Overexpressed Ly-6A.2 mediates cell-cell adhesion by binding a ligand expressed on lymphoid cells

Crosslinking of Ly6a metabolically reprograms CD8 T cells for cancer immunotherapy

T cell inhibitory mechanisms prevent autoimmune reactions, while cancer immunotherapy aims to remove these inhibitory signals. Chronic ultraviolet (UV) exposure attenuates autoimmunity through promotion of poorly understood immune-suppressive mechanisms. Here we show that mice with subcutaneous melanoma are not responsive to anti-PD1 immunotherapy following chronic UV irradiation, given prior to tumor injection, due to the suppression of T cell killing ability in skin-draining lymph nodes. Using mass cytometry and single-cell RNA-sequencing analyzes, we discover that skin-specific, UV-induced suppression of T-cells killing activity is mediated by upregulation of a Ly6ahigh T-cell subpopulation. Independently of the UV effect, Ly6ahigh T cells are induced by chronic type-1 interferon in the tumor microenvironment. Treatment with an anti-Ly6a antibody enhances the anti-tumoral cytotoxic activity of T cells and reprograms their mitochondrial metabolism via the Erk/cMyc axis. Treatment with an anti-Ly6a antibody inhibits tumor growth in mice resistant to anti-PD1 therapy. Applying our findings in humans could lead to an immunotherapy treatment for patients with resistance to existing treatments.

Phenotypic and transcriptional changes in peripheral blood mononuclear cells during alphavirus encephalitis in mice

Sindbis virus (SINV) infection of mice provides a model system for studying the pathogenesis of alphaviruses that infect the central nervous system (CNS) to cause encephalomyelitis. While studies of human viral infections typically focus on accessible cells from the blood, this compartment is rarely evaluated in mice. To bridge this gap, single-cell RNA sequencing (scRNAseq) was combined with flow cytometry to characterize the transcriptional and phenotypic changes of peripheral blood mononuclear cells (PBMCs) from SINV-infected mice. Twenty-one clusters were identified by scRNAseq at 7 days after infection, with a unique cluster and overall increase in naive B cells for infected mice. Uninfected mice had fewer immature T cells and CCR9+ CD4 T cells and a unique immature T cell cluster. Gene expression was most altered in the Ki67+ CD8 T cell cluster, with chemotaxis and proliferation-related genes upregulated. Global analysis indicated metabolic changes in myeloid cells and increased expression of Ccl5 by NK cells. Phenotypes of PBMCs and cells infiltrating the CNS were analyzed by flow cytometry over 14 days after infection. In PBMCs, CD8 and Th1 CD4 T cells increased in representation, while B cells showed a transient decrease at day 5 in total, Ly6a+, and naive cells, and an increase in activated B cells. In the brain, CD8 T cells increased for the first 7 days, while Th1 CD4 T cells and naive and Ly6a+ B cells continued to accumulate for 14 days. Therefore, dynamic immune cell changes can be identified in the blood as well as the CNS during viral encephalomyelitis.

IMPORTANCE

The outcome of viral encephalomyelitis is dependent on the host immune response, with clearance and resolution of infection mediated by the adaptive immune response. These processes are frequently studied in mouse models of infection, where infected tissues are examined to understand the mechanisms of clearance and recovery. However, studies of human infection typically focus on the analysis of cells from the blood, a compartment rarely examined in mice, rather than inaccessible tissue. To close this gap, we used single-cell RNA sequencing and flow cytometry to profile the transcriptomic and phenotypic changes of peripheral blood mononuclear cells (PBMCs) before and after central nervous system (CNS) infection in mice. Changes to T and B cell gene expression and cell composition occurred in PBMC and during entry into the CNS, with CCL5 being a differentially expressed chemokine. Therefore, dynamic changes occur in the blood as well as the CNS during the response of mice to virus infection, which will inform the analysis of human studies.

Human LY6 gene family: potential tumor-associated antigens and biomarkers of prognosis in uterine corpus endometrial carcinoma

The human Lymphocyte antigen-6 (LY6) gene family has recently gained interest for its possible role in tumor progression. We have carried out in silico analyses of all known LY6 gene expression and amplification in different cancers using TNMplot and cBioportal. We also have analyzed patient survival by Kaplan-Meier plotter after mining the TCGA database. We report that upregulated expression of many LY6 genes is associated with poor survival in uterine corpus endometrial carcinoma (UCEC) cancer patients. Importantly, the expression of several LY6 genes is elevated in UCEC when compared to the expression in normal uterine tissue. For example, LY6K expression is 8.25× higher in UCEC compared to normal uterine tissue, and this high expression is associated with poor survival with a hazard ratio of 2.42 (p-value = 0.0032). Therefore, some LY6 gene products may serve as tumor-associated antigens in UCEC, biomarkers for UCEC detection, and possibly targets for directing UCEC patient therapy. Further analysis of tumor-specific expression of LY6 gene family members and LY6-triggered signaling pathways is needed to uncover the function of LY6 proteins and their ability to endow tumor survival and poor prognosis in UCEC patients.

Ly-6A-Induced Growth Inhibition and Cell Death in a Transformed CD4+ T Cell Line: Role of Tumor Necrosis Factor-α

Ly-6A, a member of the Ly-6/uPAR supergene family of proteins, is a cell adhesion and cell signaling protein. Signaling through Ly-6A activates the cell-intrinsic apoptotic cell death pathway in CD4⁺ T cell lines, as indicated by the release of cytochrome C, and activation of caspases 9 and 3. In addition, Ly-6A induces cytokine production and growth inhibition. The mechanism underlying the distinct cellular responses that are triggered by engaging Ly-6A protein has remained unknown. To examine the relatedness of these distinct responses, we have quantified the production of pro-apoptotic, growth inhibitory and tumor suppressive cytokines, such as TNF-α, TGF-β and a related protein GDF-10, in response to Ly-6A signaling. Anti-Ly-6A monoclonal antibody-induced activation of YH16.33 CD4⁺ T cell line generated low levels of TGF-β and GDF-10 but elevated levels of TNF-α. Blocking the biological activity of TNF-α resulted in reduced Ly-6A-induced apoptosis in T cells. The Ly-6A-induced response in the T cell line was distinct, as signaling through the antigen receptor complex did not cause growth inhibition and apoptosis despite high levels of TGF-β and GDF-10 that were detected in these cultures. Additionally, in response to antigen receptor complex signaling, lower amount of TNF-α was detected. These results indicate the contribution of TNF-α in the observed Ly-6A-induced growth inhibition and apoptosis and provide a mechanistic explanation for the biologically distinct responses observed in CD4⁺ T cells after engaging Ly-6A protein. Additionally, the findings reported here will aid in the understanding of inhibitory signaling initiated by Ly-6A protein, especially in the context of its potential immune checkpoint inhibitory role in T cells.

GluR2Q and GluR2R AMPA Subunits are not Targets of lypd2 Interaction

A large family of prototoxin-like molecules endogenous to mammals, Ly6 proteins have been implicated in the regulation of cell signaling processes across multiple species. Previous work has shown that certain members of the Ly6 family are expressed in the brain and target nicotinic acetylcholine receptor and potassium channel function. Structural similarities between Ly6 proteins and alpha-neurotoxins suggest the possibility of additional ionotropic receptor targets. Here, we investigated the possibility of lypd2 as a novel regulator of AMPA receptor (AMPAR) function. In particular, we focused on potential interactions with the Q/R isoforms of the GluR2 subunit, which have profound impacts on AMPAR permeability to calcium during neuronal stimulation. We find that although lypd2 and GluR2 share overlapping expression patterns in the mouse hippocampus, there was no interaction between lypd2 and either GluR2Q or GluR2R isoform. These results underscore the importance of continuing to investigate novel targets for Ly6 interaction and regulation.

CD3+CD4-CD8- (Double-Negative) T Cells in Inflammation, Immune Disorders and Cancer

The crucial role of CD4⁺ and CD8⁺ T cells in shaping and controlling immune responses during immune disease and cancer development has been well established and used to achieve marked clinical benefits. CD3⁺CD4^-CD8^- double-negative (DN) T cells, although constituting a rare subset of peripheral T cells, are gaining interest for their roles in inflammation, immune disease and cancer. Herein, we comprehensively review the origin, distribution and functions of this unique T cell subgroup. First, we focused on characterizing multifunctional DN T cells in various immune responses. DN regulatory T cells have the capacity to prevent graft-versus-host disease and have therapeutic value for autoimmune disease. T helper-like DN T cells protect against or promote inflammation and virus infection depending on the specific settings and promote certain autoimmune disease. Notably, we clarified the role of DN tumor-infiltrating lymphocytes and outlined the potential for malignant proliferation of DN T cells. Finally, we reviewed the recent advances in the applications of DN T cell-based therapy for cancer. In conclusion, a better understanding of the heterogeneity and functions of DN T cells may help to develop DN T cells as a potential therapeutic tool for inflammation, immune disorders and cancer.

Ly-6D of Japanese flounder (Paralichthys olivaceus) functions as a complement regulator and promotes host clearance of pathogen

The Lymphocyte antigen-6 (Ly-6) superfamily has been considered to play an important role in the innate immunity of mammals. The functions of Ly-6 proteins are diverse since their low sequence homology. Currently, the function of Ly-6D, a member of Ly-6 family proteins, is completely unknown in teleost. In the present study, we identified and characterized a Ly-6D homologue (named PoLy-6D) from the teleost fish Paralichthys olivaceus and examined its immune function. PoLy-6D possesses a hydrophobic signal peptide, a LU domain including a conserved "LXCXXC" motif in N-terminus and a "CCXXXXCN" motif in C-terminus. Under normal physiological condition, PoLy-6D expression distributes in all the examined tissues, the highest three tissues are successively spleen, head kidney, and blood. When infected by extracellular and intracellular bacterial pathogens and viral pathogen, PoLy-6D expression was induced and the patterns vary with different types of microbial pathogens infection and different immune tissues. In vitro experiment showed recombinant PoLy-6D (rPoLy-6D) inhibited the lysis of rabbit red blood cells by serum and selectively improved bacterial survival in serum. After serum were treated by antibody of rPoLy-6D, bacteriostatic effect of serum was obviously enhanced. These results indicate the importance of PoLy-6D as a complement regulator. rPoLy-6D possessed the binding activity to multiple bacteria but did not exhibit antimicrobial activities. The interaction between rPoLy-6D and bacteria suggests that PoLy-6D is involved in host clearance of pathogens probably by serving as a receptor for pathogens. Overexpression of PoLy-6D in vivo promoted the host defense against invading E. piscicida. These findings add new insights into the regulation mechanism of the complement system in teleost and emphasize the importance of Ly-6D products for the control of pathogen infection.

Involvement of Lypge in the formation of eye and pineal gland in zebrafish

The proteins of Ly-6 (lymphocyte antigen-6) family are involved in the regulation of immunoreaction, cell migration and adhesion, and neuronal excitability. However, little is known about the function of Ly-6 proteins in embryogenesis. Herein, we identified a GPI anchored Ly-6 member named ly6 expressed in pineal gland and eye (lypge). Dynamic expression pattern of lypge was revealed by whole mount in situ hybridization. It was strikingly expressed in the pineal gland and cone photoreceptor, and its expression was regulated by orthodenticle homolog 5 (otx5) which has been shown to control the expression of many pineal genes. In addition, we demonstrated that lypge was rhythmically expressed in larvae from 4dpf on. Moreover, knockdown of lypge resulted in small head and small eye formed in zebrafish embryos. These suggest that Lypge is involved in the formation of the eye and pineal gland in early development of zebrafish.

Engaging Ly-6A/Sca-1 triggers lipid raft-dependent and -independent responses in CD4+ T-cell lines

INTRODUCTION

The lymphocyte antigen 6 (Ly-6) supergene family encodes proteins of 12-14 kda in molecular mass that are either secreted or anchored to the plasma membrane through a glycosyl-phosphatidylinisotol (GPI) lipid anchor at the carboxy-terminus. The lipidated GPI-anchor allows localization of Ly-6 proteins to the 10-100 nm cholesterol-rich nano-domains on the membrane, also known as lipid rafts. Ly-6A/Sca-1, a member of Ly-6 gene family is known to transduce signals despite the absence of transmembrane and cytoplasmic domains. It is hypothesized that the localization of Ly-6A/Sca-1 with in lipid rafts allows this protein to transduce signals to the cell interior.

METHODS AND RESULTS

In this study, we found that cross-linking mouse Ly-6A/Sca-1 protein with a monoclonal antibody results in functionally distinct responses that occur simultaneously. Ly-6A/Sca-1 triggered a cell stimulatory response as gauged by cytokine production with a concurrent inhibitory response as indicated by growth inhibition and apoptosis. While production of interleukin 2 (IL-2) cytokine by CD4⁺ T cell line in response to cross-linking Ly-6A/Sca-1 was dependent on the integrity of lipid rafts, the observed cell death occurred independently of it. Growth inhibited CD4⁺ T cells showed up-regulated expression of the inhibitory cell cycle protein p27^kip but not of p53. In addition, Ly-6A/Sca-1 induced translocation of cytochrome C to the cytoplasm along with activated caspase 3 and caspase 9, thereby suggesting an intrinsic apoptotic cell death mechanism.

CONCLUSIONS

We conclude that opposing responses with differential dependence on the integrity of lipid rafts are triggered by engaging Ly-6A/Sca-1 protein on the membrane of transformed CD4⁺ T cells.

Differential host gene responses from infection with neurovirulent and partially-neurovirulent strains of Venezuelan equine encephalitis virus

Background

Venezuelan equine encephalitis virus (VEEV) is an alphavirus in the family Togaviridae. VEEV causes a bi-phasic illness in mice where primary replication in lymphoid organs is followed by entry into the central nervous system (CNS). The CNS phase of infection is marked by encephalitis and large scale neuronal death ultimately resulting in death. Molecular determinants of VEEV neurovirulence are not well understood. In this study, host gene expression response to highly neurovirulent VEEV (V3000 strain) infection was compared with that of a partially neurovirulent VEEV (V3034 strain) to identify host factors associated with VEEV neurovirulence.

Methods

Whole genome microarrays were performed to identify the significantly modulated genes. Microarray observations were classified into three categories i.e., genes that were similarly modulated against both V3000 and V3034 infections, and genes that were uniquely modulated in infection with V3034 or V3000. Histologic sections of spleen and brain were evaluated by hematoxylin and eosin stains from all the mice.

Results

V3000 infection induced a greater degree of pathology in both the spleen and brain tissue of infected mice compared to V3034 infection. Genes commonly modulated in the spleens after V3000 or V3034 infection were associated with innate immune responses, inflammation and antigen presentation, however, V3000 induced a gene response profile that suggests a stronger inflammatory and apoptotic response compared to V3034. In the brain, both the strains of VEEV induced an innate immune response reflected by an upregulation of the genes involved in antigen presentation, interferon response, and inflammation. Similar to the spleen, V3000 was found to induce a stronger inflammatory response than V3034 in terms of induction of pro-inflammatory genes and associated pathways. Ccl2, Ccl5, Ccl6, and Ly6 were uniquely upregulated in V3000 infected mouse brains and correlated with the extensive inflammation observed in the brain.

Conclusion

The common gene profile identified from V3000 and V3034 exposure can help in understanding a generalized host response to VEEV infection. Inflammatory genes that were uniquely identified in mouse brains with V3000 infection will help in better understanding the lethal neurovirulence of VEEV. Future studies are needed to explore the roles played by the genes identified in VEEV induced encephalitis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2355-3) contains supplementary material, which is available to authorized users.

Investigating B Cell Development, Natural and Primary Antibody Responses in Ly-6A/Sca-1 Deficient Mice

Ly-6A/Stem cell antigen-1 (Ly-6A/Sca-1) is a glycosylphosphatidylinositol-anchored protein expressed on many cell types including hematopoietic stem cells (HSCs) and early lymphoid-specific progenitors. Ly-6A/Sca-1 is expressed on CD4⁺ T cells and plays a role in regulating cellular responses to foreign antigens. The role of Ly-6A/Sca-1 in primary antibody responses has not been defined. To investigate whether Ly-6A/Sca-1 functions in humoral immunity, we first injected Ly-6A/Sca-1-deficient and wild-type control mice with chicken ovalbumin (c-Ova) protein mixed with an adjuvant. We then assessed the ability of the mice to generate a primary antibody response against cOva. We further examined the development of B cells and circulating antibody isotypes in non-immunized Ly-6A/Sca-1deficient mice to determine if Ly6A/Sca-1 functions in development irrespective of antigen-specific immune activation. Ly-6A/Sca-1/Sca-1-deficient mice did not show any significant changes in the number of B lymphocytes in the bone marrow and peripheral lymphoid tissues. Interestingly, Ly-6A/Sca-1/Sca-1^-/- mice have significantly elevated serum levels of IgA with λ light chains compared to wild type controls. B cell clusters with high reactivity to anti-IgA λ monoclonal antibody were detected in the lamina propria of the gut, though this was not observed in the bone marrow and peripheral lymphoid tissues. Despite these differences, the Ly-6A/Sca-1deficient mice generated a similar primary antibody response when compared to the wild-type mice. In summary, we conclude that the primary antibody response to cOva antigen is similar in Ly-6A/Sca-1deficient and sufficient mice. In addition, we report significantly higher expression of the immunoglobulin λ light chain by B cells in lamina propria of Ly-6A/Sca-1deficient mice when compared to the wild-type control.

Mysm1 is required for interferon regulatory factor expression in maintaining HSC quiescence and thymocyte development

Mysm1(-/-) mice have severely decreased cellularity in hematopoietic organs. We previously revealed that Mysm1 knockout impairs self-renewal and lineage reconstitution of HSCs by abolishing the recruitment of key transcriptional factors to the Gfi-1 locus, an intrinsic regulator of HSC function. The present study further defines a large LSKs in >8-week-old Mysm1(-/-) mice that exhibit increased proliferation and reduced cell lineage differentiation compared with those of WT LSKs. We found that IRF2 and IRF8, which are important for HSC homeostasis and commitment as transcription repressors, were expressed at lower levels in Mysm1(-/-) HSCs, and Mysm1 enhanced function of the IRF2 and IRF8 promoters, suggesting that Mysm1 governs the IRFs for HSC homeostasis. We further found that the lower expressions of IRF2 and IRF8 led to an enhanced transcription of p53 in Mysm1(-/-) HSCs, which was recently defined to have an important role in mediating Mysm1(-/-)-associated defects. The study also revealed that Mysm1(-/-) thymocytes exhibited lower IRF2 expression, but had higher Sca1 expression, which has a role in mediating thymocyte death. Furthermore, we found that the thymocytes from B16 melanoma-bearing mice, which display severe thymus atrophy at late tumor stages, exhibited reduced Mysm1 and IRF2 expression but enhanced Sca1 expression, suggesting that tumors may downregulate Mysm1 and IRF2 for thymic T-cell elimination.

Identification and expression of an uncharacterized Ly-6 gene cluster in zebrafish Danio rerio

The Ly-6/uPAR/CD59/neurotoxin superfamily (Ly-6SF) identified in most metazoan has been shown to play important roles in different biological processes including immunity, cellular adhesion, and cell signaling. Members of this superfamily contain one or more conserved domains known as Ly-6/uPAR (LU) domain, which harbors 8 or 10 conserved cysteine residues forming 4-5 disulfide bonds. In this study, we reported the identification of a novel zebrafish Ly-6 gene cluster on chromosome 21, which consists of seven genes ly21.1, ly21.2, ly21.3, ly21.4, ly21.5, ly21.6, and ly21.7 and their spatiotemporal expression pattern during development. All the seven genes possess features typical of the Ly-6/neurotoxin superfamily, and phylogenetic analysis shows that these genes form a single cluster branching form other members of Ly-6 family, suggesting that the seven genes evolved by an event of intra-chromosome gene duplication. However, deduced Ly21.1-7 proteins share little homology with Ly-6 family proteins from other species, no orthologs are identified in vertebrates, including teleosts, hinting that ly21.1-7 genes are evolutionarily a novel addition to zebrafish. Expression analyses show that maternal mRNAs of ly21.1-7 genes are detected during early developmental stages, but later in development, they exhibit tissue-specific expression. Except for ly21.2 which is expressed in the skin ionocytes, all the remaining six genes are mainly expressed in the developing brain.

Fat-associated lymphoid cluster in Cyprinus carpio: Characterisation and its relation with peritoneal haemangiosarcoma

FALC cells are natural helper cells producing Th2-type cytokines, which express c-kit, Sca-1, IL7R and CD45 in mouse and human. These cells are involved in allergic responses and contribute to the inflammatory reactions of adipose tissue; however, a lack of information prevails about the presence of these cells in other species. The aim of the study was to identify and characterise FALC cells in the common carp (Cyprinus carpio) using immunohistochemistry and molecular biology techniques as well as to explore their relationships with their microenvironment. Histological description of the FALC was performed using H&E and polyclonal antibodies were used against cell-surface markers such as c-kit, Sca-1 and CD45. Furthermore, gene expression of c-kit, Sca-1 and IL7R was assessed. C. carpio FALC cells express the same surface markers reported in FALC of the mouse at both the pre- and post-transcriptional level. By exposure to the soluble fraction of helminths, FALC cells produce abundant Th2 cytokines (IL-5, IL-6 and IL-13) but do not synthesise IL-1α. Additionally, FALC cells probably participate in vascular remodelling of the intestine vessels, inducing tumours because a malignant haemangiosarcoma in the peritoneal cavity was found. In this tumour, abundant FALC with their characteristic cell-surface markers were detected. The findings of this study suggest the involvement of some proto-oncogenes such as c-kit and Sca-1, and the deregulation of Src kinases modulated by CD45 present in C. carpio FALC with the ontogeny of peritoneal haemangiosarcoma in this fish species.

Identification of a Ly-6 superfamily gene expressed in lateral line neuromasts in zebrafish

Lymphocyte antigen-6 (Ly-6) superfamily members have been identified in zebrafish, but the expression and function of these Ly-6 genes remain largely unknown. Posterior lateral line (pLL) system is produced by migrating pLL primordium (pLLp). Chemokine signaling, Notch, Wnt, and fibroblast growth factor (FGF) signaling regulate migration of pLLp cells and formation of neuromasts. However, the mechanism of neuromast deposition remains to be explored. Identification of novel genes expressed in pLLp will certainly help the study of such a process. Here we identified a Ly-6 gene called neuromast-expressed gpi-anchored lymphocyte antigen-6 (negaly6), which was specifically expressed in neuromast. Quantitative real-time PCR (qRT-PCR) analysis showed that negaly6 started to be expressed at 24 hpf, and whole-mount in situ hybridization analysis indicated that negaly6 was highly expressed in the trailing zone of pLLp and mature neuromast. Furthermore, negaly6 expression was inhibited by FGF signaling antagonist but not by Wnt signaling agonist or antagonist. Collectively, these data indicate that negaly6 may be associated with the regulation of neuromast deposition via FGF signaling pathway.

Acute lymphoid leukemia cells with greater stem cell antigen-1 (Ly6a/Sca-1) expression exhibit higher levels of metalloproteinase activity and are more aggressive in vivo

Stem cell antigen-1 (Ly6a/Sca-1) is a gene that is expressed in activated lymphocytes, hematopoietic stem cells and stem cells of a variety of tissues in mice. Despite decades of study its functions remain poorly defined. These studies explored the impact of expression of this stem cell associated gene in acute lymphoid leukemia. Higher levels of Ly6a/Sca-1 expression led to more aggressive leukemia growth in vivo and earlier death of hosts. Leukemias expressing higher levels of Ly6a/Sca-1 exhibited higher levels of matrix metalloproteinases. The results suggest the hypothesis that the more aggressive behavior of Ly6a/Sca-1 expressing leukemias is due at least in part to greater capacity to degrade microenvironmental stroma and invade tissues.

Prostate stem cell antigen and cancer risk, mechanisms and therapeutic implications

Prostate stem cell antigen (PSCA) was originally identified as a tumor antigen in prostate cancer. Recent studies indicated that PSCA was correlated with many cancer types. In this review, we will consider the origin of PSCA, discuss the expression of PSCA in normal and cancer tissue, describe PSCA polymorphisms and cancer risk, summarize potential mechanisms for PSCA involvement in cancer; and look into the therapeutic implications of PSCA. PSCA is upregulated in prostate cancer, pancreatic cancer and bladder cancer, as well as a number of others, making it an ideal clinical target for both diagnosis and therapy. Future studies will be required to explore its mechanisms on various cancer types, and to confirm its clinical utility for diagnosis and immunotherapy strategies. The study of PSCA regulation and expression may also provide information on normal prostate development and prostate carcinogenesis.

Short toxin-like proteins attack the defense line of innate immunity

ClanTox (classifier of animal toxins) was developed for identifying toxin-like candidates from complete proteomes. Searching mammalian proteomes for short toxin-like proteins (coined TOLIPs) revealed a number of overlooked secreted short proteins with an abundance of cysteines throughout their sequences. We applied bioinformatics and data-mining methods to infer the function of several top predicted candidates. We focused on cysteine-rich peptides that adopt the fold of the three-finger proteins (TFPs). We identified a cluster of duplicated genes that share a structural similarity with elapid neurotoxins, such as α-bungarotoxin. In the murine proteome, there are about 60 such proteins that belong to the Ly6/uPAR family. These proteins are secreted or anchored to the cell membrane. Ly6/uPAR proteins are associated with a rich repertoire of functions, including binding to receptors and adhesion. Ly6/uPAR proteins modulate cell signaling in the context of brain functions and cells of the innate immune system. We postulate that TOLIPs, as modulators of cell signaling, may be associated with pathologies and cellular imbalance. We show that proteins of the Ly6/uPAR family are associated with cancer diagnosis and malfunction of the immune system.

Low expression of stem cell antigen-1 on mouse haematopoietic precursors is associated with erythroid differentiation

Sca1 is a surface marker of haematopoietic stem cell but its role in erythropoiesis is still largely unknown. In this work we evaluated the ability of Sca1⁺ cells to differentiate into cells of the erythrocytic lineage. We performed FACS analysis of complete and purified Sca1⁺ bone marrow cells from C3H/HeNHsd mice and measured the expression of CD71 and Terr119 to evaluate the stages in erythroid development. Definitive erythropoiesis was evident within the complete bone marrow, while only proerythroblasts were found in Sca1⁺ cells, suggesting that Sca1 is a negative regulator of erythropoiesis. We also used FDCP-mix cells and their PU.1 and SCL transfectants. The PU.1 transfectant showed significantly increased expression of Sca1 and was not induced to differentiate into red blood cells, while the SCL transfectant showed significantly lower expression of Sca1 and produced red blood cells. The results of this study suggest that increased Sca1 expression on erythropoietic precursors inhibits erythroid differentiation.

Identification and expression of a novel member of Ly-6 superfamily in zebrafish Denio rerio

Ly-6 superfamily members are present in many metazoans and are divided into two groups: secreted proteins and glycosylphosphatidyl inositol (GPI)-anchored membrane proteins. They both contain one or more conserved domain identified as Ly-6/uPAR (LU) domain and play key roles in cellular adhesion and signaling. Here, we identify a novel member, lymphocyte antigen-6 epidermis (lye), of Ly-6 superfamily in zebrafish. In silico analyses revealed that lye codes for a predicted GPI-anchored membrane protein containing a conserved LU domain and 10 position-specific conserved cysteines typical of known Ly-6 proteins. Whole mount in situ hybridization showed that lye is predominantly expressed in epidermis. We thus named the gene lye, highlighting it is expressed in epidermis. Lye exhibits a dynamic expression pattern during development, which is initially expressed in enveloping layer at gastrula stage, then expressed in epidermis at later stages. It is also expressed in olfactory placode at 24 h post-fertilization. Subsequently, epidermal expression of lye becomes weaker gradually, whereas the expression in pharyngeal arch and pectoral fin increases at 2 and 3 days post-fertilization. Our study lays a foundation for further investigation of lye roles in early developmental stages.

The CD59 family member Leaky/Coiled is required for the establishment of the blood-brain barrier in Drosophila

The blood-brain barrier of Drosophila is established by the subperineurial glial cells that encase the CNS and PNS. The subperineurial glial cells are thin, highly interdigitated cells with epithelial character. The establishment of extensive septate junctions between these cells is crucial for the prevention of uncontrolled paracellular leakage of ions and solutes from the hemolymph into the nervous system. In the absence of septate junctions, macromolecules such as fluorescently labeled dextran can easily cross the blood-brain barrier. To identify additional components of the blood-brain barrier, we followed a genetic approach and injected Texas-Red-conjugated dextran into the hemolymph of embryos homozygous for chromosomal deficiencies. In this way, we identified the 153-aa-large protein Coiled, a new member of the Ly6 (leukocyte antigen 6) family, as being crucially required for septate junction formation and blood-brain barrier integrity. In coiled mutants, the normal distribution of septate junction markers such as NeurexinIV, Coracle, or Discs large is disturbed. EM analyses demonstrated that Coiled is required for the formation of septate junctions. We further show that Coiled is expressed by the subsperineurial glial cells in which it is anchored to the cell membrane via a glycosylphosphatidylinositol anchor and mediates adhesive properties. Clonal rescue studies indicate that the presence of Coiled is required symmetrically on both cells engaged in septate junction formation.

Association and haplotype analysis of prostate stem cell antigen with gastric cancer in Tibetans

Genetic factors are known to be important in the development of gastric cancer (GC). Prostate stem cell antigen (PSCA) has been shown to be expressed in diffuse-type GC, and PSCA variation is associated with susceptibility to diffuse-type GC in Japanese and Korean populations. The aim of this study was to investigate the association between PSCA gene polymorphisms and GC in a Tibetan population. We analyzed single-nucleotide polymorphisms of the PSCA gene in 196 patients with GC and 246 controls in a Tibetan population, using a polymerase chain reaction/ligase detection reaction test. The rs2294008 C/T polymorphism of the PSCA gene was significantly associated with the susceptibility to GC. The CT genotype was associated with a significantly higher risk of GC when compared with the CC genotype (odds ratio [OR] = 1.50; 95% confidence interval [CI], 1.01-2.23). Patients carrying the T allele had a significantly higher risk for developing GC compared with individuals carrying the C allele (OR = 1.34; 95% CI, 1.00-1.79). Haplotype analyses showed that CA haplotype was associated with a significantly decreased risk of GC when compared with the CG haplotype (OR = 0.47; 95% CI, 0.24-0.93). Our data indicate that PSCA gene polymorphisms may be associated with GC in Tibetans.

Immunohistochemical Expression of Prostate Stem Cell Antigen in Cystoprostatectomies with Incidental Prostate Cancer

High expression of Prostate Stem Cell Antigen (PSCA) has been shown to be associated with adverse prognostic features in clinically-diagnosed prostate cancer. The aim of this study is to analyze PSCA expression in cystoprostatectomies with incidental prostate carcinoma (PCa). PSCA expression was evaluated immunohistochemically in normal-looking epithelium (NEp), high-grade prostatic intraepithelial neoplasia (HGPIN) and pT2a Gleason score 6 acinar adenocarcinoma. The evaluation was carried out on 20 cystoprostatectomies (CyPs) with incidental PCa from men with bladder urothelial carcinoma (UC), and 20 radical prostatectomies (RPs) with hormonally untreated PCa from men with clinically detected PCa. Ki-67 was also investigated. The percentages of PSCA positive cells in HGPIN were significantly higher than in NEp (NEp: CyP, mean 2.92% ± standard deviation 6.26%; RP, 3.5% ± 6.46%. HGPIN: CyP, 13.67% ± 12.78%; RP, 14.67% ± 11.34%) (p<0.001). The proportions of positive cells in PCa were greater than in HGPIN (CyP, 20.25% ± 15.96%; RP, 22.58% ± 13.67%) (p0.001). For Ki-67 labeling, the proportions of positive nuclei in the CyPs significantly increased from NEp through HGPIN to PCa. A similar trend was seen in the RPs. In the CyPs the percentages of PSCA and Ki67 positive cells were lower than in the RPs, the differences between the CyP and RP compartments being not statistically significant. Our findings suggest that PSCA is a marker associated with neoplastic transformation of prostate cells, both in CyPs and RPs. However, there are no significant differences between CyPs with incidental prostate carcinoma and RPs with clinically diagnosed cancer.

A microarray analysis of the XX Wnt4 mutant gonad targeted at the identification of genes involved in testis vascular differentiation

One of the earliest morphological changes during testicular differentiation is the establishment of an XY specific vasculature. The testis vascular system is derived from mesonephric endothelial cells that migrate into the gonad. In the XX gonad, mesonephric cell migration and testis vascular development are inhibited by WNT4 signaling. In Wnt4 mutant XX gonads, endothelial cells migrate from the mesonephros and form a male-like coelomic vessel. Interestingly, this process occurs in the absence of other obvious features of testis differentiation, suggesting that Wnt4 specifically inhibits XY vascular development. Consequently, the XX Wnt4 mutant mice presented an opportunity to focus a gene expression screen on the processes of mesonephric cell migration and testicular vascular development. We compared differences in gene expression between XY Wnt4+/+ and XX Wnt4+/+ gonads and between XX Wnt4-/- and XX Wnt4+/+ gonads to identify sets of genes similarly upregulated in wildtype XY gonads and XX mutant gonads or upregulated in XX gonads as compared to XY gonads and XX mutant gonads. We show that several genes identified in the first set are expressed in vascular domains, and have predicted functions related to cell migration or vascular development. However, the expression patterns and known functions of other genes are not consistent with roles in these processes. This screen has identified candidates for regulation of sex specific vascular development, and has implicated a role for WNT4 signaling in the development of Sertoli and germ cell lineages not immediately obvious from previous phenotypic analyses.

Stem cell antigen-1 localizes to lipid microdomains and associates with insulin degrading enzyme in skeletal myoblasts

Stem cell antigen-1 (Sca-1, Ly6A/E) is a glycosylphosphotidylinositol-anchored protein that identifies many tissue progenitor cells. We originally identified Sca-1 as a marker of myogenic precursor cells and subsequently demonstrated that Sca-1 regulates proliferation of activated myoblasts, suggesting an important role for Sca-1 in skeletal muscle homeostasis. Beyond its functional role in regulating proliferation, however, little is known about the mechanism(s) that drive Sca-1-mediated events. We now report that lipid microdomain organization is essential for normal myogenic differentiation, and that Sca-1 constitutively localizes to these domains during myoblast proliferation and differentiation. We also demonstrate that Sca-1 associates with insulin degrading enzyme (IDE), a catalytic protein responsible for the cleavage of mitogenic peptides, in differentiating myoblasts. We show that chemical inhibition of IDE as well as RNAi knockdown of IDE mRNA recapitulates the phenotype of Sca-1 interference, that is, sustained myoblast proliferation and delayed myogenic differentiation. These findings identify the first signaling protein that physically and functionally associates with Sca-1 in myogenic precursor cells, and suggest a potential pathway for Sca-1-mediated signaling. Future efforts to manipulate this pathway may lead to new strategies for augmenting the myogenic proliferative response, and ultimately muscle repair.

TEX101, a germ cell-marker glycoprotein, is associated with lymphocyte antigen 6 complex locus k within the mouse testis

In adult male mice, the glycosylphosphatidyl inositol-anchored glycoprotein TEX101 is expressed only in germ cells and is thought to be involved in spermatogenesis. However, the details regarding the function of TEX101 remain to be clarified. We previously identified Ly6k as a candidate TEX101-associated protein, but as molecular probes are not currently available to detect Ly6k, we do not have conclusive evidence of the association between TEX101 and Ly6k. In this study, we confirmed the biological interaction between TEX101 and Ly6k using an established anti-mouse Ly6k polyclonal antibody (pAb). A combination of immunoprecipitation, Western blot, and immunohistochemical analyses using the pAb revealed that TEX101 is physically associated with Ly6k within the testis. In addition, these proteins simultaneously co-migrate into the detergent-resistant membrane fractions, suggesting that TEX101 collaborates with Ly6k on the cell membrane and may play a role in spermatogenesis.

Cancer-testis antigen lymphocyte antigen 6 complex locus K is a serologic biomarker and a therapeutic target for lung and esophageal carcinomas

Gene expression profile analyses of non-small cell lung carcinomas (NSCLC) and esophageal squamous cell carcinomas (ESCC) revealed that lymphocyte antigen 6 complex locus K (LY6K) was specifically expressed in testis and transactivated in a majority of NSCLCs and ESCCs. Immunohistochemical staining using 406 NSCLC and 265 ESCC specimens confirmed that LY6K overexpression was associated with poor prognosis for patients with NSCLC (P = 0.0003), as well as ESCC (P = 0.0278), and multivariate analysis confirmed its independent prognostic value for NSCLC (P = 0.0035). We established an ELISA to measure serum LY6K and found that the proportion of the serum LY6K-positive cases was 38 of 112 (33.9%) NSCLC and 26 of 81 (32.1%) ESCC, whereas only 3 of 74 (4.1%) healthy volunteers were falsely diagnosed. In most cases, there was no correlation between serum LY6K and conventional tumor markers of carcinoembryonic antigen (CEA) and cytokeratin 19-fragment (CYFRA 21-1) values. A combined ELISA for both LY6K and CEA classified 64.7% of lung adenocarcinoma patients as positive, and the use of both LY6K and CYFRA 21-1 increased sensitivity in the detection of lung squamous cell carcinomas and ESCCs up to 70.4% and 52.5%, respectively, whereas the false positive rate was 6.8% to 9.5%. In addition, knocked down of LY6K expression with small interfering RNAs resulted in growth suppression of the lung and esophageal cancer cells. Our data imply that a cancer-testis antigen, LY6K, should be useful as a new type of tumor biomarker and probably as a target for the development of new molecular therapies for cancer treatment.

Concise review: stem cell antigen-1: expression, function, and enigma

Cloned 20 years ago, stem cell antigen-1 (Sca-1) is used extensively to enrich for murine hematopoietic stem cells. The realization that many different stem cell types share conserved biochemical pathways has led to a flood of recent research using Sca-1 as a candidate marker in the search for tissue-resident and cancer stem cells. Although surprisingly little is still known about its biochemical function, the generation and analysis of knockout mice has begun to shed light on the functions of Sca-1 in stem and progenitor cells, demonstrating that it is more than a convenient marker for stem cell biologists. This review summarizes the plethora of recent findings utilizing Sca-1 as a parenchymal stem cell marker and detailing its functional role in stem and progenitor cells and also attempts to explain the lingering mysteries surrounding its biochemical function and human ortholog. Disclosure of potential conflicts of interest is found at the end of this article.

Characterization of the five novel Ly-6 superfamily members encoded in the MHC, and detection of cells expressing their potential ligands

Lymphocyte Antigen 6 (Ly-6) superfamily members are cysteine-rich, generally GPI-anchored cell surface proteins, which have definite or putative immune related roles. There are 27 members of this family described so far in the human genome and 37 in the mouse. Five of them are clustered in the class III region of the human and mouse MHCs. Following computational analyses, we functionally characterized the encoded proteins by creating epitope-tagged fusion constructs to determine molecular weight, complex formation, subcellular localization, post-translational modifications and ligand binding. We found that all human and mouse proteins were glycosylated, and most could form part of larger complexes. Human and mouse Ly6G6c and Ly6G6d, and mouse Ly6g6e were found to be GPI-anchored cell surface proteins, highly expressed at the leading edges of cells, on filopodia, which are normally involved in cell adhesion and migration. However, analysis of Ly6G5c and Ly6G5b indicated that they are potentially secreted proteins. Our results indicate that there are two subclusters of related Ly-6 proteins in this region of the MHC, with Ly6G6c, Ly6G6d, and Ly6G6e forming one and Ly6G5c and Ly6G5b forming another. In addition, by FACS analysis we have found that the potential ligands for human LY6G6C, LY6G6D, and LY6G5C are expressed on K562 cells, an undifferentiated megakaryocyte cell line, indicating a potential role in hematopoietic cell differentiation. This characterization of the five MHC class III region Ly-6 family members is of great relevance, as they represent 18% of the human Ly-6 protein family and 50% of the secreted ones.

The expression of prostate stem cell antigen in human clear cell renal cell carcinoma: a quantitative reverse transcriptase-polymerase chain reaction analysis

OBJECTIVES

To analyse the gene expression level of prostate stem cell antigen (PSCA) in human clear cell renal cell carcinoma (CC-RCC) and its relationship with conventional clinicopathological manifestations, to evaluate its prognostic value for patient outcome, and to determine the effect of PSCA on the progression of CC-RCC.

PATIENTS AND METHODS

We quantified PSCA mRNA level in human RCC cell lines (ACHN, A704, KPK-1, Caki-1, and Caki-2) and in 154 surgical tissue samples (81 from CC-RCC, 73 from normal kidney) using real-time reverse transcriptase-polymerase chain reaction (RT-PCR). The findings were analysed in relation to clinicopathological factors. Immunohistochemical expression was examined using confocal laser scanning light-microscopy.

RESULTS

PSCA was overexpressed in all RCC cell lines. PSCA mRNA levels were significantly higher in CC-RCC than in normal kidney tissue samples (P < 0.001), in G2-G3 than in G1 tumours (P = 0.028), and in advanced disease (T3-T4) than in organ-confined (T1-T2) tumours (P = 0.016). There was significantly higher PSCA mRNA expression in patients with M1 than in those with M0 disease (P = 0.029). Patients in whom the lesions had high PSCA expression levels had a significantly worse prognosis than those with low PSCA expression levels (P = 0.044). Using immunohistochemical analysis there was markedly greater PSCA expression in CC-RCC than in normal kidney, and in advanced-disease high-grade tumours than in organ-confined low-grade tumours.

CONCLUSIONS

A significant correlation was detected in the gene expression level of PSCA with histological grade, clinicopathological stage and prognosis in CC-RCC. Our data indicate that PSCA is associated with carcinogenesis and progression of CC-RCC.

A microarray analysis of the XX Wnt4 mutant gonad targeted at the identification of genes involved in testis vascular differentiation

One of the earliest morphological changes during testicular differentiation is the establishment of an XY specific vasculature. The testis vascular system is derived from mesonephric endothelial cells that migrate into the gonad. In the XX gonad, mesonephric cell migration and testis vascular development are inhibited by WNT4 signaling. In Wnt4 mutant XX gonads, endothelial cells migrate from the mesonephros and form a male-like coelomic vessel. Interestingly, this process occurs in the absence of other obvious features of testis differentiation, suggesting that Wnt4 specifically inhibits XY vascular development. Consequently, the XX Wnt4 mutant mice presented an opportunity to focus a gene expression screen on the processes of mesonephric cell migration and testicular vascular development. We compared differences in gene expression between XY Wnt4+/+ and XX Wnt4+/+ gonads and between XX Wnt4+/+ and XX Wnt4+/+ gonads to identify sets of genes similarly upregulated in wildtype XY gonads and XX mutant gonads or upregulated in XX gonads as compared to XY gonads and XX mutant gonads. We show that several genes identified in the first set are expressed in vascular domains, and have predicted functions related to cell migration or vascular development. However, the expression patterns and known functions of other genes are not consistent with roles in these processes. This screen has identified candidates for regulation of sex specific vascular development, and has implicated a role for WNT4 signaling in the development of Sertoli and germ cell lineages not immediately obvious from previous phenotypic analyses.

Identification of lynx2, a novel member of the ly-6/neurotoxin superfamily, expressed in neuronal subpopulations during mouse development

We isolated a new gene which shares all the features of the Ly-6/neurotoxin superfamily, from gene organization to predicted 3D structure. As it is preferentially expressed in the nervous system, we called this gene lynx2, by analogy with lynx1, a nAChR modulator. In embryonic and postnatal mouse, lynx2 is expressed in postmitotic central and peripheral neurons. These include subpopulations of motor neurons, sensory neurons, interneurons and neurons of the autonomous nervous system. In addition, lynx2 is transiently expressed around the growing nerves in the limb bud. Comparison of its spatio-temporal expression pattern with that of two other members of this family, lynx1 and ly-6h, shows that these genes are detected both in distinct and overlapping neuron populations.

Expression of the hematopoietic stem cell antigen Sca-1 (LY-6A/E) in liver sinusoidal endothelial cells: possible function of Sca-1 in endothelial cells

Several reports have shown that the expression of Sca-1 (Ly-6A/E), the most widely used murine hematopoietic stem cell marker, is restricted to blood vessels in several nonhematopoietic tissues. However, there is no information about which components are expressing Sca-1, and what the role of Sca-1 could be. Because we have previously shown that murine liver endothelial cells from the hepatic sinusoid (LSEC) express some HSC markers (i. e., CD34 and c-kit), we hypothesized that these cells could also express Sca-1. In this work, we show that Sca-1 is constitutively expressed in LSEC, as well as in the liver sinusoid lumen. The expression of Sca-1 in LSEC was confirmed at the mRNA and protein level by reverse transcriptase (RT)-PCR, flow cytometry, and immunofluorescence studies. The expression of Sca-1 was enhanced on the surface of LSEC by tumor necrosis factor (TNF). We examined whether Sca-1 ligation on the surface of LSEC regulates some biological response in these cells. Our results show that ligation of Sca-1 by the anti-Ly-6A/E monoclonal antibody (mAb) D7 stimulated the growth of LSEC and the production of interleukin-6 (IL-6) by these cells. To our knowledge, this is the first report that LSEC express Sca-1, which may constitute additional support to the theory of a common progenitor for the hematopoietic and endothelial cells. Our results show a novel role of Sca-1, indicating that it induces activation of LSEC to proliferate and to produce IL-6. These results suggest that Sca-1 may participate in several clinical conditions such as angiogenesis and inflammation.

Intectin, a Novel Small Intestine-specific Glycosylphosphatidylinositol-anchored Protein, Accelerates Apoptosis of Intestinal Epithelial Cells

Intestinal epithelial cells undergo rapid turnover and exfoliation especially at the villus tips. This process is modulated by various nutrients especially fat. Apoptosis is one of the important regulatory mechanisms of this turnover. Therefore, identification of the factors that control epithelial cell apoptosis should help us understand the mechanism of intestinal mucosal turnover. Here, we report the identification of a novel small intestine-specific member of the Ly-6 family, intectin, by signal sequence trap method. Intectin mRNA expression was exclusively identified in the intestine and localized at the villus tips of intestinal mucosa, which is known to undergo apoptosis. Intectin mRNA expression was modulated by nutrition. Intestinal epithelial cells expressing intectin were more sensitive to palmitate-induced apoptosis, compared with control intestinal epithelial cells, and such effect was accompanied by increased activity of caspase-3. Intectin expression also reduced cell-cell adhesion of intestinal epithelial cells.

Prostate stem cell antigen (PSCA) expression in human prostate cancer tissues: implications for prostate carcinogenesis and progression of prostate cancer

OBJECTIVE

Prostate stem cell antigen (PSCA) is a recently defined homolog of the Thy-1/Ly-6 family of glycosylphosphatidylinositol (GPI)-anchored cell surface antigens. The objective of the present study was to examine the expression status of PSCA protein and mRNA in clinical specimens of human prostate cancer (PCa) and to validate it as a potential molecular target for diagnosis and treatment of PCa.

METHODS

Immunohistochemical (IHC) and in situ hybridization (ISH) analyses of PSCA expression were simultaneously performed on paraffin-embedded sections of 20 benign prostatic hyperplasia (BPH), 20 prostatic intraepithelial neoplasm (PIN) and 48 prostate cancer (PCa) tissues, including 9 androgen-independent prostate cancers. The level of PSCA expression was semiquantitatively scored by assessing both the percentage and intensity of PSCA-positive staining cells in the specimens. We then compared the PSCA expression between BPH, PIN and PCa tissues and analyzed the correlations of PSCA expression level with pathological grade, clinical stage and progression to androgen-independence in PCa.

RESULTS

In BPH and low grade PIN, PSCA protein and mRNA staining were weak or negative and less intense and uniform than that observed in high grade PIN (HGPIN) and PCa. Moderate to strong PSCA protein and mRNA expression were noted in 8 of 11 (72.7%) HGPIN and in 40 of 48 (83.4%) PCa specimens examined by IHC and ISH analyses, and their statistical significance was compared with BPH (20%) and low-grade PIN (22.2%) specimens (P < 0.05). The expression level of PSCA increased with a higher Gleason grade, advanced stage and progression to androgen-independence (P < 0.05). In addition, IHC and ISH staining revealed a high degree of correlation between PSCA protein and mRNA overexpression.

CONCLUSIONS

Our data demonstrate that PSCA as a new cell surface marker is overexpressed in a majority of cases of human PCa. PSCA expression correlates positively with adverse tumor characteristics, such as increasing pathological grade (poor cell differentiation), worsening clinical stage and androgen-independence and speculatively with prostate carcinogenesis. PSCA may possess prognostic utility and may be a promising molecular target for diagnosis and treatment of PCa.

Prostate stem cell antigen (PSCA) expression in human prostate cancer tissues and its potential role in prostate carcinogenesis and progression of prostate cancer

BACKGROUND

Prostate stem cell antigen (PSCA) is a recently defined homologue of the Thy-1/Ly-6 family of glycosylphosphatidylinositol (GPI)-anchored cell surface antigens. The purpose of the present study was to examine the expression status of PSCA protein and mRNA in clinical specimens of human prostate cancer (Pca) and to validate it as a potential molecular target for diagnosis and treatment of Pca.

MATERIALS AND METHODS

Immunohistochemical (IHC) and in situ hybridization (ISH) analyses of PSCA expression were simultaneously performed on paraffin-embedded sections from 20 benign prostatic hyperplasia (BPH), 20 prostatic intraepithelial neoplasm (PIN) and 48 prostate cancer (Pca) tissues, including 9 androgen-independent prostate cancers. The level of PSCA expression was semiquantitatively scored by assessing both the percentage and intensity of PSCA-positive staining cells in the specimens. Then compared PSCA expression between BPH, PIN and Pca tissues and analysed the correlations of PSCA expression level with pathological grade, clinical stage and progression to androgen-independence in Pca.

RESULTS

In BPH and low grade PIN, PSCA protein and mRNA staining were weak or negative and less intense and uniform than that seen in HGPIN and Pca. There were moderate to strong PSCA protein and mRNA expression in 8 of 11 (72.7%) HGPIN and in 40 of 48 (83.4%) Pca specimens examined by IHC and ISH analyses, with statistical significance compared with BPH (20%) and low grade PIN (22.2%) samples (p < 0.05, respectively). The expression level of PSCA increased with high Gleason grade, advanced stage and progression to androgen-independence (p < 0.05, respectively). In addition, IHC and ISH staining showed a high degree of correlation between PSCA protein and mRNA overexpression.

CONCLUSIONS

Our data demonstrate that PSCA as a new cell surface marker is overexpressed by a majority of human Pca. PSCA expression correlates positively with adverse tumor characteristics, such as increasing pathological grade (poor cell differentiation), worsening clinical stage and androgen-independence, and speculatively with prostate carcinogenesis. PSCA protein overexpression results from upregulated transcription of PSCA mRNA. PSCA may have prognostic utility and may be a promising molecular target for diagnosis and treatment of Pca.

Developmentally Distinct Th Cells Control Plasma Cell Production In Vivo

Differential Ly6C expression identifies a major phenotypic division in CD44loCD62LhiCD4+ Th cells. Using two separate models of single subset adoptive transfer, we demonstrate the unique capacity of Ly6Chi Th cells to promote antigen-specific plasma cell production in vivo. In contrast, both compartments support germinal center formation and proliferate to equivalent levels upon TCR triggering in vivo and in vitro. Developmentally, CD4+CD8- thymocytes leave the thymus expressing low levels of Ly6C; 3 days later approximately 50% stably upregulate Ly6C without cell division or TCR engagement in the periphery. Interestingly, antigen-specific Th cell clonotypes unevenly assort into these peripheral compartments, creating separate TCR repertoires that underpin peripheral functional diversity. Taken together, these data reveal a developmentally distinct Ly6Chi naive Th cell compartment subspecialized to regulate plasma cell production in vivo.

Activation induced differential regulation of stem cell antigen-1 (Ly-6A/E) expression in murine B cells

Expression of stem cell antigen-1 (Ly-6A/E) is developmentally regulated in murine B cells. However, little is known about its modulation during B cell activation. We report here the differential regulation of Ly-6A/E expression in response to diverse activation signals in mature B cells. Stimulation of resting B cells through the antigen receptor (BCR) inhibited, Ly-6A/E surface expression in dose dependent manner. Activation induced downregulation of Ly-6A/E is specific to BCR mediated signaling events as stimulation of B cells with anti-CD40, lipopolysaccharide or interferon-gamma induced upregulation of Ly-6A/E surface expression. The activation induced differential modulation of Ly-6A/E expression is mediated at the mRNA levels. A role for BCR signaling in inhibition of Ly-6A/E expression was further confirmed using STAT-1(-/-) B cells, which expressed constitutive, but not inducible Ly-6A/E. The BCR induced inhibition of Ly-6A/E RNA and surface expression was mimicked by ionomycin, but not phorbol myristate acetate, indicating a role for calcium but not protein kinase C dependent signaling events. Inhibition of calcineurin reversed the BCR or ionomycin inhibited Ly-6A/E expression. Interestingly, in vitro differentiation analysis of Ly-6A/E(+) and Ly-6A/E(-) splenic B cells revealed the Ly-6A/E(+) cells to be the major source of antibody production, suggesting a potential role for Ly-6A/E in B cell differentiation. These studies provide the first evidence for activation induced differential modulation and differentiation of Ly-6A/E(+) B cells.

Characterization of the human Ly-6 antigens, the newly annotated member Ly-6K included, as molecular markers for head-and-neck squamous cell carcinoma

The E48 antigen is a successfully explored molecular marker for the diagnosis and therapy of HNSCC. The applicability of E48 as an HNSCC-associated antigen, however, is restricted due to its heterogeneous expression in 30% of tumors; and identification of additional target antigens is therefore desired. E48 belongs to the Ly-6 antigen family, comprising a group of highly homologous, low m.w., GPI-anchored surface proteins, of which some show tissue-restricted expression patterns. To identify novel human HNSCC-associated Ly-6 members with squamous cell-associated expression patterns, we performed comprehensive gene-screening consisting of BLAST searches within GenBank databases, followed by expression analysis. Using this approach, the Ly-6K gene could be annotated as a novel member of the human Ly-6 family. Expression of the human Ly-6 genes E48, Ly-6K, PSCA, GML, RIG-E, G6C and Ly-6H was prescreened by qualitative RT-PCR and subsequently analyzed by quantitative RT-PCR in normal keratinocytes, HNSCC cell lines, normal mucosa, HNSCC tumors as well as normal peripheral blood and bone marrow cells. PSCA was highly expressed in normal mucosa, but 100-fold decreased expression was seen in HNSCC. For Ly-6H, GML and G6C, no or very low expression was observed in keratinocytes and HNSCC. Expression of RIG-E was high in normal and malignant squamous cells and in peripheral blood and bone marrow cells, thus limiting its applicability as an HNSCC-associated marker. In contrast, besides the E48 gene, the Ly-6K gene also appeared to be selectively expressed in HNSCC and normal squamous cells. Moreover, expression of Ly-6K was shown in HNSCC cell lines, in which no E48 expression could be detected. These data justify further evaluation of Ly-6K as potential target antigen for the diagnosis and therapy of HNSCC.

Ly6C induces clustering of LFA-1 (CD11a/CD18) and is involved in subtype-specific adhesion of CD8 T cells

Ly6C is a hemopoietic cell differentiation Ag found on a subset of CD8 T cells in the periphery. It is involved in target cell killing by CTLs, augments TCR-mediated activation of IL-2 and IFN-gamma production in CD8 T cells, and regulates CD8 T cell homing in vivo. In this study, we show that cross-linking of Ly6C causes clustering of LFA-1 (CD11a/CD18) on the surface of CD8 T cells via a mechanism dependent on reorganization of actin cytoskeleton and intracellular protease, calpain, but not the phosphatidylinositol 3-kinase pathway. In the capillary flow-adhesion assay, Ly6C cross-linking significantly augments lymphocyte adhesion to endothelium, and this is inhibited by an Ab that blocks LFA-1 function. Furthermore, upon in vitro cross-linking and during in vivo homing into lymph nodes, Ly6C is transiently lost from cell surface but becomes re-expressed on lymph node-resident CD8 T cells. The abilities of Ly6C to induce LFA-1 clustering and to be re-expressed after signaling-associated down-regulation may be important in regulating the homing of CD8 T cells into lymph nodes and in subsequent steps of CD8 T cell activation and effector function that again involve LFA-1.

Ly-6 superfamily members Ly-6A/E, Ly-6C, and Ly-6I recognize two potential ligands expressed by B lymphocytes

Most hemopoietic cells express one or more members of the Ly-6 supergene family of small glycosylphosphatidylinositol-linked proteins. Although levels of Ly-6 proteins vary with stages of differentiation and activation, their function largely remains unknown. To ascertain whether ligands for Ly-6 proteins exist, chimeric proteins were constructed in which Ly-6E, Ly-6C, and Ly-6I were fused to the murine IgM heavy chain. These chimeras specifically stained both developing and mature B lymphocytes, as assessed by flow cytometry. Analysis of variants of the CH27 B cell lymphoma revealed that Ly-6A/E and Ly-6I recognized different molecules. CH27 cells with low levels of Ly-6A/E ligand activity also lost expression of CD22, and cells transfected with CD22 gained the ability to bind the Ly-6A/E chimera and, to a lesser extent, the Ly-6C and Ly-6I chimeric proteins. As many mature B cells coexpress Ly-6A/E and CD22, the function of Ly-6 molecules may be to associate with other membrane proteins, possibly concentrating these ligands in lipid rafts, rather than acting directly as cell:cell adhesion molecules.

Transcriptional analysis of a novel cluster of LY-6 family members in the human and mouse major histocompatibility complex: five genes with many splice forms

Lymphocyte antigen-6 (LY-6) superfamily members are cysteine-rich, generally GPI-anchored cell surface proteins, which have definite or putative immune related roles. A cluster of five potential LY-6 superfamily members is located in the human and mouse major histocompatibility complex class III region. Comparative analysis of their genomic and cDNA sequences allowed us to carry out detailed annotations of these genes. We analyzed their mRNA expression patterns by RT-PCR performed on human and mouse cell line and tissue RNA. Sequence analysis of the transcripts revealed splice variants of all these genes in humans, and all but one in mouse. These splice forms retained introns or intron fragments, mainly generating premature stop codons, such that the only potentially functional mRNA was the predicted form. In some cases, the mis-spliced form was the most abundant form, suggesting a control mechanism for gene expression. Each gene showed mRNA expression differences between human and mouse.

Expression of the Ly-6A (Sca-1) lacZ transgene in mouse haematopoietic stem cells and embryos

The Sca-1 surface glycoprotein is used routinely as a marker for haematopoietic stem cell enrichment. Two allelic genes, Ly-6A and Ly-6E, encode this marker and appear to be differentially regulated in haematopoietic cells and haematopoietic stem cells. The Sca-1 protein has been shown to be expressed at a greater frequency in these cells from Ly-6A strains of mice. To study the specific expression pattern and haematopoietic regulation of the Ly-6A gene, we constructed a 14 kb cassette from a genomic Ly-6A fragment, inserted a lacZ reporter gene and created transgenic mice. We found that the Ly-6A lacZ transgene was expressed in the haematopoietic tissues and predominantly in the T-lymphoid lineage. Some expression was also found in the B-lymphoid and myeloid lineages. We demonstrated functional haematopoietic stem cell enrichment by sorting for beta-galactosidase-expressing cells from the bone marrow. In addition, we found an interesting embryonic expression pattern in the AGM region, the site of the first haematopoietic stem cell generation. Surprisingly, when compared with data from Ly-6E lacZ transgenic mice, our results suggest that the Ly-6A cassette does not improve lacZ marker gene expression in haematopoietic cells.

Ly-6A.2 expression regulates antigen-specific CD4+ T cell proliferation and cytokine production

Ly-6 proteins appear to serve cell adhesion and cell signaling function, but the precise role of Ly-6A.2 in CD4+ T lymphocytes is still unclear. Overexpression of Ly-6A.2 in T lymphocytes has allowed us to analyze the influence of elevated Ly-6A.2 expression on T cell function. In this study we report reduced proliferation of CD4+ T cells overexpressing Ly-6A.2 in response to a peptide Ag. Moreover, the Ly-6A.2-overexpressing CD4+ cells generated elevated levels of IL-4, a key factor that propels the differentiation of naive CD4+ T cells into Th2 subset. The hyporesponsiveness of Ly-6A.2 transgenic CD4+ T cells is dependent on the interaction of Ly-6A.2 T cells with the APCs and can be reversed by blocking the interaction between Ly-6A.2 and a recently reported candidate ligand. Overexpression of Ly-6A.2 in CD4+ T cells reduced their Ca(2+) responses to TCR stimulation, therefore suggesting effects of Ly-6A.2 signaling on membrane proximal activation events. In contrast to the observed Ag-specific hyporesponsiveness, the Ly-6A.2 transgenic CD4+ T cells produced IL-4 independent of the interactions between Ly-6A.2 and the candidate Ly-6A.2 ligand. Our results suggest that 1) interaction of Ly-6A.2 with a candidate ligand regulates clonal expansion of CD4+ Th cells in response to an Ag (these results also provide further functional evidence for presence of Ly-6A.2 ligand on APC); and 2) Ly-6A.2 expression on CD4+ T cells promotes production of IL-4, a Th2 differentiation factor.

SF20/IL-25, a novel bone marrow stroma-derived growth factor that binds to mouse thymic shared antigen-1 and supports lymphoid cell proliferation

Using a forward genetic approach and phenotype-based complementation screening to search for factors that stimulate cell proliferation, we have isolated a novel secreted bone marrow stroma-derived growth factor, which we termed SF20/IL-25. This protein signals cells to proliferate via its receptor, which we have identified as mouse thymic shared Ag-1 (TSA-1). Enforced expression of TSA-1 in IL-3-dependent Ba/F3 cells that do not express endogenous TSA-1 rendered cells to proliferate in a dose-dependent manner when stimulated with SF20/IL-25. FDCP2, a factor-dependent hemopoietic cell line that expresses endogenous TSA-1, could also be stimulated to proliferate with SF20/IL-25. Binding of SF20 to TSA-1 was blocked by anti-TSA-1 Ab and SF20-induced proliferation of TSA-1-expressing cells was inhibited by anti-TSA-1. In vitro assay revealed that SF20/IL-25 has no detectable myelopoietic activity but supports proliferation of cells in the lymphoid lineage.

Inhibition of the function of the FcgammaRIIB by a monoclonal antibody to thymic shared antigen-1, a Ly-6 family antigen

Thymic shared antigen-1 (TSA-1) is a member of the Ly-6 family of glycosyl-phosphatidylinositol (GPI)-linked proteins. While it has been proposed that TSA-1 may play a role in thymic development, a physiological ligand for this antigen has not been identified. Here we report that a monoclonal antibody (mAb) to TSA-1, generated by immunizing a hamster with CD40 ligand (CD40L)-activated B cells, interferes with the function of FcgammaRIIB on splenic B cells and the B-cell lymphoma cell line, M12, by binding to TSA on the same cells. The interaction of anti-TSA with FcgammaRIIB resulted in an inhibition of the ability of the FcgammaRIIB to cross-link and/or aggregate soluble anti-CD3 or soluble anti-Cbeta T-cell receptor (TCR), leading to an inhibition of induction of expression of CD25 and CD69, interleukin (IL)-2 production and proliferation of naive T cells. Cross-blocking studies with mAbs strongly suggested that a physical association exists between TSA-1 and the FcgammaRIIB on the surface of activated B cells and favour the view that a functional intermolecular association exists between these two distinct membrane antigens.

Cloning of the Ly-6A (Sca-1) gene locus and identification of a 3' distal fragment responsible for high-level gamma-interferon-induced expression in vitro

The Ly-6A and Ly-6E allelic genes encode the Sca-1 protein, which is one of the most widely used markers in haematopoietic stem cell isolation procedures. Identification of the specific gene regulatory elements that direct haematopoietic stem cell specific expression of Sca-1 is of current interest for purposes of stem cell manipulation. Both the Ly-6E and Ly-6A alleles have been examined for regions containing DNase I hypersensitive sites thought to be indicative of transcriptional regulatory elements. In these previous studies, the Ly-6E allele with its flanking regulatory sequences was cloned, and the region responsible for high-level gamma-interferon (gamma-IFN)-induced expression was localized to a 3' distal sequence containing two strong DNase1 hypersensitive sites. Because the Ly-6A allele is thought to provide higher levels of expression in haematopoietic stem cells, we isolated over 25 kb of the Ly-6A gene and flanking regulatory regions. We show here that sequences analogous to those in the Ly-6E allele are responsible for high-level gamma-IFN-induced expression in vitro. Furthermore, we show that this 3' distal Ly-6A fragment directs high-level gamma-IFN-induced expression from a heterologous promoter, suggesting that it is a potent enhancer that could be useful for expression in haematopoietic stem cells.

Expression of Ly-6A/E in the mouse uterus during implantation period

To investigate the molecular mechanisms of implantation, we constructed a complementary DNA library of mouse uterus enriched with pregnancy-induced genes by subtractive hybridization and polymerase chain reaction. One of the isolated clones was a part of complementary DNA for the Ly-6A/E. Ly-6A/E is reported to be differentially expressed on hematopoietic stem cells and some lymphoid and nonlymphoid tissues, mediate cell-cell adhesion on lymphoid cells, and associate with cell proliferation and angiogenesis of tumor cells. Northern blot, in situ hybridization, and immunohistochemical analyses demonstrated that the Ly-6A/E mRNA and protein were expressed in the endometrial epithelial cells as well as myometrial cells and vascular endothelial cells in the uterus of nonpregnant mouse. The expression was downregulated in luminal epithelial cells during pregnancy days 1-5, while it was upregulated in decidualized stromal cells around the implanted embryo at the time of implantation. The signals were primarily localized in stromal cells at the mesometrial pole on day 9. The increased expression was also observed in stromal cells of the embryo-transferred uterus and artificially-induced deciduoma, indicating that the expression of Ly-6A/E in the endometrial cells is concurrent with decidualization. These findings suggest that Ly-6A/E plays a role in embryo implantation.