Adaptable interaction between aquaporin-1 and band 3 reveals a potential role of water channel in blood CO2 transport.

Human CO2 respiration requires rapid conversion between CO2 and HCO3- Carbonic anhydrase II facilitates this reversible reaction inside red blood cells, and band 3 [anion exchanger 1 (AE1)] provides a passage for HCO3- flux across the cell membrane. These 2 proteins are core components of the CO2 transport metabolon. Intracellular H2O is necessary for CO2/HCO3- conversion. However, abundantly expressed aquaporin 1 (AQP1) in erythrocytes is thought not to be part of band 3 complexes or the CO2 transport metabolon. To solve this conundrum, we used Förster resonance energy transfer (FRET) measured by fluorescence lifetime imaging (FLIM-FRET) and identified interaction between aquaporin-1 and band 3 at a distance of 8 nm, within the range of dipole-dipole interaction. Notably, their interaction was adaptable to membrane tonicity changes. This suggests that the function of AQP1 in tonicity response could be coupled or correlated to its function in band 3-mediated CO2/HCO3- exchange. By demonstrating AQP1 as a mobile component of the CO2 transport metabolon, our results uncover a potential role of water channel in blood CO2 transport and respiration.-Hsu, K., Lee, T.-Y., Periasamy, A., Kao, F.-J., Li, L.-T., Lin, C.-Y., Lin, H.-J., Lin, M. Adaptable interaction between aquaporin-1 and band 3 reveals a potential role of water channel in blood CO2 transport.

Silencing survivin activates autophagy as an alternative survival pathway in HCC cells.

Autophagy is a survival mechanism that is activated in response to nutrient deprivation. The link between aberrant autophagy and cancer has been increasingly recognized. Survivin, an anti-apoptotic molecule, and the autophagy pathway are correlated with therapeutic responses to cancer. However, the role of autophagy in cancer progression remains unclear. Here, we generated survivin knockdown cells (survivin-KD) by introducing a short interfering RNA (siRNA) into hepatocellular carcinoma (HCC) cells, and we observed a 20 % reduction in the survival of these survivin-KD cells, as determined by MTT assay. In addition, an increased number of stress granules, increased positive staining by acridine orange and a shift in the high side scatter (SSC) cell population in flow cytometry analysis were observed in survivin-KD cells. Furthermore, electron microscopy revealed an increased number of autophagosomes in survivin-KD cells compared with scrambled control cells. Finally, we treated cells with an autophagy inhibitor, 3-MA, and observed a decrease in cell survival in survivin-KD cells compared with scrambled control cells. Our study suggests that an autophagy signal may be activated after the anti-apoptotic molecule survivin is suppressed. This finding implies that autophagy may be an alternative survival pathway in HCC cells and may provide a basis for the development of new therapeutic strategies for HCC.

Human Pompe disease-induced pluripotent stem cells for pathogenesis modeling, drug testing and disease marker identification.

Pompe disease is caused by autosomal recessive mutations in the acid alpha-glucosidase (GAA) gene, which encodes GAA. Although enzyme replacement therapy has recently improved patient survival greatly, the results in skeletal muscles and for advanced disease are still not satisfactory. Here, we report the derivation of Pompe disease-induced pluripotent stem cells (PomD-iPSCs) from two patients with different GAA mutations and their potential for pathogenesis modeling, drug testing and disease marker identification. PomD-iPSCs maintained pluripotent features and had low GAA activity and high glycogen content. Cardiomyocyte-like cells (CMLCs) differentiated from PomD-iPSCs recapitulated the hallmark Pompe disease pathophysiological phenotypes, including high levels of glycogen and multiple ultrastructural aberrances. Drug rescue assessment showed that exposure of PomD-iPSC-derived CMLCs to recombinant human GAA reversed the major pathologic phenotypes. Furthermore, l-carnitine treatment reduced defective cellular respiration in the diseased cells. By comparative transcriptome analysis, we identified glycogen metabolism, lysosome and mitochondria-related marker genes whose expression robustly correlated with the therapeutic effect of drug treatment in PomD-iPSC-derived CMLCs. Collectively, these results demonstrate that PomD-iPSCs are a promising in vitro disease model for the development of novel therapeutic strategies for Pompe disease.

Correlations between cytoplasmic CSE1L in neoplastic colorectal glands and depth of tumor penetration and cancer stage.

BACKGROUND: Colorectal carcinomas spread easily to nearby tissues around the colon or rectum, and display strong potential for invasion and metastasis. CSE1L, the chromosome segregation 1-like protein, is implicated in cancer progression and is located in both the cytoplasm and nuclei of tumor cells. We investigated the prognostic significance of cytoplasmic vs. nuclear CSE1L expression in colorectal cancer. METHODS: The invasion- and metastasis-stimulating activities of CSE1L were studied by in vitro invasion and animal experiments. CSE1L expression in colorectal cancer was assayed by immunohistochemistry, with tissue microarray consisting of 128 surgically resected specimens; and scored using a semiquantitative method. The correlations between CSE1L expression and clinicopathological parameters were analyzed. RESULTS: CSE1L overexpression was associated with increased invasiveness and metastasis of cancer cells. Non-neoplastic colorectal glands showed minimal CSE1L staining, whereas most colorectal carcinomas (99.2%, 127/128) were significantly positive for CSE1L staining. Cytoplasmic CSE1L was associated with cancer stage (P=0.003) and depth of tumor penetration (P=0.007). Cytoplasmic CSE1L expression also correlated with lymph node metastasis of the disease in Cox regression analysis CONCLUSIONS: CSE1L regulates the invasiveness and metastasis of cancer cells, and immunohistochemical analysis of cytoplasmic CSE1L in colorectal tumors may provide a useful aid to prognosis.

CSE1L, a novel microvesicle membrane protein, mediates Ras-triggered microvesicle generation and metastasis of tumor cells.

Tumor-derived microvesicles are rich in metastasis-related proteases and play a role in the interactions between tumor cells and tumor microenvironment in tumor metastasis. Because shed microvesicles may remain in the extracellular environment around tumor cells, the microvesicle membrane protein may be the potential target for cancer therapy. Here we report that chromosome segregation 1-like (CSE1L) protein is a microvesicle membrane protein and is a potential target for cancer therapy. v-H-Ras expression induced extracellular signal-regulated kinase (ERK)-dependent CSE1L phosphorylation and microvesicle biogenesis in various cancer cells. CSE1L overexpression also triggered microvesicle generation, and CSE1L knockdown diminished v-H-Ras-induced microvesicle generation, matrix metalloproteinase (MMP)-2 and MMP-9 secretion and metastasis of B16F10 melanoma cells. CSE1L was preferentially accumulated in microvesicles and was located in the microvesicle membrane. Furthermore, anti-CSE1L antibody-conjugated quantum dots could target tumors in animal models. Our findings highlight a novel role of Ras-ERK signaling in tumor progression and suggest that CSE1L may be involved in the "early" and "late" metastasis of tumor cells in tumorigenesis. Furthermore, the novel microvesicle membrane protein, CSE1L, may have clinical utility in cancer diagnosis and targeted cancer therapy.

Survivin-mediated therapeutic efficacy of gemcitabine through glucose-regulated protein 78 in hepatocellular carcinoma.

BACKGROUND: Survivin is an antiapoptotic molecule that is widely expressed in cancers, including hepatocellular carcinoma (HCC). Survivin has become a general therapeutic target for cancers because of its selective overexpression in a majority of tumors. However, little is known regarding the effect of survivin expression in combination with gemcitabine on HCC. METHODS: We generated survivin knockdown cells (survivin-KD) via a short interfering RNA (siRNA) technique. The antiproliferation effects of gemcitabine were determined by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, TUNEL (terminal deoxynucleotidyl transferase dUTP nick-end labeling) assay, and cell cycle evaluation. RESULTS: According to the MTT assay, we found that survivin-KD cells were more sensitive than parental cells and scrambled control cells to gemcitabine treatment. The apoptotic cell population increased in survivin-KD cells that were treated with gemcitabine in comparison to scrambled control cells, as observed by the cell cycle distribution and TUNEL assays. We found that survivin knockdown resulted in a reduction of glucose-regulated protein 78 (GRP78), which may be responsible for the observed increased survivin-KD cell sensitivity to gemcitabine. CONCLUSIONS: We conclude that survivin knockdown may contribute to a therapeutic effect of gemcitabine through GRP78 on HCC cells.

Heat-induced antigen retrieval applied in zebrafish: whole-mount in situ immunofluorescence microscopy.

Whole-mount immunofluorescence technique provides a way to reveal integrated expression patterns of biological molecules in individuals. Well-documented morphological preservation ability in biology makes aldehydes the fixative of choice. Cross-linking among biocomponents and aldehydes is the key for maintaining morphology but masks the biological molecules for immunodetection. This study performs an easily accessible method by applying heat-induced retrieval, which can rescue the antigenicity of the proteins and also enhance the labeling sensitivity of the fluorescence dye in overfixed zebrafish embryos. The results show that the immunoreactivities of antibodies to myosin in the muscles, green fluorescent protein in the blood vessels and the nuclei in the cells can be recovered significantly, and the morphology of the zebrafish embryos, even the fragile mutants, is at the same time well maintained. Therefore, we provide a choice for antigen retrieval, which is effective for whole-mount immunofluorescence microscopy.

Increased cellular apoptosis susceptibility (CSE1L/CAS) protein expression promotes protrusion extension and enhances migration of MCF-7 breast cancer cells.

Microtubules are part of cell structures that play a role in regulating the migration of cancer cells. The cellular apoptosis susceptibility (CSE1L/CAS) protein is a microtubule-associated protein that is highly expressed in cancer. We report here that CSE1L regulates the association of α-tubulin with ß-tubulin and promotes the migration of MCF-7 breast cancer cells. CSE1L was associated with α-tubulin and ß-tubulin in GST (glutathione S-transferase) pull-down and immunoprecipitation assays. CSE1L-GFP (green fluorescence protein) fusion protein experiments showed that the N-terminal of CSE1L interacted with microtubules. Increased CSE1L expression resulted in decreased tyrosine phosphorylation of α-tubulin and ß-tubulin, increased α-tubulin and ß-tubulin association, and enhanced assembly of microtubules. Cell protrusions or pseudopodia are temporary extensions of the plasma membrane and are implicated in cancer cell migration and invasion. Increased CSE1L expression increased the extension of MCF-7 cell protrusions. In vitro migration assay showed that enhanced CSE1L expression increased the migration of MCF-7 cells. Our results indicate that CSE1L plays a role in regulating the extension of cell protrusions and promotes the migration of cancer cells.

In vitro Neuromuscular Junction Induced from Human Induced Pluripotent Stem Cells.

The neuromuscular junction (NMJ) is a specialized synapse that transmits action potentials from the motor neuron to skeletal muscle for mechanical movement. The architecture of the NMJ structure influences the functions of the neuron, the muscle and the mutual interaction. Previous studies have reported many strategies by co-culturing the motor neurons and myotubes to generate NMJ in vitro with complex induction process and long culture period but have struggled to recapitulate mature NMJ morphology and function. Our in vitro NMJ induction system is constructed by differentiating human iPSC in a single culture dish. By switching the myogenic and neurogenic induction medium for induction, the resulting NMJ contained pre- and post- synaptic components, including motor neurons, skeletal muscle and Schwann cells in the one month culture. The functional assay of NMJ also showed that the myotubes contraction can be triggered by Ca++ then inhibited by curare, an acetylcholine receptor (AChR) inhibitor, in which the stimulating signal is transmitted through NMJ. This simple and robust approach successfully derived the complex structure of NMJ with functional connectivity. This in vitro human NMJ, with its integrated structures and function, has promising potential for studying pathological mechanisms and compound screening.

iPSC-derived functional human neuromuscular junctions model the pathophysiology of neuromuscular diseases.

The control of voluntary skeletal muscle contraction relies on action potentials, which send signals from the motor neuron through the neuromuscular junction (NMJ). Although dysfunction of the NMJ causes various neuromuscular diseases, a reliable in vitro system for disease modeling is currently unavailable. Here, we present a potentially novel 2-step, self-organizing approach for generating in vitro human NMJs from human induced pluripotent stem cells. Our simple and robust approach results in a complex NMJ structure that includes functional connectivity, recapitulating in vivo synapse formation. We used these in vitro NMJs to model the pathological features of spinal muscular atrophy, revealing the developmental and functional defects of NMJ formation and NMJ-dependent muscular contraction. Our differentiation system is therefore useful for investigating and understanding the physiology and pathology of human NMJs.

Localization and characterization of a novel secreted protein SCUBE1 in human platelets.

OBJECTIVE: The aim of the study was to investigate the protein expression and function of a novel secreted protein in the vascular system, named SCUBE1 for signal peptide, CUB (Complement proteins C1r/C1s, Uegf, and Bmp1) and epidermal growth factor-like (EGF)-like domain containing protein 1. METHODS AND RESULTS: Immunohistochemical analysis demonstrated that the SCUBE1 staining is mainly confined to the intravascular platelet-rich thrombus in vascular tissue samples. While quantitative real-time RT-PCR verified that the SCUBE1 mRNA is expressed in human platelets, numerous immunolocalization techniques revealed that the preformed SCUBE1 protein is stored in the alpha-granules and translocated to the surface upon platelet stimulation. A smaller SCUBE1 fragment, possibly formed by limited proteolysis after being released from the storage granules, was detected in thrombus lysate by Western blot analysis. Interestingly, deposition of SCUBE1 into the subendothelial matrix of the atherosclerotic plaques was evidenced by immunohistochemistry. In addition, studies of platelet adhesion and ristocetin-induced platelet agglutination showed that fragments containing the amino-terminal EGF-like repeats were able to support platelet adhesion and enhance the ristocetin-induced platelet agglutination, respectively. CONCLUSION: These data suggest that platelet-derived SCUBE1 could function as a novel adhesive molecule and its matrix-bound and soluble fragments may play critical (patho)physiological roles in cardiovascular biology.

Interaction of glycosphingolipids GD3 and GD2 with growth factor receptors maintains breast cancer stem cell phenotype.

Many studies have suggested that disialogangliosides, GD2 and GD3, are involved in the development of various tumor types. However, the functional relationships between ganglioside expression and cancer development or aggressiveness are not fully described. GD3 is upregulated in approximately half of all invasive ductal breast carcinoma cases, and enhanced expression of GD3 synthase (GD3S, alpha-N-acetylneuraminide alpha-2,8-sialyltransferase) in estrogen receptor-negative breast tumors, was shown to correlate with reduced overall patient survival. We previously found that GD2 and GD3, together with their common upstream glycosyltransferases, GD3S and GD2/GM2 synthase, maintain a stem cell phenotype in breast cancer stem cells (CSCs). In the current study, we demonstrate that GD3S alone can sustain CSC properties and also promote malignant cancer properties. Using MALDI-MS and flow cytometry, we found that breast cancer cell lines, of various subtypes with or without ectopic GD3S-expression, exhibited distinct GD2/GD3 expression profiles. Furthermore, we found that GD3 was associated with EGFR and activated EGFR signaling in both breast CSCs and breast cancer cell lines. In addition, GD3S knockdown enhanced cytotoxicity of the EGFR-inhibitor gefitinib in resistant MDA-MB468 cells, both in vitro and in vivo. Based on this evidence, we propose that GD3S contributes to gefitinib-resistance in EGFR-positive breast cancer cells and may be an effective therapeutic target in drug-resistant breast cancers.

Study of subcellular dynamics on cell-substrate interactions by live cell imaging.

Cellular adhesiveness to biomaterial is one of the important properties for the success of tissue engineering. The cell-biomaterial interactions involve close cooperation of adhesion proteins, plasma membrane, and cytoskeletons to form focal adhesions during the process of anchoring. Dynamic development of the plasma membrane in the process reflects the cellular biocompatibility and motility. The process of cell attachment beginning from seeding, contact, attachment, and spreading has not been investigated. In this study, we monitored the whole process of cells attaching to the substrate surface by time-lapse confocal microscopy. We observed that the surface configuration of the substratum effects plasma membrane expansion and genomic materials distribution. In contrast to the cells grown on the plate, the cells attached on pillars are with rounded nuclei and with prominent lamellipodia spreading out. Membrane expansion is involved in dynamic development of the plasma membrane and lamellipodia formation for attachment, migration, or proliferation and reflects the cellular physiology status of the cells. This study provides a platform for investigation of cell behavior and dynamic development of subcellular structures regarding cell-biomaterial interactions.

Three dimensional chitosan scaffolds influence the extra cellular matrix expression in Schwann cells.

Chitosan is a choice material for scaffolds in regenerative medicine. One of the applications is to bridge the damaged peripheral nerves. Previous studies showed that combination of chitosan conduits and cultured Schwann cells could increase the opportunity for re-connection of broken nerves. It has also been known that Schwann cells can produce the ECM components which are critical for nerve regeneration. In this study, we used the rat Schwann cells (RSCs) grown on porous chitosan scaffolds for quantitative analysis of ECM protein expression. The RSCs grown on chitosan scaffolds secreted higher amount of laminin and collagen 4 than those grown on the plane. The increased laminin and collagen 4 produced by Schwann cells could create a preferable condition for stimulating peripheral nerve regeneration.

CHC promotes tumor growth and angiogenesis through regulation of HIF-1α and VEGF signaling.

Pancreatic adenocarcinoma is an aggressive disease with a high mortality rate. In this study, we have newly generated a monoclonal antibody (mAb), Pa65-2, which specifically binds to pancreatic cancer cells and tumor blood vessels. The target protein of Pa65-2 is identified as human clathrin heavy chain (CHC). In vitro and In vivo study showed that suppression of CHC either by shRNA or by Pa65-2 inhibited tumor growth and angiogenesis. One of the key functions of CHC was to bind with the hypoxia-inducing factor (HIF)-1α protein, increasing the stability of this protein and facilitating its nuclear translocation, thereby regulating the expression of VEGF. Taken together, our findings indicate that CHC plays a role in the processes of tumorigenesis and angiogenesis. Pa65-2 antibody or CHC shRNA can potentially be used for pancreatic cancer therapy.

CSE1L modulates Ras-induced cancer cell invasion: correlation of K-Ras mutation and CSE1L expression in colorectal cancer progression.

BACKGROUND: Ras plays an important role in colorectal cancer progression. CSE1L (chromosome segregation 1-like) gene maps to 20q13, a chromosomal region that correlates with colorectal cancer development. We investigated the association of CSE1L with Ras in colorectal cancer progression. METHODS: The effect of CSE1L on metastasis-stimulating activity of Ras was studied in an animal model with tumor cells expressing CSE1L-specific shRNA and v-H-Ras. CSE1L expression was evaluated by the immunohistochemical analysis of 127 surgically resected colorectal tumors. K-Ras mutations were analyzed by direct sequencing. RESULTS: CSE1L knockdown reduced Ras-induced metastasis of B16F10 melanoma cells in C57BL/6 mice. v-H-Ras expression altered the cellular trafficking of CSE1L and increased CSE1L secretion. Most colorectal tumors were positive for CSE1L staining (98.4%, 125 of 127). Colorectal tumors with K-Ras mutation or high cytoplasmic CSE1L expression were correlated with T status (depth of tumor penetration; P = .004), stage (P = .004), and lymph node metastasis (P = .019). CONCLUSIONS: CSE1L may be a target for treating Ras-associated tumors. Analysis of K-Ras mutation and CSE1L expression may provide valuable clinical and pathological information to aid in the determination of treatment options for colorectal cancer.

Micropillar substrate influences the cellular attachment and laminin expression.

Fibroblasts alter their mode of attachment and focal contact when placed on square arrays of silicon pillars. The pillars had 1-microm diameters with identical surface chemistry. Distance between pillars is 9 microm and height of pillars is 1, 5, or 10 microm on substrates. We found that these micropillars, rather than specific interactions, provided more opportunities for mechanical interlocking of the fibroblasts and acted as physical barriers that restrained cell migration. The cellular morphology and behavior is guidable by the height of pillars. In some cases, the fibroblasts filled in the intervals among several pillars; in others, a pillar protruded visibly through the cell body but did not pierce it, the cells were survived. Therefore, fibroblasts were immobilized upon in situ and the cytoplasma migrated outward to the bottom of the substrate subsequently. Laminin plays a critical role in cell attachment to the basement membrane. The results of laminin expression in fibroblasts suggest that pillar pattern appears to change cellular behavior and affect laminin expression significantly.

CSE1L/CAS, the cellular apoptosis susceptibility protein, enhances invasion and metastasis but not proliferation of cancer cells.

BACKGROUND: The cellular apoptosis susceptibility (CAS) protein is regarded as a proliferation-associated protein that associates with tumour proliferation as it associates with microtubule and functions in the mitotic spindle checkpoint. However, there is no any actual experimental study showing CAS (or CSE1 and CSE1L) can increase the proliferation of cancer cells. Previous pathological study has reported that CAS was strongly positive stained in all of the metastasis melanoma that be examined. Thus, CAS may regulate the invasion and metastasis of cancers. CAS is highly expressed in cancers; if CAS is associated with cancer proliferation, then increased CAS expression should be able to increase the proliferation of cancer cells. We studied whether increased CAS expression can increase cancer cell proliferation and whether CAS regulates the invasion of cancer cells. METHODS: We enhanced or reduced CAS expression by transfecting CAS or anti-CAS expression vectors into human MCF-7 breast cancer cells. The proliferations of cells were determined by trypan blue exclusion assay and flow cytometry analysis. Invasion of cancer cells were determined by matrigel-based invasion assay. RESULTS: Our studies showed that increased CAS expression was unable to enhance cancer cell proliferation. Immunofluorescence showed CAS was distributed in cytoplasm areas near cell membrane and cell protrusions. CAS was localized in cytoplasmic vesicle and immunogold electronmicroscopy showed CAS was located in vesicle membrane. CAS overexpression enhanced matrix metalloproteinase-2 (MMP-2) secretion and cancer cell invasion. Animal experiments showed CAS reduction inhibited the metastasis of B16-F10 melanoma cells by 56% in C57BL/6 mice. CONCLUSION: Our results indicate that CAS increases the invasion but not the proliferation of cancer cells. Thus, CAS plus ECM-degradation proteinases may be used as the markers for predicting the advance of tumour metastasis.

Activation of metabotropic glutamate receptor 5 is associated with effect of amphetamine on brain neurons.

The role of metabotropic glutamate receptor 5 (mGluR5) was explored in mechanisms underlying the action of amphetamine (AMPH). The activity of mGluR5 was monitored by measuring the level of [3H]inositol monophosphates in brain neurons, in response to stimulation of 2-choloro-5-hydroxyphenylglycine (CHPG), a selective agonist of mGluR5. Treatment with 1 microM of AMPH for 1 h or 7 days increased the CHPG (1 mM, 30 min)-evoked phosphoinositide turnover by 46% or 92% and 26% or 84% in cultured cortical and hippocampal neurons, respectively, from that of CHPG-only treated cells. When AMPH was present during CHPG application post-1 h or 7 day AMPH incubation, the rate of phosphoinositide hydrolysis in cortical neurons became 121% or 142% higher than that treated with CHPG only. The postnatal day (P) 21 (juvenile) and P60 (adult) rats received three intraperitoneal injections of 5 mg/kg of AMPH or saline daily for 6 days. They were challenged on the eighth day with one dosage and sacrificed 3 h later. Reversible 3H-glutamate binding detected increases of 22-89% in the binding levels of cortex and hippocampus of both ages following the AMPH injections. Increases of 13-18% in the levels of mGluR5 mRNA were seen in the juvenile pyramidal neurons of hippocampal CA1-4, granular cells of dentate gyrus, and ventral thalamic nuclei, as shown by in situ hybridization. The AMPH-induced altered activity of mGluR5 is probably associated with changes in the expression of the glutamate receptors, including mGluR5. AMPH may modify the sensitivity of mGluR5 or interact with the receptor itself.