RoBo-1, a novel member of the urokinase plasminogen activator receptor/CD59/Ly-6/snake toxin family selectively expressed in rat bone and growth plate cartilage

[Relationships between venomous function and innate immune function]

Venomous function is investigated in relation to innate immune function in two cases selected from scorpion venom and serpent venom. In the first case, structural analysis of scorpion toxins and defensins reveals a close interrelation between both functions (toxic and innate immune system function). In the second case, structural and functional studies of natural inhibitors of toxic snake venom phospholipases A2 reveal homology with components of the innate immune system, leading to a similar conclusion. Although there is a clear functional distinction between neurotoxins, which act by targeting membrane ion channels, and the circulating defensins which protect the organism from pathogens, the scorpion short toxins and defensins share a common protein folding scaffold with a conserved cysteine-stabilized alpha-beta motif of three disulfide bridges linking a short alpha helix and an antiparallel beta sheet. Genomic analysis suggests that these proteins share a common ancestor (long venom toxins were separated from an early gene family which gave rise to separate short toxin and defensin families). Furthermore, a scorpion toxin has been experimentally synthetized from an insect defensin, and an antibacterial scorpion peptide, androctonin (whose structure is similar to that of a cone snail venom toxin), was shown to have a similar high affinity for the postsynaptic acetylcholine receptor of Torpedo sp. Natural inhibitors of phospholipase A2 found in the blood of snakes are associated with the resistance of venomous snakes to their own highly neurotoxic venom proteins. Three classes of phospholipases A2 inhibitors (PLI-α, PLI-β, PLI-γ) have been identified. These inhibitors display diverse structural motifs related to innate immune proteins including carbohydrate recognition domains (CRD), leucine rich repeat domains (found in Toll-like receptors) and three finger domains, which clearly differentiate them from components of the adaptive immune system. Thus, in structure, function and phylogeny, venomous function in both vertebrates and invertebrates are clearly interrelated with innate immune function.

Origin and diversification of a salamander sex pheromone system

Sex pheromones form an important facet of reproductive strategies in many organisms throughout the Animal Kingdom. One of the oldest known sex pheromones in vertebrates are proteins of the Sodefrin Precursor-like Factor (SPF) system, which already had a courtship function in early salamanders. The subsequent evolution of salamanders is characterized by a diversification in courtship and reproduction, but little is known on how the SPF pheromone system diversified in relation to changing courtship strategies. Here, we combined transcriptomic, genomic, and phylogenetic analyses to investigate the evolution of the SPF pheromone system in nine salamandrid species with distinct courtship displays. First, we show that SPF originated from vertebrate three-finger proteins and diversified through multiple gene duplications in salamanders, while remaining a single copy in frogs. Next, we demonstrate that tail-fanning newts have retained a high phylogenetic diversity of SPFs, whereas loss of tail-fanning has been associated with a reduced importance or loss of SPF expression in the cloacal region. Finally, we show that the attractant decapeptide sodefrin is cleaved from larger SPF precursors that originated by a 62 bp insertion and consequent frameshift in an ancestral Cynops lineage. This led to the birth of a new decapeptide that rapidly evolved a pheromone function independently from uncleaved proteins.

The microRNA-218 and ROBO-1 signaling axis correlates with the lymphatic metastasis of pancreatic cancer

Pancreatic cancer is known for its poor prognosis and early lymphatic metastasis is a notable characteristic. microRNAs (miRNAs) have been shown to be involved in the initiation and progression of pancreatic cancer. We, therefore, established a screening strategy to find miRNAs related to the lymphatic metastasis of pancreatic cancer and explored the target genes of miRNAs. miRNA array profiles were analyzed in tissue samples [pancreatic ductal adenocarcinoma (PDAC) and matched adjacent benign tissues (MAT)] and cell lines (BxPC-3-LN and BxPC-3). Combined analysis of profiling data from tissue samples and cell lines was used to identify miRNAs related to the lymphatic metastasis of pancreatic cancer. The expression levels of miRNAs were confirmed by real‑time reverse transcription PCR (RT-PCR) in tissue samples and cell lines. The correlation between miRNAs and clinicopathological characteristics was investigated. The expression features of miRNAs in pancreatic cancer, precursor lesions and metastatic lymph nodes were characterized by in situ hybridization (ISH). Predicted target genes of miRNAs were validated by RT-PCR and the protein levels of target genes were revealed by western blotting. Seventy and 63 miRNAs were differentially expressed in pancreatic cancer and BxPC-3-LN, compared to MAT and BxPC-3, respectively. Combined microarray analysis found 4 co-differentially expressed miRNAs (miRNA-663, miRNA-145, miRNA-218 and let-7) related to the lymphatic metastasis of pancreatic cancer. miRNA-218 was significantly downregulated in BxPC-3-LN (fold-change>10) and the expression levels of miRNA-218 were confirmed by RT-PCR. The group with lymph node metastasis and the elder group (age>64) showed lower expression of miRNA-218 (P=0.003 and 0.002), compared to patients without lymph nodes metastasis and patients in the younger group (age≤64), respectively. The expression of miRNA‑218 showed a decreasing trend from normal acinar/ductal epithelium, intraductal papillary mucinous neoplasm (IPMN), pancreatic cancer to metastatic lymph nodes by ISH. Among 8 predicted target genes of miRNA-218, rodent bone (ROBO-1) was confirmed to be upregulated in both mRNA and protein levels in pancreatic cancer. In conclusion, we established a screening strategy based on microarray results and found miRNA-218 to be a notable gene related to lymphatic metastasis of pancreatic cancer. Downregulation of miRNA-218 and upregulation of ROBO-1 were first demonstrated in pancreatic cancer. The miRNA-218 and ROBO-1 signaling axis may contribute to the lymphatic metastasis of pancreatic cancer.

Body weight and leukocyte infiltration after an acute exercise-related muscle injury in ovariectomized mice treated with estrogen and progesterone

In both rats and mice, an acute skeletal muscle injury leads to leukocyte infiltration in which the leukocytes remove dead fibers and cellular debris, induce a secondary injury, and/or promote myofiber regeneration. Short-term exogenous estrogen treatment attenuates this leukocyte infiltration and prevents body weight gain in rat exercise-induced skeletal muscle injury models. But these estrogen effects may not occur in mice because body weight gain does not consistently occur in ovariectomized mice treated with estrogen. Additionally, progesterone may also attenuate this leukocyte infiltration without affecting body weight. The aim of the current study was to compare body weight and leukocyte infiltration in exercise-injured skeletal muscle of ovariectomized mice treated with exogenous estrogen and progesterone for the short period of 17 days with that of ovariectomized-placebo-treated mice and gonadal-intact male and female mice. There was no significant difference in body weight between the ovariectomized-estrogen-treated and the ovariectomized-placebo-treated mice. The amount of intramuscular leukocyte infiltration of ovariectomized mice treated with estrogen or progesterone was not significantly different from that of ovariectomized-placebo-treated mice. However, in the injured muscle, the mean area of the leukocyte antigen, 7/4, of the ovariectomized-estrogen-treated group was 2-3-fold greater than that of the ovariectomized-placebo-treated, ovariectomized-estrogen-progesterone-treated, and intact male groups (p<.05), suggesting that the 7/4-positive leukocytes of the ovariectomized-estrogen-treated group were larger or had more antigen. In conclusion, ovariectomized mice demonstrate a different body weight and leukocyte response to short-term estrogen treatment than that of ovariectomized rats, and short-term estrogen treatment modulates leukocyte phenotype. These data broaden our understanding of estrogen's effects on body weight and leukocyte infiltration, and may aid in increasing our understanding of how males and females differ in response to acute muscle injury.

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.

Epithelial progenitor 1, a novel factor associated with epithelial cell growth and differentiation

The growth and renewal of epithelial tissue is a highly orchestrated and tightly regulated process occurring in different tissue types under a variety of circumstances. We have been studying the process of pancreatic regeneration in mice. We have identified a cell surface protein, named EP1, which is expressed on the duct epithelium during pancreatic regeneration. Whereas it is not detected in the pancreas of normal mice, it is found in the intestinal epithelium of normal adult mice, as well as during pancreatic repair following cerulein-induced destruction of the acinar tissue. The distinctive situations in which EP1 is expressed, all of which share in common epithelial cell growth in the gastrointestinal tract, suggest that EP1 is involved in the growth and renewal of epithelial tissues in both the intestine and the pancreas.

Identification and characterization of human LYPD6, a new member of the Ly-6 superfamily

The Ly-6 protein superfamily is usually identified as a group of proteins with a LU protein domain. LU domain is about 80 amino acids long and characterized by a conserved pattern of 10 cysteine residues. Here we report the cloning and characterization of a novel human LU domain containing gene, LYPD6, isolated from human testis cDNA library, and mapped to 2q23.1-23.2 by searching the UCSC genomic database. The LYPD6 cDNA sequence of 3,501 base pairs contains an open reading frame encoding 171 amino acids. Subcellular localization of LYPD6 demonstrated that the protein was localized in the cytoplasm when overexpressed in COS-7 cells. RT-PCR analysis showed that LYPD6 was widely expressed in human tissues and the expression levels in brain and heart were relatively high. Furthermore, the subsequent analysis based on reporter gene assays suggested that overexpression of LYPD6 in HEK 293T cells was able to suppress the transcriptional activities of AP1.

Coral bleaching under thermal stress: putative involvement of host/symbiont recognition mechanisms

BACKGROUND

Coral bleaching can be defined as the loss of symbiotic zooxanthellae and/or their photosynthetic pigments from their cnidarian host. This major disturbance of reef ecosystems is principally induced by increases in water temperature. Since the beginning of the 1980s and the onset of global climate change, this phenomenon has been occurring at increasing rates and scales, and with increasing severity. Several studies have been undertaken in the last few years to better understand the cellular and molecular mechanisms of coral bleaching but the jigsaw puzzle is far from being complete, especially concerning the early events leading to symbiosis breakdown. The aim of the present study was to find molecular actors involved early in the mechanism leading to symbiosis collapse.

RESULTS

In our experimental procedure, one set of Pocillopora damicornis nubbins was subjected to a gradual increase of water temperature from 28 degrees C to 32 degrees C over 15 days. A second control set kept at constant temperature (28 degrees C). The differentially expressed mRNA between the stressed states (sampled just before the onset of bleaching) and the non stressed states (control) were isolated by Suppression Subtractive Hybridization. Transcription rates of the most interesting genes (considering their putative function) were quantified by Q-RT-PCR, which revealed a significant decrease in transcription of two candidates six days before bleaching. RACE-PCR experiments showed that one of them (PdC-Lectin) contained a C-Type-Lectin domain specific for mannose. Immunolocalisation demonstrated that this host gene mediates molecular interactions between the host and the symbionts suggesting a putative role in zooxanthellae acquisition and/or sequestration. The second gene corresponds to a gene putatively involved in calcification processes (Pdcyst-rich). Its down-regulation could reflect a trade-off mechanism leading to the arrest of the mineralization process under stress.

CONCLUSION

Under thermal stress zooxanthellae photosynthesis leads to intense oxidative stress in the two partners. This endogenous stress can lead to the perception of the symbiont as a toxic partner for the host. Consequently, we propose that the bleaching process is due in part to a decrease in zooxanthellae acquisition and/or sequestration. In addition to a new hypothesis in coral bleaching mechanisms, this study provides promising biomarkers for monitoring coral health.

GPIHBP1, a GPI-anchored protein required for the lipolytic processing of triglyceride-rich lipoproteins

GPIHBP1, a small glycosylphosphatidylinositol-anchored glycoprotein, is required for the lipolytic processing of triglyceride-rich lipoproteins. GPIHBP1 knockout mice exhibit chylomicronemia, even on a low-fat diet, with plasma triglyceride levels of 3,500-5,000 mg/dl. GPIHBP1 is expressed highly in heart, adipose tissue, and skeletal muscle, the same tissues that express high levels of lipoprotein lipase (LPL). In each of these tissues, GPIHBP1 is located in capillary endothelial cells. Chinese hamster ovary (CHO) cells transfected with a GPIHBP1 expression vector bind LPL and chylomicrons avidly. The expression of GPIHBP1 in mice is modulated by fasting and refeeding and is also regulated by peroxisome proliferator-activated receptor (PPAR)gamma agonists. Here, we review recent progress in understanding GPIHBP1 and discuss its role in lipolysis.

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.

Altered mRNA expression of genes related to nerve cell activity in the fracture callus of older rats: A randomized, controlled, microarray study

Background

The time required for radiographic union following femoral fracture increases with age in both humans and rats for unknown reasons. Since abnormalities in fracture innervation will slow skeletal healing, we explored whether abnormal mRNA expression of genes related to nerve cell activity in the older rats was associated with the slowing of skeletal repair.

Methods

Simple, transverse, mid-shaft, femoral fractures with intramedullary rod fixation were induced in anaesthetized female Sprague-Dawley rats at 6, 26, and 52 weeks of age. At 0, 0.4, 1, 2, 4, and 6 weeks after fracture, a bony segment, one-third the length of the femur, centered on the fracture site, including the external callus, cortical bone, and marrow elements, was harvested. cRNA was prepared and hybridized to 54 Affymetrix U34A microarrays (3/age/time point).

Results

The mRNA levels of 62 genes related to neural function were affected by fracture. Of the total, 38 genes were altered by fracture to a similar extent at the three ages. In contrast, eight neural genes showed prolonged down-regulation in the older rats compared to the more rapid return to pre-fracture levels in younger rats. Seven genes were up-regulated by fracture more in the younger rats than in the older rats, while nine genes were up-regulated more in the older rats than in the younger.

Conclusions

mRNA of 24 nerve-related genes responded differently to fracture in older rats compared to young rats. This differential expression may reflect altered cell function at the fracture site that may be causally related to the slowing of fracture healing with age or may be an effect of the delayed healing.

Natural phospholipase A(2) myotoxin inhibitor proteins from snakes, mammals and plants

A renewed interest in the phenomenon of inter- and intra-species resistance towards the toxicity of snake venoms, coupled with the search for new strategies for treatment of snake envenomations, has prompted the discovery of proteins which neutralize the major toxic components of these venoms. Among these emerging groups of proteins are inhibitors of toxic phospholipases A2 (PLA2s), many of which exhibit a wide range of toxic effects including muscle-tissue damage, neurotoxicity, and inflammation. These proteins have been isolated from both venomous and non-venomous snakes, mammals, and most recently from medicinal plant extracts. The snake blood-derived inhibitors have been grouped into three major classes, alpha, beta, and gamma, based on common structural motifs found in other proteins with diverse physiological properties. In mammals, DM64, an anti-myotoxic protein isolated from opossum serum, belongs to the immunoglobulin super gene family and is homologous to human alpha1B-glycoprotein and DM43, a metalloproteinase inhibitor from the same organism. In plants, a short note is made of WSG, a newly described anti-toxic-PLA2 glycoprotein isolated from Withania somnifera (Ashwaganda), a medicinal plant whose aqueous extracts neutralize the PLA2 activity of the Naja naja venom. The implications of these new groups of PLA2 toxin inhibitors in the context of our current understanding of snake biology as well as in the development of novel therapeutic reagents in the treatment of snake envenomations worldwide are discussed.

Phospholipase A(2) isoforms: a perspective

Several new PLA(2)s have been identified based on their nucleotide gene sequences. They were classified mainly into three groups: cytosolic PLA(2) (cPLA(2)), secretary PLA(2) (sPLA(2)), and intracellular PLA(2) (iPLA(2)). They differ from each other in terms of substrate specificity, Ca(2+) requirement and lipid modification. The questions that still remain to be addressed are the subcellular localization and differential regulation of the isoforms in various cell types and under different physiological conditions. It is required to identify the downstream events that occur upon PLA(2) activation, particularly target protein or metabolic pathway for liberated arachidonic acid or other fatty acids. Understanding the same will greatly help in the development of potent and specific pharmacological modulators that can be used for basic research and clinical applications. The information of the human and other genomes of PLA(2)s, combined with the use of proteomics and genetically manipulated mouse models of different diseases, will illuminate us about the specific and potentially overlapping roles of individual phospholipases as mediators of physiological and pathological processes. Hopefully, such understanding will enable the development of specific agents aimed at decreasing the potential contribution of individual secretary phospholipases to vascular diseases. The signaling cascades involved in the activation of cPLA(2) by mitogen activated protein kinases (MAPKs) is now evident. It has been demonstrated that p44 MAPK phosphorylates cPLA(2) and increases its activity in cells and tissues. The phosphorylation of cPLA(2) at ser505 occurs before the increase in intracellular Ca(2+) that facilitate the binding of the lipid binding domain of cPLA(2) to phospholipids, promoting its translocation to cellular membranes and AA release. Recently, a negative feed back loop for cPLA(2) activation by MAPK has been proposed. If PLA(2) activation in a given model depends on PKC, PKA, cAMP, or MAPK then inhibition of these phosphorylating enzymes may alter activities of PLA(2) isoforms during cellular injury. Understanding the signaling pathways involved in the activation/deactivation of PLA(2) during cellular injury will point to key events that can be used to prevent the cellular injury. Furthermore, to date, there is limited information available regarding the regulation of iPLA(2) or sPLA(2) by these pathways.

Cloning and characterization of HEP21, a new member of the uPAR/Ly6 protein superfamily predominantly expressed in hen egg white

Using two-dimensional (2D)-PAGE, partial protein internal sequencing, and PCR with degenerate primers, we cloned a novel cDNA named HEP21 from hen egg white. The 0.5-kb cDNA encodes a 106 amino acid protein with a cysteine spacing pattern suggesting that HEP21 is a new member of the uPAR/CD59/Ly-6/ snake neurotoxin superfamily. The closest homology of HEP21 is to mouse Ly-6C. Unlike most members of this protein family, HEP21 is not glycosylphosphatidylinositol (GPI)-anchored but is a secreted protein, as indicated by its localization and the presence of a signal peptide in its sequence. Moreover, HEP21 appears as an original member of this protein superfamily because it is predominantly expressed in a tissue, i.e., the oviduct, and especially the magnum where the egg white components are secreted.

The characterisation of novel secreted Ly-6 proteins from rat urine by the combined use of two-dimensional gel electrophoresis, microbore high performance liquid chromatography and expressed sequence tag data

A proteomic study of rat urine was undertaken using two-dimensional gel electrophoresis, microbore high performance liquid chromatography, mass spectrometry and N-terminal sequencing. Five known urinary proteins were identified but two novel peptide fragments matched a large number of rat expressed sequence tags (ESTs) from a liver library. By combining protein chemical and nucleotide data, two 101-residue open reading frames with 90% amino acid identity were determined, rat urinary protein 1 (RUP-1) and RUP-2. The data established signal peptide removal and provided evidence for N-glycosylation. A third related sequence, rat spleen protein (RSP-1) was confirmed from EST searches. These three proteins have been submitted to SWISS-PROT as P81827, P81828 and Q9QXN2, respectively. A fourth novel homologue was found in porcine and bovine ESTs from embryo libraries. Alignment with known homologues showed conserved cysteine positions characteristic of a secreted subfamily of Ly-6 proteins. In two cases, antineoplastic urinary protein and caltrin, these homologues have unverified functional annotations. The RUP sequences showed high scoring matches to three unrelated rat mRNAs subsequently established to be chimeric. Two of these share extended sectional identity to RUP-1 but the third may represent another novel Ly-6 homologue. These chimeras have caused serious annotation errors in secondary databases.

Functional site of endogenous phospholipase A2 inhibitor from python serum

The functional site of 'phospholipase A2 inhibitor from python' (PIP) was predicted based on the hypothesis of proline brackets. Using different sources of secretory phospholipase A2 (sPLA2s) as enzyme, and [3H]arachidonate-labelled Escherichia coli as substrate, short synthetic peptides representing the proposed site were examined for their secretory phospholipase A2 (sPLA2) inhibitory activity. A decapeptide P-PB.III proved to be the most potent of the tested peptides in inhibiting sPLA2 enzymatic activity in vitro, and exhibited striking anti-inflammatory effects in vivo in a mouse paw oedema model. P-PB.III inhibited the enzymatic activity of class I, II and III PLA2s, including that of human synovial fluid from arthritis patients. When tested by ELISA, biotinylated P-PB.III interacted positively with various PLA2s, suggesting that the specific region of PIP corresponding to P-PB.III, is likely to be involved in the PLA2-PLI interaction. The effect of P-PB.III on the peritoneal inflammatory response after surgical trauma in rats was also examined. P-PB.III effectively reduced the extent of postsurgical peritoneal adhesions as compared to controls. sPLA2 levels at seventh postoperative day in the peritoneal tissue of P-PB.III-treated rats were also significantly reduced (P < 0.05) in comparison to those of the untreated controls. The present results shed additional insight on the essential structural elements for PLA2 binding, and may be useful as a basis for the design of novel therapeutic agents.

Snake inhibitors of phospholipase A(2) enzymes

Phospholipase A(2) (PLA(2)) enzymes consist of a large family of proteins which share the same enzymatic function and display considerable sequence homology. These enzymes have been identified and characterised in mammalian tissue and snake venoms. Numerous physiological functions have been attributed to mammalian PLA(2)s and they are nontoxic. In comparison, venom PLA(2)s are toxic and induce a variety of pharmacological effects that are probably mediated via membrane receptors. Snake PLA(2) inhibitors (PLIalpha), with a similar structure to the M-type receptor, have been identified as soluble complexes in the serum of viperinae and crotalinae snakes. These inhibitors showed selective binding to crotalid group II PLA(2)s and appeared to be restricted to the serum of this snake family. Analysis of PLA(2) binding to recombinant fragments of PLIalpha indicated that the CRD region was most likely responsible for enzyme inhibition. A second type of inhibitor, PLIbeta, has been identified in serum from one viperid snake and consists of a leucine-rich structure. The third type of inhibitor, PLIgamma, was found in the serum of five snake families and contains a pattern of cysteine residues that define a three-finger structure. PLIgamma inhibitors isolated from the serum of Elapidae, Hydrophidae, Boidae and Colubridae families were able to inhibit a broad range of enzymes including the nontoxic mammalian group IB and IIA PLA(2)s, and bee venom group III PLA(2). However, differences in the binding affinities indicated specificity for particular PLA(2)s. A different representation has emerged for crotalid and viperid snakes. Their PLIgammas did not inhibit bee venom group III, mammalian group IB and IIA enzymes. Furthermore, inhibition data for the gamma-type inhibitor from Crotalus durissus terrificus (CICS) showed that this inhibitor was specific for viperid beta-neurotoxins and did not inhibit beta-neurotoxins from elapids [1]. Further studies are required to determine if this phenomenon is true for all gamma-type inhibitors from Crotalidae snakes. The relative distribution of these inhibitors, their specificities and the structural features involved in binding are discussed in this review.

Increasing molecular diversity of secreted phospholipases A(2) and their receptors and binding proteins

Secreted phospholipases A(2) (sPLA(2)s) form a large family of structurally related enzymes which are widespread in nature. Snake venoms are known for decades to contain a tremendous molecular diversity of sPLA(2)s which can exert a myriad of toxic and pharmacological effects. Recent studies indicate that mammalian cells also express a variety of sPLA(2)s with ten distinct members identified so far, in addition to the various other intracellular PLA(2)s. Furthermore, scanning of nucleic acid databases fueled by the different genome projects indicates that several sPLA(2)s are also present in invertebrate animals like Drosophila melanogaster as well as in plants. All of these sPLA(2)s catalyze the hydrolysis of glycerophospholipids at the sn-2 position to release free fatty acids and lysophospholipids, and thus could be important for the biosynthesis of biologically active lipid mediators. However, the recent identification of a variety of membrane and soluble proteins that bind to sPLA(2)s suggests that the sPLA(2) enzymes could also function as high affinity ligands. So far, most of the binding data have been accumulated with venom sPLA(2)s and group IB and IIA mammalian sPLA(2)s. Collectively, venom sPLA(2)s have been shown to bind to membrane and soluble mammalian proteins of the C-type lectin superfamily (M-type sPLA(2) receptor and lung surfactant proteins), to pentraxin and reticulocalbin proteins, to factor Xa and to N-type receptors. Venom sPLA(2)s also associate with three distinct types of sPLA(2) inhibitors purified from snake serum that belong to the C-type lectin superfamily, to the three-finger protein superfamily and to proteins containing leucine-rich repeats. On the other hand, mammalian group IB and IIA sPLA(2)s can bind to the M-type receptor, and group IIA sPLA(2)s can associate with lung surfactant proteins, factor Xa and proteoglycans including glypican and decorin, a mammalian protein containing a leucine-rich repeat.

Interaction of the neurotoxic and nontoxic secretory phospholipases A2 with the crotoxin inhibitor from Crotalus serum

Crotalus durissus terrificus snakes possess a protein in their blood, named crotoxin inhibitor from Crotalus serum (CICS), which protects them against crotoxin, the main toxin of their venom. CICS neutralizes the lethal potency of crotoxin and inhibits its phospholipase A2 (PLA2) activity. The aim of the present study is to investigate the specificity of CICS towards snake venom neurotoxic PLA2s (beta-neurotoxins) and nontoxic mammalian PLA2s. This investigation shows that CICS does not affect the enzymatic activity of pancreatic and nonpancreatic PLA2s, bee venom PLA2 and Elapidae beta-neurotoxins but strongly inhibits the PLA2 activity of Viperidae beta-neurotoxins. Surface plasmon resonance and PAGE studies further demonstrated that CICS makes complexes with monomeric and multimeric Viperidae beta-neurotoxins but does not interact with nontoxic PLA2s. In the case of dimeric beta-neurotoxins from Viperidae venoms (crotoxin, Mojave toxin and CbICbII), which are made by the noncovalent association of a PLA2 with a nonenzymatic subunit, CICS does not react with the noncatalytic subunit, instead it binds tightly to the PLA2 subunit and induces the dissociation of the heterocomplex. In vitro assays performed with Torpedo synaptosomes showed a protective action of CICS against Viperidae beta-neurotoxins but not against other PLA2 neurotoxins, on primary and evoked liberation of acetylcholine. In conclusion, CICS is a specific PLA2 inhibitor of the beta-neurotoxins from the Viperidae family.

Differential expression of egr-1 in osteoarthritic compared to normal adult human articular cartilage

OBJECTIVE

The purpose of this study was to identify genes that are differentially expressed in normal versus osteoarthritic human articular cartilage as either potential novel therapeutic targets or diagnostic markers of this disease.

DESIGN

mRNA was isolated from histologically normal and osteoarthritic adult human articular cartilage. The Differential Display technique was employed which identified differentially expressed genes in the normal and diseased tissue. Northern and reverse Northern hybridization were used to confirm the gene expression pattern. Immunohistochemistry and in-situ hybridization were used to localize expression of Egr-1 protein and mRNA respectively in cartilage.

RESULTS

A transcription factor, early growth response protein-1 (Egr-1) was found to be down-regulated more than six-fold in multiple human OA cartilage samples when compared to normal tissue. Immunohistochemistry indicated that Egr-1 was expressed throughout normal adult cartilage, in deep-, mid- and superficial-zones. In contrast, in OA cartilage there was expression of Egr-1 mRNA and protein only in the chondrocytes undergoing cloning.

CONCLUSIONS

Egr-1 is differentially expressed in OA versus normal cartilage and because of its role in transcriptional activation and repression and regulation of proliferation, differentiation and apoptosis, Egr-1 may play an important role in the pathogenesis of OA. Up-regulation of Egr-1 may therefore provide a novel therapeutic approach for either the prevention or treatment of OA.

Cloning of PRV-1, a novel member of the uPAR receptor superfamily, which is overexpressed in polycythemia rubra vera

Polycythemia vera (PV) is a clonal stem cell disorder characterized by hyperproliferation of the erythroid, myeloid, and megakaryocytic lineages. Although it has been shown that progenitor cells of patients with PV are hypersensitive to several growth factors, the molecular pathogenesis of this disease remains unknown. To investigate the molecular defects underlying PV, we used subtractive hybridization to isolate complementary DNAs (cDNAs) differentially expressed in patients with PV versus normal controls. We isolated a novel gene, subsequently named PRV-1, which is highly expressed in granulocytes from patients with PV (n = 19), but not detectable in normal control granulocytes (n = 21). Moreover, PRV-1 is not expressed in mononuclear cells from patients with chronic myelogenous leukemia (n = 4) or acute myelogenous leukemia (n = 5) or in granulocytes from patients with essential thrombocythemia (n = 4) or secondary erythrocytosis (n = 4). Northern blot analysis showed that PRV-1 is highly expressed in normal human bone marrow and to a much lesser degree in fetal liver. It is not expressed in a variety of other tissues tested. Although PRV-1 is not expressed in resting granulocytes from normal controls, stimulation of these cells with granulocyte colony-stimulating factor induces PRV-1 expression. The PRV-1 cDNA encodes an open reading frame of 437 amino acids, which contains a signal peptide at the N-terminus and a hydrophobic segment at the C-terminus. In addition, PRV-1 contains 2 cysteine-rich domains homologous to those found in the uPAR/Ly6/CD59/snake toxin-receptor superfamily. We therefore propose that PRV-1 represents a novel hematopoietic receptor.

Cloning of PRV-1, a novel member of the uPAR receptor superfamily, which is overexpressed in polycythemia rubra vera

Polycythemia vera (PV) is a clonal stem cell disorder characterized by hyperproliferation of the erythroid, myeloid, and megakaryocytic lineages. Although it has been shown that progenitor cells of patients with PV are hypersensitive to several growth factors, the molecular pathogenesis of this disease remains unknown. To investigate the molecular defects underlying PV, we used subtractive hybridization to isolate complementary DNAs (cDNAs) differentially expressed in patients with PV versus normal controls. We isolated a novel gene, subsequently named PRV-1, which is highly expressed in granulocytes from patients with PV (n = 19), but not detectable in normal control granulocytes (n = 21). Moreover, PRV-1 is not expressed in mononuclear cells from patients with chronic myelogenous leukemia (n = 4) or acute myelogenous leukemia (n = 5) or in granulocytes from patients with essential thrombocythemia (n = 4) or secondary erythrocytosis (n = 4). Northern blot analysis showed that PRV-1 is highly expressed in normal human bone marrow and to a much lesser degree in fetal liver. It is not expressed in a variety of other tissues tested. Although PRV-1 is not expressed in resting granulocytes from normal controls, stimulation of these cells with granulocyte colony-stimulating factor induces PRV-1 expression. The PRV-1 cDNA encodes an open reading frame of 437 amino acids, which contains a signal peptide at the N-terminus and a hydrophobic segment at the C-terminus. In addition, PRV-1 contains 2 cysteine-rich domains homologous to those found in the uPAR/Ly6/CD59/snake toxin-receptor superfamily. We therefore propose that PRV-1 represents a novel hematopoietic receptor.

Mapping part of the functional epitope for ligand binding on the receptor for urokinase-type plasminogen activator by site-directed mutagenesis

The urokinase-type plasminogen activator receptor (uPAR) is a glycolipid anchored multidomain member of the Ly-6/uPAR protein domain superfamily. Studies by site-directed photoaffinity labeling, chemical cross-linking, and ligand-induced protection against chemical modification have highlighted the possible involvement of uPAR domain I and particularly loop 3 thereof in ligand binding (Ploug, M. (1998) Biochemistry 37, 16494-16505). Guided by these results we have now performed an alanine scanning analysis of this region in uPAR by site-directed mutagenesis and subsequently measured the effects thereof on the kinetics of uPA binding in real-time by surface plasmon resonance. Only four positions in loop 3 of uPAR domain I exhibited significant changes in the contribution to the free energy of uPA binding (DeltaDeltaG >/= 1.3 kcal mol(-1)) upon single-site substitutions to alanine (i.e. Arg(53), Leu(55), Tyr(57), and Leu(66)). The energetic impact of these four alanine substitutions was not caused by gross structural perturbations, since all monoclonal antibodies tested having conformation-dependent epitopes on this domain exhibited unaltered binding kinetics. These sites together with a three-dimensional structure for uPAR may provide an appropriate target for rational drug design aimed at developing new receptor binding antagonists with potential application in cancer therapy.

Chondrocyte-mediated catabolism of aggrecan: evidence for a glycosylphosphatidylinositol-linked protein in the aggrecanase response to interleukin-1 or retinoic acid

The control of chondrocyte-mediated degradation of aggrecan has been studied in rat chondrosarcoma cells and bovine cartilage explants treated with either IL-1 or retinoic acid. The capacity of glucosamine to inhibit the aggrecanase-mediated response (J. D. Sandy, D. Gamett, V. Thompson, and C. Verscharen (1998) Biochem. J. 335, 59-66) has been extended to an investigation of the effect of other hexosamines. Mannosamine inhibits the aggrecanase response to both IL-1 and RA at about one-tenth the concentration of glucosamine in both rat cell and bovine explant systems. This effect of mannosamine appears to be due to its capacity to inhibit the synthesis of glycosylphosphatidylinositol (GPI)-linked proteins by chondrocytes since the GPI synthesis inhibitor 2-deoxyfluoroglucose (2-DFG) also inhibited the aggrecanase response to IL-1b and RA in rat cells. Moreover, phosphatidylinositol-specific phospholipase C (PIPLC) treatment of rat cells markedly inhibited the aggrecanase response to IL-1b and RA. These inhibitory effects of mannosamine, 2-DFG, and PIPLC in rat cells did not appear to be due to an interference with general biosynthetic activity of the cells as measured by [3H]proline incorporation into secreted proteins. We suggest that the aggrecanase response by chondrocytes to IL-1 and RA is dependent on the activity of a GPI-anchored protein on the chondrocyte cell surface.