Controlled dimerization of ErbB receptors provides evidence for differential signaling by homo- and heterodimers

ATP citrate lyase is increased in human breast cancer, depletion of which promotes apoptosis

Breast cancer is a malignant tumor that is harmful to women’s health around the world. Investigating the biological mechanism is, therefore, of pivotal importance to improve patients’ prognoses. Compared to non-neoplastic tissues, enhanced glucose and lipid metabolism is one of the most common properties of malignant breast cancer. Adenosine triphosphate (ATP) citrate lyase is a key enzyme linking aerobic glycolysis and fatty acid synthesis and is of high biological and prognostic significance in breast cancer. In our clinical study, fresh clinical tissues were used to analyze ATP citrate lyase expression by western blotting, and paraffin archived samples from 62 breast cancer patients were used to analyze ATP citrate lyase expression by immunohistochemistry. In the cellular study, following small interfering RNA–mediated inhibition of ATP citrate lyase in MCF-7 cells, cell viability and apoptosis were measured using the Cell Counting Kit-8 and flow cytometry, respectively. Breast cancer tissues showed strong expression of ATP citrate lyase, whereas adjacent normal tissues showed weak expression. Silencing of endogenous ATP citrate lyase expression by small interfering RNA in MCF-7 cells suppressed cell viability and increased cell apoptosis. Collectively, our study revealed that expression of ATP citrate lyase was significantly increased in breast cancer tissue compared with normal tissue. In addition, we found that depletion of ATP citrate lyase suppressed tumor growth, which suggests that ATP citrate lyase–related inhibitors might be potential therapeutic approaches for breast cancer.

The glucose transporter GLUT1 is required for ErbB2-induced mammary tumorigenesis

BACKGROUND

Altered tumor cell metabolism is an emerging hallmark of cancer; however, the precise role for glucose in tumor initiation is not known. GLUT1 (SLC2A1) is expressed in breast cancer cells and is likely responsible for avid glucose uptake observed in established tumors. We have shown that GLUT1 was necessary for xenograft tumor formation from primary mammary cells transformed with the polyomavirus middle-T antigen but that it was not necessary for growth after tumors had formed in vivo, suggesting a differential requirement for glucose depending on the stage of tumorigenesis.

METHODS

To determine whether GLUT1 is required early during mammary tumorigenesis, we crossed MMTV-NIC mice, which express activated HER2/NEU/ERBB2 and Cre recombinase, to Slc2a1 ^Flox/Flox (GLUT1^Flox/Flox) mice to generate NIC-GLUT1^+/+, NIC-GLUT1^Flox/+, and NIC-GLUT1^Flox/Flox mice. In addition, we evaluated effects of glucose restriction or GLUT1 inhibition on transformation in MCF10A-ERBB2 breast epithelial cells in three-dimensional culture. Finally, we utilized global gene expression profiling data of primary human breast tumors to determine the relationship between SLC2A1 and stage of tumorigenesis.

RESULTS

All of the NIC-GLUT1^+/+ mice developed tumors in less than 200 days. In contrast, only 1 NIC-GLUT1^Flox/Flox mouse and 1 NIC-GLUT1^Flox/+ mouse developed mammary tumors, even after 18 months. Mammary gland development was not disrupted in NIC mice lacking GLUT1; however, epithelial content of mature glands was reduced compared to NIC-GLUT1^Flox/+ mice. In MCF10A-ERBB2 cells, glucose restriction or GLUT1 inhibition blocked transformation induced by activated ERBB2 through reduced cell proliferation. In human breast cancers, SLC2A1 was higher in ductal carcinoma in situ compared to the normal breast, but lower in invasive versus in situ lesions, suggesting the requirement for GLUT1 decreases as tumors progress.

CONCLUSIONS

This study demonstrates a strict requirement for GLUT1 in the early stages of mammary tumorigenesis in vitro and in vivo. While metabolic adaptation has emerged as a hallmark of cancer, our data indicate that early tumor cells rely heavily on glucose and highlight the potential for glucose restriction as a breast cancer preventive strategy.

Cadm3 (Necl-1) interferes with the activation of the PI3 kinase/Akt signaling cascade and inhibits Schwann cell myelination in vitro

Axo-glial interactions are critical for myelination and the domain organization of myelinated fibers. Cell adhesion molecules belonging to the Cadm family, and in particular Cadm3 (axonal) and its heterophilic binding partner Cadm4 (Schwann cell), mediate these interactions along the internode. Using targeted shRNA-mediated knockdown, we show that the removal of axonal Cadm3 promotes Schwann cell myelination in the in vitro DRG neuron/Schwann cell myelinating system. Conversely, over-expressing Cadm3 on the surface of DRG neuron axons results in an almost complete inability by Schwann cells to form myelin segments. Axons of superior cervical ganglion (SCG) neurons, which do not normally support the formation of myelin segments by Schwann cells, express higher levels of Cadm3 compared to DRG neurons. Knocking down Cadm3 in SCG neurons promotes myelination. Finally, the extracellular domain of Cadm3 interferes in a dose-dependent manner with the activation of ErbB3 and of the pro-myelinating PI3K/Akt pathway, but does not interfere with the activation of the Mek/Erk1/2 pathway. While not in direct contradiction, these in vitro results shed lights on the apparent lack of phenotype that was reported from in vivo studies of Cadm3^-/- mice. Our results suggest that Cadm3 may act as a negative regulator of PNS myelination, potentially through the selective regulation of the signaling cascades activated in Schwann cells by axonal contact, and in particular by type III Nrg-1. Further analyses of peripheral nerves in the Cadm^-/- mice will be needed to determine the exact role of axonal Cadm3 in PNS myelination. GLIA 2016;64:2247-2262.

Molecular tools for acute spatiotemporal manipulation of signal transduction

The biochemical activities involved in signal transduction in cells are under tight spatiotemporal regulation. To study the effects of the spatial patterning and temporal dynamics of biochemical activities on downstream signaling, researchers require methods to manipulate signaling pathways acutely and rapidly. In this review, we summarize recent developments in the design of three broad classes of molecular tools for perturbing signal transduction, classified by their type of input signal: chemically induced, optically induced, and magnetically induced.

Protein engineering strategies with potential applications for altering clinically relevant cellular pathways at the protein level

All diseases can be fundamentally viewed as the result of malfunctioning cellular pathways. Protein engineering offers the potential to develop new tools that will allow these dysfunctional pathways to be better understood, in addition to potentially providing new routes to restore proper function. Here we discuss different approaches that can be used to change the intracellular activity of a protein by intervening at the protein level: targeted protein sequestration, protein recruitment, protein degradation, and selective inhibition of binding interfaces. The potential of each of these tools to be developed into effective therapeutic treatments will also be discussed, along with any major barriers that currently block their translation into the clinic.

Similar requirement for clathrin in EGF- and HGF- stimulated Akt phosphorylation

Receptor tyrosine kinases, such as the epidermal growth factor (EGF) receptor (EGFR) and Met lead to activation of intracellular signals including Akt, a critical regulator of cell survival, metabolism and proliferation. Upon binding their respective ligands, each of these receptors is recruited into clathrin coated pits (CCPs) eventually leading to endocytosis. We have recently shown that phosphorylation of Gab1 and Akt following EGFR activation requires clathrin, but does not require receptor endocytosis. We examined whether clathrin regulates Akt signaling downstream of Met, as it does for EGFR signaling. Stimulation with the Met ligand Hepatocyte Growth Factor (HGF) leads to enrichment of phosphorylated Gab1 (pGab1) within CCPs in ARPE-19 cells. Perturbation of clathrin using the inhibitor pitstop2 decreases HGF-stimulated Akt phosphorylation. These results indicate that clathrin may regulate Met signaling leading to Akt phosphorylation similarly as it does for EGFR signaling.

Molecular basis for multimerization in the activation of the epidermal growth factor receptor

The epidermal growth factor receptor (EGFR) is activated by dimerization, but activation also generates higher-order multimers, whose nature and function are poorly understood. We have characterized ligand-induced dimerization and multimerization of EGFR using single-molecule analysis, and show that multimerization can be blocked by mutations in a specific region of Domain IV of the extracellular module. These mutations reduce autophosphorylation of the C-terminal tail of EGFR and attenuate phosphorylation of phosphatidyl inositol 3-kinase, which is recruited by EGFR. The catalytic activity of EGFR is switched on through allosteric activation of one kinase domain by another, and we show that if this is restricted to dimers, then sites in the tail that are proximal to the kinase domain are phosphorylated in only one subunit. We propose a structural model for EGFR multimerization through self-association of ligand-bound dimers, in which the majority of kinase domains are activated cooperatively, thereby boosting tail phosphorylation.

DOI:http://dx.doi.org/10.7554/eLife.14107.001

Techniques for studying protein trafficking and molecular motors in neurons

This review focused on techniques that facilitated the visualization of protein trafficking. In the mid-1990s the cloning of GFP allowed fluorescently tagged proteins to be expressed in cells and then visualized in real time. This advance allowed a glimpse, for the first time, of the complex system within cells for distributing proteins. It quickly became apparent, however, that time-lapse sequences of exogenously expressed GFP-labeled proteins can be difficult to interpret. Reasons for this include the relatively low signal that comes from moving proteins and high background rates from stationary proteins and other sources, as well as the difficulty of identifying the origins and destinations of specific vesicular carriers. In this review a range of techniques that have overcome these issues to varying degrees was reviewed and the insights into protein trafficking that they have enabled were discussed. Concentration will be on neurons, as they are highly polarized and, thus, their trafficking systems tend to be accessible for study. © 2016 Wiley Periodicals, Inc.

Epidermal growth factor receptor mediated proliferation depends on increased lipid droplet density regulated via a negative regulatory loop with FOXO3/Sirtuin6

The proliferation of colon cancer cells is mediated in part by epidermal growth factor receptor (EGFR) signaling and requires sustained levels of cellular energy to meet its high metabolic needs. Intracellular lipid droplets (LDs) are a source of energy used for various cellular functions and they are elevated in density in human cancer, yet their regulation and function are not well understood. Here, in human colon cancer cells, EGF stimulates increases in LD density, which depends on EGFR expression and activation as well as the individual cellular capacity for lipid synthesis. Increases in LDs are blockaded by inhibition of PI3K/mTOR and PGE2 synthesis, supporting their dependency on select upstream pathways. In colon cancer cells, silencing of the FOXO3 transcription factor leads to down regulation of SIRT6, a negative regulator of lipid synthesis, and consequent increases in the LD coat protein PLIN2, revealing that increases in LDs depend on loss of FOXO3/SIRT6. Moreover, EGF stimulates loss of FOXO3/SIRT6, which is blockaded by the inhibition of upstream pathways as well as lipid synthesis, revealing existence of a negative regulatory loop between LDs and FOXO3/SIRT6. Elevated LDs are utilized by EGF treatment and their depletion through the inhibition of lipid synthesis or silencing of PLIN2 significantly attenuates proliferation. This novel mechanism of proliferative EGFR signaling leading to elevated LD density in colon cancer cells could potentially be therapeutically targeted for the treatment of tumor progression.

Molecular architecture of the ErbB2 extracellular domain homodimer

Human epidermal growth factor receptors (HERs or ErbBs) play crucial roles in numerous cellular processes. ErbB2 is a key member of ErbB family, and its overexpression is recognized as a frequent molecular abnormality. In cancer, this overexpression correlates with aggressive disease and poor patient outcomes. Dimer-dependent phosphorylation is a key event for the signal transduction of ErbBs. However, the molecular mechanism of the dimerization of ErbB2 remains elusive. In the present work, we report the homodimer architecture of the ErbB2 extracellular domain (ECD) which is unique compared with other dimer-models of ErbBs. The structure of the ErbB2 ECD homodimer represents a "back to head" interaction, in which a protruding β-hairpin arm in domain II of one ErbB2 protomer is inserted into a C-shaped pocket created by domains I-III of the adjacent ErbB2 protomer. This dimerized architecture and its impact on the phosphorylation of ErbB2 intracellular domain were further verified by a mutagenesis study. We also elucidated the different impacts of two clinically administered therapeutic antibodies, trastuzumab and pertuzumab, on ErbB2 dimerization. This information not only provides an understanding of the molecular mechanism of ErbBs dimerization but also elucidates ErbB2-targeted therapy at the molecular level.

The Conserved Phenylalanine in the Transmembrane Domain Enhances Heteromeric Interactions of Syndecans

The transmembrane domain (TMD) of the syndecans, a family of transmembrane heparin sulfate proteoglycans, is involved in forming homo- and heterodimers and oligomers that transmit signaling events. Recently, we reported that the unique phenylalanine in TMD positively regulates intramolecular interactions of syndecan-2. Besides the unique phenylalanine, syndecan-2 contains a conserved phenylalanine (SDC2-Phe-169) that is present in all syndecan TMDs, but its function has not been determined. We therefore investigated the structural role of SDC2-Phe-169 in syndecan TMDs. Replacement of SDC2-Phe-169 by tyrosine (S2F169Y) did not affect SDS-resistant homodimer formation but significantly reduced SDS-resistant heterodimer formation between syndecan-2 and -4, suggesting that SDC2-Phe-169 is involved in the heterodimerization/oligomerization of syndecans. Similarly, in an in vitro binding assay, a syndecan-2 mutant (S2(F169Y)) showed a significantly reduced interaction with syndecan-4. FRET assays showed that heteromolecular interactions between syndecan-2 and -4 were reduced in HEK293T cells transfected with S2(F169Y) compared with syndecan-2. Moreover, S2(F169Y) reduced downstream reactions mediated by the heterodimerization of syndecan-2 and -4, including Rac activity, cell migration, membrane localization of PKCα, and focal adhesion formation. The conserved phenylalanine in syndecan-1 and -3 also showed heterodimeric interaction with syndecan-2 and -4. Taken together, these findings suggest that the conserved phenylalanine in the TMD of syndecans is crucial in regulating heteromeric interactions of syndecans.

State of the art management of metastatic gastroesophageal cancer

The anatomical locations of upper gastrointestinal (GI) tumors have changed remarkably in the western world and reflect the increasing impact of obesity and gastroesophageal (GE) reflux rather than infectious etiologies. Incidence rates of GE tumors are rising rapidly and survival rates for patients with metastatic disease remain poor. Traditionally, cytotoxic chemotherapy has had some survival advantages but increasingly complex combination regimens are limited by toxicities. The advent of molecularly targeted therapy has provided additional options for patients with advanced disease including trastuzumab and ramucirumab. There has also been detailed molecular characterization of upper GI tumors which hopefully will result in improved tailoring of clinical trial design accounting for the heterogeneity inherent in GE tumors. While numerous targeted therapies are currently being studied in clinical trials, there is much excitement regarding the role of immunotherapy in GE cancers. Although further investigation is warranted, it represents a promising avenue for patients with advanced GE tumors.

The Metastasis Suppressor, N-MYC Downstream-regulated Gene-1 (NDRG1), Down-regulates the ErbB Family of Receptors to Inhibit Downstream Oncogenic Signaling Pathways

N-MYC downstream-regulated gene-1 (NDRG1) is a potent growth and metastasis suppressor that acts through its inhibitory effects on a wide variety of cellular signaling pathways, including the TGF-β pathway, protein kinase B (AKT)/PI3K pathway, RAS, etc. To investigate the hypothesis that its multiple effects could be regulated by a common upstream effector, the role of NDRG1 on the epidermal growth factor receptor (EGFR) and other members of the ErbB family, namely human epidermal growth factor receptor 2 (HER2) and human epidermal growth factor receptor 3 (HER3), was examined. We demonstrate that NDRG1 markedly decreased the expression and activation of EGFR, HER2, and HER3 in response to the epidermal growth factor (EGF) ligand, while also inhibiting formation of the EGFR/HER2 and HER2/HER3 heterodimers. In addition, NDRG1 also decreased activation of the downstream MAPKK in response to EGF. Moreover, novel anti-tumor agents of the di-2-pyridylketone class of thiosemicarbazones, namely di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone and di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone, which markedly up-regulate NDRG1, were found to inhibit EGFR, HER2, and HER3 expression and phosphorylation in cancer cells. However, the mechanism involved appeared dependent on NDRG1 for di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone, but was independent of this metastasis suppressor for di-2-pyridylketone 4-cyclohexyl-4-methyl-3-thiosemicarbazone. This observation demonstrates that small structural changes in thiosemicarbazones result in marked alterations in molecular targeting. Collectively, these results reveal a mechanism for the extensive downstream effects on cellular signaling attributed to NDRG1. Furthermore, this study identifies a novel approach for the treatment of tumors resistant to traditional EGFR inhibitors.

Characterization of the rapamycin-inducible EBV LMP1 activation system

Epstein-Barr virus (EBV) latent infection membrane protein 1 (LMP1) is required for EBV-mediated B lymphocyte transformation into proliferating lymphoblastoid cell lines (LCL). LMP1 oligomerizes spontaneously in membrane lipid rafts via its transmembrane domain and constitutively activates signal transduction pathways, including NF-κB, p38 Mitogen-Activated Protein Kinase (MAPK), and c-Jun N-terminal Kinase (JNK). Since LMP1 mimics the tumor necrosis factor receptor (TNFR), CD40, it may be effectively utilized to study the effects of constitutive activation of signal transduction pathways on cellular physiology. On the other hand, LMP1 presents a disadvantage in terms of determining the sequential events and factors involved in signaling pathways. A CD40-LMP1 chimeric molecule has been generated to overcome this limitation but does not represent the authentic and physiological nature of LMP1. In the current study, a ligand-dependent activation system for LMP1 using rapamycin-inducible dimerization was generated to delineate the LMP1 signaling pathway.

INTRACELLULAR TRANSPORT. PI4P/phosphatidylserine countertransport at ORP5- and ORP8-mediated ER-plasma membrane contacts

Lipid transfer between cell membrane bilayers at contacts between the endoplasmic reticulum (ER) and other membranes help to maintain membrane lipid homeostasis. We found that two similar ER integral membrane proteins, oxysterol-binding protein (OSBP)-related protein 5 (ORP5) and ORP8, tethered the ER to the plasma membrane (PM) via the interaction of their pleckstrin homology domains with phosphatidylinositol 4-phosphate (PI4P) in this membrane. Their OSBP-related domains (ORDs) harbored either PI4P or phosphatidylserine (PS) and exchanged these lipids between bilayers. Gain- and loss-of-function experiments showed that ORP5 and ORP8 could mediate PI4P/PS countertransport between the ER and the PM, thus delivering PI4P to the ER-localized PI4P phosphatase Sac1 for degradation and PS from the ER to the PM. This exchange helps to control plasma membrane PI4P levels and selectively enrich PS in the PM.

Epidermal growth factor-stimulated Akt phosphorylation requires clathrin or ErbB2 but not receptor endocytosis

Upon ligand binding, the epidermal growth factor receptor (EGFR) activates signaling and undergoes endocytosis. EGFR signaling leading to Akt activation is impaired by perturbation of clathrin but not by inhibition of internalization through perturbation of dynamin. Clathrin may thus directly regulate receptor signaling at the cell surface.

Epidermal growth factor (EGF) binding to its receptor (EGFR) activates several signaling intermediates, including Akt, leading to control of cell survival and metabolism. Concomitantly, ligand-bound EGFR is incorporated into clathrin-coated pits—membrane structures containing clathrin and other proteins—eventually leading to receptor internalization. Whether clathrin might regulate EGFR signaling at the plasma membrane before vesicle scission is poorly understood. We compared the effect of clathrin perturbation (preventing formation of, or receptor recruitment to, clathrin structures) to that of dynamin2 (allowing formation of clathrin structures but preventing EGFR internalization) under conditions in which EGFR endocytosis is clathrin dependent. Clathrin perturbation by siRNA gene silencing, with the clathrin inhibitor pitstop2, or knocksideways silencing inhibited EGF-simulated Gab1 and Akt phosphorylation in ARPE-19 cells. In contrast, perturbation of dynamin2 with inhibitors or by siRNA gene silencing did not affect EGF-stimulated Gab1 or Akt phosphorylation. EGF stimulation enriched Gab1 and phospho-Gab1 within clathrin structures. ARPE-19 cells have low ErbB2 expression, and overexpression and knockdown experiments revealed that robust ErbB2 expression bypassed the requirement for clathrin for EGF-stimulated Akt phosphorylation. Thus clathrin scaffolds may represent unique plasma membrane signaling microdomains required for signaling by certain receptors, a function that can be separated from vesicle formation.

Blockade of a key region in the extracellular domain inhibits HER2 dimerization and signaling

BACKGROUND

Several treatment strategies target the human epidermal growth factor receptor 2 (HER2) in breast carcinomas, including monoclonal antibodies directed against HER2's extracellular domain (ECD) and small molecule inhibitors of its tyrosine kinase activity. Yet, novel therapies are needed that prevent HER2 dimerization with other HER family members, because current treatments are only partially effective.

METHODS

To test the hypothesis that HER2 activation requires a protein sequence in the HER2-ECD that mediates HER2 homo- and heterodimerization, we introduced a series of deletion mutations in the third subdomain of HER2-ECD. These deletion mutants were retrovirally expressed in breast cancer (BC) cells that naturally overexpress HER2 and in noncancerous, HER2-negative breast epithelial cells. One-factor analysis of variance or Student's t test were used to analyze differences. All statistical tests were two-sided.

RESULTS

The smallest deletion in the ECD domain of HER2, which removed only 16 amino acids (HER2-ECDΔ451-466), completely disrupted the oncogenic potential of HER2. In contrast to wild-type HER2, the mutant-inhibited anchorage-independent growth (mean number of colonies: mutant, 70, 95% confidence interval [CI] = 55 to 85; wild-type, 400, 95% CI = 320 to 480, P < .001) increased sensitivity to paclitaxel treatment in both transformed and nontransformed cells. Overexpression of HER2Δ451-466 efficiently inhibited activation of HER1, HER2, and HER3 in all cell lines tested.

CONCLUSIONS

These findings reveal that an essential "activating" sequence exists in the extracellular domain of HER2. Disruption of this sequence disables the HER2 dimerization loop, blocks subsequent activation of HER2-driven oncogenic signaling, and generates a dominant-negative form of HER2. Reagents specifically against this molecular activation switch may represent a novel targeted approach for the management of HER2-overexpressing carcinomas.

In Utero exposure to low-dose alcohol induces reprogramming of mammary development and tumor risk in MMTV-erbB-2 transgenic mice

There is increasing evidence that prenatal exposure to environmental factors may modify breast cancer risk later in life. This study aimed to investigate the effects of in utero exposure to low-dose alcohol on mammary development and tumor risk. Pregnant MMTV-erbB-2 mice were exposed to alcohol (6 g/kg/day) between day 13 and day 19 of gestation, and the female offspring were examined for tumor risk. Whole mount analysis indicated that in utero exposure to low-dose alcohol induced significant increases in ductal extension at 10 weeks of age. Molecular analysis showed that in utero alcohol exposure induced upregulation of ERα signaling and activation of Akt and Erk1/2 in pubertal mammary glands. However, enhanced signaling in the EGFR/erbB-2 pathway appeared to be more prominent in 10-week-old glands than did signaling in the other pathways. Interestingly, tumor development in mice with in utero exposure to low-dose alcohol was slightly delayed compared to control mice, but tumor multiplicity was increased. The results indicate that in utero exposure to low-dose alcohol induces the reprogramming of mammary development by mechanisms that include altered signaling in the estrogen receptor (ER) and erbB-2 pathways. The intriguing tumor development pattern might be related to alcohol dose and exposure conditions, and warrants further investigation.

NF-kB as a key player in regulation of cellular radiation responses and identification of radiation countermeasures

Nuclear factor (NF)-κB is a transcription factor that plays significant role in immunity, cellular survival and inhibition of apoptosis, through the induction of genetic networks. Depending on the stimulus and the cell type, the members of NF-κB related family (RelA, c-Rel, RelB, p50, and p52), forms different combinations of homo and hetero-dimers. The activated complexes (Es) translocate into the nucleus and bind to the 10bp κB site of promoter region of target genes in stimulus specific manner. In response to radiation, NF-κB is known to reduce cell death by promoting the expression of anti-apoptotic proteins and activation of cellular antioxidant defense system. Constitutive activation of NF-κB associated genes in tumour cells are known to enhance radiation resistance, whereas deletion in mice results in hypersensitivity to IR-induced GI damage. NF-κB is also known to regulate the production of a wide variety of cytokines and chemokines, which contribute in enhancing cell proliferation and tissue regeneration in various organs, such as the GI crypts stem cells, bone marrow etc., following exposure to IR. Several other cytokines are also known to exert potent pro-inflammatory effects that may contribute to the increase of tissue damage following exposure to ionizing radiation. Till date there are a series of molecules or group of compounds that have been evaluated for their radio-protective potential, and very few have reached clinical trials. The failure or less success of identified agents in humans could be due to their reduced radiation protection efficacy. In this review we have considered activation of NF-κB as a potential marker in screening of radiation countermeasure agents (RCAs) and cellular radiation responses. Moreover, we have also focused on associated mechanisms of activation of NF-κB signaling and their specified family member activation with respect to stimuli. Furthermore, we have categorized their regulated gene expressions and their function in radiation response or modulation. In addition, we have discussed some recently developed radiation countermeasures in relation to NF-κB activation

Direct visualization of alpha-synuclein oligomers reveals previously undetected pathology in Parkinson's disease brain

Oligomeric forms of alpha-synuclein are emerging as key mediators of pathogenesis in Parkinson's disease. Our understanding of the exact contribution of alpha-synuclein oligomers to disease is limited by the lack of a technique for their specific detection. We describe a novel method, the alpha-synuclein proximity ligation assay, which specifically recognizes alpha-synuclein oligomers. In a blinded study with post-mortem brain tissue from patients with Parkinson's disease (n = 8, age range 73-92 years, four males and four females) and age- and sex-matched controls (n = 8), we show that the alpha-synuclein proximity ligation assay reveals previously unrecognized pathology in the form of extensive diffuse deposition of alpha-synuclein oligomers. These oligomers are often localized, in the absence of Lewy bodies, to neuroanatomical regions mildly affected in Parkinson's disease. Diffuse alpha-synuclein proximity ligation assay signal is significantly more abundant in patients compared to controls in regions including the cingulate cortex (1.6-fold increase) and the reticular formation of the medulla (6.5-fold increase). In addition, the alpha-synuclein proximity ligation assay labels very early perikaryal aggregates in morphologically intact neurons that may precede the development of classical Parkinson's disease lesions, such as pale bodies or Lewy bodies. Furthermore, the alpha-synuclein proximity ligation assay preferentially detects early-stage, loosely compacted lesions such as pale bodies in patient tissue, whereas Lewy bodies, considered heavily compacted late lesions are only very exceptionally stained. The alpha-synuclein proximity ligation assay preferentially labels alpha-synuclein oligomers produced in vitro compared to monomers and fibrils, while stained oligomers in human brain display a distinct intermediate proteinase K resistance, suggesting the detection of a conformer that is different from both physiological, presynaptic alpha-synuclein (proteinase K-sensitive) and highly aggregated alpha-synuclein within Lewy bodies (proteinase K-resistant). These disease-associated conformers represent previously undetected Parkinson's disease pathology uncovered by the alpha-synuclein proximity ligation assay.

Dual agonist occupancy of AT1-R-α2C-AR heterodimers results in atypical Gs-PKA signaling

Hypersecretion of norepinephrine (NE) and angiotensin II (AngII) is a hallmark of major prevalent cardiovascular diseases that contribute to cardiac pathophysiology and morbidity. Herein, we explore whether heterodimerization of presynaptic AngII AT1 receptor (AT1-R) and NE α2C-adrenergic receptor (α2C-AR) could underlie their functional cross-talk to control NE secretion. Multiple bioluminescence resonance energy transfer and protein complementation assays allowed us to accurately probe the structures and functions of the α2C-AR-AT1-R dimer promoted by ligand binding to individual protomers. We found that dual agonist occupancy resulted in a conformation of the heterodimer different from that induced by active individual protomers and triggered atypical Gs-cAMP-PKA signaling. This specific pharmacological signaling unit was identified in vivo to promote not only NE hypersecretion in sympathetic neurons but also sympathetic hyperactivity in mice. Thus, we uncovered a new process by which GPCR heterodimerization creates an original functional pharmacological entity and that could constitute a promising new target in cardiovascular therapeutics.

From molecular classification to targeted therapeutics: the changing face of systemic therapy in metastatic gastroesophageal cancer

Histological classification of adenocarcinoma or squamous cell carcinoma for esophageal cancer or using the Lauren classification for intestinal and diffuse type gastric cancer has limited clinical utility in the management of advanced disease. Germline mutations in E-cadherin (CDH1) or mismatch repair genes (Lynch syndrome) were identified many years ago but given their rarity, the identification of these molecular alterations does not substantially impact treatment in the advanced setting. Recent molecular profiling studies of upper GI tumors have added to our knowledge of the underlying biology but have not led to an alternative classification system which can guide clinician's therapeutic decisions. Recently the Cancer Genome Atlas Research Network has proposed four subtypes of gastric cancer dividing tumors into those positive for Epstein-Barr virus, microsatellite unstable tumors, genomically stable tumors, and tumors with chromosomal instability. Unfortunately to date, many phase III clinical trials involving molecularly targeted agents have failed to meet their survival endpoints due to their use in unselected populations. Future clinical trials should utilize molecular profiling of individual tumors in order to determine the optimal use of targeted therapies in preselected patients.

A novel phosphatidic acid-protein-tyrosine phosphatase D2 axis is essential for ERBB2 signaling in mammary epithelial cells

We used a loss-of-function screen to investigate the role of classical protein-tyrosine phosphatases (PTPs) in three-dimensional mammary epithelial cell morphogenesis and ERBB2 signaling. The study revealed a novel role for PTPD2 as a positive regulator of ERBB2 signaling. Suppression of PTPD2 attenuated the ERBB2-induced multiacinar phenotype in three-dimensional cultures specifically by inhibiting ERBB2-mediated loss of polarity and lumen filling. In contrast, overexpression of PTPD2 enhanced the ERBB2 phenotype. We also found that a lipid second messenger, phosphatidic acid, bound PTPD2 in vitro and enhanced its catalytic activity. Small molecule inhibitors of phospholipase D (PLD), an enzyme that produces phosphatidic acid in cells, also attenuated the ERBB2 phenotype. Exogenously added phosphatidic acid rescued the PLD-inhibition phenotype, but only when PTPD2 was present. These findings illustrate a novel pathway involving PTPD2 and the lipid second messenger phosphatidic acid that promotes ERBB2 function.

The breast cancer susceptibility FGFR2 provides an alternate mode of HER2 activation

Fibroblast growth factor receptor 2 (FGFR2) has been shown reproducibly in genome-wide association studies to be associated with increased breast cancer risk. Here we show that mouse mammary tumor virus-neu mice develop breast carcinomas with FGFR2 immunoreactivity that parallels HER2 expression. FGFR2 signaling promotes HER2 shedding through the metalloprotease ADAM10 leading to intracellular accumulation of the truncated p95HER2 protein. This is accompanied by enhanced HER2 signaling and diminished sensitivity to trastuzumab. Functionally, FGFR2 facilitates HER2-mediated cell proliferation, acinar growth in three-dimensional morphogenesis assays and promotes tumor progression in mouse xenografts. These data implicate FGFR2 in a novel mechanism of ErbB activation and demonstrate an important interaction between FGFR2 and HER2 in promoting breast cancer progression.Oncogene advance online publication, 2 February 2015; doi:10.1038/onc.2014.440.

A novel assay reveals preferential binding between Rabs, kinesins, and specific endosomal subpopulations

A novel assay based on expressing FRB-tagged candidate vesicle-binding protein reveals that KIF13A and KIF13B bind preferentially to early endosomes, whereas KIF1A and KIF1Bβ bind preferentially to late endosomes and lysosomes.

Identifying the proteins that regulate vesicle trafficking is a fundamental problem in cell biology. In this paper, we introduce a new assay that involves the expression of an FKBP12-rapamycin–binding domain–tagged candidate vesicle-binding protein, which can be inducibly linked to dynein or kinesin. Vesicles can be labeled by any convenient method. If the candidate protein binds the labeled vesicles, addition of the linker drug results in a predictable, highly distinctive change in vesicle localization. This assay generates robust and easily interpretable results that provide direct experimental evidence of binding between a candidate protein and the vesicle population of interest. We used this approach to compare the binding of Kinesin-3 family members with different endosomal populations. We found that KIF13A and KIF13B bind preferentially to early endosomes and that KIF1A and KIF1Bβ bind preferentially to late endosomes and lysosomes. This assay may have broad utility for identifying the trafficking proteins that bind to different vesicle populations.

Dimerization drives EGF receptor endocytosis through two sets of compatible endocytic codes

We have shown that epidermal growth factor (EGF) receptor (EGFR) endocytosis is controlled by EGFR dimerization. However, it is not clear how the dimerization drives receptor internalization. We propose that EGFR endocytosis is driven by dimerization, bringing two sets of endocytic codes, one contained in each receptor monomer, in close proximity. Here, we tested this hypothesis by generating specific homo- or hetero-dimers of various receptors and their mutants. We show that ErbB2 and ErbB3 homodimers are endocytosis-deficient due to the lack of endocytic codes. Interestingly, EGFR-ErbB2 or EGFR-ErbB3 heterodimers are also endocytosis-deficient. Moreover, the heterodimer of EGFR and the endocytosis-deficient mutant EGFRΔ1005–1017 is also impaired in endocytosis. These results indicate that two sets of endocytic codes are required for receptor endocytosis. We found that an EGFR/PDGFR heterodimer is endocytosis-deficient, although both EGFR and PDGFR homodimers are endocytosis-competent, indicating that two compatible sets of endocytic codes are required. Finally, we found that to mediate the endocytosis of the receptor dimer, the two sets of compatible endocytic codes, one contained in each receptor molecule, have to be spatially coordinated.

Kinome-wide screening of HER2+ breast cancer cells for molecules that mediate cell proliferation or sensitize cells to trastuzumab therapy

Understanding the signaling differences that distinguish human HER2-amplified (HER2-positive (HER2+)) breast cancers from other breast cancer subtypes may help to identify protein drug targets for the specific treatment of HER2+ breast cancers. We performed two kinome-wide small interfering RNA (siRNA) screens on five HER2+ breast cancer cell lines, seven breast cancer cell lines in which HER2 was not amplified and two normal breast cell lines. To pinpoint the main kinases driving HER2 signaling, we performed a comprehensive siRNA screen that identified loss of the HER2/HER3 heterodimer as having the most prominent inhibitory effect on the growth of HER2+ breast cancer cells. In a second siRNA screen focused on identifying genes that could sensitize HER2+ cells to trastuzumab treatment, we found that loss of signaling members downstream of phosphatidylinositol 3 kinase (PI3K) potentiated the growth inhibitory effects of trastuzumab. Loss of HER2 and HER3, as well as proteins involved in mitogenic and environmental stress pathways inhibited the proliferation of HER2+ cells only in the absence of trastuzumab, suggesting that these pathways are inhibited by trastuzumab treatment. Loss of essential G2/M cell cycle mediators or proteins involved in vesicle organization exerted inhibitory effects on HER2+ cell growth that were unaffected by trastuzumab. Furthermore, the use of a sensitization index (SI) identified targeting the PI3K pathway to sensitize to trastuzumab treatment. Antagonism using the SI identified MYO3A, MYO3B and MPZL1 as antagonizers to trastuzumab treatment among HER2+ cell lines. Our results suggest that the dimerization partners of HER2 are important for determining the activation of downstream proliferation pathways. Understanding the complex layers of signaling triggered downstream of HER2 homodimers and heterodimers will facilitate the selection of better targets for combination therapies intended to treat HER2+ breast cancers.

LOXL2 induces aberrant acinar morphogenesis via ErbB2 signaling

INTRODUCTION

Lysyl oxidase-like 2 (LOXL2) is a matrix-remodeling enzyme that has been shown to play a key role in invasion and metastasis of breast carcinoma cells. However, very little is known about its role in normal tissue homeostasis. Here, we investigated the effects of LOXL2 expression in normal mammary epithelial cells to gain insight into how LOXL2 mediates cancer progression.

METHODS

LOXL2 was expressed in MCF10A normal human mammary epithelial cells. The 3D acinar morphogenesis of these cells was assessed, as well as the ability of the cells to form branching structures on extracellular matrix (ECM)-coated surfaces. Transwell-invasion assays were used to assess the invasive properties of the cells. Clinically relevant inhibitors of ErbB2, lapatinib and Herceptin (traztuzumab), were used to investigate the role of ErbB2 signaling in this model. A retrospective study on a previously published breast cancer patient dataset was carried out by using Disease Specific Genomic Analysis (DSGA) to investigate the correlation of LOXL2 mRNA expression level with metastasis and survival of ErbB2-positive breast cancer patients.

RESULTS

Fluorescence staining of the acini revealed increased proliferation, decreased apoptosis, and disrupted polarity, leading to abnormal lumen formation in response to LOXL2 expression in MCF10A cells. When plated onto ECM, the LOXL2-expressing cells formed branching structures and displayed increased invasion. We noted that LOXL2 induced ErbB2 activation through reactive oxygen species (ROS) production, and ErbB2 inhibition by using Herceptin or lapatinib abrogated the effects of LOXL2 on MCF10A cells. Finally, we found LOXL2 expression to be correlated with decreased overall survival and metastasis-free survival in breast cancer patients with ErbB2-positive tumors.

CONCLUSIONS

These findings suggest that LOXL2 expression in normal epithelial cells can induce abnormal changes that resemble oncogenic transformation and cancer progression, and that these effects are driven by LOXL2-mediated activation of ErbB2. LOXL2 may also be a beneficial marker for breast cancer patients that could benefit most from anti-ErbB2 therapy.

Characterization of a new dual-targeting fully human antibody with potent antitumor activity against nasopharyngeal carcinoma

Despite the effectiveness of the anti-EGFR chimeric antibody (mAb), cetuximab, in treating nasopharyngeal carcinoma (NPC), its efficacy remains variable and often modest. In this study, a full human dual targeted anti-EGFR/HER3 antibody, CA1182, was generated from phage display library. CA1182 was as effective as cetuximab or trastuzumab in inhabiting phosphorylation of EGFR or HER2, but it exhibited as much more potent than cetuximab or trastuzumab. Moreover, our studies showed that CA1182 was significantly more effective than cetuximab in prolonging the survival of severe combined immune deficient mice bearing human NPC, suggesting that it might be a promising therapeutic agent for NPC.

RETRACTED: Silencing EGFR/HER3 signaling with a novel anti-EGFR domain II/IV antibody

Dysfunction of the epidermal growth factor receptor (EGFR) family, is the key process in tumorigenesis, and anti-EGFR therapeutic strategies such as cetuximab therapy now are used in the treatment of cancer. However, resistance to cetuximab is commonly reported. Comprehensive blockade of EGFR signaling using different antibodies might be critical to treat cancer effectively and limit drug resistance with potent novel mechanisms. Here, we launch a screen of a phage display library to isolate a novel anti-EGFR antibody, YAH627. YAH627 exhibits superior efficacy in inhibiting EGFR activation, particularly by blocking EGF/HRG-induced EGFR/HER3 heterodimerization and signaling, verifying it as an impressive candidate for clinical translation as a therapeutic antibody. Moreover, we use epitope analysis validates that the epitope of this antibody is within domains II and IV of EGFR and traps EGFR in a silent conformation. Moreover, combining YAH627 with cetuximab produces synergistic antitumor activity in vitro and in vivo. Taken together, our report establishes that YAH627 possesses a novel mechanism of action that, in combination with cetuximab, may achieve clinical efficacy in EGFR-driven cancers.

Lhx3 is required to maintain cancer cell development of high-grade oligodendroglioma

The LHX genes play a substantial role in an amount of adorning processes. Potential roles of LHXs have been accepted and approved in an assortment of neoplastic tissues as bump suppressors or promoters depending on bump cachet and types. The aim of this abstraction was to investigate the action role of LHXs in the animal High-grade Oligodendroglioma (HG-OT). The gene announcement changes of LHXs in HG-OT tissues compared with non-cancerous colorectal tissues were detected using application real-time quantitative about-face transcriptase-polymerase alternation acknowledgment (QRT-PCR) assay and immunohistochemistry. And we articulate the gene LHX3 that was decidedly up-regulated in HG-OT by QRT-PCR assay and immunohistochemistry. Furthermore, it was obvious that LHX3 responds to blight corpuscle admeasurement in vitro and LHX3 announcement activated with animated β-catenin levels in HG-OT and β-catenin action was appropriate for LHX3's oncogenic effects.  Mechanistically, LHX3 facilitates TCF4 to bind to β-catenin and facilitates LHX3/TCF4/β-catenin circuitous and trans-active it's after ambition gene. LHX3 mutations that agitate the LHX3-β-catenin alternation partially anticipate its action in bump cells. All in all, LHX3 is a frequently activated bump apostle that actuates Wnt/β-catenin signaling in blight beef of HG-OT.

Combinatorial immunotherapy of sorafenib and blockade of programmed death-ligand 1 induces effective natural killer cell responses against hepatocellular carcinoma

Sorafenib, a multi-tyrosine kinase inhibitor, is a standard treatment for advanced hepatocellular carcinoma (HCC). Herein, we report that the combinatorial therapy of sorafenib and anti-programmed death-ligand 1 (PD-L1) monoclonal antibody (mAb) can be implemented with good results for HCC. Cancer mouse models were used to evaluate therapeutic efficacy and examine the immunologic mechanisms of the sorafenib/anti-PD-L1 mAb therapy. The combined administration of sorafenib and anti-PD-L1 mAb into tumor-bearing mice generated potent immune responses resulting in the complete eradication or remarkable reduction of tumor growth. In some instances, the sorafenib/anti-PD-L1 mAb therapy induced long-lasting protection against tumor rechallenges. The results indicate that NK cells but not CD4T cells or CD8 cells mediated the therapeutic efficacy of this combinatorial therapy. The overall results suggest that immunotherapy consisting of the combination of sorafenib/anti-PD-L1 mAb could be a promising new approach for treating patients with HCC.

SOX10 is a novel oncogene in hepatocellular carcinoma through Wnt/β-catenin/TCF4 cascade

SOX (high mobility group) genes play an important role in a number of developmental processes. Potential roles of SOXs have been demonstrated in various neoplastic tissues as tumor suppressors or promoters depending on tumor status and types. The aim of this study was to investigate the function role of SOXs in the human hepatocellular carcinoma (HCC). The gene expression changes of SOXs in HCC tissues compared with those in noncancerous hepatic tissues were detected using real-time quantitative reverse transcriptase polymerase chain reaction (QRT-PCR) analysis and immunohistochemistry. In addition, we identified the gene SOX10 that was significantly upregulated in HCC by QRT-PCR analysis and immunohistochemistry. Furthermore, we discovered that SOX10 promoted cancer cell proliferation in vitro, and SOX10 expression correlated with elevated β-catenin levels in HCC, and β-catenin function was required for SOX10's oncogenic effects. Mechanistically, SOX10 facilitates TCF4 to bind to β-catenin and form a stable SOX10/TCF4/β-catenin complex and trans-activate its downstream target gene. SOX10 mutations that disrupt the SOX10-β-catenin interaction partially prevent its function in tumor cells. All in all, SOX10 is a commonly activated tumor promoter that activates Wnt/β-catenin signaling in cancer cells of HCC.

Insights into HER2 signaling from step-by-step optimization of anti-HER2 antibodies

HER2, a ligand-free tyrosine kinase receptor of the HER family, is frequently overexpressed in breast cancer. The anti-HER2 antibody trastuzumab has shown significant clinical benefits in metastatic breast cancer; however, resistance to trastuzumab is common. The development of monoclonal antibodies that have complementary mechanisms of action results in a more comprehensive blockade of ErbB2 signaling, especially HER2/HER3 signaling. Use of such antibodies may have clinical benefits if these antibodies can become widely accepted. Here, we describe a novel anti-HER2 antibody, hHERmAb-F0178C1, which was isolated from a screen of a phage display library. A step-by-step optimization method was employed to maximize the inhibitory effect of this anti-HER2 antibody. Crystallographic analysis was used to determine the three-dimensional structure to 3.5 Å resolution, confirming that the epitope of this antibody is in domain III of HER2. Moreover, this novel anti-HER2 antibody exhibits superior efficacy in blocking HER2/HER3 heterodimerization and signaling, and its use in combination with pertuzumab has a synergistic effect. Characterization of this antibody revealed the important role of a ligand binding site within domain III of HER2. The results of this study clearly indicate the unique potential of hHERmAb-F0178C1, and its complementary inhibition effect on HER2/HER3 signaling warrants its consideration as a promising clinical treatment.

β-Adrenergic receptor-mediated transactivation of epidermal growth factor receptor decreases cardiomyocyte apoptosis through differential subcellular activation of ERK1/2 and Akt

β-Adrenergic receptor (βAR)-mediated transactivation of epidermal growth factor receptor (EGFR) has been shown to relay pro-survival effects via unknown mechanisms. We hypothesized that acute βAR-mediated EGFR transactivation in the heart promotes differential subcellular activation of ERK1/2 and Akt, promoting cell survival through modulation of apoptosis. C57BL/6 mice underwent acute i.p. injection with isoproterenol (ISO)±AG 1478 (EGFR antagonist) to assess the impact of βAR-mediated EGFR transactivation on the phosphorylation of ERK1/2 (P-ERK1/2) and Akt (P-Akt) in distinct cardiac subcellular fractions. Increased P-ERK1/2 and P-Akt were observed in cytosolic, plasma membrane and nuclear fractions following ISO stimulation. Whereas the P-ERK1/2 response was EGFR-sensitive in all fractions, the P-Akt response was EGFR-sensitive only in the plasma membrane and nucleus, results confirmed in primary rat neonatal cardiomyocytes (RNCM). βAR-mediated EGFR-transactivation also decreased apoptosis in serum-depleted RNCM, as measured via TUNEL as well as caspase 3 activity/cleavage, which were sensitive to the inhibition of either ERK1/2 (PD184352) or Akt (LY-294002) signaling. Caspase 3 activity/cleavage was also sensitive to the inhibition of transcription, which, with an increase in nuclear P-ERK1/2 and P-Akt in response to ISO, suggested that βAR-mediated EGFR transactivation may regulate apoptotic gene transcription. An Apoptosis PCR Array identified tnfsf10 (TRAIL) to be altered by ISO in an EGFR-sensitive manner, results confirmed via RT-PCR and ELISA measurement of both membrane-bound and soluble cardiomyocyte TRAIL levels. βAR-mediated EGFR transactivation induces differential subcellular activation of ERK1/2 and Akt leading to increased cell survival through the modulation of caspase 3 activity and apoptotic gene expression in cardiomyocytes.

Spatio-temporally precise activation of engineered receptor tyrosine kinases by light

Receptor tyrosine kinases (RTKs) are a large family of cell surface receptors that sense growth factors and hormones and regulate a variety of cell behaviours in health and disease. Contactless activation of RTKs with spatial and temporal precision is currently not feasible. Here, we generated RTKs that are insensitive to endogenous ligands but can be selectively activated by low-intensity blue light. We screened light-oxygen-voltage (LOV)-sensing domains for their ability to activate RTKs by light-activated dimerization. Incorporation of LOV domains found in aureochrome photoreceptors of stramenopiles resulted in robust activation of the fibroblast growth factor receptor 1 (FGFR1), epidermal growth factor receptor (EGFR) and rearranged during transfection (RET). In human cancer and endothelial cells, light induced cellular signalling with spatial and temporal precision. Furthermore, light faithfully mimicked complex mitogenic and morphogenic cell behaviour induced by growth factors. RTKs under optical control (Opto-RTKs) provide a powerful optogenetic approach to actuate cellular signals and manipulate cell behaviour.

Mutational and expressional analysis of ERBB3 gene in common solid cancers

ERBB3 is a member of EGFR family receptor tyrosine kinases, genetic alterations of which are common and therapeutically targeted in human cancers. Recently, somatic mutations of ERBB3 gene, including recurrent mutation in exon 3 altering Val104, were reported in gastric cancers (GC) and colorectal cancers (CRC), strongly suggesting its role in the development of GC and CRC. To examine whether the recurrent ERBB3 mutations of exon 3 occur in GC and CRC, and other malignancies as well, we analyzed the ERBB3 in 1677 cancer tissues by a single-strand conformation polymorphism (SSCP) assay. We identified ERBB3 mutations altering the Val104 mutations in GC (0.5%) and CRC (2.2%). However, we did not find the ERBB3 mutations in the other cancers besides GC and CRC. We observed that an increased intensity of phosphorylated ERBB3 (pERBB3) in GC and CRC. Of note, all of the cancers with ERBB3 mutations displayed an increased intensity of pERBB3 immunostaining. Our data indicate that the recurrent ERBB3 mutations altering Val104 occur predominantly in GC and CRC. Also, the data suggest that ERBB3 is altered in GC and CRC by various ways, including somatic mutations and increased expression that might play roles in tumorigenesis.

Light-inducible receptor tyrosine kinases that regulate neurotrophin signalling

Receptor tyrosine kinases (RTKs) are a family of cell-surface receptors that have a key role in regulating critical cellular processes. Here, to understand and precisely control RTK signalling, we report the development of a genetically encoded, photoactivatable Trk (tropomyosin-related kinase) family of RTKs using a light-responsive module based on Arabidopsis thaliana cryptochrome 2. Blue-light stimulation (488 nm) of mammalian cells harbouring these receptors robustly upregulates canonical Trk signalling. A single light stimulus triggers transient signalling activation, which is reversibly tuned by repetitive delivery of blue-light pulses. In addition, the light-provoked process is induced in a spatially restricted and cell-specific manner. A prolonged patterned illumination causes sustained activation of extracellular signal-regulated kinase and promotes neurite outgrowth in a neuronal cell line, and induces filopodia formation in rat hippocampal neurons. These light-controllable receptors are expected to create experimental opportunities to spatiotemporally manipulate many biological processes both in vitro and in vivo.

Neuregulin-ErbB4 signaling in the developing lung alveolus: a brief review

Lung immaturity is the major cause of morbidity and mortality in premature infants, especially those born <28 weeks gestation. Proper lung development from 23-28 weeks requires coordinated cell proliferation and differentiation. Infants born at this age are at high risk for respiratory distress syndrome (RDS), a lung disease characterized by insufficient surfactant production due to immaturity of the alveoli and its constituent cells in the lung. The ErbB4 receptor and its stimulation by neuregulin (NRG) plays a critical role in surfactant synthesis by alveolar type II epithelial cells. In this review, we first provide an introduction to normal human alveolar development, followed by a discussion of the neuregulin and ErbB4-mediated mechanisms regulating alveolar development and surfactant production.

Plasma membrane phosphoinositide balance regulates cell shape during Drosophila embryo morphogenesis

The ratio of different phosphoinositide species coordinates actomyosin contractility and plasma membrane expansion during tissue morphogenesis, thus ensuring proper cell shape.

Remodeling of cell shape during morphogenesis is driven by the coordinated expansion and contraction of specific plasma membrane domains. Loss of this coordination results in abnormal cell shape and embryonic lethality. Here, we show that plasma membrane lipid composition plays a key role in coordinating plasma membrane contraction during expansion. We found that an increase in PI(4,5)P₂ levels caused premature actomyosin contraction, resulting in the formation of shortened cells. Conversely, acute depletion of PI(4,5)P₂ blocked plasma membrane expansion and led to premature actomyosin disassembly. PI(4,5)P₂-mediated contractility is counteracted by PI(3,4,5)P₃ and the zygotic gene bottleneck, which acts by limiting myosin recruitment during plasma membrane expansion. Collectively, these data support a model in which the ratio of PI(4,5)P₂/PI(3,4,5)P₃ coordinates actomyosin contractility and plasma membrane expansion during tissue morphogenesis, thus ensuring proper cell shape.

Pharmacologically controlled protein switch for ON-OFF regulation of growth factor activity

The precise manipulation of growth factor signaling is central to the progress of tissue engineering. Methods for direct time-resolved activation of signaling pathways through controlled receptor dimerization have been reported; however, these suffer from the risks associated with gene transfer. Here we present an alternative gene transfer-free approach in the form of a protein switch featuring pharmacologically controlled ON-OFF regulation of growth factor activity. The reversible operation of the switch enables stimulation of target processes within a defined period of time. The protein switch provides a means for both studying and manipulating signaling processes, and is thus believed to be a valuable tool for basic research as well as tissue engineering and biomedical applications.

SOX2 oncogenes amplified and operate to activate AKT signaling in gastric cancer and predict immunotherapy responsiveness

INTRODUCTION

Gastric cancer is the second leading cause of cancer mortality in the world. Whether the oncogene, amplified on chromosome 3q26, SOX2, a master transcriptional regulator of stemness, operate to drive strong growth phenotype in gastric cancer were unknown.

MATERIALS AND METHODS

The gene expression changes of SOX2 in human gastric cancer tissues compared with non-cancerous tissues was detected using real-time quantitative reverse transcriptase-polymerase chain reaction (QRT-PCR) analysis and immunohistochemistry, which identified the gene overexpression of SOX2 in gastric cancer. Moreover, we discovered that SOX2 promoted cancer cell proliferation in vitro/vivo and SOX2 expression correlated with elevated AKT phosphorylation in gastric cancer, while the AKT phosphorylation was required for SOX2's oncogenic effects. Next, our data point to the usefulness of SOX2 overexpression, as a new predictive marker for responsiveness to trastuzumab.

CONCLUSION

SOX2 is a commonly activated tumor promoter that activate AKT signaling in gastric cancer and a new predictive marker for targeted therapy.

The composition of EphB2 clusters determines the strength in the cellular repulsion response

Graded responses to cell–cell repulsion signals mediated by Ephrin–Eph receptor interactions are specified by EphB2 cluster composition, such that the relative abundance of inactive dimers and active higher-order clusters determines the strength of the repulsive response.

Trans interactions of erythropoietin-producing human hepatocellular (Eph) receptors with their membrane-bound ephrin ligands generate higher-order clusters that can form extended signaling arrays. The functional relevance of the cluster size for repulsive signaling is not understood. We used chemical dimerizers and fluorescence anisotropy to generate and visualize specific EphB2 cluster species in living cells. We find that cell collapse responses are induced by small-sized EphB2 clusters, suggesting that extended EphB2 arrays are dispensable and that EphB2 activation follows an ON–OFF switch with EphB2 dimers being inactive and trimers and tetramers being fully functional. Moreover, the strength of the collapse response is determined by the abundance of multimers over dimers within a cluster population: the more dimers are present, the weaker the response. Finally, we show that the C-terminal modules of EphB2 have negative regulatory effects on ephrin-induced clustering. These results shed new light on the mechanism and regulation of EphB2 activation and provide a model on how Eph signaling translates into graded cellular responses.

Endocytosis and cancer

Endocytosis entails selective packaging of cell-surface proteins, such as receptors for cytokines and adhesion components, in cytoplasmic vesicles (endosomes). The series of sorting events that determines the fate of internalized proteins, either degradation in lysosomes or recycling back to the plasma membrane, relies on intrinsic sequence motifs, posttranslational modifications (e.g., phosphorylation and ubiquitination), and transient assemblies of both Rab GTPases and phosphoinositide-binding proteins. This multicomponent process is enhanced and skewed in cancer cells; we review mechanisms enabling both major drivers of cancer, p53 and Ras, to bias recycling of integrins and receptor tyrosine kinases (RTKs). Likewise, cadherins and other junctional proteins of cancer cells are constantly removed from the cell surface, thereby disrupting tissue polarity and instigating motile phenotypes. Mutant forms of RTKs able to evade Cbl-mediated ubiquitination, along with overexpression of the wild-type forms and a variety of defective feedback regulatory loops, are frequently detected in tumors. Finally, we describe pharmacological attempts to harness the peculiar endocytic system of cancer, in favor of effective patient treatment.