Analysis Of Cell Surface Proteins Research Articles

Human iPSC-Derived NK Cells with Knock-in of the BCL2 G101V Mutation Are Resistant to Venetoclax and Demonstrate Improved Anti-AML Activity In Vivo

Treatment options for acute myeloid leukemia (AML) patients who are unfit for intensive chemotherapy are limited. Both targeted therapy and cellular therapy have been investigated, typically as separate treatments. For patients with AML unfit for intensive induction chemotherapy, venetoclax, a BCL-2 inhibitor, containing regimens have significantly improved treatment outcomes. However, patients treated long-term with venetoclax can develop resistance. Based on the characterization of the BCL2 G101V mutation that mediates resistance to venetoclax, we investigated the ability of homozygous BCL2 G101V knock-in in induced pluripotent stem cell (iPSC)-derived natural killer (NK) cells to promote resistance to venetoclax in these effector cells to enable concurrent treatment with venetoclax and the engineered iPSC-derived NK cells that we hypothesize will provide improved NK cell-mediated killing of AML. Our group has pioneered the production of genetically modified NK cells from human iPSCs. iPSCs provide an advantage of a stable platform for genome engineering and previous studies demonstrate we can engineer iPSCs to express or delete genes of interest to derive genetically modified iPSC-NK cells with improved anti-tumor activity. To generate iPSC-derived NK cells with resistance to venetoclax, we employed CRISPR-Cas9 technology to knock-in the BCL2 G101V mutation (BCL2 G101V) in iPSCs. iPSCs homozygous for BCL2 G101V were selected and differentiated to NK cells. Homozygous BCL2 G101V engineered iPSC-NK cells demonstrated resistance to venetoclax compared to wildtype (WT) iPSC-NK cells in vitro. BCL2 G101V iPSC-NK cells were 94-fold more resistant to venetoclax compared to wildtype iPSC NK cells with an EC50 of 6018 nM, above the serum levels of patients receiving venetoclax. Analysis of cell surface proteins demonstrated that both sets of iPSC-NK cells had a typical NK cell phenotype with no differences in expression of receptors analyzed. There was no difference seen in cytotoxicity against K562 tumor cells between BCL2 G101V iPSC-NK cells and WT-iPSC NK cells. Additional functional analyses demonstrated that activity of the BCL2 G101V iPSC NK cells was preserved upon exposure to venetoclax. Cytotoxic activity, as measured by CD107a expression on WT iPSC-NK cells stimulated by MOLM13 AML tumors cells, was reduced nearly 3-fold upon addition of venetoclax. In contrast, activation of BCL2 G101V iPSC NK cells was not significantly affected by addition of venetoclax. This resistance to venetoclax was confirmed in longer term 36-hour Incucyte cytotoxicity assays where BCL2 G101V iPSC-NK cells demonstrated more than 10-fold increase in anti-AML activity compared to the WT-iPSC-NK cells. We then conducted in vivo studies to test the WT and engineered NK cells with and without addition of venetoclax in an AML xenograft model using NSG mice (Figure Panels A-D). These studies used MOLM13 AML cells made resistant to venetoclax and demonstrated that without venetoclax treatment, both the WT and the BCL2 G101V iPSC NK cells mediate effective anti-AML killing. With addition of venetoclax, the WT NK cells were unable to effectively kill the AML cells while the BCL2 G101V iPSC cells mediated potent anti-AML activity and demonstrated significantly improved survival when the NK cells are given in combination with venetoclax. Specifically, in this system, the mice treated with WT iPSC-NK cells had a median survival of 22.8 days while the median survival of mice treated with the BCL2 G101V iPSC NK cells was not reached (p<0.01) Intriguingly, BCL2 G101V iPSC NK cells also demonstrated improved activity against MOLM13 cells resistant to venetoclax. Together our results demonstrate that iPSC-NK cells can be engineered to generate venetoclax-resistance for use in combination with concurrent venetoclax therapy to markedly improve treatment of AML. Furthermore, this work demonstrates that novel drug resistance mechanisms can be introduced via genome engineering into iPSC-derived NK cells as a new strategy to produce improved cell products for “off-the-shelf” therapy.

Integrated screens uncover a cell surface tumor suppressor gene KIRREL involved in Hippo pathway

Cell surface proteins play essential roles in various biological processes and are highly related to cancer development. They also serve as important markers for cell identity and targets for pharmacological intervention. Despite their great potentials in biomedical research, comprehensive functional analysis of cell surface proteins remains scarce. Here, with a de novo designed library targeting cell surface proteins, we performed invivo CRISPR screens to evaluate the effects of cell surface proteins on tumor survival and proliferation. We found that Kirrel1 loss markedly promoted tumor growth invivo. Moreover, KIRREL was significantly enriched in a separate CRISPR screen based on a specific Hippo pathway reporter. Further studies revealed that KIRREL binds directly to SAV1 to activate the Hippo tumor suppressor pathway. Together, our integrated screens reveal a cell surface tumor suppressor involved in the Hippo pathway and highlight the potential of these approaches in biomedical research.

Flow Cytometry Analysis of Cell-Surface Markers to Identify Human Naïve Pluripotent Stem Cells.

Cell-surface proteins provide excellent biomarkers to identify specific cell types and resolve heterogeneous cell populations. The analysis of cell-surface proteins by flow cytometry produces robust and quantitative information with single-cell resolution, and allows live target cells to be purified and characterized or re-cultured. Studies using antibody screens, proteomics, and candidate analysis have identified a comprehensive set of proteins that are expressed on the surface of naïve and primed human pluripotent stem cells. These findings have led to the development of suitable protein markers and antibodies to accurately distinguish between these two cell types. Here, a detailed protocol is provided that uses multi-color flow cytometry to analyze cell-surface protein expression in naïve and primed human pluripotent stem cells. This method enables the unambiguous identification of pluripotent cell types and the opportunity to sort target cells including during cell state transitions. The protocol can be combined to additionally investigate the expression of reporter genes and other informative features, such as DNA content.

Longitudinal Large-Scale Semiquantitative Proteomic Data Stability Across Multiple Instrument Platforms.

With the rapid developments in mass spectrometry (MS)-based proteomics methods, label-free semiquantitative proteomics has become an increasingly popular tool for profiling global protein abundances in an unbiased manner. However, the reproducibility of these data across time and LC-MS platforms is not well characterized. Here, we evaluate the performance of three LC-MS platforms (Orbitrap Elite, Q Exactive HF, and Orbitrap Fusion) in label-free semiquantitative analysis of cell surface proteins over a six-year period. Sucrose gradient ultracentrifugation was used for surfaceome enrichment, following gel separation for in-depth protein identification. With our established workflow, we consistently detected and reproducibly quantified >2300 putative cell surface proteins in a human acute myeloid leukemia (AML) cell line on all three platforms. To our knowledge this is the first study reporting highly reproducible semiquantitative proteomic data collection of biological replicates across multiple years and LC-MS platforms. These data provide experimental justification for semiquantitative proteomic study designs that are executed over multiyear time intervals and on different platforms. Multiyear and multiplatform experimental designs will likely enable larger scale proteomic studies and facilitate longitudinal proteomic studies by investigators lacking access to high throughput MS facilities. Data are available via ProteomeXchange with identifier PXD022721.

Clonal evolution of acute myeloid leukemia revealed by high-throughput single-cell genomics

Clonal diversity is a consequence of cancer cell evolution driven by Darwinian selection. Precise characterization of clonal architecture is essential to understand the evolutionary history of tumor development and its association with treatment resistance. Here, using a single-cell DNA sequencing, we report the clonal architecture and mutational histories of 123 acute myeloid leukemia (AML) patients. The single-cell data reveals cell-level mutation co-occurrence and enables reconstruction of mutational histories characterized by linear and branching patterns of clonal evolution, with the latter including convergent evolution. Through xenotransplantion, we show leukemia initiating capabilities of individual subclones evolving in parallel. Also, by simultaneous single-cell DNA and cell surface protein analysis, we illustrate both genetic and phenotypic evolution in AML. Lastly, single-cell analysis of longitudinal samples reveals underlying evolutionary process of therapeutic resistance. Together, these data unravel clonal diversity and evolution patterns of AML, and highlight their clinical relevance in the era of precision medicine.

Glabridin Averts Biofilms Formation in Methicillin-Resistant Staphylococcus aureus by Modulation of the Surfaceome.

Staphylococcus aureus is an opportunistic bacterium of the human body and a leading cause of nosocomial infections. Methicillin resistant S. aureus (MRSA) infections involving biofilm lead to higher mortality and morbidity in patients. Biofilm causes serious clinical issues, as it mitigates entry of antimicrobials to reach the etiological agents. It plays an important role in resilient chronic infections which place an unnecessary burden on antibiotics and the associated costs. To combat drug-resistant infection involving biofilm, there is a need to discover potential anti-biofilm agents. In this study, activity of polyphenolic flavonoid glabridin against biofilm formation of methicillin resistant clinical isolates of S. aureus is being reported for the first time. Crystal violet assay and scanning electron microscopy evidences shows that glabridin prevents formation of cells clusters and attachment of methicillin resistant clinical isolate (MRSA 4423) of S. aureus to the surface in a dose dependent manner. Gel free proteomic analysis of biofilm matrix by LC-ESI-QTOF confirmed the existence of several proteins known to be involved in cells adhesion. Furthermore, expression analysis of cell surface proteins revealed that glabridin significantly down regulates an abundance of several surface-associated adhesins including fibronectin binding proteins (FnbA, FnbB), serine-aspartate repeat-containing protein D (SdrD), immunoglobulin-binding protein G (Sbi), and other virulence factors which were induced by extracellular glucose in MRSA 4423. In addition, several moonlighting proteins (proteins with multiple functions) such as translation elongation factors (EF-Tu, EF-G), chaperone protein (DnaK), glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and pyruvate kinase (PK) were detected on the cell surface wherein their abundance was inversely proportional to surface-associated adhesins. This study clearly suggests that glabridin prevents biofilm formation in S. aureus through modulation of the cell surface proteins.

Aggregation, adhesion and efficacy studies of probiotic candidate Pediococcus acidilactici NCDC 252: a strain of dairy origin.

Aggregation and adhesion capability and survival efficacy of candidate probiotic strain Pediococcus acidilactici NCDC 252 under simulated gastric, intestinal and vaginal conditions was studied. The strain exhibited strong autoaggregation phenotype and coaggregation with other Lactic acid bacteria (LAB) and E. coli. The adhesion studies of NCDC 252 to pig's intestinal epithelial cells showed its adhesive ability. Aggregation and adhesiveness were related through cell surface proteins as removal/extraction of surface proteins resulted in altered aggregation and no adhesiveness. Cell surface proteins were analysed by SDS-PAGE and also in silico analysed from its genome. SDS-PAGE analysis of cell surface proteins of NCDC 252 revealed two potential proteins of approximately 74.3 and 53.6kDa to be involved in host-probiotic interaction. Removal of cell surface proteins by LiCl-treatment (5moll-1) resulted in loss of aggregation and adhesiveness. Further survival of NCDC 252 under simulated gastrointestinal and vaginal conditions in terms of high viable counts confirmed its efficacy for its survival under gut and urogenital conditions. These observations suggest that it can be used further in functional foods, nutraceuticals and in combating urogenital infections. As NCDC 252 was able to survive in intestinal conditions, interaction of its cell surface proteins with intestinal mucins was studied in silico by docking. Highest affinity of adhesion was observed for MUC3B. In conclucion, NCDC 252, exhibited aggregation phenotype and adhesion capability. Survivability of NCDC 252 under simulated conditions and its interaction with human mucins confirms its efficacy to be used as probiotic.

Identification and typing of Vagococcus salmoninarum using genomic and proteomic techniques.

This study reports on the characterization of Vagococcus salmoninarum using phenotypic, serological, antigenic, genetic and proteomic methods. All strains of V.salmoninarum were resistant to most of the antimicrobials tested, and only 10% of strains were sensitive to florfenicol. Serological analysis demonstrated a high antigenic homogeneity within the species. No cross-reaction was detected with other fish pathogenic species causing streptococcosis (Lactococcus garvieae, Streptococcus parauberis, Streptococcus iniae, Streptococcus agalactiae, Carnobacterium maltaromaticum) using serum against V.salmoninarum CECT 5810. Electrophoretic analysis of cell surface proteins and immunoblot supported the antigenic homogeneity within V.salmoninarum strains. Moreover, limited diversity was detected using genomic (RAPD, ERIC-PCR and REP-PCR) and MALDI-TOF-MS analyses. The phenotypic, genomic and proteomic methods tested allowed the rapid differentiation of V.salmoninarum from the other species causing streptococcosis. However, MALDI-TOF-MS is the most promising method for typing and characterization of V.salmoninarum.

Effects of EGTA on cell surface structures of Corynebacterium glutamicum.

The mycolic acid layer and S-layer of Corynebacterium glutamicum have been considered as permeability barriers against lytic agents. EGTA, a calcium chelator, inhibited C. glutamicum growth at relatively lower concentrations compared with other Gram-positive bacteria. We investigated the effect of EGTA on C. glutamicum cell surface structures. Simultaneous addition of EGTA and lysozyme resulted in cell lysis, whereas addition of these reagents separately had no such effect. Analysis of cell surface proteins showed that CspB, an S-layer protein, was released into the culture media and degraded to several sizes upon EGTA treatment. These findings suggest that EGTA treatment causes release and proteolysis of the CspB protein, resulting in increased cell surface permeability. FE-SEM visualization further confirmed alteration of cell surface structures in EGTA-treated cells. This is the first report suggesting the importance of calcium ions in cell surface integrity of C. glutamicum.

Magnetic capture of polydopamine-encapsulated Hela cells for the analysis of cell surface proteins

A novel method to characterize cell surface proteins and complexes has been developed. Polydopamine (PDA)-encapsulated Hela cells were prepared for plasma membrane proteome research. Since the PDA protection, the encapsulated cells could be maintained for more than two weeks. Amino groups functionalized magnetic nanoparticles were also used for cell capture by the reaction with the PDA coatings. Plasma membrane fragments were isolated and enriched with assistance of an external magnetic field after disruption of the coated cells by ultrasonic treatment. Plasma membrane proteins (PMPs) and complexes were well preserved on the fragments and identified by shot-gun proteomic analytical strategy. 385 PMPs and 1411 non-PMPs were identified using the method. 85.2% of these PMPs were lipid-raft associated proteins. Ingenuity Pathway Analysis was employed for bio-information extraction from the identified proteins. It was found that 653 non-PMPs had interactions with 140 PMPs. Among them, epidermal growth factor receptor and its complexes, and a series of important pathways including STAT3 pathway were observed. All these results demonstrated that the new approach is of great importance in applying to the research of physiological function and mechanism of the plasma membrane proteins. SignificanceThis work developed a novel strategy for the proteomic analysis of cell surface proteins. According to the results, 73.3% of total identified proteins were lipid-raft associated proteins, which imply that the proposed method is of great potential in the identification of lipid-raft associated proteins. In addition, a series of protein-protein interactions and pathways related to Hela cells were pointed out. All these results demonstrated that our proposed approach is of great importance and could well be applied to the physiological function and mechanism research of plasma membrane proteins.

Precision-cut Mouse Lung Slices to Visualize Live Pulmonary Dendritic Cells.

Inhalation of allergens and pathogens elicits multiple changes in a variety of immune cell types in the lung. Flow cytometry is a powerful technique for quantitative analysis of cell surface proteins on immune cells, but it provides no information on the localization and migration patterns of these cells within the lung. Similarly,chemotaxis assays can be performed to study the potential of cells to respond to chemotactic factors in vitro, but these assays do not reproduce the complex environment of the intact lung. In contrast to these aforementioned techniques, the location of individual cell types within the lung can be readily visualized by generating Precision-cut Lung Slices (PCLS), staining them with commercially available, fluorescently tagged antibodies, and visualizing the sections by confocal microscopy. PCLS can be used for both live and fixed lung tissue, and the slices can encompass areas as large as a cross section of an entire lobe. We have used this protocol to successfully visualize the location of a wide variety of cell types in the lung, including distinct types of dendritic cells, macrophages, neutrophils, T cells and B cells, as well as structural cells such as lymphatic, endothelial, and epithelial cells. The ability to visualize cellular interactions, such as those between dendritic cells and T cells, in live, three-dimensional lung tissue, can reveal how cells move within the lung and interact with one another at steady state and during inflammation. Thus, when used in combination with other procedures, such as flow cytometry and quantitative PCR, PCLS can contribute to a comprehensive understanding of cellular events that underlie allergic and inflammatory diseases of the lung.

Abstract 3894: A xenograft mouse model coupled with in-depth cell surface proteome analysis facilitates further elucidation of K-Ras driven tumorigenesis in lung carcinoma

Abstract The purpose of this study was to develop a proteomic approach for analysis of cell surface proteins in tissue specimens and applied it on a K-Ras driven mouse model of metastatic lung carcinoma. Metastatic disease is the leading cause of lung cancer-related mortality in the United States. In spite of continuous efforts, effective treatments targeting oncogenic K-Ras in lung and other K-Ras driven malignancies are slow to develop. To expand the treatment options for lung cancer and facilitate better understanding of metastasis new targets need to be identified and characterized at the surface of cancer cells, preferably in their native tissue microenvironment. Towards this goal we developed a mass-spectrometry (MS)-based glyco-proteomic approach targeting specifically cell surface proteins in tissue specimens and applied it on a xenograft lung cancer mouse model. We used A549 cells expressing endogenous K-RasG12S to induce lung tumor xenografts in BALB/c mice via tail vein injection. A comparative surface glyco-proteomics of cultured A549 cells, dissected tumor tissue (TT), adjacent tumor (AT) tissue and normal mouse lung tissue (NT) obtained from saline-injected age-matched littermates yielded high enrichment (i.e., ≥80%) of surface proteins. It resulted in extensive catalogue/map of more than 400 glycoproteins identified on tumor cell surface. More than 50% of proteins identified on the surface of A549 cultured cells were unambiguously identified in mouse TT, featuring proteins and pathways implicated in metastasis, invadopodia formation and cancer cell migration. These markers also provide insight regarding species determination of tissue origin (i.e., human vs. mouse) differentiation of tumor parenchyma from stroma, and regulation of tumor immune response. Citation Format: Xiaoying Ye, Gordon Whiteley, Dwight Nissley, Frank McCormick, Josip Blonder. A xenograft mouse model coupled with in-depth cell surface proteome analysis facilitates further elucidation of K-Ras driven tumorigenesis in lung carcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3894.

Proteolytic cleavage in the S1–S2 linker of the Kv1.5 channel does not affect channel function

Kv1.5 channels mediate the ultra-rapidly activating delayed rectifier potassium current (IKur), which is important for atrial repolarization. It has been shown that cell-surface Kv1.5 channels are sensitive to cleavage by the extracellular serine protease, proteinase K (PK). Here, we investigated the effects of extracellular proteolytic digestion on the function of Kv1.5 channels stably expressed in HEK 293 cells. Our data demonstrate that PK treatment cleaved mature membrane-bound (75kDa) Kv1.5 channels at a single locus in the S1–S2 linker, producing 42-kDa N-terminal fragments and 33-kDa C-terminal fragments. Interestingly, such PK treatment did not affect the Kv1.5 current (IKv1.5) recorded using the whole-cell patch clamp technique. Analysis of cell-surface proteins isolated using biotinylation indicated that the PK-generated N- and C-terminal fragments were both present in the plasma membrane. Co-immunoprecipitation (co-IP) experiments indicated that the N- and C-terminal fragments are no longer associated after cleavage. Furthermore, following PK digestion, the N- and C-fragments degraded at different rates. PK is frequently used as a tool to analyze cell-surface localization of membrane proteins, and cleavage of cell-surface channels has been shown to abolish channel function (e.g. hERG). Our data, for the first time, demonstrate that cleavage of cell-surface channels assessed by Western blot analysis does not necessarily correlate with an elimination of the channel activities.

The calcium-sensing receptor and integrins modulate cerebellar granule cell precursor differentiation and migration.

In the developing cerebellum granule cell precursors (GCPs) proliferate in the external granule cell layer before differentiating and migrating to the inner granule cell layer. Aberrant GCP proliferation leads to medulloblastoma, the most prevalent form of childhood brain cancer. Here, we demonstrate that the calcium-sensing receptor (CaSR), a homodimeric G-protein coupled receptor, functions in conjunction with cell adhesion proteins, the integrins, to enhance GCP migration and cell homing by promoting GCP differentiation. During the second postnatal week a robust peak in CaSR expression was observed in GCPs; reciprocal immunoprecipitation experiments conducted during this period established that the CaSR and β1 integrins are present together in a macromolecular protein complex. Analysis of cell-surface proteins demonstrated that activation of the CaSR by positive allosteric modulators promoted plasma membrane expression of β1 integrins via ERK2 and AKT phosphorylation and resulted in increased GCP migration toward an extracellular matrix protein. The results of in vivo experiments whereby CaSR modulators were injected i.c.v. revealed that CaSR activation promoted radial migration of GCPs by enhancing GCP differentiation, and conversely, a CaSR inhibitor disrupted GCP differentiation and promoted GCP proliferation. Our results demonstrate that an ion-sensing G-protein coupled receptor acts to promote neuronal differentiation and homing during cerebellar maturation. These findings together with those of others also suggest that CaSR/integrin complexes act to transduce extracellular calcium signals into cellular movement, and may function in this capacity as a universal cell migration/homing complex in the developing brain.

Quantitative Analysis of Signal Transduction with In-Cell Western Immunofluorescence Assays.

Protein levels and signaling events can be efficiently quantified in many samples with the In-Cell Western (ICW) cell-based assay. This quantitative immunofluorescence method streamlines experimental procedures and data analysis, so hundreds of samples can be processed in parallel with quantitative data output. Cells are cultured in microplates and treated with various drugs or conditions. After fixation and permeabilization of cells in the microplate wells, immunostaining is used to detect target proteins. Secondary antibodies conjugated with IRDye near-infrared (NIR) fluorescent dyes are used for multiplex detection and normalization; cell stains and DNA stains can also be used for cell number normalization. Fluorescent signals reflect the protein expression levels or signaling status of the cell population in each well. ICW assays are a powerful alternative to western blotting. Time-consuming, error-prone steps such as cell lysis, gel electrophoresis, and membrane transfer are eliminated. In situ detection of protein targets in fixed cells provides a relevant cellular context, and enables very rapid and precise quenching of cellular treatments. Results are consistent with western blotting, but precision and reproducibility are enhanced. ICW functional assays are used to analyze protein phosphorylation, monitor the timing and kinetics of signal transduction events, monitor cellular response to agonists and antagonists, and determine IC50 and EC50 values. Modified On-Cell Western (OCW) assays are used for analysis of cell surface proteins, receptor internalization and recycling, and fluorescent ligand binding studies. Here, we describe the basic methodology for In-Cell Western quantitative immunofluorescence assays.

VHL-dependent regulation of a β-dystroglycan glycoform and glycogene expression in renal cancer

Identification of novel biomarkers and targets in renal cell carcinoma (RCC) remains a priority and one cellular compartment that is a rich potential source of such molecules is the plasma membrane. A shotgun proteomic analysis of cell surface proteins enriched by cell surface biotinylation and avidin affinity chromatography was explored using the UMRC2- renal cancer cell line, which lacks von Hippel-Lindau (VHL) tumour suppressor gene function, to determine whether proteins of interest could be detected. Of the 814 proteins identified ∼22% were plasma membrane or membrane-associated, including several with known associations with cancer. This included β-dystroglycan, the transmembrane subunit of the DAG1 gene product. VHL-dependent changes in the form of β-dystroglycan were detected in UMRC2−/+VHL transfectants. Deglycosylation experiments showed that this was due to differential sialylation. Analysis of normal kidney cortex and conventional RCC tissues showed that a similar change also occurred in vivo. Investigation of the expression of genes involved in glycosylation in UMRC2−/+VHL cells using a focussed microarray highlighted a number of enzymes involved in sialylation; upregulation of bifunctional UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) was validated in UMRC2− cells compared with their +VHL counterparts and also found in conventional RCC tissue. These results implicate VHL in the regulation of glycosylation and raise interesting questions regarding the extent and importance of such changes in RCC.

Development of theca specific antisera for the profiling of cell surface proteins in the marine toxic dinoflagellate genus Alexandrium Halim

Revealing the profile of dinoflagellate cell surface proteins (CSPs) is a crucial step for developing molecular probes for effective identification, separation and enumeration of toxic and non-toxic dinoflagellates. This study aimed to develop theca-specific antibodies against the dinoflagellates Alexandrium affine (non-toxic) and A. tamarense (toxic) to distinguish the two species, and verify if these antibodies would enable the analysis of multiple CSPs for probing phytoplankton's nutrient physiology, and facilitating rapid detection and enumeration of these harmful algal species. Using 2-DE immunoblots, we evaluated the specificity and effectiveness of the theca-specific polyclonal antisera against two types of antigens generated from fresh or fixed whole cell and insoluble cellular fractions, respectively. Our results showed that, of the four cell surface antigens, paraformaldehyde fixed whole cell antigen derived antiserum specifically recognized weakly bound theca-associated CSPs in toxic Alexandrium strain. Using the optimized theca-specific antisera, about 187 and 110 cell surface associated antigenic spots were identified on the 2-DE immunoblots of A. affine and A. tamarense, respectively. This immunoproteomic approach is proven to be very useful for phytoplankton CSP studies, permitting a more in-depth elucidation of the relationship among nutrient condition, bloom dynamic and toxin production of the harmful algae in the marine environment.

Post‐translational modifications regulate signalling by Ror1

In this study, we analysed the post-translational modification of receptor tyrosine kinase-like orphan receptor (Ror1). Ror1 is highly upregulated in B cells of patients with chronic lymphocytic leukaemia (CLL). Molecularly, Ror1 acts as the Wnt receptor in the non-canonical Wnt pathway. The level of Ror1 glycosylation in HEK293 cells and in primary human CLL cells was analysed by treatment of inhibitors interfering with different steps of glycosylation process and by direct treatment of cell lysates with N-glycosidase. Ror1 ubiquitination was determined by ubiquitination assay. Functional consequences of post-translational modifications were analysed by immunohistochemistry and by analysis of cell surface proteins. Differences in Ror1 glycosylation were confirmed by analysis of 14 samples of B cells from CLL patients. We demonstrate that Ror1 is extensively modified by N-linked glycosylation. Glycosylation produces several variants of Ror1 with electrophoretic migration of approx. 100, 115 and 130 kDa. Inhibition of glycosylation interferes with cell surface localization of the 130-kDa variant of Ror1 and prevents Ror1-induced formation of filopodia. Moreover, we show that 130-kDa Ror1 is mono-ubiquitinated. Furthermore, individual CLL patients show striking differences in the electrophoretic migration of Ror1, which correspond to the level of glycosylation. Our data show that Ror1 undergoes complex post-translational modifications by glycosylation and mono-ubiquitination. These modifications regulate Ror1 localization and signalling, and are highly variable among individual CLL patients. These may suggest that Ror1 signals only in a subset of CLL patients despite Ror1 levels are ubiquitously high in all CLL patients.

Abstract 5265: Development of a microfluidic device for tagless analysis of cell surface proteins directing lung metastasis

Abstract Diagnostic analysis of the few tumor cells obtained by needle aspirates is currently limited to the cells’ morphologic characteristics. We are investigating tagless analysis of cell surface protein composition, when limited cell numbers are available, using a flow retardation microfluidic device. Expression of biologically significant cell surface proteins by individual cells is scored positive by achievement of flow retardation due to transient binding of cell surface proteins to cognizant antibodies immobilized on tandem patches of the channel. This permits repetitive queries of the same cell for several proteins that predict specific malignant behavior. We are adapting the model to LM2 cells, derived from lung metastases of MDA-MB-231 breast cancer cells, which selectively metastasize to the lung*. The original study identified 95 unique genes either overexpressed or underexpressed in LM2 cells compared to parental cells. Of these we identified three cell surface proteins, VCAM1, IL13RA2, and EMP1, as heterogeneously upregulated in a subset of LM2 cells and CXCR4, as downregulated in a subset of LM2 cells when compared with MDA-MB-231 cells. VCAM1 and IL13RA2 promote lung metastasis*. We sterile sorted LM2 cells into fractions expressing none, medium and high levels of these four proteins. We built a prototype microfluidic device able to retard the flow of streptavidin-coated silica oxide beads by immobilized biotin and used optical imaging and a tracking program for simultaneous analysis of multiple particles. We developed efficient and stable protein coating of microchannels and are generating patches with cognizant antibodies to these 4 antigens and to endothelial, macrophage, lymphocyte, fibroblast and endothelial cell markers as controls. We will correlate antigen expression levels with flow retardation efficiency. We will optimize shear rates affecting bond formation and shear stress affecting bond dissociation by optimizing velocity, viscosity, detergent and divalent cation concentrations to maximize cell separation. We will adapt the channel to select LM2 cells from excess controls in vitro and from tumor xenograft aspirates. *Minn AJ, Gupta GP, Siegel PM, Bos PD, Shu W, Giri DD, Viale A, Olshen AB, Gerald WL and Massague J (2005) Genes that mediate breast cancer metastasis to lung. Nature 436:518-524. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5265. doi:10.1158/1538-7445.AM2011-5265

Cloning and expression of a novel lactococcal aggregation factor from Lactococcus lactis subsp. lactis BGKP1.

BackgroundAggregation may play a main role in the adhesion of bacteria to the gastrointestinal epithelium and their colonization ability, as well as in probiotic effects through co-aggregation with intestinal pathogens and their subsequent removal. The aggregation phenomenon in lactococci is directly associated with the sex factor and lactose plasmid co-integration event or duplication of the cell wall spanning (CWS) domain of PrtP proteinase.ResultsLactococcus lactis subsp. lactis BGKP1 was isolated from artisanal semi-hard homemade cheese and selected due to its strong auto-aggregation phenotype. Subsequently, non-aggregating derivative (Agg-) of BGKP1, designated as BGKP1-20, was isolated, too. Comparative analysis of cell surface proteins of BGKP1 and derivative BGKP1-20 revealed a protein of approximately 200 kDa only in the parental strain BGKP1. The gene involved in aggregation (aggL) was mapped on plasmid pKP1 (16.2 kb), cloned and expressed in homologous and heterologous lactococci and enterococci. This novel lactococcal aggregation protein was shown to be sufficient for cell aggregation in all tested hosts. In addition to the aggL gene, six more ORFs involved in replication (repB and repX), restriction and modification (hsdS), transposition (tnp) and possible interaction with mucin (mbpL) were also located on plasmid pKP1.ConclusionAggL is a new protein belonging to the collagen-binding superfamily of proteins and is sufficient for cell aggregation in lactococci.