Decay-accelerating factor (CD55): a versatile acting molecule in human malignancies

Chromosome 1 instability in multiple myeloma: Aberrant gene expression, pathogenesis, and potential therapeutic target

Multiple myeloma (MM), the terminally differentiated B cells malignancy, is widely considered to be incurable since many patients have either developed drug resistance or experienced an eventual relapse. To develop precise and efficient therapeutic strategies, we must understand the pathogenesis of MM. Thus, unveiling the driver events of MM and its further clonal evolution will help us understand this complicated disease. Chromosome 1 instabilities are the most common genomic alterations that participate in MM pathogenesis, and these aberrations of chromosome 1 mainly include copy number variations and structural changes. The chromosome 1q gains/amplifications and 1p deletions are the most frequent structural changes of chromosomes in MM. In this review, we intend to focus on the genes that are affected by chromosome 1 instability: some tumor suppressors were lost or down regulated in 1p deletions, and others that contributed to tumorigenesis were upregulated in 1q gains/amplifications. We have summarized their biological function as well as their roles in the MM pathogenesis, hoping to uncover potential novel therapeutical targets and promote the development of future therapeutic approaches.

Cytolytic Properties and Genome Analysis of Rigvir® Oncolytic Virotherapy Virus and Other Echovirus 7 Isolates

Rigvir® is a cell-adapted, oncolytic virotherapy enterovirus, which derives from an echovirus 7 (E7) isolate. While it is claimed that Rigvir® causes cytolytic infection in several cancer cell lines, there is little molecular evidence for its oncolytic and oncotropic potential. Previously, we genome-sequenced Rigvir® and five echovirus 7 isolates, and those sequences are further analyzed in this paper. A phylogenetic analysis of the full-length data suggested that Rigvir® was most distant from the other E7 isolates used in this study, placing Rigvir® in its own clade at the root of the phylogeny. Rigvir® contained nine unique mutations in the viral capsid proteins VP1-VP4 across the whole data set, with a structural analysis showing six of the mutations concerning residues with surface exposure on the cytoplasmic side of the viral capsid. One of these mutations, E/Q/N162G, was located in the region that forms the contact interface between decay-accelerating factor (DAF) and E7. Rigvir® and five other isolates were also subjected to cell infectivity assays performed on eight different cell lines. The used cell lines contained both cancer and non-cancer cell lines for observing Rigvir®'s claimed properties of being both oncolytic and oncotropic. Infectivity assays showed that Rigvir® had no discernable difference in the viruses' oncolytic effect when compared to the Wallace prototype or the four other E7 isolates. Rigvir® was also seen infecting non-cancer cell lines, bringing its claimed effect of being oncotropic into question. Thus, we conclude that Rigvir®'s claim of being an effective treatment against multiple different cancers is not warranted under the evidence presented here. Bioinformatic analyses do not reveal a clear mechanism that could elucidate Rigvir®'s function at a molecular level, and cell infectivity tests do not show a discernable difference in either the oncolytic or oncotropic effect between Rigvir® and other clinical E7 isolates used in the study.

Evaluation of Protein Purification Techniques and Effects of Storage Duration on LC-MS/MS Analysis of Archived FFPE Human CRC Tissues

To elucidate cancer pathogenesis and its mechanisms at the molecular level, the collecting and characterization of large individual patient tissue cohorts are required. Since most pathology institutes routinely preserve biopsy tissues by standardized methods of formalin fixation and paraffin embedment, these archived FFPE tissues are important collections of pathology material that include patient metadata, such as medical history and treatments. FFPE blocks can be stored under ambient conditions for decades, while retaining cellular morphology, due to modifications induced by formalin. However, the effect of long-term storage, at resource-limited institutions in developing countries, on extractable protein quantity/quality has not yet been investigated. In addition, the optimal sample preparation techniques required for accurate and reproducible results from label-free LC-MS/MS analysis across block ages remains unclear. This study investigated protein extraction efficiency of 1, 5, and 10-year old human colorectal carcinoma resection tissue and assessed three different gel-free protein purification methods for label-free LC-MS/MS analysis. A sample size of n = 17 patients per experimental group (with experiment power = 0.7 and α = 0.05, resulting in 70% confidence level) was selected. Data were evaluated in terms of protein concentration extracted, peptide/protein identifications, method reproducibility and efficiency, sample proteome integrity (due to storage time), as well as protein/peptide distribution according to biological processes, cellular components, and physicochemical properties. Data are available via ProteomeXchange with identifier PXD017198. The results indicate that the amount of protein extracted is significantly dependent on block age (p < 0.0001), with older blocks yielding less protein than newer blocks. Detergent removal plates were the most efficient and overall reproducible protein purification method with regard to number of peptide and protein identifications, followed by the MagReSyn® SP3/HILIC method (with on-bead enzymatic digestion), and lastly the acetone precipitation and formic acid resolubilization method. Overall, the results indicate that long-term storage of FFPE tissues (as measured by methionine oxidation) does not considerably interfere with retrospective proteomic analysis (p > 0.1). Block age mainly affects initial protein extraction yields and does not extensively impact on subsequent label-free LC-MS/MS analysis results.

Overexpression of CD55 correlates with tumor progression and poor prognosis in gastric stromal tumors

Backgrounds: Accumulating evidences have demonstrated that CD55 can protect cells from complement-mediated attack, and is involved in tumor dedifferentiation, migration, invasiveness, and metastasis. However, the role of CD55 in gastrointestinal stromal tumors (GISTs) has not been investigated. Aims: Our study aimed to analyze the expression of CD55 in gastric GISTs and its correlations with clinicopathologic characteristics and prognosis. Materials and methods: A total of 118 gastric GIST patients were included in our study. CD55 expression in GIST tissue samples was evaluated using immunohistochemistry. Cumulative survival was conducted using the Kaplan-Meier method. Cox regression analyses were performed to identify factors associated with progression-free survival (PFS) for patients with gastric GISTs. Results: Of 118 gastric GISTs patients included in our study, 44 (37.3%) were positive for CD55 expression. Positive CD55 expression in gastric GISTs was closely associated with tumor size (13.52±7.35 vs 5.07±1.90 cm, respectively; P<0.001), Ki 67 labeling index (P=0.001), mitotic counts (P=0.005), NIH risk classification (P<0.001), PLR (P<0.001), and metastasis at initial diagnosis (P=0.002). Kaplan-Meier analyses revealed that tumor size (P<0.001), mitotic counts (P<0.001), Ki 67 labeling index (P<0.001), PLR (P<0.001), metastasis at initial diagnosis (P=0.031), and CD55 expression (P<0.001) were statistically significant risk factors affecting PFS of patients with gastric GISTs. Cox multivariate survival analysis showed that mitotic counts, Ki 67 labeling index, and CD55 expression were independent predictors of PFS for gastric GISTs. Conclusion: CD55 may be a potential prognostic marker in gastric GISTs patients.

Strategies to Circumvent Host Innate Immune Response by Hepatitis C Virus

Innate immune responses generate interferons, proinflammatory cytokines, complement activation, and natural killer (NK) cell response. Ultimately, this leads to the induction of a robust virus-specific adaptive immunity. Although the host innate immune system senses and responds to eliminate virus infection, hepatitis C virus (HCV) evades immune attack and establishes persistent infection within the liver. Spontaneous clearance of HCV infection is associated with a prompt induction of innate immunity generated in an infected host. In this review, we have highlighted the current knowledge of our understanding of host⁻HCV interactions, especially for endogenous interferon production, proinflammatory response, NK cell response, and complement activation, which may impair the generation of a strong adaptive immune response for establishment of chronicity. The information may provide novel strategies in augmenting therapeutic intervention against HCV.

Activation of the complement cascade enhances motility of leukemic cells by downregulating expression of HO-1

As a crucial arm of innate immunity, the complement cascade (ComC) is involved both in mobilization of normal hematopoietic stem/progenitor cells (HSPCs) from bone marrow (BM) into peripheral blood and in their homing to BM. Despite the fact that ComC cleavage fragments alone do not chemoattract normal HSPCs, we found that leukemia cell lines as well as clonogenic blasts from chronic myeloid leukemia and acute myeloid leukemia patients respond robustly to C3 and C5 cleavage fragments by chemotaxis and increased adhesion. This finding was supported by the detection of C3a and C5a receptors in cells from human malignant hematopoietic cell lines and patient blasts at the mRNA (reverse transcriptase-polymerase chain reaction) and protein level (fluorescence-activated cell sorting), and by the demonstration that these receptors respond to stimulation by C3a and C5a by phosphorylation of p42/44 and p38 mitogen-activated protein kinases (MAPK), and protein kinase B (PKB/AKT). We also found that inducible heme oxygenase 1 (HO-1) is a negative regulator of ComC-mediated trafficking of leukemic cells, and that stimulation of leukemic cells by C3 or C5 cleavage fragments activates p38 MAPK, which downregulates HO-1 expression, rendering cells more mobile. We conclude that activation of the ComC in leukemia/lymphoma patients (for example, as a result of accompanying infections) enhances the motility of malignant cells and contributes to their spread in a p38 MAPK-HO-1-dependent manner. Therefore, inhibition of p38 MAPK or upregulation of HO-1 by small-molecule modulators would have a beneficial effect on ameliorating cell migration-mediated expansion of leukemia/lymphoma cells when the ComC becomes activated.

The dual role of complement in cancer and its implication in anti-tumor therapy

Chronic inflammation has been linked to the initiation of carcinogenesis, as well as the advancement of established tumors. The polarization of the tumor inflammatory microenvironment can contribute to either the control, or the progression of the disease. The emerging participation of members of the complement cascade in several hallmarks of cancer, renders it a potential target for anti-tumor treatment. Moreover, the presence of complement regulatory proteins (CRPs) in most types of tumor cells is known to impede anti-tumor therapies. This review focuses on our current knowledge of complement's potential involvement in shaping the inflammatory tumor microenvironment and its role on the regulation of angiogenesis and hypoxia. Furthermore, we discuss approaches using complement-based therapies as an adjuvant in tumor immunotherapy.

Distinct CD55 Isoform Synthesis and Inhibition of Complement-Dependent Cytolysis by Hepatitis C Virus

CD55/DAF, one of the regulators of complement activation, is known to limit excess complement activation on the host cell surface by accelerating the decay of C3 convertase. We reported previously that hepatitis C virus (HCV) infection or virus core protein expression upregulates CD55 expression. CD55 associates with HCV particles, potentially protecting HCV from lysis in circulation. An increase in CD55 on the surface of HCV-infected cells may inhibit complement-mediated cell killing. In this study, we show that Abs against cancer cell surface proteins induce complement-dependent cytolysis or Ab-dependent cell-mediated cytotoxicity of immortalized human hepatocytes in the presence of CD55-blocking Ab. CD55 has a secreted isoform (sCD55) that is generated by alternative splicing. We observed that sCD55 is induced in HCV-infected or HCV replicon-harboring cells, as well as in liver biopsy samples from chronically HCV-infected patients. Conditioned medium from HCV-infected hepatoma cells (Huh7.5 cells) or immortalized human hepatocytes inhibited C3 convertase activity and complement-dependent cytolysis of sheep blood erythrocytes. Chronically HCV-infected patient sera inhibited C3 convertase activity, further implicating HCV-specific impairment of complement function in infected humans. CD55-blocking Ab inhibited erythrocyte lysis by conditioned medium, suggesting that CD55/sCD55 impairs convertase activity. Together, our data show that HCV infection induces sCD55 expression in HCV-infected cell culture-conditioned medium and inhibits C3 convertase activity. This may have implications for modulating complement-mediated immune function in the microenvironment and on HCV-harboring cells.

Targeting Tumor Cells by Natural Anti-Carbohydrate Antibodies Using Rhamnose-Functionalized Liposomes

Recruitment of antibodies in human immune systems for targeted destruction of tumor cells has emerged as an exciting area of research due to its low occurrence of side effects, high efficacy, and high specificity. The presence of large amounts of anticarbohydrate natural antibodies in human sera has prompted research efforts to utilize carbohydrate epitopes for immune recruitment. Here, we have developed a general strategy for specific targeted destruction of tumor cells based on rhamnose-functionalized liposomes. Tumor cells artificially decorated with rhamnose epitopes were subjected to complement-mediated cytotoxicity in vitro and showed delayed tumor growth in vivo. This study highlights the therapeutic potential for activation of endogenous immune response through cell-surface glycan engineering.

Rhamnose glycoconjugates for the recruitment of endogenous anti-carbohydrate antibodies to tumor cells

Immunotherapy is a promising strategy for targeting tumors. One emerging approach is to harness the immune effector functions of natural antibodies to destroy tumor cells. Dinitrophenyl (DNP) and the galactose-α-1,3-galactose (αGal) epitope are two haptens that bind endogenous antibodies. One potential alternative is the deoxysugar L-rhamnose. We compared these candidates by using a biosensor assay to evaluate human sera for endogenous antibody concentration, antibody isotype distribution, and longevity of antibody-hapten interactions. Antibodies recognizing α-rhamnose are of equal or greater abundance and affinity as those recognizing αGal. Moreover, both rhamnose and αGal epitopes are more effective than DNP at recruiting the IgG antibody subtype. Exposure of tumor cells to rhamnose-bearing glycolipids and human serum promotes complement-mediated cytotoxicity. These data highlight the utility of α-rhamnose-containing glycoconjugates to direct the immune system to target cells.

The glycome of normal and malignant plasma cells

The glycome, i.e. the cellular repertoire of glycan structures, contributes to important functions such as adhesion and intercellular communication. Enzymes regulating cellular glycosylation processes are related to the pathogenesis of cancer including multiple myeloma. Here we analyze the transcriptional differences in the glycome of normal (n = 10) and two cohorts of 332 and 345 malignant plasma-cell samples, association with known multiple myeloma subentities as defined by presence of chromosomal aberrations, potential therapeutic targets, and its prognostic impact. We found i) malignant vs. normal plasma cells to show a characteristic glycome-signature. They can ii) be delineated by a lasso-based predictor from normal plasma cells based on this signature. iii) Cytogenetic aberrations lead to distinct glycan-gene expression patterns for t(11;14), t(4;14), hyperdiploidy, 1q21-gain and deletion of 13q14. iv) A 38-gene glycome-signature significantly delineates patients with adverse survival in two independent cohorts of 545 patients treated with high-dose melphalan and autologous stem cell transplantation. v) As single gene, expression of the phosphatidyl-inositol-glycan protein M as part of the targetable glycosyl-phosphatidyl-inositol-anchor-biosynthesis pathway is associated with adverse survival. The prognostically relevant glycome deviation in malignant cells invites novel strategies of therapy for multiple myeloma.

Runx1 is a tumor suppressor gene in the mouse gastrointestinal tract

The Runx1 transcription factor plays an important role in tissue homeostasis through its effects on stem/progenitor cell populations and differentiation. The effect of Runx1 on epithelial differentiation of the secretory cell lineage of the colon was recently demonstrated. This study aimed to examine the role of Runx1 in tumor development in epithelial cells of the gastrointestinal tract. Conditional knockout mice that lacked Runx1 expression in epithelial cells of the GI tract were generated. These mice were crossed onto the Apc(Min) background, killed and their intestinal tumor phenotypes were compared with Apc(Min) Runx1 wild-type control mice. Apc-wild-type Runx1-mutant mice were also examined for tumor development. Colons from Runx1 knockout and wild-type mice were used for genome-wide mRNA expression analyses followed by gene-specific quantitative RT-PCR of whole colon and colon epithelium to identify Runx1 target genes. Runx1 deficiency in intestinal epithelial cells significantly enhanced tumorigenesis in Apc(Min) mice. Notably, epithelial Runx1 deficiency in Apc-wild-type mice was sufficient to cause tumor development. Absence of Runx1 was associated with global changes in the expression of genes involved in inflammation and intestinal metabolism, and with gene sets indicative of a metastatic phenotype and poor prognosis. Gene-specific analysis of Runx1-deficient colon epithelium revealed increased expression of genes linked to an expansion of the stem/progenitor cell population. These results identify Runx1 as a novel tumor suppressor gene for gastrointestinal tumors and support a role for Runx1 in maintaining the balance between the intestinal stem/progenitor cell population and epithelial differentiation of the GI tract.

Complement activation: an emerging player in the pathogenesis of cardiovascular disease

A wealth of evidence indicates a fundamental role for inflammation in the pathogenesis of cardiovascular disease (CVD), contributing to the development and progression of atherosclerotic lesion formation, plaque rupture, and thrombosis. An increasing body of evidence supports a functional role for complement activation in the pathogenesis of CVD through pleiotropic effects on endothelial and haematopoietic cell function and haemostasis. Prospective and case control studies have reported strong relationships between several complement components and cardiovascular outcomes, and in vitro studies and animal models support a functional effect. Complement activation, in particular, generation of C5a and C5b-9, influences many processes involved in the development and progression of atherosclerosis, including promotion of endothelial cell activation, leukocyte infiltration into the extracellular matrix, stimulation of cytokine release from vascular smooth muscle cells, and promotion of plaque rupture. Complement activation also influences thrombosis, involving components of the mannose-binding lectin pathway, and C5b-9 in particular, through activation of platelets, promotion of fibrin formation, and impairment of fibrinolysis. The participation of the complement system in inflammation and thrombosis is consistent with the physiological role of the complement system as a rapid effector system conferring protection following vessel injury. However, in the context of CVD, these same processes contribute to development of atherosclerosis, plaque rupture, and thrombosis.

Role of Src kinases in mobilization of glycosylphosphatidylinositol-anchored decay-accelerating factor by Dr fimbria-positive adhering bacteria

Afa/Dr fimbriae constitute the major virulence factor of diffusely adhering Escherichia coli (Afa/Dr DAEC). After recognizing membrane-bound signaling receptors, they trigger cell responses. One of these receptors is the human decay-accelerating factor (hDAF). It has previously been reported that the binding of Afa/Dr fimbriae to hDAF quickly induces recruitment of hDAF around adhering bacteria. The aim of our study is to analyze the role of Src kinases in the Dr fimbria-induced recruitment of hDAF. Using biochemical methods and confocal microscopy followed by 3-dimensional (3D) analysis, we have shown that the activation and cell membrane targeting of Src kinases are necessary for the recruitment and organization of hDAF around adhering bacteria. We identified c-Src to be the specific kinase involved in this process. Using a set of Src-green fluorescent protein mutants, we showed that the catalytic activity and the Src homology 2 (SH2) and SH3 domains of the Src kinases are necessary for Dr fimbria-induced hDAF mobilization to occur. In addition, using mutated Dr fimbriae and a set of mutated hDAFs in which each of the complement control protein (CCP) domains had successively been deleted, we found that the aspartic acids at position 54 in the Dr fimbriae and in CCP domain 4 of hDAF played pivotal roles in the mobilization of the Src kinases and hDAF, respectively.

Dynamic control of the complement system by modulated expression of regulatory proteins

The complement system serves many biological functions, including the eradication of invasive pathogens and the removal of damaged cells and immune-complexes. Uncontrolled complement activation causes injury to host cells, however, so adequate regulation of the system is essential. Control of the complement system is maintained by a group of cell surface and circulating proteins referred to as complement regulatory proteins. The expression of the cell surface complement regulatory proteins varies from tissue to tissue. Furthermore, specific cell types can upregulate or downregulate the expression of these proteins in response to a variety of signals or insults. Altered regulation of the complement regulatory proteins can have important effects on local complement activation. In some circumstances this can be beneficial, such as in the setting of certain infections. In other circumstances, however, this can be a cause of complement-mediated injury of the tissue. A full understanding of the mechanisms by which the complement system is modulated at the local level can have important implications for how we diagnose and treat a wide range of inflammatory diseases.

Temporal resolution of protein-protein interactions in the live-cell plasma membrane

We have recently devised a method to quantify interactions between a membrane protein ("bait") and a fluorophore-labeled protein ("prey") directly in the live-cell plasma membrane (Schwarzenbacher et al. Nature Methods 5:1053-1060 2008). The idea is to seed cells on surfaces containing micro-patterned antibodies against the exoplasmic domain of the bait, and monitor the co-patterning of the fluorescent prey via fluorescence microscopy. Here, we characterized the time course of bait and prey micropattern formation upon seeding the cells onto the micro-biochip. Patterns were formed immediately after contact of the cells with the surface. Cells were able to migrate over the chip surface without affecting the micropattern contrast, which remained constant over hours. On single cells, bait contrast may be subject to fluctuations, indicating that the bait can be released from and recaptured on the micropatterns. We conclude that interaction studies can be performed at any time-point ranging from 5 min to several hours post seeding. Monitoring interactions with time opens up the possibility for new assays, which are briefly sketched in the discussion section.

The impact of expressions of CD97 and its ligand CD55 at the invasion front on prognosis of rectal adenocarcinoma

BACKGROUND

Various evidence show that CD97 plays an important role in tumor differentiation, migration, invasiveness, and metastasis by binding its cellular ligand CD55. CD55 is a complement regulatory protein expressed by cells to protect them from bystander attack by complement, and it has been shown to be an indicator of poor prognostic in several cancers.

METHODS

CD97 and CD55 stains were detected in tumor tissues from 71 cases of rectal adenocarcinomas and their corresponding normal colorectal tissues by immunohistochemistry.

RESULTS

The expressions of CD97 and CD55 in rectal tumor tissues were significantly higher than those in normal colorectal tissues (P < 0.05, both). The patients with recurrence and/or metastasis had significantly higher expressions of CD97 at tumor cells and CD55 at stroma (67.8% [21/31] and 63.6% [21/33]) at the invasion front than those patients without recurrence and/or metastasis (25.0% [10/40] and 26.3% [10/38]). The expression of CD97 at tumor cell at the invasion front showed modest correlation with that of CD55 in the stroma at the invasion front(r = 0.392, P < 0.01). Univariate analysis revealed that lymph node metastasis (P = 0.001), stages II-IV (P = 0.026), and strong CD97 expression at tumor invasion front (P = 0.002) were shown to have a significant adverse impact on the postoperative survival rate. Moreover, lymph node metastasis (P = 0.037) and strong CD97 expression (P = 0.015) were associated with poor survival in a multivariate analysis.

CONCLUSIONS

Elevated expression of CD97 and its ligand CD55 at the invasion front correlate with tumor recurrence and metastasis, and CD95 may be a poor prognostic factor for rectal adenocarcinoma.

Hypoxia induces trimethylated H3 lysine 4 by inhibition of JARID1A demethylase

Histone H3 lysine 4 (H3K4) trimethylation (H3K4me3) at the promoter region of genes has been linked to transcriptional activation. In the present study, we found that hypoxia (1% oxygen) increased H3K4me3 in both normal human bronchial epithelial Beas-2B cells and human lung carcinoma A549 cells. The increase of H3K4me3 from hypoxia was likely caused by the inhibition of H3K4 demethylating activity, as hypoxia still increased H3K4me3 in methionine-deficient medium. Furthermore, an in vitro histone demethylation assay showed that 1% oxygen decreased the activity of H3K4 demethylases in Beas-2B nuclear extracts because ambient oxygen tensions were required for the demethylation reaction to proceed. Hypoxia only minimally increased H3K4me3 in the BEAS-2B cells with knockdown of JARID1A, which is the major histone H3K4 demethylase in this cell line. However, the mRNA and protein levels of JARID1A were not affected by hypoxia. GeneChip and pathway analysis in JARID1A knockdown Beas-2B cells revealed that JARID1A regulates the expression of hundreds of genes involved in different cellular functions, including tumorigenesis. Knocking down of JARID1A increased H3K4me3 at the promoters of HMOX1 and DAF genes. Thus, these results indicate that hypoxia might target JARID1A activity, which in turn increases H3K4me3 at both the global and gene-specific levels, leading to the altered programs of gene expression and tumor progression.

Decay accelerating factor (CD55) protects neuronal cells from chemical hypoxia-induced injury

Background

Activated complement system is known to mediate neuroinflammation and neurodegeneration following exposure to hypoxic-ischemic insults. Therefore, inhibition of the complement activation cascade may represent a potential therapeutic strategy for the management of ischemic brain injury. Decay-accelerating factor (DAF, also known as CD55) inhibits complement activation by suppressing the function of C3/C5 convertases, thereby limiting local generation or deposition of C3a/C5a and membrane attack complex (MAC or C5b-9) production. The present study investigates the ability of DAF to protect primary cultured neuronal cells subjected to sodium cyanide (NaCN)-induced hypoxia from degeneration and apoptosis.

Methods

Cultured primary cortical neurons from embryonic Sprague-Dawley rats were assigned one of four groups: control, DAF treatment alone, hypoxic, or hypoxic treated with DAF. Hypoxic cultures were exposed to NaCN for 1 hour, rinsed, followed by 24 hour exposure to 200 ng/ml of recombinant human DAF in normal medium. Human DAF was used in the present study and it has been shown to effectively regulate complement activation in rats. Neuronal cell function, morphology and viability were investigated by measuring plateau depolarization potential, counting the number dendritic spines, and observing TUNEL and MTT assays. Complement C3, C3a, C3a receptor (R) production, C3a-C3aR interaction and MAC formation were assessed along with the generation of activated caspase-9, activated caspase-3, and activated Src.

Results

When compared to controls, hypoxic cells had fewer dendritic spines, reduced plateau depolarization accompanied by increased apoptotic activity and accumulation of MAC, as well as up-regulation of C3, C3a and C3aR, enhancement of C3a-C3aR engagement, and elevated caspase and Src activity. Treatment of hypoxic cells with 200 ng/ml of recombinant human DAF resulted in attenuation of neuronal apoptosis and exerted significant protection against neuronal dendritic spine loss and plateau depolarization reduction. Furthermore, treatment with DAF resulted in decreased accumulation of C3a, MAC, C3a-C3aR interaction, caspase-9, activated caspase-3, and pTyr416-Src (activated Src) tyrosine kinase.

Conclusion

DAF was found to reduce neuronal cell death and apoptosis in NaCN induced hypoxia. This effect is attributed to the ability of DAF to limit complement activation and inhibit the activity of Src and caspases 9 and 3. This study supports the inhibiting of complement as a neuroprotective strategy against CNS ischemia/reperfusion injury.

Transcriptional control of complement receptor gene expression

Immune complement is a critical system in the immune response and protection of host cells from damage by complement is critical during inflammation. The expression of the receptors for the inflammatory anaphylatoxin molecules is also key in immunity. In order to fully appreciate the biology of complement, a basic understanding of the molecular regulation of complement receptor gene expression is critical, yet these kinds of studies are lacking for many genes. Importantly, recent genetic studies have demonstrated that promoter-enhancer polymorphisms can contribute to pathology in diseases such as atypical hemolytic uremic syndrome. This review will focus on what is currently known about the genetic regulation of key protective complement receptors genes including CR1 (CD35), CR2 (CD21), Crry, MCP (CD46), DAF (CD55), and CD59. In addition, the regulation of the anaphylatoxin receptors genes, C3aR and C5aR (CD88) will also be discussed. Since new research continuously uncovers novel functions for these proteins, a greater appreciation of the mechanisms involved in gene regulation will be critical for understanding the biology of these molecules.