Grb2 dominantly associates with dynamin II in human hepatocellular carcinoma HepG2 cells

Overexpression of cytoplasmic dynamin 2 is associated with worse outcomes in patients with clear cell renal cell carcinoma

BACKGROUND: Dynamin 2 (DNM2) involved in tumor progression in various malignancies. OBJECTIVE: For the first time, we evaluated DNM2 expression pattern, its association with clinicopathological characteristics and survival outcomes in RCC subtypes. METHODS: We evaluated the DNM2 expression pattern in RCC tissues as well as adjacent normal tissue using immunohistochemistry on tissue microarray (TMA) slides. RESULTS: Our findings revealed increased DNM2 expression in RCC samples rather than in adjacent normal tissues. The results indicated that there was a statistically significant difference between cytoplasmic expression of DNM2 among subtypes of RCC in terms of intensity of staining, percentage of positive tumor cells, and H-score (P= 0.024, 0.049, and 0.009, respectively). The analysis revealed that increased cytoplasmic expression of DNM2 in ccRCC is associated with worse OS (log rank: P= 0.045), DSS (P= 0.049), and PFS (P= 0.041). Furthermore, cytoplasmic expression of DNM2 was found as an independent prognostic factor affecting DSS and PFS in multivariate analysis. CONCLUSIONS: Our results indicated that DNM2 cytoplasmic expression is associated with tumor aggressiveness and poor outcomes. DNM2 could serve as a promising prognostic biomarker and therapeutic target in patients with ccRCC.

A review of Dynamin 2 involvement in cancers highlights a promising therapeutic target

Dynamin 2 (DNM2) is an ubiquitously expressed large GTPase well known for its role in vesicle formation in endocytosis and intracellular membrane trafficking also acting as a regulator of cytoskeletons. During the last two decades, DNM2 involvement, through mutations or overexpression, emerged in an increasing number of cancers and often associated with poor prognosis. A wide panel of DNM2-dependent processes was described in cancer cells which explains DNM2 contribution to cancer pathomechanisms. First, DNM2 dysfunction may promote cell migration, invasion and metastasis. Second, DNM2 acts on intracellular signaling pathways fostering tumor cell proliferation and survival. Relative to these roles, DNM2 was demonstrated as a therapeutic target able to reduce cell proliferation, induce apoptosis, and reduce the invasive phenotype in a wide range of cancer cells in vitro. Moreover, proofs of concept of therapy by modulation of DNM2 expression was also achieved in vivo in several animal models. Consequently, DNM2 appears as a promising molecular target for the development of anti-invasive agents and the already provided proofs of concept in animal models represent an important step of preclinical development.

Src homolog and collagen homolog1 isoforms in acute and chronic liver injuries

Src homolog and collagen homolog (SHC) proteins are adaptor proteins bound to cell surface receptors that play an important role in signal transduction and related diseases. As an important member of the SHC protein family, SHC1 regulates cell proliferation and apoptosis, reactive oxygen species (ROS) production, and oxidative stress. Three isomeric proteins namely, p46shc, p52shc, and p66shc, are produced from the same SHC1 gene locus. All the three proteins are found in the liver, and are widely expressed in various hepatic cells. SHC1 has been proven to be associated with acute and chronic liver injuries of different etiologies, and plays important roles in liver fibrosis and hepatocellular carcinoma (HCC). Therefore, this review summarizes recent studies that discuss and explore the role of SHC1 in the occurrence and progression of liver diseases. We also provide a theoretical basis for future studies.

Molecular cloning and characterization of growth factor receptor bound-protein in Clonorchis sinensis

Background

Clonorchis sinensis causes clonorchiasis, a potentially serious disease. Growth factor receptor-bound protein 2 (Grb2) is a cytosolic protein conserved among animals and plays roles in cellular functions such as meiosis, organogenesis and energy metabolism. In the present study, we report first molecular characters of growth factor receptor bound-protein (CsGrb2) from C. sinensis as counter part of Grb2 from animals and its possible functions in development and organogenesis of C. sinensis.

Methodology/Principal Findings

A CsGrb2 cDNA clone retrieved from the C. sinensis transcriptome encoded a polypeptide with a SH3-SH2-SH3 structure. Recombinant CsGrb2 was bacterially produced and purified to homogeneity. Native CsGrb2 with estimated molecular weight was identified from C. sinensis adult extract by western blotting using a mouse immune serum to recombinant CsGrb2. CsGrb2 transcripts was more abundant in the metacercariae than in the adults. Immunohistochemical staining showed that CsGrb2 was localized to the suckers, mesenchymal tissues, sperms in seminal receptacle and ovary in the adults, and abundantly expressed in most organs of the metacercariae. Recombinant CsGrb2 was evaluated to be little useful as a serodiagnostic reagent for C. sinesis human infections.

Conclusion

Grb2 protein found in C. sinensis was conserved among animals and suggested to play a role in the organogenesis, energy metabolism and mitotic spermatogenesis of C. sinensis. These findings from C. sinensis provide wider understanding on diverse function of Grb2 in lower animals such as platyhelminths.

Identification of GRB2 and GAB1 coexpression as an unfavorable prognostic factor for hepatocellular carcinoma by a combination of expression profile and network analysis

Aim

To screen novel markers for hepatocellular carcinoma (HCC) by a combination of expression profile, interaction network analysis and clinical validation.

Methods

HCC significant molecules which are differentially expressed or had genetic variations in HCC tissues were obtained from five existing HCC related databases (OncoDB.HCC, HCC.net, dbHCCvar, EHCO and Liverome). Then, the protein-protein interaction (PPI) network of these molecules was constructed. Three topological features of the network ('Degree', 'Betweenness', and 'Closeness') and the k-core algorithm were used to screen candidate HCC markers which play crucial roles in tumorigenesis of HCC. Furthermore, the clinical significance of two candidate HCC markers growth factor receptor-bound 2 (GRB2) and GRB2-associated-binding protein 1 (GAB1) was validated.

Results

In total, 6179 HCC significant genes and 977 HCC significant proteins were collected from existing HCC related databases. After network analysis, 331 candidate HCC markers were identified. Especially, GAB1 has the highest k-coreness suggesting its central localization in HCC related network, and the interaction between GRB2 and GAB1 has the largest edge-betweenness implying it may be biologically important to the function of HCC related network. As the results of clinical validation, the expression levels of both GRB2 and GAB1 proteins were significantly higher in HCC tissues than those in their adjacent nonneoplastic tissues. More importantly, the combined GRB2 and GAB1 protein expression was significantly associated with aggressive tumor progression and poor prognosis in patients with HCC.

Conclusion

This study provided an integrative analysis by combining expression profile and interaction network analysis to identify a list of biologically significant HCC related markers and pathways. Further experimental validation indicated that the aberrant expression of GRB2 and GAB1 proteins may be strongly related to tumor progression and prognosis in patients with HCC. The overexpression of GRB2 in combination with upregulation of GAB1 may be an unfavorable prognostic factor for HCC.

A simple and reliable protocol for mouse serum proteome profiling studies by use of two-dimensional electrophoresis and MALDI TOF/TOF mass spectrometry

Background

Unravelling the serum proteome is the subject of intensified research. In this regard, two-dimensional electrophoresis coupled with MALDI MS analysis is still one of the most commonly used method. Despite some improvements, there is the need for better protocols to enable comprehensive identification of serum proteins.

Here we report a combination of two proteomic strategies, zoom in acidic and neutral part of 2-D gels and an application of two optimised matrix preparations for MALDI-MS analyses to simplify serum proteome mapping.

Results

Mouse serum proteins were separated by 2-D electrophoresis at the pH ranges 3–10 and 4–7, respectively. Then in gel tryptic digests were analysed by MALDI-MS. Notably, sample-matrix preparations consisted of either a thin-layer α-ciano-4-hydroxycinnamic acid (CHCA) matrix deposition or a matrix-layer 2,5-dihydroxybenzoic acid (DHB). This enabled an identification of 90 proteins. The herein reported method enhanced identification of proteins by 32% when compared with previously published studies of mouse serum proteins, using the same approaches. Furthermore, experimental improvements of matrix preparations enabled automatic identification of mouse proteins, even when one of the two matrices failed.

Conclusion

We report a simple and reliable protocol for serum proteome analysis that combines an optimized resolution of 2-D gels spots and improved sample-matrix preparations for MALDI-MS analysis. The protocol allowed automated data acquisition for both CHCA and DHB and simplified the MS data acquisition therefore avoiding time-consuming procedures. The simplicity and reliability of the developed protocol may be applied universally.

Amyloid Precursor Protein and Presenilin1 Interact with the Adaptor GRB2 and Modulate ERK 1,2 Signaling

The amyloid precursor protein (APP) and the presenilins 1 and 2 are genetically linked to the development of familial Alzheimer disease. APP is a single-pass transmembrane protein and precursor of fibrillar and toxic amyloid-beta peptides, which are considered responsible for Alzheimer disease neurodegeneration. Presenilins are multipass membrane proteins, involved in the enzymatic cleavage of APP and other signaling receptors and transducers. The role of APP and presenilins in Alzheimer disease development seems to be related to the formation of amyloid-beta peptides; however, their physiological function, reciprocal interaction, and molecular mechanisms leading to neurodegeneration are unclear. APP and presenilins are also involved in multiple interactions with intracellular proteins, the significance of which is under investigation. Among the different APP-interacting proteins, we focused our interest on the GRB2 adaptor protein, which connects cell surface receptors to intracellular signaling pathways. In this study we provide evidence by co-immunoprecipitation experiments, confocal and electron microscopy, and by fluorescence resonance energy transfer experiments that both APP and presenilin1 interact with GRB2 in vesicular structures at the centrosome of the cell. The final target for these interactions is ERK1,2, which is activated in mitotic centrosomes in a PS1- and APP-dependent manner. These data suggest that both APP and presenilin1 can be part of a common signaling pathway that regulates ERK1,2 and the cell cycle.

Amyloid precursor protein modulates ERK-1 and -2 signaling

The amyloid precursor protein (APP) is a transmembrane protein with a short cytoplasmic tail whose physiological function is unclear, although it is well documented that the proteolytic processing of APP could influence the development of Alzheimer's disease (AD) through the formation of membrane-bound C-terminal fragments (CTFs) and of beta-amyloid peptides (Abeta). We have recently shown that tyrosine-phosphorylated APP and CTFs may interact with Grb2 and ShcA adaptor proteins and that this coupling occurs at a higher extent in AD subjects only. To study the interaction between APP or CTFs and ShcA/Grb2 and to investigate their molecular target we have used as experimental model two different cell lines: H4 human neuroglioma cells and APP/APLP null mouse embryonic fibroblast cells (MEFs). Here we show that in H4 cells APP interacts with Grb2; conversely in APP/APLP-null MEF cells this interaction is possible only after the reintroduction of human APP by transfection. We have also shown that in MEF cells the transfection of a plasmid encoding for human APP wild-type enhances the phosphorylation of ERK-1 and -2 as revealed by Western blotting and immunofluorescence experiments. Finally, also in H4 cells the overexpression of APP upregulates the levels of phospho-ERK-1 and -2. In summary our data suggest that APP may influence phospho-ERK-1 and -2 signaling through its binding with Grb2 and ShcA adaptors. The meaning of this event is not clear, but APP interaction with these adaptors could be relevant to regulate mitogenic pathway.

Ever-expanding network of dynamin-interacting proteins

Clathrin-mediated endocytosis is a major cellular pathway for internalization of proteins and lipids and for recycling of synaptic vesicles. The GTPase dynamin plays a key role in this process, and the proline-rich domain of dynamin participates in various protein-protein interactions to ensure a proper coordination of endocytic processes. Although dynamin is not directly associated with actin, several dynamin-binding proteins can interact with actin or with proteins that regulate actin assembly, thereby coordinately regulating actin assembly and trafficking events. This article summarizes dynamin interactions with various Src homology 3-containing proteins, many of which are actin-binding proteins. It also discusses the recently identified two new dynamin binding proteins, SH3 protein interacting with Nck, 90 kDa/Wiskott-Aldrich syndrome protein interacting with SH3 protein (SPIN90/WISH) and sorting nexin 9, and outlines their potential role as a link between endocytosis and actin dynamics.

The amyloid precursor protein and its network of interacting proteins: physiological and pathological implications

The amyloid precursor protein (APP) is an ubiquitous receptor-like molecule involved in the pathogenesis of Alzheimer's disease that generates beta-amyloid peptides and causes plaque formation. APP and some of its C-terminal proteolytic fragments (CTFs) have also been shown to be in the center of a complex protein-protein network, where selective phosphorylation of APP C-terminus may regulate the interaction with cytosolic phosphotyrosine binding (PTB) domain or Src homology 2 (SH2) domain containing proteins involved in cell signaling. We have recently described an interaction between tyrosine-phosphorylated CTFs and ShcA adaptor protein which is highly enhanced in AD brain, and a new interaction between APP and the adaptor protein Grb2 both in human brain and in neuroblastoma cultured cells. These data suggest a possible role in cell signaling for APP and its CTFs, in a manner similar to that previously reported for other receptors, through a tightly regulated coupling with intracellular adaptors to control the signaling of the cell. In this review, we discuss the significance of these novel findings for AD development.

Apoptotic Cell Death and Amyloid Precursor Protein Signaling in Neuroblastoma SH-SY5Y Cells

We have recently shown that the amyloid precursor protein (APP) and a subset of its C-terminal fragments (CTFs) are tyrosine phosphorylated in human brain and in cultured cells. Tyrosine phosphorylation generates a substrate that is sequentially bound by the adaptor proteins ShcA and Grb2, and this interaction is significantly enhanced in Alzheimer's disease brains. Here we have studied the APP/CTFs phosphorylation and ShcA activation in a human neuroblastoma cell line, SH-SY5Y, under basal and apoptotic conditions. To commit these cells to apoptosis, we used staurosporin, a well-known apoptotic inducer and protein kinase C blocker. Our data suggest the following: (1) in normally proliferating SH-SY5Y cells, full-length APP is complexed with Grb2[Q3], likely through its SH2 domain; (2) upon induction of apoptosis, APP is degraded and ShcA-Grb2 coimmunoprecipitates with CTFs recognized by anti-APP antibodies; and (3) caspase inhibitors partially block the degradation of APP and the coprecipitation of CTFs with ShcA-Grb2 adaptors. In summary, our data suggest that in SH-SY5Y cells, tyrosine-phosphorylated APP is involved in a complex with ShcA-Grb2 adaptors that is disrupted during apoptosis. The abnormal degradation of APP and consequent increased levels of CTFs (as has been observed in Alzheimer's disease and Down's syndrome) generate a complex between tyrosine-phosphorylated CTFs and intracellular adaptors. The signaling through APP and its CTFs may have significant relevance for apoptotic cell death in Alzheimer's disease.