A novel form of the membrane protein CD147 that contains an extra Ig-like domain and interacts homophilically

Embigin deficiency leads to delayed embryonic lung development and high neonatal mortality in mice

Embigin (Gp70), a receptor for fibronectin and an ancillary protein for monocarboxylate transporters, is known to regulate stem cell niches in sebaceous gland and bone marrow. Here, we show that embigin expression is at high level during early mouse embryogenesis and that embigin is essential for lung development. Markedly increased neonatal mortality of Emb-/- mice can be explained by the compromised lung maturation: in Emb-/- mice (E17.5) the number and the size of the small airways and distal airspace are significantly smaller, there are fewer ATI and ATII cells, and the alkaline phosphatase activity in amniotic fluid is lower. Emb-/- lungs show less peripheral branching already at E12.5, and embigin is highly expressed in lung primordium. Thus, embigin function is essential at early pseudoglandular stage or even earlier. Furthermore, our RNA-seq analysis and Ki67 staining results support the idea that the development of Emb-/- lungs is rather delayed than defected.

Role of Human Monocarboxylate Transporter 1 (hMCT1) and 4 (hMCT4) in Tumor Cells and the Tumor Microenvironment

In recent years, the abnormal glucose metabolism of tumor cells has attracted increasing attention. Abnormal glucose metabolism is closely related to the occurrence and development of tumors. Monocarboxylate transporters (MCTs) transport the sugar metabolites lactic acid and pyruvate, which affect glucose metabolism and tumor progression in a variety of ways. Thus, research has recently focused on MCTs and their potential functions in cancer. The MCT superfamily consists of 14 members. MCT1 and MCT4 play a crucial role in the maintenance of intracellular pH in tumor cells by transporting monocarboxylic acids (such as lactate, pyruvate and butyrate). MCT1 and MCT4 are highly expressed in a variety of tumor cells and are involved the proliferation, invasion and migration of tumor cells, which are closely related to the prognosis of cancer. Because of their important functions in tumor cells, MCT1 and MCT4 have become potential targets for cancer treatment. In this review, we focus on the structure, function and regulation of MCT1 and MCT4 and discuss the developed inhibitors of MCT1 and MCT4 to provide more comprehensive information that might aid in the development of strategies targeting MCTs in cancer.

The retina-specific basigin isoform does not induce IL-6 expression in mouse monocytes

Purpose

Basigin gene products are positioned on adjacent cell types in the neural retina and are thought to compose a lactate metabolon important for photoreceptor cell function. The Ig0 domain of basigin isoform 1 (basigin-1) is highly conserved throughout evolution, which suggests a conserved function. It has been suggested that the Ig0 domain has proinflammatory properties, and it is hypothesized to interact with basigin isoform 2 (basigin-2) for cell adhesion and lactate metabolon formation. Therefore, the purpose of the present study was to determine whether the Ig0 domain of basigin-1 binds to basigin-2 and whether the region of the domain used for binding is also used to stimulate interleukin-6 (IL-6) expression.

Methods

Binding was assessed using recombinant proteins corresponding to the Ig0 domain of basigin-1 and endogenously expressed basigin-2 from mouse neural retina and brain protein lysates. The proinflammatory properties of the Ig0 domain were analyzed with exposure of the recombinant proteins to the mouse monocyte RAW 264.7 cell line and subsequent measurement of the IL-6 concentration in the culture medium via enzyme-linked immunosorbent assay (ELISA).

Results

The data indicate that the Ig0 domain interacts with basigin-2 through a region within the amino half of the domain and that the Ig0 domain does not stimulate the expression of IL-6 in mouse cells in vitro.

Conclusions

The Ig0 domain of basigin-1 binds to basigin-2 in vitro. In addition, contrary to previous reports, there was no evidence that the Ig0 domain potentiates IL-6 expression in a mouse monocyte cell line in vitro. However, it is possible that the Ig0 domain stimulates the expression of proinflammatory cytokines other than IL-6, or that the potential involvement of the Ig0 domain of basigin-1 in the acute inflammatory response is dependent on species.

Extracellular matrix metalloproteinase inducer in brain ischemia and intracerebral hemorrhage

Increasing evidence from preclinical and clinical studies link neuroinflammation to secondary brain injury after stroke, which includes brain ischemia and intracerebral hemorrhage (ICH). Extracellular matrix metalloproteinase inducer (EMMPRIN), a cell surface transmembrane protein, is a key factor in neuroinflammation. It is widely elevated in several cell types after stroke. The increased EMMPRIN appears to regulate the expression of matrix metalloproteinases (MMPs) and exacerbate the pathology of stroke-induced blood-brain barrier dysfunction, microvascular thrombosis and neuroinflammation. In light of the neurological effects of EMMPRIN, we present in this review the complex network of roles that EMMPRIN has in brain ischemia and ICH. We first introduce the structural features and biological roles of EMMPRIN, followed by a description of the increased expression of EMMPRIN in brain ischemia and ICH. Next, we discuss the pathophysiological roles of EMMPRIN in brain ischemia and ICH. In addition, we summarize several important treatments for stroke that target the EMMPRIN signaling pathway. Finally, we suggest that EMMPRIN may have prospects as a biomarker of stroke injury. Overall, this review collates experimental and clinical evidence of the role of EMMPRIN in stroke and provides insights into its pathological mechanisms.

The Immunoglobulin Superfamily Member Basigin Is Required for Complex Dendrite Formation in Drosophila

Coordination of dendrite growth with changes in the surrounding substrate occurs widely in the nervous system and is vital for establishing and maintaining neural circuits. However, the molecular basis of this important developmental process remains poorly understood. To identify potential mediators of neuron-substrate interactions important for dendrite morphogenesis, we undertook an expression pattern-based screen in Drosophila larvae, which revealed many proteins with expression in dendritic arborization (da) sensory neurons and in neurons and their epidermal substrate. We found that reporters for Basigin, a cell surface molecule of the immunoglobulin (Ig) superfamily previously implicated in cell-cell and cell-substrate interactions, are expressed in da sensory neurons and epidermis. Loss of Basigin in da neurons led to defects in morphogenesis of the complex dendrites of class IV da neurons. Classes of sensory neurons with simpler branching patterns were unaffected by loss of Basigin. Structure-function analyses showed that a juxtamembrane KRR motif is critical for this function. Furthermore, knock down of Basigin in the epidermis led to defects in dendrite elaboration of class IV neurons, suggesting a non-autonomous role. Together, our findings support a role for Basigin in complex dendrite morphogenesis and interactions between dendrites and the adjacent epidermis.

Homotypic targeting and drug delivery in glioblastoma cells through cell membrane-coated boron nitride nanotubes

Glioblastoma multiforme (GBM) is one of the most aggressive types of brain cancer, characterized by rapid progression, resistance to treatments, and low survival rates; the development of a targeted treatment for this disease is still today an unattained objective. Among the different strategies developed in the latest few years for the targeted delivery of nanotherapeutics, homotypic membrane-membrane recognition is one of the most promising and efficient. In this work, we present an innovative drug-loaded nanocarrier with improved targeting properties based on the homotypic recognition of GBM cells. The developed nanoplatform consists of boron nitride nanotubes (BNNTs) loaded with doxorubicin (Dox) and coated with cell membranes (CM) extracted from GBM cells (Dox-CM-BNNTs). We demonstrated as Dox-CM-BNNTs are able to specifically target and kill GBM cells in vitro, leaving unaffected healthy brain cells, upon successful crossing an in vitro blood-brain barrier model. The excellent targeting performances of the nanoplatform can be ascribed to the protein component of the membrane coating, and proteomic analysis of differently expressed membrane proteins present on the CM of GBM cells and of healthy astrocytes allowed the identification of potential candidates involved in the process of homotypic cancer cell recognition.

Genitourinary Tumors: Update on Molecular Biomarkers for Diagnosis, Prognosis and Prediction of Response to Therapy

BACKGROUND

Research of biomarkers in genitourinary tumors goes along with the development of complex emerging techniques ranging from next generation sequencing platforms, applied to archival pathology specimens, cytological samples, liquid biopsies, and to patient-derived tumor models.

METHODS

This contribution is an update on molecular biomarkers for diagnosis, prognosis and prediction of response to therapy in genitourinary tumors. The following major topics are dealt with: Immunological biomarkers, including the microbiome, and their potential role and caveats in renal cell carcinoma, bladder and prostate cancers and testicular germ cell tumors; Tissue biomarkers for imaging and therapy, with emphasis on Prostate-specific membrane antigen in prostate cancer; Liquid biomarkers in prostate cancer, including circulating tumor cell isolation and characterization in renal cell carcinoma, bladder cancer with emphasis on biomarkers detectable in the urine and testicular germ cell tumors; and Biomarkers and economic sustainability.

CONCLUSION

The identification of effective biomarkers has become a major focus in cancer research, mainly due to the necessity of selecting potentially responsive patients in order to improve their outcomes, as well as to reduce the toxicity and costs related to ineffective treatments.

CD147 Is a Promising Target of Tumor Progression and a Prognostic Biomarker

Microenvironment plays a crucial role in tumor development and progression. Cancer cells modulate the tumor microenvironment, which also contribute to resistance to therapy. Identifying biomarkers involved in tumorigenesis and cancer progression represents a great challenge for cancer diagnosis and therapeutic strategy development. CD147 is a glycoprotein involved in the regulation of the tumor microenvironment and cancer progression by several mechanisms—in particular, by the control of glycolysis and also by its well-known ability to induce proteinases leading to matrix degradation, tumor cell invasion, metastasis and angiogenesis. Accumulating evidence has demonstrated the role of CD147 expression in tumor progression and prognosis, suggesting it as a relevant tumor biomarker for cancer diagnosis and prognosis, as well as validating its potential as a promising therapeutic target in cancers.

The CD147-HYALURONAN Axis in Cancer

CD147 (basigin; EMMPRIN), hyaluronan, and hyaluronan receptors (e.g., CD44) are intimately involved in several phenomena that underlie malignancy. A major avenue whereby they influence tumor progression is most likely their role in the characteristics of cancer stem cells (CSCs), subpopulations of tumor cells that exhibit chemoresistance, invasiveness, and potent tumorigenicity. Both CD147 and hyaluronan have been strongly implicated in chemoresistance and invasiveness, and may be drivers of CSC characteristics, since current evidence indicates that both are involved in epithelial-mesenchymal transition, a crucial process in the acquisition of CSC properties. Hyaluronan is a prominent constituent of the tumor microenvironment whose interactions with cell surface receptors influence several signaling pathways that lead to chemoresistance and invasiveness. CD147 is an integral plasma membrane glycoprotein of the Ig superfamily and cofactor in assembly and activity of monocarboxylate transporters (MCTs). CD147 stimulates hyaluronan synthesis and interaction of hyaluronan with its receptors, in particular CD44 and LYVE-1, which in turn result in activation of multiprotein complexes containing members of the membrane-type matrix metalloproteinase, receptor tyrosine kinase, ABC drug transporter, or MCT families within lipid raft domains. Multivalent hyaluronan-receptor interactions are essential for formation or stabilization of these lipid raft complexes and for downstream signaling pathways or transporter activities. We conclude that stimulation of hyaluronan-receptor interactions by CD147 and the consequent activities of these complexes may be critical to the properties of CSCs and their role in malignancy. Anat Rec, 2019. © 2019 Wiley Periodicals, Inc.

CD147 Is a Novel Chemotherapy or Prevention Target in Melanoma

CD147, also named as BSG, was first identified from F9 embryonal carcinoma cells (Miyauchi et al., 1990) and the human BSG locus on chromosome 19p13.3 containing 10 exons (Belton et al., 2008; Kaname et al., 1993; Liao et al., 2011), which encodes four alternatively spliced transcripts:CD147/Bsg-1,2,3,4 (Kaname et al., 1993; Liao et al., 2011). Bsg-1 has three Ig-like domains (CD147/Bsg-1) (Hanna et al., 2003; Ochrietor et al., 2003), while CD147/Bsg-3,4 contains a single Ig-like domain (Belton et al., 2008; Liao et al., 2011). Evidence shows that CD147/Bsg-2 is the most abundant and best characterized splice product, which contains two Ig-like domains (Weidle et al., 2010). Analysis of amino acids showed that CD147 contains a single-chain type I transmembrane domain composed of a 21-amino acid signal sequence, an extracellular domain consisting of 186 amino acids with two Ig-like domains and a cytoplasmic domain of 41 residues (Kanekura et al., 2010; Yurchenko et al., 2005). There are three glycosylation sites at three conserved asparagine (Asn 44, 152, and 186) in the CD147 N-terminal domain (Fadool et al., 1993; Tang et al., 2004; Yu et al., 2006), which could explain the molecular mass of CD147 shifts from a predicted molecular weight of about 27 kDa to 40-65 kDa with Western blotting. Inhibition of glycosylation by specific inhibitors showed that on carbohydrate side groups bearing β-1,6-branched, polylactosamine-type sugars, fucosylations are the major glycosylation type in N-glycosylation of CD147 (Ni et al., 2014; Riethdorf et al., 2006; Tang et al., 2004). In addition, N-glycosylation of CD147 has been identified as low glycosylated (approximately 32 kDa) or high glycosylated (approximately 45-65 kDa). The fully glycosylated mature CD147 (high-glycosylated CD147) is translocated to the plasma membrane, while low-glycosylated CD147 is the precursor of high-glycosylated CD147 in the endoplasmic reticulum, which requires additional modification in the Golgi prior to being expressed on the cell surface; high levels of glycosylation are a primary biochemical property of CD147 (Jia et al., 2006; Jiang et al., 2014; Ni et al., 2014; Tang et al., 2004).

Crosstalk in cancer resistance and metastasis

The main obstacles that lead to clinical failure in cancer treatment are the development of resistant to chemotherapy and a rise in invasive characteristics in cancer tumor cells due to prolonged chemotherapeutic processes. Recent studies have revealed some evidence about the existence of a direct relationship between development of drug resistance and triggering of invasive capability in tumor cells. Therefore, devising and application of chemotherapeutic procedures that are not prone to the development of chemotherapy resistance are necessary. Here, we focus on CD147, CD44, ANAX2, P-gp, MMPs, and UCH-L1 proteins involved in the crosstalk between metastasis and cancer treatment. We think that further structural and functional analysis of these proteins may direct scientists towards designing highly effective chemotherapy procedures.

Up-regulated expression of CD147 gene in malignant bone tumor and the possible induction mechanism during osteoclast formation

It is increasingly evident that the microenvironment of bone can influence cancer phenotype in many ways that favor growth in bone. CD147, a transmembrane protein of the immunoglobulin (Ig) superfamily, was identified independently in different species and has many designations across different species. However, expression levels of CD147 mRNA in bone cancer have not been described. In this study, we have used real-time fluorescence quantification (RT-PCR) to demonstrate CD147 expression in malignant bone cancer and benign bone tumor tissues. The results suggested that the expression of CD147 gene was significantly up-regulated in malignant bone cancer. Moreover, we found that over-expressed RANKL progressively enhanced osteoclast formation up to 48 h, which suggested that RANKL could promote the formation of osteoclast, indicating that both CD147 and RANKL play important roles in the formation of osteoclasts. Furthermore, the expressions of four osteoclast specific expression genes, including TRACP, MMP-2, MMP-9 and c-Src, were analyzed using RT-PCR. The results indicated that four osteoclast-specific expression genes were detectable in all osteoclast with different treatments. However, the highest expression level of these four osteoclast-specific expression genes appears in the CD147+ RANKL group and the lowest expression level of these four osteoclast-specific expression genes appears with si-RANKL treatment. Characterization of the role of CD147 in the development of tumors should lead to a better understanding of the changes occurring at the molecular level during the development and progression of primary human bone cancer.

Up-regulated basigin-2 in microglia induced by hypoxia promotes retinal angiogenesis

Retinal microglia cells contribute to vascular angiogenesis and vasculopathy induced by relative hypoxia. However, its concrete molecular mechanisms in shaping retinal angiogenesis have not been elucidated. Basigin, being involved in tumour neovasculogenesis, is explored to exert positive effects on retinal angiogenesis induced by microglia. Therefore, we set out to investigate the expression of basigin using a well-characterized mouse model of oxygen-induced retinopathy, which recapitulated hypoxia-induced aberrant neovessel growth. Our results elucidate that basigin is overexpressed in microglia, which accumulating in retinal angiogenic sprouts. In vitro, conditioned media from microglia BV2 under hypoxia treatment increase migration and tube formation of retinal capillary endothelia cells, compared with media from normoxic condition. The angiogenic capacity of BV2 is inhibited after basigin knockdown by small interfering RNAs. A new molecular mechanism for high angiogenic capacity, whereby microglia cells release basigin via up-regulation of PI3K-AKT and IGF-1 pathway to induce angiogenesis is unveiled. Collectively, our results demonstrate that basigin from hypoxic microglia plays a pivotal pro-angiogenic role, providing new insights into microglia-promoting retinal angiogenesis.

Basigin (CD147), a multifunctional transmembrane glycoprotein with various binding partners

Basigin, also called CD147 or EMMPRIN, is a transmembrane glycoprotein that belongs to the immunoglobulin superfamily. Basigin has isoforms; the common form (basigin or basigin-2) has two immunoglobulin domains, and the extended form (basigin-1) has three. Basigin is the receptor for cyclophilins, S100A9 and platelet glycoprotein VI, whereas basigin-1 serves as the receptor for the rod-derived cone viability factor. Basigin tightly associates with monocarboxylate transporters and is essential for their cell surface translocation and activities. In the same membrane plane, basigin also associates with other proteins including GLUT1, CD44 and CD98. The carbohydrate portion of basigin is recognized by lectins, such as galectin-3 and E-selectin. These molecular recognitions form the basis for the role of basigin in the transport of nutrients, migration of inflammatory leukocytes and induction of matrix metalloproteinases. Basigin is important in vision, spermatogenesis and other physiological phenomena, and plays significant roles in the pathogenesis of numerous diseases, including cancer. Basigin is also the receptor for an invasive protein RH5, which is present in malaria parasites.

How, with whom and when: an overview of CD147-mediated regulatory networks influencing matrix metalloproteinase activity

Matrix metalloproteinases (MMPs) comprise a family of 23 zinc-dependent enzymes involved in various pathologic and physiologic processes. In cancer, MMPs contribute to processes from tumour initiation to establishment of distant metastases. Complex signalling and protein transport networks regulate MMP synthesis, cell surface presentation and release. Earlier attempts to disrupt MMP activity in patients have proven to be intolerable and with underwhelming clinical efficacy; thus targeting ancillary proteins that regulate MMP activity may be a useful therapeutic approach. Extracellular matrix metalloproteinase inducer (EMMPRIN) was originally characterized as a factor present on lung cancer cells, which stimulated collagenase (MMP-1) production in fibroblasts. Subsequent studies demonstrated that EMMPRIN was identical with several other protein factors, including basigin (Bsg), all of which are now commonly termed CD147. CD147 modulates the synthesis and activity of soluble and membrane-bound [membrane-type MMPs (MT-MMPs)] in various contexts via homophilic/heterophilic cell interactions, vesicular shedding or cell-autonomous processes. CD147 also participates in inflammation, nutrient and drug transporter activity, microbial pathology and developmental processes. Despite the hundreds of manuscripts demonstrating CD147-mediated MMP regulation, the molecular underpinnings governing this process have not been fully elucidated. The present review summarizes our present knowledge of the complex regulatory systems influencing CD147 biology and provides a framework to understand how CD147 may influence MMP activity.

EtpE Binding to DNase X Induces Ehrlichial Entry via CD147 and hnRNP-K Recruitment, Followed by Mobilization of N-WASP and Actin

Obligate intracellular bacteria, such as Ehrlichia chaffeensis, perish unless they can enter eukaryotic cells. E. chaffeensis is the etiological agent of human monocytic ehrlichiosis, an emerging infectious disease. To infect cells, Ehrlichia uses the C terminus of the outer membrane invasin entry-triggering protein (EtpE) of Ehrlichia (EtpE-C), which directly binds the mammalian cell surface glycosylphosphatidyl inositol-anchored protein, DNase X. How this binding drives Ehrlichia entry is unknown. Here, using affinity pulldown of host cell lysates with recombinant EtpE-C (rEtpE-C), we identified two new human proteins that interact with EtpE-C: CD147 and heterogeneous nuclear ribonucleoprotein K (hnRNP-K). The interaction of CD147 with rEtpE-C was validated by far-Western blotting and coimmunoprecipitation of native EtpE with endogenous CD147. CD147 was ubiquitous on the cell surface and also present around foci of rEtpE-C-coated-bead entry. Functional neutralization of surface-exposed CD147 with a specific antibody inhibited Ehrlichia internalization and infection but not binding. Downregulation of CD147 by short hairpin RNA (shRNA) impaired E. chaffeensis infection. Functional ablation of cytoplasmic hnRNP-K by a nanoscale intracellular antibody markedly attenuated bacterial entry and infection but not binding. EtpE-C also interacted with neuronal Wiskott-Aldrich syndrome protein (N-WASP), which is activated by hnRNP-K. Wiskostatin, which inhibits N-WASP activation, and cytochalasin D, which inhibits actin polymerization, inhibited Ehrlichia entry. Upon incubation with host cell lysate, EtpE-C but not an EtpE N-terminal fragment stimulated in vitro actin polymerization in an N-WASP- and DNase X-dependent manner. Time-lapse video images revealed N-WASP recruitment at EtpE-C-coated bead entry foci. Thus, EtpE-C binding to DNase X drives Ehrlichia entry by engaging CD147 and hnRNP-K and activating N-WASP-dependent actin polymerization.

Ehrlichia chaffeensis, an obligate intracellular bacterium, causes a blood-borne disease called human monocytic ehrlichiosis, one of the most prevalent life-threatening emerging tick-transmitted infectious diseases in the United States. The survival of Ehrlichia bacteria, and hence, their ability to cause disease, depends on their specific mode of entry into eukaryotic host cells. Understanding the mechanism by which E. chaffeensis enters cells will create new opportunities for developing effective therapies to prevent bacterial entry and disease in humans. Our findings reveal a novel cellular signaling pathway triggered by an ehrlichial surface protein called EtpE to induce its infectious entry. The results are also important from the viewpoint of human cell physiology because three EtpE-interacting human proteins, DNase X, CD147, and hnRNP-K, are hitherto unknown partners that drive the uptake of small particles, including bacteria, into human cells.

Hypoxia, cancer metabolism and the therapeutic benefit of targeting lactate/H(+) symporters

Since Otto Warburg reported the 'addiction' of cancer cells to fermentative glycolysis, a metabolic pathway that provides energy and building blocks, thousands of studies have shed new light on the molecular mechanisms contributing to altered cancer metabolism. Hypoxia, through hypoxia-inducible factors (HIFs), in addition to oncogenes activation and loss of tumour suppressors constitute major regulators of not only the "Warburg effect" but also many other metabolic pathways such as glutaminolysis. Enhanced glucose and glutamine catabolism has become a recognised feature of cancer cells, leading to accumulation of metabolites in the tumour microenvironment, which offers growth advantages to tumours. Among these metabolites, lactic acid, besides imposing an acidic stress, is emerging as a key signalling molecule that plays a pivotal role in cancer cell migration, angiogenesis, immune escape and metastasis. Although interest in lactate for cancer development only appeared recently, pharmacological molecules blocking its metabolism are already in phase I/II clinical trials. Here, we review the metabolic pathways generating lactate, and we discuss the rationale for targeting lactic acid transporter complexes for the development of efficient and selective anticancer therapies.

The role of EMMPRIN in T cell biology and immunological diseases

Review on EMMPRIN in numerous immunological/inflammatory disease conditions and its complex roles in T cell biology.

EMMPRIN (CD147), originally described as an inducer of the expression of MMPs, has gained attention in its involvement in various immunologic diseases, such that anti‐EMMPRIN antibodies are considered as potential therapeutic medications. Given that MMPs are involved in the pathogenesis of various disease states, it is relevant that targeting an upstream inducer would make for an effective therapeutic strategy. Additionally, EMMPRIN is now appreciated to have multiple roles apart from MMP induction, including in cellular functions, such as migration, adhesion, invasion, energy metabolism, as well as T cell activation and proliferation. Here, we review what is known about EMMPRIN in numerous immunologic/inflammatory disease conditions with a particular focus on its complex roles in T cell biology.

EMMPRIN in gynecologic cancers: pathologic and therapeutic aspects

The highly glycosylated transmembrane protein extracellular matrix metalloproteinase inducer (EMMPRIN) is associated with several pathological conditions, including various types of cancers. In different gynecological malignancies, such as ovarian, cervical, and endometrial cancers, EMMPRIN plays significant roles in cell adhesion modulation, tumor growth, invasion, angiogenesis, and metastasis by inducing the production of various molecules, including matrix metalloproteinases and vascular endothelial growth factor. Because of its high level of expression, EMMPRIN can possibly be used as a diagnostic marker of gynecological cancers. Recent studies have showed that targeting EMMPRIN, especially by RNA interference (RNAi) technology, has promising therapeutic potential in basic research on gynecological cancer treatments, which make a platform for the future clinical success. This review study focused on the association of EMMPRIN in gynecological cancers in the perspectives of pathogenesis, diagnosis, and therapeutics.

CD147: regulator of hyaluronan signaling in invasiveness and chemoresistance

Major determinants that influence negative outcome in cancer patients are the abilities of cancer cells to resist current therapies and to invade surrounding host tissue, consequently leading to local and metastatic dissemination. Hyaluronan (HA), a prominent constituent of the tumor microenvironment, not only provides structural support but also interacts with cell surface receptors, especially CD44, that influence cooperative signaling pathways leading to chemoresistance and invasiveness. CD147 (emmprin; basigin) is a member of the Ig superfamily that has also been strongly implicated in chemoresistance and invasiveness. CD147 both regulates HA synthesis and interacts with the HA receptors, CD44, and LYVE-1. Increased CD147 expression induces formation of multiprotein complexes containing CD44 (or LYVE-1) as well as members of the membrane-type matrix metalloproteinase, receptor tyrosine kinase, ABC drug transporter, or monocarboxylate transporter families, which become assembled in specialized lipid raft domains along with CD147 itself. In each case, multivalent HA-receptor interactions are essential for formation or stabilization of the lipid raft complexes and for downstream signaling pathways or transporter activities that are driven by these complexes. We conclude that cooperativity between HA, HA receptors, and CD147 may be a major driver of the interconnected pathways of invasiveness and chemoresistance widely critical to malignancy.

Function of CD147 in atherosclerosis and atherothrombosis

CD147, a member of the immunoglobulin super family, is a well-known potent inducer of extracellular matrix metalloproteinases. Studies show that CD147 is upregulated in inflammatory diseases. Atherosclerosis is a chronic inflammatory disease of the artery wall. Further understanding of the functions of CD147 in atherosclerosis and atherothrombosis may provide a new strategy for preventing and treating cardiovascular disease. In this review, we discuss how CD147 contributes to atherosclerosis and atherothrombosis.

The biological function and clinical utilization of CD147 in human diseases: a review of the current scientific literature

CD147 or EMMPRIN is a member of the immunoglobulin superfamily in humans. It is widely expressed in human tumors and plays a central role in the progression of many cancers by stimulating the secretion of matrix metalloproteinases (MMPs) and cytokines. CD147 regulates cell proliferation, apoptosis, and tumor cell migration, metastasis and differentiation, especially under hypoxic conditions. CD147 is also important to many organ systems. This review will provide a detailed overview of the discovery, characterization, molecular structure, diverse biological functions and regulatory mechanisms of CD147 in human physiological and pathological processes. In particular, recent studies have demonstrated the potential application of CD147 not only as a phenotypic marker of activated regulatory T cells but also as a potential diagnostic marker for early-stage disease. Moreover, CD147 is recognized as an effective therapeutic target for hepatocellular carcinoma (HCC) and other cancers, and exciting clinical progress has been made in HCC treatment using CD147-directed monoclonal antibodies.

Importance of N-glycosylation on CD147 for its biological functions

Glycosylation of glycoproteins is one of many molecular changes that accompany malignant transformation. Post-translational modifications of proteins are closely associated with the adhesion, invasion, and metastasis of tumor cells. CD147, a tumor-associated antigen that is highly expressed on the cell surface of various tumors, is a potential target for cancer diagnosis and therapy. A significant biochemical property of CD147 is its high level of glycosylation. Studies on the structure and function of CD147 glycosylation provide valuable clues to the development of targeted therapies for cancer. Here, we review current understanding of the glycosylation characteristics of CD147 and the glycosyltransferases involved in the biosynthesis of CD147 N-glycans. Finally, we discuss proteins regulating CD147 glycosylation and the biological functions of CD147 glycosylation.

Overexpression of EMMPRIN isoform 2 is associated with head and neck cancer metastasis

Extracellular matrix metalloproteinase inducer (EMMPRIN), a plasma membrane protein of the immunoglobulin (Ig) superfamily, has been reported to promote cancer cell invasion and metastasis in several human malignancies. However, the roles of the different EMMPRIN isoforms and their associated mechanisms in head and neck cancer progression remain unknown. Using quantitative real-time PCR, we found that EMMPRIN isoform 2 (EMMPRIN-2) was the only isoform that was overexpressed in both head and neck cancer tissues and cell lines and that it was associated with head and neck cancer metastasis. To determine the effects of EMMPRIN-2 on head and neck cancer progression, we transfected head and neck cancer cells with an EMMPRIN-2 expression vector and EMMPRIN-2 siRNA to exogenously modulate EMMPRIN-2 expression and examined the functional importance of EMMPRIN-2 in head and neck cancer invasion and metastasis. We found that EMMPRIN-2 promoted head and neck cancer cell invasion, migration, and adhesion in vitro and increased lung metastasis in vivo. Mechanistic studies revealed that EMMPRIN-2 overexpression promoted the secretion of extracellular signaling molecules, including matrix metalloproteinases-2(MMP-2), urokinase-type plasminogen activator(uPA) and Cathepsin B, in head and neck cancer cells. While MMP-2 and uPA have been demonstrated to be important mediators of EMMPRIN signaling, the role of Cathepsin B in EMMPRIN-mediated molecular cascades and tumorigenesis has not been established. We found that EMMPRIN-2 overexpression and Cathepsin B down-regulation significantly inhibited the invasion, migration and adhesion of Tca8133 cells, suggesting that Cathepsin B is required for EMMPRIN-2 enhanced cell migration and invasion in head and neck cancer. The results of our study demonstrate the important role of EMMPRIN-2 in head and neck cancer progression for the first time and reveal that increased extracellular secretion of Cathepsin B may be a novel mechanism underlying EMMPRIN-2 enhanced tumor progression in head and neck cancer.

CD147 in ovarian and other cancers

Ovarian cancer, a gynecological malignancy, is the most common cause of death in older women worldwide. The overall 5-year survival of ovarian cancer patients is only 20% because of late diagnosis, as well as distant metastasis and multidrug resistance. Therefore, predictive and prognostic markers are urgently required for the early diagnosis of ovarian cancer. CD147, an extracellular matrix metalloproteinase inducer, is overexpressed in ovarian cancers. Current knowledge suggests that CD147 is associated with the survival and progression of ovarian cancer, and is considered as a biomarker of poor outcome. Here, we specifically review the roles of CD147 in ovarian cancer progression and discuss the diagnostic and prognostic value of CD147 in patients with ovarian cancer. CD147 promotes ovarian cancer progression by its involvement in every facet of malignancy, including invasion, metastasis, survival, angiogenesis, and drug resistance. Although it is not fully confirmed, the combination of CD147 with other biomarkers might be of diagnostic value.

Basigin-2 is the predominant basigin isoform that promotes tumor cell migration and invasion and correlates with poor prognosis in epithelial ovarian cancer

Background

Basigin, which has four isoforms, has been demonstrated to be involved in progression of various human cancers. The aim of this study was to examine the prognostic value of basigin-2 protein expression in epithelial ovarian cancer. Furthermore, the function of basigin-2 in ovarian cancer was further investigated in cell culture models.

Methods

Immunohistochemistry staining was performed to investigate basigin-2 expression in a total of 146 ovarian tissue specimens. Kaplan Meier analysis and Cox proportional hazards model were applied to assess the relationship between basigin-2 and progression-free survival (PFS) and overall survival (OS). Real-time PCR, RT-PCR and western blot were used to explore basigin-2, basigin-3 and basigin-4 expression in ovarian cancer cell lines and tissues. To evaluate possible contributions of basigin-2 to MMP secretion and cell migration and invasion, the overexpression vectors pcDNA3.1-basigin-2 and basigin-2 siRNA were transfected into HO-8910 and HO-8910 PM cells respectively.

Results

High basigin-2 expression was associated with lymph-vascular space involvement, lymph node metastasis and poor prognosis of epithelial ovarian cancer. Multivariate analyses indicated that basigin-2 positivity was an independent prognostic factor for PFS (P = 0.006) and OS (P = 0.019), respectively. Overexpression of basigin-2 increased the secretion of MMP-2/9 and cancer cell migration and invasion of HO-8910 cells, whereas knockdown of basigin-2 reduced active MMP-2/9 production, migration and invasion of HO-8910 PM cells.

Conclusions

The expression of basigin-2 might be an independent prognostic marker and basigin-2 inhibition would be a potential strategy for epithelial ovarian cancer patients, especially in inhibiting and preventing cancer cell invasion and metastasis.

Basigin: a multifunctional membrane protein with an emerging role in infections by malaria parasites

INTRODUCTION

Malaria is one of the most serious infectious diseases at the beginning of the twenty-first century. Various membrane proteins are present in Plasmodium falciparum, the principal malaria pathogen. Among them, P. falciparum reticulocyte-binding protein homolog 5 (PfRh5) is indispensable for erythrocyte invasion, and has become a promising vaccine target. Basigin (CD147, EMMPRIN) has been identified as the erythrocyte receptor of PfRh5, and shown to be essential for the invasion of multiple strains of the pathogen.

AREAS COVERED

Fundamental information on basigin is fully described, including structure as a member of the immunoglobulin superfamily and function based on its interactions with external molecules and with proteins within the same membrane. The involvement of basigin in many diseases such as cancer and inflammatory diseases is also described, the implication being that anti-basigin therapy might be helpful to treat certain illnesses. Finally, PfRh5 as a vaccine candidate is covered, and its interaction with basigin is evaluated.

EXPERT OPINION

The identification of basigin, a well-characterized membrane protein, as a receptor essential for malaria infection will contribute significantly to prevention and treatment of malaria. As an example, anti-basigin therapy can be considered an alternative approach to the treatment of drug-resistant malaria.

The retinal specific CD147 Ig0 domain: from molecular structure to biological activity

CD147 is a type I transmembrane protein that is involved in inflammatory diseases, cancer progression, and multiple human pathogens utilize CD147 for efficient infection. CD147 expression is so high in several cancers that it is now used as a prognostic marker. The two primary isoforms of CD147 that are related to cancer progression have been identified, differing in their number of immunoglobulin (Ig)-like domains. These include CD147 Ig1-Ig2, which is ubiquitously expressed in most tissues, and CD147 Ig0-Ig1-Ig2, which is retinal specific and implicated in retinoblastoma. However, little is known in regard to the retinal specific CD147 Ig0 domain despite its potential role in retinoblastoma. We present the first crystal structure of the human CD147 Ig0 domain and show that the CD147 Ig0 domain is a crystallographic dimer with an I-type domain structure, which maintained in solution. Furthermore, we have utilized our structural data together with mutagenesis to probe the biological activity of CD147-containing proteins, both with and without the CD147 Ig0 domain, within several model cell lines. Our findings reveal that the CD147 Ig0 domain is a potent stimulator of interleukin-6 and suggest that the CD147 Ig0 domain has its own receptor distinct from that of the other CD147 Ig-like domains, CD147 Ig1-Ig2. Finally, we show that the CD147 Ig0 dimer is the functional unit required for activity and can be disrupted by a single point mutation.

Characterization of basigin isoforms and the inhibitory function of basigin-3 in human hepatocellular carcinoma proliferation and invasion

Basigin, which has four isoforms, plays an important role in invasion of hepatocellular carcinoma (HCC). Detailed transcriptional regulation and functions of the basigin isoforms have not been reported except in the case of the predominant isoform basigin-2, which act as inducer of matrix metalloproteinases (MMPs). Here we determined that basigin-2, basigin-3, and basigin-4 were the most abundant transcript variants in human cell lines. GeneRacer PCR and luciferase reporter assays showed that basigin-3 and basigin-4 were initiated from an alternative promoter. Basigin-3 and basigin-4 were widely expressed in various normal human tissues at the mRNA level and were upregulated in HCC tissues compared to in normal tissues. Western blotting and confocal imaging showed that glycosylated basigin-3 and basigin-4 were expressed and localized to the plasma membrane. However, in cultured cell lines, only native basigin-3, and not basigin-4, was detected at protein level. Overexpression of basigin-3 inhibited HCC cell proliferation, MMP induction, and cell invasion in vitro and in vivo. Bimolecular fluorescence complementation assays and nuclear magnetic resonance (NMR) analysis indicated that basigin-3 interacted with basigin-2 to form hetero-oligomers. In conclusion, we systematically investigated the alternative splicing of basigin and found that basigin-3 could inhibit HCC proliferation and invasion, probably through interaction with basigin-2 as an endogenous inhibitor via hetero-oligomerization.

The many faces of EMMPRIN - roles in neuroinflammation

The central nervous system (CNS) is a relatively immune-privileged organ, wherein a well-instated barrier system (the blood-brain barrier) prevents the entry of blood cells into the brain with the exception of regular immune surveillance cells. Despite this tight security immune cells are successful in entering the CNS tissue where they result in states of neuroinflammation, tissue damage and cell death. Various components of the blood-brain barrier and infiltrating cells have been examined to better understand how blood cells are able to breach this secure barrier. Proteases, specifically matrix metalloproteinases (MMP), have been found to be the common culprits in most diseases involving neuroinflammation. MMPs secreted by infiltrating cells act specifically upon targets on various components of the blood-brain barrier, compromising this barrier and allowing cell infiltration into the CNS. Extracellular matrix metalloproteinase inducer (EMMPRIN) is an upstream inducer of several MMPs and is suggested to be the master regulator of MMP production in disease states such as cancer metastasis. EMMPRIN in the context of the CNS is still relatively understudied. In this review we will introduce EMMPRIN, discuss its ligands and roles in non-CNS conditions that can help implicate its involvement in CNS disorders, showcase its expression within the CNS in healthy and disease conditions, elucidate its ligands and receptors, and briefly discuss the emerging roles it plays in various diseases of the CNS involving inflammation.

Cyclophilin-CD147 interactions: a new target for anti-inflammatory therapeutics

CD147 is a widely expressed plasma membrane protein that has been implicated in a variety of physiological and pathological activities. It is best known for its ability to function as extracellular matrix metalloproteinase inducer (hence the other name for this protein, EMMPRIN), but has also been shown to regulate lymphocyte responsiveness, monocarboxylate transporter expression and spermatogenesis. These functions reflect multiple interacting partners of CD147. Among these CD147-interacting proteins cyclophilins represent a particularly interesting class, both in terms of structural considerations and potential medical implications. CD147 has been shown to function as a signalling receptor for extracellular cyclophilins A and B and to mediate chemotactic activity of cyclophilins towards a variety of immune cells. Recent studies using in vitro and in vivo models have demonstrated a role for cyclophilin-CD147 interactions in the regulation of inflammatory responses in a number of diseases, including acute lung inflammation, rheumatoid arthritis and cardiovascular disease. Agents targeting either CD147 or cyclophilin activity showed significant anti-inflammatory effects in experimental models, suggesting CD147-cyclophilin interactions may be a good target for new anti-inflammatory therapeutics. Here, we review the recent literature on different aspects of cyclophilin-CD147 interactions and their role in inflammatory diseases.

Immunolocalization of EMMPRIN (Cd147) in the Human Eye and Detection of Soluble Form of EMMPRIN in Ocular Fluids

PURPOSE

To study the cellular distribution of extracellular matrix metalloproteinase inducer (EMMPRIN; CD147) in the human eye and the corneal and retinal pigment epithelium cell lines and its possible existence as a soluble protein in ocular fluids.

METHODS

Immunohistochemistry was performed on human eyes and for cell cultures. Different EMMPRIN isoforms were analyzed by Western blotting in ocular fluids.

RESULTS

EMMPRIN immunostaining could be detected in the corneal and conjunctival epithelium, the endothelium, and in the stromal keratocytes, the retinal pigment epithelium, several retinal layers and nerve fibers in the optic nerve head. Both cell lines deposit EMMPRIN on the cell membranes. Soluble EMMPRIN could also be detected in the tear fluid, aqueous humor, and vitreous samples in the form of multiple immunoreactive species.

CONCLUSIONS

EMMPRIN is specifically expressed in the human eye only by certain tissue structures, thus suggesting specialized functions. The protein also exists naturally in soluble forms in ocular fluids representing presumably monomeric and multimeric forms, a notion that confirm and further extends its previously known role mainly as a transmembrane protein. These findings suggest that EMMPRIN can regulate not only cell surface functions in the human eye but also certain peri- and extracellular functions.

Solution characterization of the extracellular region of CD147 and its interaction with its enzyme ligand cyclophilin A

The CD147 receptor plays an integral role in numerous diseases by stimulating the expression of several protein families and serving as the receptor for extracellular cyclophilins; however, neither CD147 nor its interactions with its cyclophilin ligands have been well characterized in solution. CD147 is a unique protein in that it can function both at the cell membrane and after being released from cells where it continues to retain activity. Thus, the CD147 receptor functions through at least two mechanisms that include both cyclophilin-independent and cyclophilin-dependent modes of action. In regard to CD147 cyclophilin-independent activity, CD147 homophilic interactions are thought to underlie its activity. In regard to CD147 cyclophilin-dependent activity, cyclophilin/CD147 interactions may represent a novel means of signaling since cyclophilins are also peptidyl–prolyl isomerases. However, direct evidence of catalysis has not been shown within the cyclophilin/CD147 complex. In this report, we have characterized the solution behavior of the two most prevalent CD147 extracellular isoforms through biochemical methods that include gel-filtration and native gel analysis as well as directly through multiple NMR methods. All methods indicate that the extracellular immunoglobulin-like domains are monomeric in solution and, thus, suggest that CD147 homophilic interactions in vivo are mediated through other partners. Additionally, using multiple NMR techniques, we have identified and characterized the cyclophilin target site on CD147 and have shown for the first time that CD147 is also a substrate of its primary cyclophilin enzyme ligand, cyclophilin A.

Basigin-2 is a cell surface receptor for soluble basigin ligand

The metastatic spread of a tumor is dependent upon the ability of the tumor to stimulate surrounding stromal cells to express enzymes required for tissue remodeling. The immunoglobulin superfamily protein basigin (EMMPRIN/CD147) is a cell surface glycoprotein expressed by tumor cells that stimulates matrix metalloproteinase and vascular endothelial growth factor expression in stromal cells. The ability of basigin to stimulate expression of molecules involved in tissue remodeling and angiogenesis makes basigin a potential target for the development of strategies to block metastasis. However, the identity of the cell surface receptor for basigin remains controversial. The goal of this study was to determine the identity of the receptor for basigin. Using a novel recombinant basigin protein (rBSG) corresponding to the extracellular domain of basigin, it was demonstrated that the native, nonglycosylated rBSG protein forms dimers in solution. Furthermore, rBSG binds to the surface of uterine fibroblasts, activates the ERK1/2 signaling pathway, and induces expression of matrix metalloproteinases 1, 2, and 3. Proteins that interact with rBSG were isolated using a biotin label transfer technique and sequenced by matrix-assisted laser desorption ionization tandem mass spectrophotometry. The results demonstrate that rBSG interacts with basigin expressed on the surface of fibroblasts and is subsequently internalized. During internalization, rBSG associates with a novel form of human basigin (basigin-3). It was concluded that cell surface basigin functions as a membrane receptor for soluble basigin and this homophilic interaction is not dependent upon glycosylation of the basigin ligand.

CD147 immunoglobulin superfamily receptor function and role in pathology

The immunoglobulin superfamily member CD147 plays an important role in fetal, neuronal, lymphocyte and extracellular matrix development. Here we review the current understanding of CD147 expression and protein interactions with regard to CD147 function and its role in pathologic conditions including heart disease, Alzheimer's disease, stroke and cancer. A model linking hypoxic conditions found within the tumor microenvironment to upregulation of CD147 expression and tumor progression is introduced.

Emmprin (basigin/CD147): Matrix metalloproteinase modulator and multifunctional cell recognition molecule that plays a critical role in cancer progression

Emmprin (basigin, CD147) is a cell surface glycoprotein that belongs to the immunoglobulin superfamily. It is highly expressed on the surface of tumor cells and stimulates adjacent fibroblasts or tumor cells to produce matrix metalloproteinases. Moreover, it has recently been shown that emmprin also stimulates expression of vascular endothelial growth factor and hyaluronan, which leads to angiogenesis and anchorage-independent growth/multidrug resistance, respectively. These findings have made emmprin an important molecule in tumor progression and, thus, more attractive as a target for antitumor treatment. However, other functions of emmprin, including as an activator of T cells, a chaperone for monocarboxylate transporters, a receptor for cyclophilin A and a neural recognition molecule, are also being identified in physiological and pathological conditions. Therefore, it is essential to develop specific means to control particular functions of emmprin, for which elucidation of each mechanism is crucial. This review will discuss the role of emmprin in tumor progression and recent advances in the molecular mechanisms of diverse phenomena regulated by emmprin.

Dealing with the family: CD147 interactions with cyclophilins

CD147 is a widely expressed plasma membrane protein that has been implicated in a variety of physiological and pathological activities. It is best known for its ability to function as extracellular matrix metalloproteinase inducer (hence the other name for this protein, EMMPRIN), but has also been shown to regulate lymphocyte responsiveness, monocarboxylate transporter expression and spermatogenesis. These functions reflect multiple interacting partners of CD147. Recently, interaction of CD147 with proteins of the cyclophilin family has been demonstrated and activity of CD147 as a signalling receptor to extracellular cyclophilins A and B has been shown. Given that extracellular cyclophilins are potent chemotactic agents for various immune cells, further studies of the role of cyclophilin-CD147 interaction in inflammation followed. They demonstrated that agents targeting CD147 or cyclophilin had a significant anti-inflammatory effect in animal models of acute or chronic lung diseases and rheumatoid arthritis. Here, we review the current knowledge about interactions between CD147 and cyclophilins.

The NEIBank project for ocular genomics: data-mining gene expression in human and rodent eye tissues

NEIBank is a project to gather and organize genomic resources for eye research. The first phase of this project covers the construction and sequence analysis of cDNA libraries from human and animal model eye tissues to develop an overview of the repertoire of genes expressed in the eye and a resource of cDNA clones for further studies. The sequence data are grouped and identified using the tools of bioinformatics and the results are displayed through a web site where they can be interrogated by keyword search, chromosome location, by Blast (sequence comparison) or by alignment on completed genomes. Many novel proteins and novel splice forms of known genes have already emerged from analysis of the accumulating data. This review provides an overview of the current state of the database for human eye tissues, with specific comparisons to some parallel data from mouse and rat, and with illustrative examples of the kinds of insights and discoveries these data can produce. One of the major themes that emerges is that at the molecular level human eye tissues have significant differences from those of rodents, encompassing species specific genes, alternative splice forms and great variation in levels of gene expression. These point to specific adaptations and mechanisms in the human eye and emphasize that care needs to be taken in the application of appropriate animal model systems.

Multivalent recombinant proteins for probing functions of leucocyte surface proteins such as the CD200 receptor

CD200 (OX2) is a membrane glycoprotein that interacts with a structurally related receptor (CD200R) involved in the regulation of macrophage function. The interaction is of low affinity (K(D) approximately 1 microm) but can be detected using CD200 displayed in a multivalent form on beads or with dimeric fusion proteins consisting of the extracellular region of CD200 and immunoglobulin Fc regions. We prepared putative pentamers and trimers of mouse CD200 with sequences from cartilage oligomeric matrix protein (COMP) and surfactant protein D (SP-D), respectively. The COMP protein gave high-avidity binding and was a valuable tool for showing the interaction whilst the SP-D protein gave weak binding. In vivo experiments showed that an agonistic CD200R monoclonal antibody caused some amelioration in a model of experimental autoimmune encephalomyelitis but the COMP protein was cleared rapidly and had minimal effect. Pentameric constructs also allowed detection of the rat CD48/CD2 interaction, which is of much lower affinity (K(D) approximately 70 microm). These reagents may have an advantage over Fc-bearing hybrid molecules for probing cell surface proteins without side-effects due to the Fc regions. The CD200-COMP gave strong signals in protein microarrays, suggesting that such reagents may be valuable in high throughput detection of weak interactions.

5A11/Basigin Gene Products Are Necessary for Proper Maturation and Function of the Retina

5A11/Basigin gene products are important membrane glycoproteins for development and maturation of the retina. The gene encodes two immunoglobulin-like, membrane-bound glycoproteins as a result of splice variation. The smaller protein product, named 5A11/Basigin, is expressed by many tissues within the mouse, whereas the larger protein product, named 5A11/Basigin-2, is expressed only by the photoreceptor cells (PCs) of the retina. Mice in which the gene for 5A11/Basigin has been deleted have several abnormalities, including blindness from the time of eye opening with subsequent degeneration of the PCs. Studies by this laboratory suggest that a developmental deficiency is the underlying cause of the blindness. However, definitive biological functions for 5A11/Basigin and 5A11/Basigin-2 have yet to be defined. It is known that 5A11/Basigin is multifunctional and can interact with several different proteins. Preliminary studies indicate that 5A11/Basigin-2 may be multifunctional as well. Studies by this laboratory and others have demonstrated that 5A11/Basigin (and probably 5A11/Basigin-2) acts as a chaperone for monocarboxylate transporter-1 (MCT-1) translocation to the cell membrane. We have proposed that a lactate metabolon exists within the retina and functions to shuttle lactate, an energy source, from glial cells to the PCs. This metabolon is not present within 5A11/Basigin null mouse retinas, which may be the underlying cause of the retinal dysfunction and subsequent degeneration. Further studies will be necessary to determine which of the functions are critical for proper development of the retina.

Survey of the year 2003 commercial optical biosensor literature

In the year 2003 there was a 17% increase in the number of publications citing work performed using optical biosensor technology compared with the previous year. We collated the 962 total papers for 2003, identified the geographical regions where the work was performed, highlighted the instrument types on which it was carried out, and segregated the papers by biological system. In this overview, we spotlight 13 papers that should be on everyone's 'must read' list for 2003 and provide examples of how to identify and interpret high-quality biosensor data. Although we still find that the literature is replete with poorly performed experiments, over-interpreted results and a general lack of understanding of data analysis, we are optimistic that these shortcomings will be addressed as biosensor technology continues to mature.