible interaction interface of the FYCO1 RUN domain with small GTPases of the Ras superfamily.

Safeguarding intestine cells against enteropathogenic Escherichia coli by intracellular protein reaction, a preventive antibacterial mechanism

A critical problem in the fight against bacterial infection is the rising rates of resistance and the lack of new antibiotics. The discovery of new targets or new antibacterial mechanisms is a potential solution but is becoming more difficult. Here we report an antibacterial mechanism that safeguards intestine cells from enteropathogenic Escherichia coli (EPEC) by shutting down an infection-responsive signal of the host intestine cell. A key step in EPEC infection of intestinal cells involves Tir-induced actin reorganization. Nck mediates this event by binding with Tir through its SH2 domain (Nck-SH2) and with WIP through its second SH3 domain (Nck-SH3.2). Here we report the design of a synthetic peptide that reacts precisely with a unique cysteine of the Nck-SH3.2 domain, blocks the binding site of the Nck protein, and prevents EPEC infection of Caco-2 cells. Oral update of this nontoxic peptide before EPEC administration safeguards mice from EPEC infection and diarrhea. This study demonstrates domain-specific blockage of an SH3 domain of a multidomain adaptor protein inside cells and the inhibition of Tir-induced rearrangement of the host actin cytoskeleton as a previously unknown antibacterial mechanism.

Biological Functions of the ING Proteins.

The proteins belonging to the inhibitor of growth (ING) family of proteins serve as epigenetic readers of the H3K4Me3 histone mark of active gene transcription and target histone acetyltransferase (HAT) or histone deacetylase (HDAC) protein complexes, in order to alter local chromatin structure. These multidomain adaptor proteins interact with numerous other proteins to facilitate their localization and the regulation of numerous biochemical pathways that impinge upon biological functions. Knockout of some of the ING genes in murine models by various groups has verified their status as tumor suppressors, with ING1 knockout resulting in the formation of large clear-cell B-lymphomas and ING2 knockout increasing the frequency of ameloblastomas, among other phenotypic effects. ING4 knockout strongly affects innate immunity and angiogenesis, and INGs1, ING2, and ING4 have been reported to affect apoptosis in different cellular models. Although ING3 and ING5 knockouts have yet to be published, preliminary reports indicate that ING3 knockout results in embryonic lethality and that ING5 knockout may have postpartum effects on stem cell maintenance. In this review, we compile the known information on the domains of the INGs and the effects of altering ING protein expression, to better understand the functions of this adaptor protein family and its possible uses for targeted cancer therapy.

Behavioral analysis in mice deficient for GAREM2 (Grb2-associated regulator of Erk/MAPK subtype2) that is a subtype of highly expressing in the brain

Grb2-associated regulator of Erk/MAPK (GAREM), is an adaptor protein related to the several cell growth factor receptor-signaling. The GAREM family has two subtypes, GAREM1 and GAREM2, both encoded in the human and mouse genome. Recent genome-wide research identified GAREM2 as a candidate of neurodegenerative diseases. Here, we use knockout (KO) mice to show the role of GAREM2, that is highly expressed in the brain. According to the comprehensive behavioral battery, they exhibited less anxiety both in elevated plus maze and open field tests, mildly increased social approaching behavior in the reciprocal social interaction test, and longer latency to immobility in the tail suspension test as compared to wild-type (WT). Additionally, the extension of neurites in the primary cultured neurons was suppressed in ones derived from GAREM2 KO mice. Furthermore, we also identified Intersectin, as a binding partner of GAREM2 in this study. Intersectin is also a multi-domain adaptor protein that regulates endocytosis and cell signaling, which can potentially alter the subcellular localization of GAREM2. The important molecules, such as the neurotrophin receptor and Erk family, that are involved in the signaling pathway of the neural cell growth in the mouse brain, have been reported to participate in emotional behavior. As GAREM plays a role in the cellular growth factor receptor signaling pathway, GAREM2 may have a common role related to the transduction of Erk signaling in the higher brain functions.

Loss of ASAP1 in mice impairs adipogenic and osteogenic differentiation of mesenchymal progenitor cells through dysregulation of FAK/Src and AKT signaling.

ASAP1 is a multi-domain adaptor protein that regulates cytoskeletal dynamics, receptor recycling and intracellular vesicle trafficking. Its expression is associated with poor prognosis for a variety of cancers, and promotes cell migration, invasion and metastasis. Little is known about its physiological role. In this study, we used mice with a gene-trap inactivated ASAP1 locus to study the functional role of ASAP1 in vivo, and found defects in tissues derived from mesenchymal progenitor cells. Loss of ASAP1 led to growth retardation and delayed ossification typified by enlarged hypertrophic zones in growth plates and disorganized chondro-osseous junctions. Furthermore, loss of ASAP1 led to delayed adipocyte development and reduced fat depot formation. Consistently, deletion of ASAP1 resulted in accelerated chondrogenic differentiation of mesenchymal cells in vitro, but suppressed osteo- and adipogenic differentiation. Mechanistically, we found that FAK/Src and PI3K/AKT signaling is compromised in Asap1GT/GT MEFs, leading to impaired adipogenic differentiation. Dysregulated FAK/Src and PI3K/AKT signaling is also associated with attenuated osteogenic differentiation. Together these observations suggest that ASAP1 plays a decisive role during the differentiation of mesenchymal progenitor cells.

Grb7, a Critical Mediator of EGFR/ErbB Signaling, in Cancer Development and as a Potential Therapeutic Target.

The partner of activated epidermal growth factor receptor (EGFR), growth factor receptor bound protein-7 (Grb7), a functionally multidomain adaptor protein, has been demonstrated to be a pivotal regulator for varied physiological and pathological processes by interacting with phospho-tyrosine-related signaling molecules to affect the transmission through a number of signaling pathways. In particular, critical roles of Grb7 in erythroblastic leukemia viral oncogene homolog (ERBB) family-mediated cancer development and malignancy have been intensively evaluated. The overexpression of Grb7 or the coamplification/cooverexpression of Grb7 and members of the ERBB family play essential roles in advanced human cancers and are associated with decreased survival and recurrence of cancers, emphasizing Grb7′s value as a prognostic marker and a therapeutic target. Peptide inhibitors of Grb7 are being tested in preclinical trials for their possible therapeutic effects. Here, we review the molecular, functional, and clinical aspects of Grb7 in ERBB family-mediated cancer development and malignancy with the aim to reveal alternative and effective therapeutic strategies.

Syntenin-targeted peptide blocker inhibits progression of cancer cells

The multidomain adaptor protein syntenin is known to mediate cancer cell metastasis and invasion through its tandem PDZ1 and PDZ2 domains, leading to the postulation that the PDZ tandem may serve as a potential drug target for cancer treatment. Here we report the development of high-affinity peptide blockers to target the syntenin tandem PDZ domain, and elucidate that blocking syntenin correlates with the inhibition of cell migration and spreading. Two strategies are employed to derive high-affinity blockers from the low-affinity natural binding peptides: first, dimerization of the C termini of natural syntenin-binding peptides confers dimer peptides with much higher affinity than the monomers; second, unnatural amino acid substitution at P-1 and P-2 positions of the PDZ-binding sequence increases the binding affinity. Through several rounds of optimization, we discovered a dimeric peptide that binds tightly to syntenin tandem PDZ domain, with a dissociation constant of 0.21 μM based on fluorescence polarization measurement. The peptide dimer inhibits the migration and invasion of syntenin high-expression human cancer cells through attenuating the ERK phosphorylation of the MAPK kinase pathway. This work showcases an effective strategy to derive high-affinity blocker of multidomain adaptor proteins, which resulted in a syntenin-targeted antagonist with potential pharmaceutical values for the treatment of syntenin over-expressing cancers.

Possible involvement of a cell adhesion molecule, Migfilin, in brain development and pathogenesis of autism spectrum disorders.

Migfilin, encoded by FBLIM1 at the 1p36 locus, is a multi-domain adaptor protein essential for various cellular processes such as cell morphology and migration. Small deletions and duplications at the 1p36 locus, monosomy of which results in neurodevelopmental disorders and multiple congenital anomalies, have also been identified in patients with autism spectrum disorder (ASD). However, the impact of FBLIM1, the gene within 1p36, on the pathogenesis of ASD is unknown. In this study, we performed morphological analyses of migfilin to elucidate its role in brain development. Migfilin was detected specifically in the embryonic and perinatal stages of the mouse brain. Either silencing or overexpression of migfilin in embryos following in utero electroporation disrupted Neocortical neuronal migration. Additionally, neurite elongation was impaired when migfilin was silenced in cultured mouse hippocampal neurons. We then screened FBLIM1 for rare exonic deletions/duplications in 549 Japanese ASD patients and 824 controls, detecting one case of ASD and intellectual delay that harbored a 26-kb deletion at 1p36.21 that solely included the C-terminal exon of FBLIM1. The FBLIM1 mRNA expression level in this case was reduced compared to levels in individuals without FBLIM1 deletion. Our findings indicate that tightly regulated expression of migfilin is essential for neuronal development and that FBLIM1 disruption may be related to the phenotypes associated with ASD and related neurodevelopmental disorders.

Grb7 is over-expressed in cervical cancer and facilitate invasion and inhibit apoptosis in cervical cancer cells

Growth factor receptor bound protein-7 (Grb7) is a multi-domain adaptor protein that is co-opted by numerous tyrosine kinases involved in various cellular signaling. The objective of this study was to investigate the expression of Grb7 and its clinicopathological significance in cervical cancer. Utilising immunohistochemical staining, we examined the expression of Grb7 in 120 cases of human cervical cancer tissue and 10 cases of adjacent non-cancerous cervical tissue. The positive rate of Grb7 protein expression was 34.2%, which was significantly higher than that in adjacent non-cancerous cervical tissue (0%, p<0.05). The expression of Grb7 was found to be correlated with age, tumor size, serosal invasion, differentiated degree, tumor stage, early or advanced stage and lymph node metastasis. Kaplan-Meier survival analysis showed that patients with positive Grb7 protein expression had a lower overall survival rate than patients without Grb7 expression. In addition, Grb7 plays an important role in promoting tumor progression, including invasion and anti-apoptosis, in cervical cancer cell line. Down-regulation of Grb7 repressed the expression of MMP-9 and Bcl-2, and increased the expression of Bax in Grb7 knockdown Hela cells. Cell invasion assay showed decreased number of Grb7 knockdown Hela cells (18.7±2.1) compared to Hela cells (65.3±2.5, P<0.05). Our results indicated that Grb7 over-expression may facilitate invasion and inhibit apoptosis in cervical cancer and Grb7 is a potentially molecular target of cervical cancer chemotherapy.

The crystal structure of mouse LC3B in complex with the FYCO1 LIR reveals the importance of the flanking region of the LIR motif.

FYVE and coiled-coil domain-containing protein 1 (FYCO1), a multidomain autophagy adaptor protein, mediates microtubule plus-end-directed autophagosome transport by interacting with kinesin motor proteins and with the autophagosomal membrane components microtubule-associated protein 1 light chain 3 (LC3), Rab7 and phosphatidylinositol 3-phosphate (PI3P). To establish the structural basis for the recognition of FYCO1 by LC3, the crystal structure of mouse LC3B in complex with the FYCO1 LC3-interacting region (LIR) motif peptide was determined. Structural analysis showed that the flanking sequences N-terminal and C-terminal to the LIR core sequence of FYCO1, as well as the tetrapeptide core sequence, were specifically recognized by LC3B and contributed to the binding. Moreover, comparisons of related structures revealed a conserved mechanism of FYCO1 recognition by different LC3 isoforms among different species.

P62 in Liver Disease: Good Guy or Bad Guy?

The multidomain adaptor protein p62 has been suggested to exert pro-oncogenic functions in hepatocytes and other epithelial cells. In this issue of Cancer Cell, Duran etal. show that p62 acts as a non-cell-autonomous tumor suppressor in liver cancer by counteracting the activation of hepatic stellate cells.

Grb7 Protein Stability Modulated by Pin1 in Association with Cell Cycle Progression.

Growth factor receptor bound protein-7 (Grb7) is a multi-domain adaptor protein that is co-opted by numerous tyrosine kinases involved in various cellular signaling and functions. The molecular mechanisms underlying the regulation of Grb7 remain unclear. Here, we revealed a novel negative post-translational regulation of Grb7 by the peptidyl-prolyl cis/trans isomerase, Pin1. Our data show that phosphorylation of Grb7 protein on the Ser194-Pro motif by c-Jun N-terminal kinase facilitates its binding with the WW domain of Pin1. Subsequently, Grb7 is degraded by the ubiquitin- and proteasome-dependent proteolytic pathway. Indeed, we found that Pin1 exerts its peptidyl-prolyl cis/trans isomerase activity in the modulation of Grb7 protein stability in regulation of cell cycle progression at the G2-M phase. This study illustrates a novel regulatory mechanism in modulating Grb7-mediated signaling, which may take part in pathophysiological consequences.

Rac1-mediated cytoskeleton rearrangements induced by intersectin-1s deficiency promotes lung cancer cell proliferation, migration and metastasis.

BackgroundThe mechanisms involved in lung cancer (LC) progression are poorly understood making discovery of successful therapies difficult. Adaptor proteins play a crucial role in cancer as they link cell surface receptors to specific intracellular pathways. Intersectin-1s (ITSN-1s) is an important multidomain adaptor protein implicated in the pathophysiology of numerous pulmonary diseases. To date, the role of ITSN-1s in LC has not been studied.MethodsHuman LC cells, human LC tissue and A549 LC cells stable transfected with myc-ITSN-1s construct (A549 + ITSN-1s) were used in correlation with biochemical, molecular biology and morphological studies. In addition scratch assay with time lapse microscopy and in vivo xenograft tumor and mouse metastasis assays were performed.ResultsITSN-1s, a prevalent protein of lung tissue, is significantly downregulated in human LC cells and LC tissue. Restoring ITSN-1s protein level decreases LC cell proliferation and clonogenic potential. In vivo studies indicate that immunodeficient mice injected with A549 + ITSN-1s cells develop less and smaller metastatic tumors compared to mice injected with A549 cells. Our studies also show that restoring ITSN-1s protein level increases the interaction between Cbl E3 ubiquitin ligase and Eps8 resulting in enhanced ubiquitination of the Eps8 oncoprotein. Subsequently, downstream unproductive assembly of the Eps8-mSos1 complex leads to impaired activation of the small GTPase Rac1. Impaired Rac1 activation mediated by ITSN-1s reorganizes the cytoskeleton (increased thick actin bundles and focal adhesion (FA) complexes as well as collapse of the vimentin filament network) in favor of decreased LC cell migration and metastasis.ConclusionITSN-1s induced Eps8 ubiquitination and impaired Eps8-mSos1 complex formation, leading to impaired activation of Rac1, is a novel signaling mechanism crucial for abolishing the progression and metastatic potential of LC cells.Electronic supplementary materialThe online version of this article (doi:10.1186/s12943-016-0543-1) contains supplementary material, which is available to authorized users.

Conformational landscape of an amyloid intra-cellular domain and Landau-Ginzburg-Wilson paradigm in protein dynamics.

The Landau-Ginzburg-Wilson paradigm is proposed as a framework, to investigate the conformational landscape of intrinsically unstructured proteins. A universal Cα-trace Landau free energy is deduced from general symmetry considerations, with the ensuing all-atom structure modeled using publicly available reconstruction programs Pulchra and Scwrl. As an example, the conformational stability of an amyloid precursor protein intra-cellular domain (AICD) is inspected; the reference conformation is the crystallographic structure with code 3DXC in Protein Data Bank (PDB) that describes a heterodimer of AICD and a nuclear multi-domain adaptor protein Fe65. Those conformations of AICD that correspond to local or near-local minima of the Landau free energy are identified. For this, the response of the original 3DXC conformation to variations in the ambient temperature is investigated, using the Glauber algorithm. The conclusion is that in isolation the AICD conformation in 3DXC must be unstable. A family of degenerate conformations that minimise the Landau free energy is identified, and it is proposed that the native state of an isolated AICD is a superposition of these conformations. The results are fully in line with the presumed intrinsically unstructured character of isolated AICD and should provide a basis for a systematic analysis of AICD structure in future NMR experiments.