A summary of reptile and anuran amphibian species from Brazilian sandy coastal plains: 31 years of sampling efforts of the "Laboratório de Ecologia de Vertebrados, Universidade do Estado do Rio de Janeiro"

Although currently there is already a set of studies regarding ecological aspects of some particular reptile and amphibian species living in Brazilian sandy coastal plains (including the so-called "restinga" and "campo nativo" habitats), there is comparatively few information on the species composition usually associated to these environments. During 31 years (1988-2019) of herpetological studies carried out in sandy coastal plains environments by our research team of the Laboratory of Vertebrate Ecology (Department of Ecology, Universidade do Estado do Rio de Janeiro, in Rio de Janeiro Brazil) we have surveyed reptile and amphibian communities and performed different studies with similar methods in 70 sites from 10 different states along the Brazilian coast. Our surveys resulted in records of 87 species of reptile (five turtles, two crocodylians, six amphisbaenians, 36 lizards and 39 snakes) from 24 families, and 77 species of anuran amphibians from nine families. We have studied multiple natural history topics for anurans and reptiles which resulted in the publication of some specific ecological studies, especially regarding some species, encompassing population and community ecology, foraging and feeding habits, species activity, thermoregulation, reproduction, use of microhabitats, and parasitism by ecto and endoparasites. Our results along these three decades have also contributed for the description of four new lizard species (Ameivula nativo, Glaucomastix littoralis, G. abaetensis and G. itabaianensis). Our studies constitute an important contribution to the knowledge of the ecology of anuran amphibians and reptiles in these ecosystems, as well as to the conservation of sandy coastal plains environment. The checklist presented in this study, based on our records of sandy coastal plains herpetofauna, provides for many localities along the Brazilian coast, the needed knowledge on species occurrence, including the presence of endemic and/or endangered species, which can be of value for many conservation actions.

Differential success in sampling of Atlantic Forest amphibians among different periods of the day

In general, anurans tend to be nocturnal, though diurnal activity is characteristic of some groups. Studies show that frog activity may be inferred based on the number of individuals collected at different periods of the day, during large-scale field surveys. We investigated the best period of the day to conduct amphibian sampling in nine Atlantic Rainforest areas in southeastern Brazil, based on intensive field surveys. At each locality we employed similar sampling effort during diurnal, crepuscular and nocturnal searches (totaling 704.5 sampling hours). We pooled data from all localities for each period and estimated the proportion of frogs of each species active at each period based on the total number of individuals and on the number of species found during all surveys for that period. We recorded a total of 817 individual frogs from 69 species. Species richness was highest at night (median = 12 species), intermediate at dusk (median = 8), and lowest during the day (median = 4). The percentage of the total number of individual frogs found (pooled species) was highest during the night (ca. 53%) and lowest during the day (ca. 14%). Analyzing each species separately, the number of individuals recorded was consistently higher at dusk and night for most species. Our study evidences a trend for nocturnal activity for most Atlantic Rainforest frogs, with few species having primarily diurnal habits. Those results may favor future studies and conservation efforts for amphibian species.

Clutch and egg size of the tropical lizard Tropidurus torquatus (Tropiduridae) along its geographic range in coastal eastern Brazil

The tropidurid lizard Tropidurus torquatus (Wied, 1820) has a set of populations inhabiting coastal sand dune habitats (“restinga”) along the eastern Brazilian coast. Despite its wide geographic range, there is no information about geographic variation in reproductive features among its populations. In the present study we compared some reproductive aspects of females in 10 coastal populations of T. torquatus, aiming to evaluate to what extension they vary geographically. The minimum size at maturity was relatively similar to most populations, but mean female body size had a considerable variation. Clutch size of almost all coastal populations of T. torquatus had little variation and was composed predominantly of two eggs. Interpopulational variation in the mean egg volume was relatively wide and strongly influenced by the variation in mean female body size. The data of the present study indicated that females of almost all coastal populations of T. torquatus produce, predominantly, clutches with two eggs and invest more energy in egg size instead of clutch size, probably as a consequence of morphological and environmental factors. The increased reproductive investment in egg size was confirmed by the values obtained for the relative clutch mass, which remained relatively constant along the coastal geographic distribution of T. torquatus.

Multimeric forms of satellite of tobacco ringspot virus RNA

An approximately 350-nucleotide residue RNA replicates in association with tobacco ringspot virus (TobRV) and becomes encapsidated in TobRV coat protein. Here we show by electrophoretic analyses that this small satellite RNA, RNA S, is the most abundant and most rapidly migrating of a series of at least ten encapsidated RNAs with RNA S sequences. A largely double-stranded RNA fraction from infected tissue, when denatured, gave a similar series of up to 12 zones that contained both RNA S sequences and sequences that hybridized to RNA S. Analysis of the mobilities suggests a weight increment between each zone corresponding approximately to the size of RNA S. Thus the more slowly migrating zones appear to contain covalent multimers of RNA S or, for tissue RNA, both multimers of RNA S and multimers of the complement of RNA S sequences. Neither terminal structure of TobRV genomic RNAs was found in the satellite RNA. RNA S lacks detectable polyadenylate or oligoadenylate. Covalently linked protein was not detected in RNA S or its more slowly migrating forms, and satellite RNA biological activity, unlike that of the TobRV RNAs, was not protease sensitive. Polynucleotide kinase catalyzed the phosphorylation of satellite RNAs, indicating free 5'-hydroxyl groups.

[About the functional aspect of septorhinoplasty]

INTRODUCTION

Rhinosurgeons emphasize the functional aspect of septorhinoplasty (SRP). So far only a few publications with exact data exist.

PATIENTS AND METHODS

Fifty-two patients (33 male symbol; 19 female symbol, average age: 37 years) were examined before and approx. 1 year after SRP. Rhinomanometry, olfactometry, and photographic documentation were carried out. Using a questionnaire they were asked about the functional outcome and about their original personal aims concerning the SRP.

RESULTS

All patients suffered from a deviated septum. Regarding the external aspect 38 patients had a crooked nose with or without a hump, 7 patients had a hump without external deviated nose, and 7 patients had a saddle nose or other deformities. If total nasal airflow is considered rhinomanometry showed no significant improvement postoperatively (p=0.115). If only the worse nasal side is considered rhinometry showed a highly significant improvement (p=0.002). In the questionnaire 34 patients (65%) indicated an improvement, 14 patients (27%) no change, and 4 patients a deterioration of the nasal airflow. The final aesthetic outcome was assessed by 39 patients (75%) as an improvement, by 12 patients (23%) as unchanged, and by 1 patient (2%) as worse. There were no significant changes in the olfactory function. Asked about their personal aims 29 patients (56%) wished first of all an improvement of nasal airflow, 5 patients (10%) a good aesthetic result, and 18 patients (34%) both aspects.

CONCLUSIONS

The results show that use of the term "functional" SRP is justified. In the majority of cases a simultaneously existing functional-plastic problem is solved. Our results support the importance of rhinomanometry as an objective parameter in the perioperative diagnostic battery of nasal obstruction.

A central domain binding site in insulin-like growth factor binding protein-5 for the acid-labile subunit

Like insulin-like growth factor binding protein-3 (IGFBP-3), IGFBP-5 forms a ternary complex with insulin-like growth factor (IGF)-I or IGF-II, and the acid-labile subunit (ALS). The study of IGFBP-5/IGFBP-6 chimeric proteins with amino-terminal and middle domain swaps, has revealed the existence of a site in the middle domain of IGFBP-5, that binds to ALS in the absence of the IGFBP-5 carboxy-terminal domain. An IGFBP-6 chimeric protein containing the central domain of IGFBP-5 complexed efficiently with ALS, and a carboxy-terminally truncated IGFBP-5 mutant, IGFBP-5'(1-169), also bound to ALS in the presence of IGFs, although with much less potency than full length rhIGFBP-5. In contrast to the latter, IGFBP-5(1-169) preferentially formed ternary complexes with IGF-II rather than IGF-I. These results indicate that a site which binds ALS exists in IGFBP-5 mutants which lack the IGFBP-5 carboxy-terminal domain.

Analysis of the Bak protein expression in human polymorphonuclear neutrophils

In this study, we investigated the expression of Bak, a member of the Bcl-2 protein family, in human polymorphonuclear neutrophils. Northern blot and Western blot analyses revealed that Bak messenger RNA and protein were constitutively expressed in peripheral polymorphonuclear neutrophils and mononuclear cells, as well as in several hematopoietic cell lines. Remarkably, culturing neutrophils for 24 h in the presence or absence of interferon-gamma or tumor necrosis factor-alpha, which have been described to modulate the survival rate of these cells, did not influence the expression of antigenic Bak. Taken together, our data indicate that the expression of the pro-apoptotic protein Bak in polymorphonuclear neutrophils is constitutive, is not subject to modulation, and does not correlate with the neutrophil life span in culture.

Insulin-like growth factor-binding protein 5 complexes with the acid-labile subunit. Role of the carboxyl-terminal domain

We have recently shown that insulin-like growth factor (IGF)-binding protein 5 forms ternary complexes with IGF-I or IGF-II and the acid-labile subunit (ALS) (Twigg, S. M., and Baxter, R. C. (1998) J. Biol. Chem. 273, 6074-6079). Because IGF-binding protein 3 (IGFBP-3) binds to ALS through its basic carboxyl-terminal domain, we tested whether a homologous region present in IGFBP-5 is involved in IGFBP-5 binding to ALS. Chimeric peptides were generated by carboxyl-terminal domain interchange between recombinant human IGF-BP-5 and IGFBP-6, producing two IGFBP peptides designated 5-5-6 and 6-6-5. Determined by immunoprecipitation and by Superose chromatography, 6-6-5 formed ternary complexes, albeit less potently than IGF-BP-5. In contrast, 5-5-6, like IGFBP-6, did not form ternary complexes by these methods. Whereas 6-6-5, like IGFBP-6, had a marked preference for binary complex formation with IGF-II rather than IGF-I, it formed ternary complexes more efficiently with IGF-I, like IGF-BP-5. The glycosaminoglycans heparin and heparan sulfate bind to IGFBP-5 through its basic carboxyl-terminal domain. At high concentrations, these glycosaminoglycans inhibited ALS binding to binary complexed IGF-BP-5. In addition, in the absence of IGFs, IGFBP-5, a synthetic peptide representing the basic carboxyl-terminal sequence IGFBP-5(201-218), and the corresponding IGFBP-3 basic sequence IGFBP-3(215-232), competed weakly for ALS binding to covalent IGF-IGFBP-5 complex, as did a random-sequence synthetic peptide with the same composition as IGFBP-5(201-218). These findings are consistent with the basic carboxyl-terminal domain on IGFBP-5 being the principal site in IGFBP-5 that binds to ALS.

Genomic structure and domain organisation of the human Bak gene

The Bcl-2 homologue, Bak, is a potent inducer of apoptosis. FISH data presented here located the gene to 6p21.3. Mapping was consistent with its location centromeric of the HSET locus and approximately 400kb from the MHC. The construction of a contig of genomic clones across the locus facilitated the sequencing of a PAC containing the gene. Comparison of the gene structure to functional and physical domains revealed a good agreement between the physical structure and the intron-exon organisation. The position of a single intron was conserved in comparison to other members of the Bcl-2 family, namely Bax, CED-9, Bcl-X and Bcl-2, but all other introns were displaced, consistent with a divergent phylogeny.

Edg-2/Vzg-1 couples to the yeast pheromone response pathway selectively in response to lysophosphatidic acid

We have functionally expressed the human cDNA encoding the putative lysophosphatidic acid (LPA) receptor Edg-2 (Vzg-1) in Saccharomyces cerevisiae in an attempt to determine the agonist specificity of this G-protein-coupled receptor. LPA activated the pheromone response pathway in S. cerevisiae expressing Edg-2 in a time- and dose-dependent manner as determined by induction of a pheromone-responsive FUS1::lacZ reporter gene. LPA-mediated activation of the pheromone response pathway was dependent on mutational inactivation of the SST2 gene, the GTPase-activating protein for the yeast G alpha protein (the GPA1 gene product). This indicates that, in sst2 delta yeast cells, Edg-2 can efficiently couple to the yeast heterotrimeric G-protein in response to LPA and activate the yeast mitogen-activated protein kinase pathway. The Edg-2 receptor showed a high degree of specificity for LPA; other lyso-glycerophospholipids, sphingosine 1-phosphate, and diacyl-glycerophospholipids did not activate FUS1::lacZ. LPA analogs including a cyclic phosphoester form and ether-linked forms of LPA activated FUS1::lacZ, although fatty acid chains of 6 and 10 carbons did not activate FUS1::lacZ, suggesting a role for the side chain in ligand binding or receptor activation. These results indicate that Edg-2 encodes a highly specific LPA receptor.

SARPs: a family of secreted apoptosis-related proteins

Quiescent mouse embryonic C3H/10T1/2 cells are more resistant to different proapoptotic stimuli than are these cells in the exponential phase of growth. However, the exponentially growing 10T1/2 cells are resistant to inhibitors of RNA or protein synthesis, whereas quiescent cells die upon these treatments. Conditioned medium from quiescent 10T1/2 cells possesses anti-apoptotic activity, suggesting the presence of protein(s) that function as an inhibitor of the apoptotic program. Using differential display technique, we identified and cloned a cDNA designated sarp1 (secreted apoptosis-related protein) that is expressed in quiescent but not in exponentially growing 10T1/2 cells. Hybridization studies with sarp1 revealed two additional family members. Cloning and sequencing of sarp2 and sarp3 revealed 38% and 40% sequence identity to sarp1, respectively. Human breast adenocarcinoma MCF7 cells stably transfected with sarp1 or infected with SARP1-expressing adenovirus became more resistant, whereas cells transfected with sarp2 displayed increased sensitivity to different proapoptotic stimuli. Expression of sarp family members is tissue specific. sarp mRNAs encode secreted proteins that possess a cysteine-rich domain (CRD) homologous to the CRD of frizzled proteins but lack putative membrane-spanning segments. Expression of SARPs modifies the intracellular levels of beta-catenin, suggesting that SARPs interfere with the Wnt-frizzled proteins signaling pathway.

Maspin is an intracellular serpin that partitions into secretory vesicles and is present at the cell surface

The tumor suppressor maspin (mammary serpin) was originally identified as a component of human mammary epithelial cells that is downregulated as mammary tumor cells progress from the benign to the invasive and metastatic states. Maspin inhibits cellular invasion, motility, and proliferation, but its mechanism of action is currently unknown. Because the cellular machinery responsible for these processes is cytoplasmic, we have reexamined the tissue distribution and subcellular localization of maspin. We find that maspin, or a maspin-like protein, is present in many human organs, in which it localizes to epithelia. In cultured human mammary myoepithelial cells, maspin is predominantly a soluble cytoplasmic protein that associates with secretory vesicles and is present at the cell surface. In vitro assays show that the vesicle association is due to the existence of an uncleaved facultative secretion signal that allows small amounts of maspin to partition into the endoplasmic reticulum. These results demonstrate that maspin is more widespread than previously believed. The subcellular localization studies indicate that soluble intracellular and vesicle-associated maspin probably play an important role in controlling the invasion, motility, and proliferation of cells expressing it, whereas extracellular maspin may also regulate these processes in adjacent cells.

Interferon-gamma modulates a p53-independent apoptotic pathway and apoptosis-related gene expression

Interferon (IFN)-gamma increases the sensitivity of tumor cell lines, many of which are p53 mutants, to tumor necrosis factor-alpha-mediated and anti-Fas antibody-mediated cell death. To better understand the mechanism of IFN-gamma action in modulating the cell death response independently of p53 function, we analyzed the death of the human colon adenocarcinoma cell line, HT-29, following treatment with IFN-gamma and various cytotoxic agents. Here we show that IFN-gamma modulates cell death by sensitizing the cells to killing by numerous pro-apoptotic stimuli but not pro-necrotic stimuli. Furthermore, we show that select genes from several important apoptosis-related gene families are induced by IFN-gamma, including the apoptosis-signaling receptors CD95 (Fas/APO-1) and TNFR 1 and interleukin-1beta-converting enzyme (Ice) family members Ice, CPP32 (Yama, apopain), ICErel-II (TX, Ich-2), Mch-3 (ICE-LAP3, CMH-1), Mch-4, and Mch-5 (MACH, FLICE). Of the bcl-2 family members, IFN-gamma directly induced bak but notably not bax, which is activated by p53. The IFN-responsive transcriptional activator interferon regulatory factor-1 was also strongly induced and translocated into the nucleus following IFN-gamma treatment. We propose that IFN-gamma modulates a p53-independent apoptotic pathway by both directly and indirectly inducing select apoptosis-related genes.

Fas-mediated apoptosis in human prostatic carcinoma cell lines

Of six prostatic carcinoma cell lines examined (ALVA31, DU145, JCA1, LNCaP, ND1, and PC3) by flow cytometric analysis, all were found to be positive for Fas antigen. Furthermore, of the prostate tissue specimens studied (six cases), all revealed Fas expression in benign and malignant epithelial cells. The agonistic anti-Fas monoclonal antibody (IPO-4) induced apoptosis in only two of six cell lines investigated, PC3 and ALVA31. PCR analysis indicated that all cell lines expressed normal transmembrane and death domains of Fas antigen. Using Western blot analysis, we found abundant expression of p53 in the cytoplasm of two Fas-resistant cell lines, DU145 and ND1, and did not find p53 in two Fas-sensitive cell lines, PC3 and ALVA31. Western blot and PCR analysis did not show consistent differences between cell lines examined in the expression of Bcl-2, Bcl-X(L), Bcl-X(S), and Bak. In contrast, Bax protein was not detected in two Fas-resistant cell lines, DU145 and ND1. We also showed that three Fas-resistant cell lines, DU145, ND1, and JCA1, expressed CD40, whereas the two Fas-sensitive cell lines, PC3 and ALVA31, were CD40 negative. Fas-sensitive cell lines were transfected with the cDNA encoding CD40, and the CD40-positive transfectant became more resistant to growth inhibition mediated by treatment with TNF-alpha and anti-Fas monoclonal antibody. Treatment with cycloheximide converted the phenotype of resistant cell lines from Fas resistant to Fas sensitive. Moreover, anti-Fas treatment of both resistant and sensitive cell lines induced rapid tyrosine phosphorylation or dephosphorylation of multiple proteins. These results suggest that the apoptotic machinery involved in DNA fragmentation is already in place in Fas-resistant cell lines, and thus, Fas-mediated apoptosis could be a target for therapeutic intervention.

Molecular cloning and characterization of Porphyromonas gingivalis lysine-specific gingipain. A new member of an emerging family of pathogenic bacterial cysteine proteinases

The proteinases of Porphyromonas gingivalis are key virulence factors in the etiology and progression of periodontal disease. Previous work in our laboratories resulted in the purification of arginine- and lysine-specific cysteine proteinases, designated gingipains, that consist of several tightly associated protein subunits. Recent characterization of arginine-specific gingipain-1 (gingipain R1; RGP-1) revealed that the sequence is unique and that the protein subunits are initially translated as a polyprotein encoding a proteinase domain and multiple adhesin domains (Pavloff, N., Potempa, J., Pike, R. N., Prochazka, V., Kiefer, M. C., Travis, J., and Barr, P. J. (1995) J. Biol. Chem. 270, 1007-1010). We now show that the lysine-specific gingipain (gingipain K; KGP) is also biosynthesized as a polyprotein precursor that contains a proteinase domain that is 22% homologous to the proteinase domain of RGP-1 and multiple adhesin domains. This precursor is similarly processed at distinct sites to yield active KGP. The key catalytic residues in the proteinase domain of KGP are identical to those found in RGP-1, but there are significant differences elsewhere within this domain that likely contribute to the altered substrate specificity of KGP. Independent expression of the proteinase domain in insect cells has shown that KGP does not require the presence of the adhesin domains for correct folding to confer proteolytic activity.

Molecular cloning of a high-affinity receptor for the growth factor-like lipid mediator lysophosphatidic acid from Xenopus oocytes

Lysophosphatidic acid (1-acyl-2-lyso-snglycero-3-phosphate, LPA) is a multifunctional lipid mediator found in a variety of organisms that span the phylogenetic tree from humans to plants. Although its physiological function is not clearly understood, LPA is a potent regulator of mammalian cell proliferation; it is one of the major mitogens found in blood serum. In Xenopus laevis oocytes, LPA elicits oscillatory Cl- currents. This current, like other effects of LPA, is consistent with a plasma membrane receptor-mediated activation of G protein-linked signal transduction pathways. Herein we report the identification of a complementary DNA from Xenopus that encodes a functional high-affinity LPA receptor. The predicted structure of this protein of 372 amino acids contains features common to members of the seven transmembrane receptor superfamily with a predicted extracellular amino and intracellular carboxyl terminus. An antisense oligonucleotide derived from the first 5-11 predicted amino acids, selectively inhibited the expression of the endogenous high-affinity LPA receptors in Xenopus oocytes, whereas the same oligonucleotide did not affect the low-affinity LPA receptor. Expression of the full-length cRNA in oocytes led to an increase in maximal Cl- current due to increased expression of the high-affinity LPA receptor, but activation of the low-affinity receptor was, again, unaffected. Oocytes expressing cRNA prepared from this clone showed no response to other lipid mediators including prostaglandins, leukotrienes, sphingosine 1-phosphate, sphingosylphosphorylcholine, and platelet-activating factor, suggesting that the receptor is highly selective for LPA.

Identification and cloning of a locus of serine repeat antigen (sera)-related genes from Plasmodium vivax

Polymerase chain reaction (PCR) primers based on the cysteine proteinase-like active site regions of the Plasmodium falciparum serine repeat antigen (SERA) were used to identify related sequences within the genome of P. vivax. Molecular cloning and sequence analysis of approximately 25 kb of P. vivax genomic DNA revealed a cluster of five repeated SERA-like genes (V-SERA-1-5), each encoding a cysteine proteinase-related protein. In addition to DNA sequence homology, significant similarities in deduced intron/exon organizations were also observed. The characteristic polyserine sequence found in SERA was not present in any of the deduced V-SERA sequences. Instead, in this region of the five genes, considerable sequence differences were found, suggesting the potential for antigenic variation in the V-SERA molecules. In common with SERA, however, the codon at the position corresponding to the active site cysteine residue of active mammalian and plant cysteinyl proteinases was found to be that of a serine residue in each of the V-SERA genes. Furthermore, in four of the five genes, including the expressed V-SERA-5 gene, the codon for the active site histidine residue was changed to that of a leucine residue. These critical differences reinforce the concept that a biological activity other than proteolysis is likely to be the primary function of the proteins encoded by this family of genes.

The tumor suppressor maspin does not undergo the stressed to relaxed transition or inhibit trypsin-like serine proteases. Evidence that maspin is not a protease inhibitory serpin

The role of tumor suppressor proteins in the development of malignancy has made the understanding of their molecular mechanisms of action of great importance. Maspin is a tumor suppressor produced by a number of cell types of epithelial origin. Exogenous recombinant maspin has been shown to block the growth, motility, and invasiveness of breast tumor cell lines in vitro and in vivo. Although belonging to the the serine proteinase inhibitor (serpin) superfamily of proteins, the molecular mechanism of maspin is currently unknown. Here we show that the reactive site loop of maspin exists in an exposed conformation that does not require activation by cofactors. The reactive site loop of maspin, however, does not act as an inhibitor of proteinases such as chymotrypsin, elastase, plasmin, thrombin, and trypsin but rather as a substrate. Maspin is also unable to inhibit tissue and urokinase type plasminogen activators. Stability studies show that maspin cannot undergo the stressed-relaxed transition typical of proteinase-inhibitory serpins, and the protein is capable of spontaneous polymerization induced by changes in pH. It is likely, therefore, that maspin is structurally more closely related to ovalbumin and angiotensinogen, and its tumor suppressor activity is independent of a latent or intrinsic trypsin-like serine proteinase-inhibitory activity.

Modulation of apoptosis by the widely distributed Bcl-2 homologue Bak

Members of the Bcl-2 family of proteins are characterized by their ability to modulate cell death. Bcl-2 and some of its homologues inhibit apoptosis, whereas other family members, such as Bax, will accelerate apoptosis under certain conditions. Here we describe the identification and characterization of a complementary DNA that encodes a previously unknown Bcl-2 homologue designated Bak. Like Bax, the bak gene product primarily enhances apoptotic cell death following an appropriate stimulus. Unlike Bax, however, Bak can inhibit cell death in an Epstein-Barr-virus-transformed cell line. The widespread tissue distribution of Bak messenger RNA, including those containing long-lived, terminally differentiated cell types, suggests that cell-death-inducing activity is broadly distributed, and that tissue-specific modulation of apoptosis is controlled primarily by regulation of molecules that inhibit apoptosis.

Cleavage analysis of insulin-like growth factor (IGF)-dependent IGF-binding protein-4 proteolysis and expression of protease-resistant IGF-binding protein-4 mutants

Cultured human fibroblasts and osteoblast-like cells secrete an insulin-like growth factor (IGF)-dependent protease that cleaves IGF-binding protein-4 (IGFBP-4) into two fragments of approximately 18 and 14 kDa. Edman degradation of the isolated proteins established the amino termini of the reaction products. Sequence analysis of the 14-kDa carboxyl-terminal half of IGFBP-4 suggested cleavage after methionine at position 135 of the mature protein. Four variant IGFBP-4 molecules with single amino acid substitutions around this cleavage site were constructed and expressed. Wild-type and mutant IG-FBPs-4 bound IGF-I and IGF-II with equivalent affinities and, in the intact state, were equally effective inhibitors of IGF-I action. However, the IGFBP-4 mutants were relatively resistant to IGF-dependent proteolysis. A 5-6-h incubation in human fibroblast conditioned medium in the presence of IGF-II was sufficient for near total hydrolysis of wild-type IGFBP-4, whereas the mutant IGFBPs-4 were only minimally affected at this time. After a 24-h incubation with IGF-II, all mutant IGFBPs-4 showed extensive proteolysis, generating 18- and 14-kDa fragments. Pre-exposure of human fibroblasts in serum-free conditioned medium to IGF-II for 5 h potentiated subsequent IGF-I stimulation of DNA synthesis. When added with IGF-II, the protease-resistant mutant IG-FBPs-4, but not wild-type IGFBP-4, suppressed IGF-II enhancement of IGF-I-stimulated DNA synthesis. These biological studies suggest that the IGFBP-4/IGFBP-4 protease system may play a role modulating local cellular response to IGF-I.

IGFBP-3 and IGFBP-5 association with endothelial cells: role of C-terminal heparin binding domain

IGFBP-3 and IGFBP-5, but not the other 4 IGF binding proteins, specifically bound to endothelial cell (EC) monolayers. Charged compounds, such as heparin and heparan sulfate, competed for this binding. Of the 6 IGFBPs, IGFBP-3 and IGFBP-5 had the greatest heparin affinity. Peptides of 18 amino acids were synthesized, corresponding to a common basic region of IGFBP-3 (P3), IGFBP-5 and IGFBP-6 (P6) which contained a heparin binding sequence. P3 and P6 inhibited IGFBP-3 and -5 binding to endothelial cell monolayers and the peptides bound directly to EC extracellular matrix. This suggested that the C-terminal basic segment of IGFBP-3/-5 is important for the association of the binding protein with the EC monolayer.

Molecular cloning and structural characterization of the Arg-gingipain proteinase of Porphyromonas gingivalis. Biosynthesis as a proteinase-adhesin polyprotein

The identification of proteinases of Porphyromonas gingivalis that act as virulence factors in periodontal disease has important implications in the study of host-pathogen interactions as well as in the discovery of potential therapeutic and immunoprophylactic agents. We have cloned and characterized a gene that encodes the 50-kDa cysteine proteinase gingipain or Arg-gingipain-1 (RGP-1) described previously (Chen, Z., Potempa, J., Polanowski, A., Wikstrom, M., and Travis, J. (1992) J. Biol. Chem. 267, 18896-18901). Analysis of the amino acid sequence of RGP-1 deduced from the cloned DNA sequence showed that the biosynthesis of this proteinase involves processing of a polyprotein that contains multiple adhesin molecules located at its carboxyl terminus. This finding corroborates previous evidence (Pike R., McGraw, W., Potempa, J., and Travis, J. (1994) J. Biol. Chem. 269, 406-411) that RGP-1 is closely associated with adhesin molecules, and that high molecular weight forms of the proteinase are involved in the binding of erythrocytes.

Role of muscle insulin-like growth factors in nerve sprouting: suppression of terminal sprouting in paralyzed muscle by IGF-binding protein 4

The protracted absence of muscle activation initiates complex cellular and molecular reactions aimed at restoring functional neuromuscular transmission and preventing degenerative processes. A central aspect of these reactions is the sprouting of intramuscular nerves in the vicinity of inactivated muscle fibers. Sprouts emerging from terminal nerve branches and nodes of Ranvier can reestablish functional contacts with inactive muscle fibers, and this is an essential restorative process in pathological conditions of the neuromuscular system. Due to their rapid upregulation in inactive skeletal muscle fibers and their ability to induce nerve sprouting in adult muscle, insulin-like growth factors (IGFs) are candidate signaling molecules to promote restorative reactions in the neuromuscular system. In this study we have exploited the high affinity and specificity of IGF-binding protein 4 (IGF-BP4) and IGF-BP5 for IGF1 and IGF2 to determine whether these growth factors are involved in the nerve sprouting reaction in paralyzed skeletal muscle. In tissue culture experiments with sensory- and motoneurons we demonstrate that the neurite promoting activity of IGF1 is blocked by IGF-BP4, and that a similar IGF-BP-sensitive activity is detected in muscle extracts from paralyzed, but not from control muscle. In in vivo experiments, we show that local delivery of IGF-BP4 to Botulinum toxin A-paralyzed skeletal muscle effectively prevents nerve sprouting in that muscle. Our findings indicate that muscle IGFs play an essential role in intramuscular nerve sprouting. In addition, these findings suggest that IGFs are major signaling factors from inactivated muscle to promote local restorative reactions, including interstitial cell proliferation and nerve sprouting.

Characterization of the chromosomal gene and promoter for human insulin-like growth factor binding protein-5

To better understand the regulation of insulin-like growth factor binding protein-5 (IGFBP-5) expression, we cloned the IGFBP-5 gene from human genomic libraries and identified a region in the 5' flanking sequence which functions as a promoter. The human IGFBP-5 gene is divided into four exons which, primarily due to a first intron of approximately 25 kilobases, span approximately 33 kilobases of DNA. Southern analysis identified a single copy of the IGFBP-5 gene in the haploid human genome, and several independent mapping strategies found this gene tightly linked with, and in opposite transcriptional orientation to, the IGFBP-2 gene at chromosomal region 2q33-34. Primer extension studies identified the IGFBP-5 mRNA cap site 772 base pairs (bp) 5' to the first nucleotide of the translation start codon. Analysis of the 5'-flanking sequence identified a potential TATA element beginning 33 bp 5' to the mRNA cap site. When a DNA fragment containing this cap site and 461 bp of upstream sequence was placed 5' to the chloramphenicol acetyltransferase reporter gene and transfected into MDA-MB-468 human breast cancer cells, it directed chloramphenicol acetyltransferase expression in an orientation-specific manner, suggesting that this region contains elements essential for IGFBP-5 promoter activity.

Protection from Fas-mediated apoptosis by a soluble form of the Fas molecule

Fas is an apoptosis-signaling receptor molecule on the surface of a number of cell types. Molecular cloning and nucleotide sequence analysis revealed a human Fas messenger RNA variant capable of encoding a soluble Fas molecule lacking the transmembrane domain because of the deletion of an exon encoding this region. The expression of soluble Fas was confirmed by flow cytometry and immunocytochemical analysis. Supernatants from cells transfected with the variant messenger RNA blocked apoptosis induced by the antibody to Fas. Levels of soluble Fas were elevated in patients with systemic lupus erythematosus, and mice injected with soluble Fas displayed autoimmune features.

Regulation of insulin-like growth factor binding protein 4 by a specific insulin-like growth factor binding protein 4 proteinase in normal human osteoblast-like cells: implications in bone cell physiology

Insulin-like growth factor binding protein 4 (IGFBP-4) is secreted by normal human osteoblast-like cells (hOB) and is a potent inhibitor of insulin-like growth factor (IGF) action in vitro. In previous studies, IGF treatment of hOB in culture led to markedly reduced medium levels of IGFBP-4 as detected by western ligand blotting. In the present study, incubation of hOB-conditioned medium (hOB-CM) with IGF under cell-free conditions resulted in a similar loss of IGFBP-4. Both IGF-I and IGF-II were capable of inducing a decrease in IGFBP-4; however, IGF-II was more effective. When the six characterized IGFBP were added to hOB-CM, only IGFBP-4 disappeared in response to IGF-II addition. This IGF-regulated loss of IGFBP-4 was inhibited by metalloproteinase inhibitors and appeared to be due to a proteinase that cleaved IGFBP-4 in 18 and 14 kD fragments identified by western immunoblotting. Conditioned media from eight of eight different donor hOB lines tested exhibited IGFBP-4 proteinase activity. To assess the biologic consequences of IGF-II-induced IGFBP-4 proteolysis, we treated hOB with IGF-II for 5 h, which decreased medium IGF-BP-4 by 70%, and then measured IGF-I and insulin stimulation of [3H]thymidine incorporation. IGF-II itself was not mitogenic and had no effect on insulin-stimulated [3H]thymidine incorporation. However, pretreatment of cultured hOB with IGF-II enhanced IGF-I-stimulated [3H]thymidine incorporation threefold.(ABSTRACT TRUNCATED AT 250 WORDS)

Carboxy-truncated insulin-like growth factor binding protein-5 stimulates mitogenesis in osteoblast-like cells

Recently we demonstrated that a 23 kDa form of IGFBP-5, derived from osteoblast-like cells, stimulates osteoblast mitogenesis and enhances IGF-I action. Because osteoblast-derived IGFBP-5 is smaller than recombinant intact IGFBP-5 (23 vs 30 kDa) and has decreased binding affinity for IGF-I, we proposed that the native 23 kDa form of IGFBP-5 was truncated at a carboxy-terminal position. We now show that a recombinant form of carboxy-truncated IGFBP-5 binds IGF-I with reduced affinity and stimulates mitogenesis in mouse osteoblasts. We also show that 125I-truncated IGFBP-5 specifically binds to osteoblast monolayers with low binding affinity, similar to that seen with native 23 kDa IGFBP-5. These data indicate that carboxy-truncated IGFBP-5 stimulates osteoblast mitogenesis and suggest that reduced IGF-binding and cell-surface attachment are local mediators of this response.

Rat ovarian insulin-like growth factor-binding protein-6: a hormonally regulated theca-interstitial-selective species with limited antigonadotropic activity

Most but not all of the established insulin-like growth factor-binding proteins (IGFBPs) are expressed in the rat ovary. To continue the process of characterizing these ovarian IGFBPs, a solution hybridization/RNase protection assay was used to study IGFBP-6 gene expression, cellular localization, and hormonal regulation in the immature rat ovary. Total RNA was hybridized with a 458-base long 32P-labeled rat IGFBP-6 cRNA. A single protected fragment (380 bases long) corresponding to IGFBP-6 transcripts was identified in RNA from ovary and lung, but not kidney or liver. The amount of IGFBP-6 transcripts was higher in ovaries from immature rats (25-28 days old) than in ovaries from adult rats and was higher in theca-interstitial than in granulosa cell preparations. Hypophysectomy resulted in a significant (P < 0.05) 2.3 +/- 0.7-fold (mean +/- SD) increase in whole ovarian IGFBP-6 transcripts. This suggests that ovarian IGFBP-6 gene expression is subject to inhibition by one or more pituitary hormones. Therefore, the effect of replacement of FSH, GH, diethylstilbestrol (DES), or combinations thereof was evaluated. Treatment with FSH resulted in a 2.4-fold decrease (P < 0.05) in the abundance of ovarian IGFBP-6 transcripts relative to that in hypophysectomized controls. Provision of DES yielded comparable results. Moreover, the combined provision of FSH and DES resulted in a synergistic decrease (6.0-fold) in ovarian IGFBP-6 transcripts. In contrast, treatment of hypophysectomized rats with GH proved without effect. However, treatment with FSH or DES in addition to GH resulted in a decrease in ovarian IGFBP-6 transcripts (3.9- and 2.7-fold, respectively). To assess the role of ovarian IGFBP-6, its influence on gonadotropin action in primary cultures of rat granulosa cells was also studied. Increasing concentrations (0.01-1 micrograms/ml) of recombinantly expressed human IGFBP-6 did not inhibit the FSH-supported accumulation of either progesterone or estradiol. These findings 1) establish the theca-interstitial compartment of the immature rat ovary as a prominent site of IGFBP-6 gene expression, 2) implicate FSH and DES as inhibitors of IGFBP-6 transcript levels in the whole ovary, 3) and disclose the limited antigonadotropic action of IGBP-6F on the rat granulosa cell.

Regulation and biological effect of endogenous insulin-like growth factor binding protein-5 in human osteoblastic cells

U-2 human osteosarcoma cells secrete a 29/32/34 kilodalton (kDa) insulin-like growth factor binding protein (IGFBP) identified as O-glycosylated IGFBP-5. Treatment of U-2 cells with IGF-I markedly increased medium levels of IGFBP-5 in a concentration- and time-dependent manner; other skeletal regulatory factors (GH, insulin, PTH, dexamethasone, beta-estradiol, 1,25-dihydroxyvitamin D3, transforming growth factor-beta) had no effect. IGF-I increased IGFBP-5 levels in the culture medium 10-fold without influencing IGFBP-5 messenger RNA abundance. IGF-I, IGF-II, and the IGF-I analog [1-27Gly(4)38-70] IGF-I bound IGFBP-5 with high affinity and, when added to U-2 cultures, effectively promoted IGFBP-5 accumulation in the medium. On the other hand, des(1-3)IGF-I and [QAYL]IGF-I, IGF-I analogs that did not bind IGFBP-5, failed to elicit an increase in medium IGFBP-5. Cell-free incubation of recombinant human (rh) IGFBP-5 in U-2 conditioned medium resulted in a marked reduction of detectable rhIGFBP-5; the presence of IGF-I or IGF-II peptide partially prevented this decrease. By immunoblot analysis, loss of intact rhIGFBP-5 (29-kDa unreduced, 34-kDa reduced) coincided with the appearance of a 16-kDa proteolytic fragment. U-2 conditioned medium contained immunoreactive IGFBP-5 at 29-34-kDa, 20-kDa, 17-kDa, and 16-kDa. Endogenous IGFBP-5 inhibited IGF-I but not des(1-3)IGF-I-stimulated U-2 cell proliferation. In conclusion, IGF peptides can regulate the availability of IGFBP-5 in osteoblast-like cells by impeding IGFBP-5 proteolysis. The biological consequence of increased medium IGFBP-5 appears to be decreased cell responsiveness to IGF-I stimulation.

Structure and biological activities of a heparin-derived hexasaccharide with high affinity for basic fibroblast growth factor

We demonstrated previously that heparin-derived hexasaccharides are the smallest fragments of the polysaccharide with comparable basic fibroblast growth factor (bFGF)-modulating activity in vitro (Ishihara, M., Tyrrell, D.J., Stauber, G.B., Brown, S., Cousens, L., and Stack, R.J. (1993) J. Biol. Chem. 268, 4675-4683. In this report, a specific hexasaccharide having high affinity for recombinant human bFGF was isolated and its structure deduced by analysis of its reduced disaccharide products after treatment with nitrous acid at pH 1.5, and by 1H NMR spectroscopy. The hexasaccharide has the structure [IdoA(2-OSO3)alpha 1-4GlcNSO3(6-OSO3)alpha 1-4]2IdoA(2-OSO3)alpha 1-4 AManR(6-OSO3). The hexasaccharide effectively inhibits the binding of syndecan-transfected RO-12 UC cells to bFGF-coated wells (Ishihara, M., Tyrrell, D.J., Kiefer, M.C., Barr, P.J., and Swiedler, S.J. (1992) Anal. Biochem. 202, 310-315), prevents the binding of 125I-bFGF to confluent monolayers of adrenocortical endothelial (ACE) cells, and inhibits the bFGF-dependent proliferation of ACE cells. Unlike the heparin from which it was derived, however, the hexasaccharide cannot promote the binding of 125I-bFGF to a recombinant high affinity bFGF receptor (flg) or restore the bFGF-dependent proliferative response to ACE cells grown in the presence of 5 mM sodium chlorate. Collectively, these data indicate that a hexasaccharide can be as effective as heparin as an antagonist of bFGF-mediated cell mitogenesis.

Recombinant human insulin-like growth factor binding proteins 4, 5, and 6: biological and physiochemical characterization

We have recently cloned cDNAs encoding human insulin-like growth factor binding proteins (IGFBP)-4, -5 and -6 and have now expressed these BPs in yeast as ubiquitin (Ub)-IGFBP fusion proteins. Western ligand blotting with 125I-IGF II under nonreducing conditions of recombinant human (rh) IGFBP-containing yeast lysates revealed specific binding bands for IGFBP-4, -5, and -6 at apparent molecular masses of 24-26, 30-32, and 24-26 kDa, respectively, indicating expression and processing of the fusion proteins. HPLC purified rhIGFBPs had virtually the same amino acid composition, amino acid number, and NH2-terminal sequences as the native BPs. Rabbit antiserum directed against each rhIGFBP-4, -5 and -6 reacted specifically with the respective rhIGFBP as well as with the native human counterpart and displayed very low cross-reactivity with other IGFBPs. Except for the affinity of rhIGFBP-6 for IGF I (Ka = 8.5 x 10(8) M-1), the affinity constants of the three IGFBPs for IGF I and II lie between 1.7 and 3.3 x 10(10) M-1. When present in excess, rhIGFBP-4, -5, and -6 inhibited IGF I- and II-stimulated DNA and glycogen synthesis in human osteoblastic cells, although rh-IGFBP-6 had only a weak inhibitory effect on IGF I in agreement with its relatively lower IGF I affinity constant.

Posttranslational regulation of insulin-like growth factor binding protein-4 in normal and transformed human fibroblasts. Insulin-like growth factor dependence and biological studies

Insulin-like growth factor binding protein-4 (IGFBP-4) is a 24-26-kD protein expressed by a variety of cell types in vivo and in vitro. Treatment of normal adult human fibroblasts with 10 nM insulin-like growth factor II (IGF-II) for 24 h resulted in an 85% decrease in endogenous IGFBP-4, as assessed by Western ligand blot analysis of the conditioned medium. Incubation of human fibroblast-conditioned medium (HFCM) with IGF-II under cell-free conditions led to a similar loss of IGFBP-4. This posttranslationally regulated decrease in IGFBP-4 appeared to be due to a protease in HFCM: (a) It could be prevented with specific protease inhibitors or incubation at 4 degrees C; (b) proteolysis of recombinant human (rh) IGFBP-4 required HFCM; (c) immunoblotting and radiolabeling confirmed cleavage of IGFBP-4 into 18- and 14-kD IGFBP-4 fragments. The protease was specific for IGFBP-4, and was strictly dependent on IGFs for activation. IGF-II was the most effective of the natural and mutant IGFs tested, inducing complete hydrolysis of rhIGFBP-4 at a molar ratio of 0.25:1 (IGF/IGFBP-4). Simian virus 40-transformed adult human fibroblasts also expressed IGFBP-4 and IGFBP-4 protease, as well as an inhibitor of IGFBP-4 proteolysis. In biological studies, intact rhIGFBP-4 potently inhibited IGF-I-stimulated [3H]aminoisobutyric acid uptake, whereas proteolyzed rhIGFBP-4 had no inhibitory effect. In conclusion, these data provide evidence for a novel IGF-dependent IGFBP-4-specific protease that modifies IGFBP-4 structure and function, and indicate a preferential role for IGF-II in its activation. Posttranslational regulation of IGFBP-4 may provide a means for cooperative control of local cell growth by IGF-I and IGF-II.

Selection of COS cell mutants defective in the biosynthesis of heparan sulfate proteoglycan

A simple procedure using human basic fibroblast growth factor (FGF) was utilized for the selection of COS cell mutants with defects in the biosynthesis or expression of heparan sulfate proteoglycan (HSPG). Our approach was based on the strong binding affinity exhibited by COS cells to human basic FGF that had been adsorbed to plastic dishes. Cell binding to basic FGF could be inhibited by heparin and heparan sulfate (HS), but not by chondroitin sulfate, dermatan sulfate, keratan sulfate, or hyaluronic acid, suggesting that the cell binding involved an interaction between basic FGF and cell surface heparin-like molecules. COS cells were treated with ethyl methanesulfonate and four stable mutants were subsequently isolated that did not bind strongly to basic FGF adsorbed to plastic. These mutants cell lines (CM-2, CM-8, CM-9, and CM-15) exhibited significantly reduced 35SO4 incorporation into HS (40-70% depending on the cellular pool analyzed). In one of these cell lines, CM-15, the incorporation of [6-3H]glucosamine into HS was unaltered, suggesting that the extent of oligosaccharide polymerization was equivalent to that observed for the wild-type cells. Structural analysis revealed that N-sulfated glucosamine residues were present much less frequently in HS derived from these cells as compared with that derived from wild-type cells. Furthermore, CM-15 was found to be three-fold deficient in HS N-sulfotransferase activity, but contained wild-type levels of HS O-sulfotransferase activities.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of recombinant human insulin-like growth factor binding proteins 4, 5, and 6 produced in yeast

The insulin-like growth factor binding protein (IGFBP) family comprises six structurally distinct, but highly homologous proteins. They have been identified in serum and other biological fluids, tissue extracts, and cell culture media. We have recently cloned cDNAs encoding human IGFBP-4, -5, and -6 and have now expressed these BPs in yeast as ubiquitin (Ub)-IGFBP fusion proteins. Western ligand blotting with 125I-IGF II under nonreducing conditions of recombinant human (rh) IGFBP-containing yeast lysates revealed specific binding bands for IGFBP-4, -5, and -6 at apparent molecular masses of 24-26, 30-32, and 24-26 kDa, respectively, indicating processing of the fusion proteins. High-performance liquid chromatography-purified rhIGFBPs had virually the same amino acid composition, amino acid number, and NH2-terminal sequences as the native BPs. Except for the affinity of rhIGFBP-6 for IGF I (Ka = 8.5 x 10(8) M-1), the affinity constants of the three IGFBPs for IGF I and II lie between 1.7 and 3.3 x 10(10) M-1, i.e. 25-100 times higher than the IGF I and II affinities of the type I IGF receptor. When present in excess, rhIGFBP-4, -5, and -6 inhibited IGF I- and II-stimulated DNA and glycogen synthesis in human osteoblastic cells, but rhIGFBP-6 had only a weak inhibitory effect on IGF I in agreement with its relatively lower IGF I affinity constant. The results of this study show that the primary effect of the three rhIGFBPs is the attenuation of IGF activity and suggest that IGFBPs contribute to the control of IGF-mediated cell growth and metabolism.

A cell-based assay for evaluating the interaction of heparin-like molecules and basic fibroblast growth factor

A simple panning procedure that allows for the evaluation of interactions between various heparin-like molecules and basic FGF has been developed. This assay measures the ability of compounds to inhibit the interaction of transfected human lymphoblastoid cells, UC 729-6 (UC cells), expressing hamster syndecan and basic FGF-coated plastic plates. The transfected cells bind rapidly to basic FGF-coated plates while the control cells do not bind well. Binding of the transfected cells to basic FGF was inhibited by heparin and heparin sulfate (HS), but not by chondroitin sulfate, dermatan sulfate, keratan sulfate, and hyaluronic acid. There was little inhibition of binding by chemically modified heparin such as completely desulfated, N-acetylated heparin, completely desulfated, N-sulfated heparin, and N-desulfated, N-acetylated heparin. These results suggested that both the N-sulfate and O-sulfate groups of heparin are required for binding to basic FGF. In addition, inhibition by oligosaccharides derived from depolymerized heparin increased with fragment size; partial inhibition was observed with oligosaccharides as small as hexamers. The biochemical basis for the binding of transfected cells to basic FGF was established by showing a significant increase of 35SO4 incorporation into HS. In particular, the level of 35SO4-HS in the trypsin-releasable (cell surface) pool increased fivefold. This increase was accounted for by demonstration of the presence of HS on immunoprecipitated syndecan from the transfected cells.

Structure and expression of the gene for Pv200, a major blood-stage surface antigen of Plasmodium vivax

Molecular cloning and structure analysis of the gene encoding the Pv200 protein of the Sal-1 strain of Plasmodium vivax revealed an overall identity of 34-37% when the deduced amino acid sequence was compared with the sequences of various major merozoite surface antigens of Plasmodium falciparum, Plasmodium yoelii and Plasmodium chabaudi. When the Sal-1 Pv200 sequence was compared with the corresponding sequence from the Belèm strain of P. vivax, it was found that the two merozoite surface antigens were relatively well conserved with an overall amino acid sequence identity of 81%. A region of 23 repeated glutamine residues, found in the sequence of the Belèm isolate was not found, however, in the Sal-1 sequence. Amino- and carboxy-terminal domains of the Pv200 protein were expressed in the yeast Saccharomyces cerevisiae. Each recombinant protein was shown to react with antibodies in sera from splenectomized Bolivian Saimiri monkeys that had been infected previously with P. vivax, and in human sera from individuals with a history of exposure to vivax malaria. The availability of recombinant DNA-derived Pv200 proteins will now allow a full assessment of their utility in the diagnosis and immunoprophylaxis of the benign tertian malaria associated with P. vivax infection.

The molecular biology of heparan sulfate fibroblast growth factor receptors

Two distinct classes of cell surface FGF-binding proteins have been identified. These receptors differ in both mode of interaction and in affinity for the FGFs. cDNAs that encode the low-affinity receptor were isolated from a hamster kidney cell line cDNA library by expression cloning. Transfected cells that contained these heparan sulfate proteoglycan FGF receptor cDNAs were enriched for by panning on basic FGF-coated plates. The analogous human cDNA was isolated from a hepatoma cell line cDNA library. The homology of our hamster cDNAs to the previously described murine integral membrane proteoglycan syndecan, together with an exact amino acid sequence match of our human-cDNA-encoded product to human syndecan, clearly indicates the identity of these independently isolated proteoglycans. Further confirmation that the expressed molecule serves as a proteoglycan core protein was achieved by immunoprecipitation of 35SO4-labeled material from solubilized transfected cells. Nitrous acid treatment and chondroitinase digestion revealed that 77% of the label was associated with heparan sulfate chains and 22% with chondroitin sulfate chains. These heparan sulfate chains contributed to the fivefold increase in the total heparan sulfate found to be present on the surface of the transfected cells compared with cells transfected with a vector lacking the cDNA insert.

Identification of a second human subtilisin-like protease gene in the fes/fps region of chromosome 15

A cDNA encoding a novel human subtilisin-like protease was identified by a polymerase chain reaction (PCR) methodology. PCR primers were designed to be specific for the subfamily of eukaryotic subtilisin-like proteases with specificity for paried basic amino acid residue processing motifs. The gene encoding this protease, designated PACE4, also encoded a smaller subtilisin-related polypeptide derived by alternate mRNA splicing. The deduced PACE4 protein sequence contained a number of interesting features not present in other family members, including an extended signal peptide region, and a relatively large carboxyl-terminal cysteine-rich region with no obvious membrane anchor sequence. As with the fur gene product, the tissue distribution of PACE4 was widespread, with comparatively higher levels in the liver. An additional relationship to the fur gene product was shown by chromosomal localization studies. The close proximity of the fur and PACE4 genes on chromosome 15 suggests that these genes probably evolved from a common ancestor by gene duplication.

Distribution and organization of a tandemly repeated 352-bp sequence in the oryzae family

A 352-bp EcoRI fragment from rice DNA was cloned and shown to be a member of a tandem repeat. Sequence determination revealed homologies with human alpha satellite DNA and maize knob heterochromatin specific repeat. This 352-bp sequence is highly specific for the AA genome of rice. However, copy number and sequence organization are variable, depending on the accession analyzed. Several examples of amplification were observed in O. rufipogon and O. longistaminata. Use of resolutive polyacrylamide gel electrophoresis and 4-bp cutter enzymes allowed one to distinguish between the Indica and Japonica subtypes of O. sativa. The same method also discriminates between two groups of O. rufipogon, the presumed ancestor of O. sativa, suggesting that the present day Indica and Japonica subtypes originated independently from two O. rufipogon distinct populations.

cDNA and gene structure for a human subtilisin-like protease with cleavage specificity for paired basic amino acid residues

A cDNA encoding the human fur gene product was isolated from a human hepatoma cell line. The cDNA encodes a protein with significant amino acid sequence identity to the prokaryotic subtilisin family of serine proteases. More extensive sequence identity was found when the protein was compared with eukaryotic proteases such as PRB1 of Saccharomyces cerevisiae, and with PC2 and PC3, the only other known mammalian subtilisin-like proteases. In contrast to these proteins, however, the fur gene product shares a more extensive topographic and functional homology with the KEX2 endoprotease of S. cerevisiae. Each protease contains a signal peptide, a glycosylated extra cytoplasmic domain, a hydrophobic membrane-spanning region, and a short, hydrophilic "tail" sequence. As with KEX2, the expressed human protease was shown to cleave mammalian proproteins at their paired basic amino acid processing sites. We have, therefore, proposed the function-based acronym PACE (paired basic amino acid cleaving enzyme) for this prototypic mammalian proprotein processing enzyme.

Identification and molecular cloning of two new 30-kDa insulin-like growth factor binding proteins isolated from adult human serum

Three insulin-like growth factor binding proteins (IGFBP) with apparent molecular masses of 24, 28-30, and 30 kDa, nonreduced, have been isolated from human serum. The 15 NH2-terminal amino acids of the 24-kDa binding protein are identical with those of the 30-kDa BP. The apparent molecular mass of the latter is reduced to 24 kDa by N-glycanase, suggesting that the 30-kDa BP is the glycosylated form of the isolated 24-kDa BP. The complete amino acid sequences derived from the cloned cDNAs represent two new IGFBPs. They are tentatively termed IGFBP-4 and -5. The prepeptide sequences of BP-4 and -5 contain 27 and 21, the mature proteins 213 and 237 amino acids, respectively (Mr = 22,610 and 25,980). The NH2- and COOH-terminal thirds of BP-4 and -5 display pronounced homology to the other three human BPs. 16 of the 16-20 cysteines and 37 of the 213-289 amino acids (12.8-17.1%) are conserved in all five mature BPs. 10 amino acid positions located in the NH2-terminal region and shared by BP-1, -2, -3, and -5 are different in BP-4. These differences may account for the preferential affinity of BP-4 for IGF II. A most intriguing homology exists between the COOH-terminal quarter of the five IGFBPs, 10 repetitive domains of human thyroglobulin, a gastrointestinal tumor-associated antigen, and the invariant chain of the class II histocompatibility antigen. The cDNAs of five human IGFBPs are now available. They will allow their expression and production in sufficient quantities for in vivo studies to unravel their role in growth and metabolism.

Molecular cloning of a new human insulin-like growth factor binding protein

We have cloned a new insulin-like growth factor's binding protein (IGFBP) from a human osteosarcoma cDNA library. Two conserved regions in the COOH-terminal third of the five known human IGFBPs were used to design primers and to perform polymerase chain reaction (PCR) with osteosarcoma cDNA as a template. One of the eight PCR products encoded a unique IGFBP sequence. The DNA sequence was used to synthesize probes to screen an osteosarcoma cDNA library and isolate full length cDNA clones. The amino acid sequence was deduced from one of them. It contains two possible signal peptidase cleavage sites yielding a mature molecule of 257 or 252 amino acids, and 18 cysteines in identical positions to the other IGFBPs. The most pronounced homology exists with human IGFBP-3 (50% in the NH2- and 45% in the COOH-terminal region).

Molecular cloning of a human basic fibroblast growth factor receptor cDNA and expression of a biologically active extracellular domain in a baculovirus system

A cDNA clone encoding a human fibroblast growth factor (FGF) receptor was isolated from a hepatoma cell line cDNA library. The cDNA encodes a three immunoglobulinlike-domain FGF receptor that is similar to a human placental FGF receptor cDNA but lacks two amino acids. The variation observed at these two amino acids, also seen in the two immunoglobulinlike-domain FGF-receptors, can be explained by an alternate splicing mechanism. We have used a baculovirus expression system to produce high levels of a soluble, extracellular domain form of the FGF receptor (EC-FGF receptor). Spodoptera frugiperda (Sf9) insect cells infected with recombinant EC-FGF receptor viruses synthesized and secreted an EC-FGF receptor of apparent Mr = 58,000. The EC-FGF receptor purified from conditioned media of infected Sf9 cells by lentil lectin affinity chromatography was shown to bind basic FGF with high affinity (Kd = 1-5 nM), to inhibit the binding of radioiodinated basic FGF to its high affinity receptor and to inhibit endothelial cell proliferation. Furthermore, binding of basic FGF to the EC-FGF receptor was shown to be significantly enhanced by heparin. The availability of biologically active FGF receptors will allow an analysis of their interaction with members of the FGF family of proteins and viruses of the herpes family that have been shown to use the FGF receptor system for cell entry.

Expression of a human proprotein processing enzyme: correct cleavage of the von Willebrand factor precursor at a paired basic amino acid site

Intracellular proteolytic processing of precursor polypeptides is an essential step in the maturation of many proteins, including plasma proteins, hormones, neuropeptides, and growth factors. Most frequently, propeptide cleavage occurs after paired basic amino acid residues. To date, no mammalian propeptide processing enzyme with such specificity has been purified or cloned and functionally characterized. We report the isolation and functional expression of a cDNA encoding a propeptide-cleaving enzyme from a human liver cell line. The encoded protein, called PACE (paired basic amino acid cleaving enzyme), has structural homology to the well-characterized subtilisin-like protease Kex2 from yeast. The functional specificity of PACE for mediating propeptide cleavage at paired basic amino acid residues was demonstrated by the enhancement of propeptide processing of human von Willebrand factor when coexpressed with PACE in COS-1 cells.

Ligand-affinity cloning and structure of a cell surface heparan sulfate proteoglycan that binds basic fibroblast growth factor

Expression cloning of cDNAs encoding a basic fibroblast growth factor (FGF) binding protein confirms previous hypotheses that this molecule is a cell-surface heparan sulfate proteoglycan. A cDNA library constructed from a hamster kidney cell line rich in FGF receptor activity was transfected into a human lymphoblastoid cell line. Clones expressing functional basic FGF binding proteins at their surfaces were enriched by panning on plastic dishes coated with human basic FGF. The amino acid sequence deduced from the isolated cDNAs revealed several interesting features, including hydrophobic signal and transmembrane domains that flank an extracellular region containing six potential attachment sites for glycosaminoglycan side chains. The structure also contains a short hydrophilic cytoplasmic tail sequence homologous to previously reported actin binding domains. Binding of basic FGF to cells expressing the binding protein could be inhibited by heparin and heparan sulfate but not by chondroitin sulfate, dermatan sulfate, or keratan sulfate. In addition to binding basic FGF, this protein or related surface proteins may function as an initial cellular attachment site for other growth factors and for viruses, such as herpes simplex virus.

Cloning of three human multifunctional de novo purine biosynthetic genes by functional complementation of yeast mutations

Functional complementation of mutations in the yeast Saccharomyces cerevisiae has been used to clone three multifunctional human genes involved in de novo purine biosynthesis. A HepG2 cDNA library constructed in a yeast expression vector was used to transform yeast strains with mutations in adenine biosynthetic genes. Clones were isolated that complement mutations in the yeast ADE2, ADE3, and ADE8 genes. The cDNA that complemented the ade8 (phosphoribosylglycinamide formyltransferase, GART) mutation, also complemented the ade5 (phosphoribosylglycinamide synthetase) and ade7 [phosphoribosylaminoimidazole synthetase (AIRS; also known as PAIS)] mutations, indicating that it is the human trifunctional GART gene. Supporting data include homology between the AIRS and GART domains of this gene and the published sequence of these domains from other organisms, and localization of the cloned gene to human chromosome 21, where the GART gene has been shown to map. The cDNA that complemented ade2 (phosphoribosylaminoimidazole carboxylase) also complemented ade1 (phosphoribosylaminoimidazole succinocarboxamide synthetase), supporting earlier data suggesting that in some organisms these functions are part of a bifunctional protein. The cDNA that complemented ade3 (formyltetrahydrofolate synthetase) is different from the recently isolated human cDNA encoding this enzyme and instead appears to encode a related mitochondrial enzyme.

Genetic and molecular mapping of the Hmt region of mouse

We have mapped a new region of the mouse major histocompatibility complex (MHC) that contains the nuclear gene, Hmt, for the maternally transmitted antigen, Mta. The Hmt region of chromosome 17 lies between a recombinational breakpoint distal to Tla and another proximal to Tpx-1, thus including Pgk-2. A novel MHC class I gene fragment, R4B2, was cloned and mapped to this region as was another new class I gene, Thy19.4. Both lie proximal to Pgk-2, within the distal inversion in t-haplotypes. The presence of several other MHC class I genes in the Hmt region is predicted from analysis of the recombinants that define the region.