Purification of an autocrine growth factor homologous with mouse epithelin precursor from a highly tumorigenic cell line

PC cell line is a highly tumorigenic insulin-independent variant from the teratoma-derived adipogenic cell line 1246. Culture medium of PC cells contains a growth promoting activity for 3T3 cells and producer cells. PC cell-derived growth factor (PCDGF) was purified to homogeneity from PC cell-conditioned medium as an apparent 88-kDa protein by chromatography on heparin-Sepharose, Sephacryl S-200, and phenyl-Sepharose. Digestion with peptide-N-glycosidase F yielded an apparent 68-kDa protein component indicating that PCDGF is a glycoprotein containing about 20 kDa of carbohydrate. Partial sequence from Edman degradation of peptide fragments obtained by digestion of PCDGF with cyanogen bromide and trypsin demonstrates that PCDGF contains regions of sequence identity to that deduced from the granulin or epithelin precursor cDNAs. Granulins are small polypeptides purified from granulocyte extracts with no apparent biological functions. Epithelins are cell growth modulators purified as small molecular mass 6-kDa polypeptides from kidney extracts. The existence of a large molecular mass precursor for granulin or epithelin has been predicted based upon recently cloned cDNAs encoding these biomolecules within a 63.5-kDa protein with putative glycosylation sites. No biological activity has previously been attributed to the precursor. The present results indicate that PCDGF is a potential precursor for epithelin and/or granulin, that this 88-kDa protein is secreted and glycosylated, and that it can function as a mitogen for 3T3 cells as well as an autocrine growth factor for PC cells.

Complement-mediated binding of naturally glycosylated and glycosylation-modified human immunodeficiency virus type 1 to human CR2 (CD21)

Particulate glycoproteins lacking sialic acid, such as desialylated enveloped viruses, readily activate complement through the alternative pathway. Human immunodeficiency virus type 1 (HIV-1) contains two heavily glycosylated and partially sialylated envelope glycoproteins: a surface gp120 and a transmembrane gp41. The abilities of naturally glycosylated HIV-1 and glycosylation-modified HIV-1 to interact with the complement system were examined with a biological assay which measured the binding of whole virus particles to cells expressing CR2 (CD21), the complement receptor found naturally in abundance on follicular dendritic cells and immature B cells. HIV-1 IIIB was synthesized in the presence or absence of the mannosidase II inhibitor, swainsonine, to give rise to high-mannose-type, nonsialylated, nonfucosylated carbohydrate moieties. The virus also was treated with neuraminidase or endo-beta-galactosidase to remove terminal sialic acids. An enzyme immunoassay specific for HIV-1 p24 core protein was used to quantitate the amount of virus bound to cell surfaces. Virus particles incubated with 1:3-diluted, fresh HIV-1-negative human serum as a source of complement readily bound to MT-2 (CD4+ CR2+) and Raji-3 (CD4- CR2+) cells but not to CEM (CD4+ CR2-) cells, suggesting that the virus bound to CR2 independently of CD4. Compared with heat-inactivated or C3-deficient sera, fresh complement increased binding by as much as 62 times for naturally glycosylated virus, and 5 times more than this for glycosylation-modified virus. Similar observations were made with freshly isolated, non-mitogen-stimulated peripheral blood mononuclear cells. Additional evidence that HIV-1 bound to CR2 independently of CD4 was provided by the fact that binding was blocked by monoclonal antibody OKB7 (anti-CR2) but not by OKT4a (anti-CD4). Also, the virus bound to transfected K562 cells (CD4-) which expressed recombinant human CR2 but did not bind to untransfected K562 cells. Results obtained with complement component-deficient sera indicated that binding required the alternative complement pathway. Raji-3 and transfected K562 cells could not be infected with HIV-1 in the presence of complement, suggesting that utilization of CR2 as a receptor in the absence of CD4 does not allow virus entry. The demonstration of CR2 as a receptor for HIV-1 in the presence of complement, together with the ability to enhance binding by desialylation, provides new insights into mechanisms of HIV-1-induced immunity and immunopathogenesis.

Glycosylation of human papillomavirus type 16 L1 protein

We examined glycosylation of the L1 capsid protein of human papillomavirus type 16, using HPV16 L1 protein expressed from various recombinant vaccinia viruses in CV-1 and HaCaT cells. A minority of L1 protein was N-glycosylated, and all four potential N-glycosylation sites appeared to be used. Glycosylation was of the high-mannose type, as shown by reactivity with biotin-labeled Concanavalin A and by exoglycosidase digestions. A series of mutant L1 proteins were used to establish that an N-terminal hydrophobic sequence, common to all sequenced papillomavirus L1 capsid proteins, was a major determinant of the proportion of L1 protein glycosylated, whereas C-terminus nuclear localization signal sequences were unimportant. Subcellular localization studies showed that whereas the majority of L1 protein was found in the cell nucleus, glycosylated L1 was retained in the endoplasmic reticulum and was neither exported from the cell nor translocated to the cell membrane or the cell nucleus. We conclude that glycosylated L1 is unlikely to be an important component of the papillomavirus virion, a finding of importance for the design of papillomavirus-specific vaccines.

Synthesis and assembly of infectious bovine papillomavirus particles in vitro

Bovine papillomavirus type 1 (BPV-1) virions were produced in vitro using vaccinia virus (VV) recombinants expressing the BPV-1 L1 and L2 capsid proteins. Particles morphologically resembling papillomaviruses were observed in the nucleus of cells infected with a VV recombinant for the BPV-1 L1 protein, and greater numbers of similar particles were seen in the nuclei of cells infected with a VV double recombinant for L1 and L2. Virus-like particles (VLPs) assembled in cells infected with the VV double recombinant for BPV-1 L1 and L2, and not those assembled in cells infected with the VV recombinant for BPV-1 L1 alone, were able to package BPV-1 DNA. Transcription of the BPV-1 E1 viral open reading frame was observed after a mouse fibroblast cell line was exposed to VLPs produced using a BPV-1 L1/L2 VV recombinant in a cell line containing episomal BPV-1 DNA. E1 transcription was not observed when the VLPs were pre-incubated with antibodies to the capsid protein of BPV-1. This system should allow an in vitro approach to the definition of the BPV-1 cellular receptor.

Functional consequences of a Na+ channel mutation causing hyperkalemic periodic paralysis

Hyperkalemic periodic paralysis (HYPP), one of several inheritable myotonic diseases, results from genetic defects in the human skeletal muscle Na+ channel. In some pedigrees, HYPP is correlated with a single base pair substitution resulting in a Met replacing Thr704 in the fifth transmembrane segment of the second domain. This region is totally conserved between the human and rat channels. We have introduced the human mutation into the corresponding region of the rat muscle Na+ channel cDNA and expressed it in human embryonic kidney 293 cells. Patch-clamp recordings show that this mutation shifts the voltage dependence of activation by 10-15 mV in the negative direction. The shift results in a persistent Na+ current that activates near -70 mV; this phenomenon could underlie the abnormal muscle activity observed in patients with HYPP.

Hyperkalemic periodic paralysis: rapid molecular diagnosis and relationship of genotype to phenotype in 12 families

We studied mutations of the adult voltage-gated skeletal muscle sodium channel gene in 12 families, from diverse ethnic backgrounds, with hyperkalemic periodic paralysis (HyperPP). We describe a novel procedure, using ligase chain reaction (LCR), to simultaneously identify two different point mutations (previously described) and one rare, apparently benign polymorphism that results in a nonconservative amino acid substitution. Three of 12 families showed the Met1592Val mutation, and six of 12 had the Thr704Met mutation. The mutation in three of the 12 families was not identified. In one of these three families, the disease was not linked to the adult voltage-gated sodium channel gene, suggesting the existence of a clinically similar but genetically distinct form of HyperPP. Genotype/phenotype correlations based on patient records and interviews in these families showed the variable and subjective nature of the illness, although the clinical distinctions between hyperkalemic periodic paralysis and paramyotonia congenita were reinforced by the molecular data.

Anatomical and developmental patterns of facilitative glucose transporter gene expression in the rat kidney

In situ hybridization was used to map cellular patterns of gene expression for facilitative glucose transporters (GTs) 1-5 in the developing and adult rat kidney. GT3 was not detected. GT1 mRNA was present in the proximal straight tubule (PST), distal nephron and collecting duct. GT2 mRNA was localized in both proximal convoluted and PST, while GT5 mRNA was detected only in the PST. GT4 mRNA and immunoreactivity were focally localized in the thick ascending limb of Henle's loop and were coexpressed with IGF-I. Thus, each of the four different isoforms demonstrated a distinct renal distribution, with GTs 1, 2, and 5 coexpressed in the PST. Renal GT1 and GT5 gene expression were unchanged throughout development, while GT2 was most abundant before weaning and GT4 was first detected after weaning. Only GT4 appeared to be hormonally regulated: It was decreased after hypophysectomy and increased after vasopressin treatment, but was not affected by 1 or 4 d of insulinopenic diabetes mellitus. The coexpression of GT4 and IGF-I in the thick ascending limb segment of the nephron suggests a novel autocrine/paracrine mechanism by which cells may control local fuel economy independently from that of the larger structure to which they belong and from the systemic hormonal milieu.

Signal transduction mediated by angiotensin II receptor subtypes expressed in rat renal mesangial cells

Recent evidence suggests that there are two classes of receptors for angiotensin II (AngII), AT1 which is sensitive to losartan (DuP753) and is G-protein coupled, and AT2 which is sensitive to both PD123319 and CGP42112A, and is non-G-protein coupled. In rat mesangial cells two subtypes of AT1 receptor could be distinguished, AT1A subtype is more sensitive to losartan whereas AT1B subtype is more sensitive to PD123319, but insensitive to CGP42112A. The present studies were designed to ascertain which receptor subtype mediates three AngII-induced physiologic functions in rat mesangial cells namely intracellular Ca2+ mobilization, adenylyl cyclase inhibition and protein synthesis as monitored via [3H]leucine incorporation. The rank order of potency for inhibition of AngII-induced [Ca(2+)]i mobilization and adenylyl cyclase regulation was PD123319 > or = losartan > CGP42112A. By contrast, losartan was quite effective at inhibiting protein synthesis (IC50 = 8 nM) while PD123319 was without effect. These findings are consistent with AngII mediated signal transduction through AT1A and AT1B sites for phospholipase C mediated [Ca(2+)]i mobilization and inhibition of adenylyl cyclase. On the other hand, AT1A receptors appear to exclusively mediate AngII-induced protein synthesis. These observations underscore the complexity of AngII mediated signal transduction in glomerular mesangium.

Anatomy of the human ovarian insulin-like growth factor system

In situ hybridization was used to map insulin-like growth factor (IGF) system gene expression in ovaries from an anencephalic infant and several young women. Growing oocytes in infant and mature ovaries expressed transcripts for IGF-I and IGF-II, respectively, and all oocytes expressed abundant IGF-I receptor transcripts, raising the possibility of autocrine IGF function in oocyte maturation. IGF-I mRNA was not detected in the mature ovary, but IGF-II mRNA was localized in follicular blood vessels and in granulosa cells (GC) and was especially abundant in the GC of atretic as opposed to young follicles. IGF-I receptor mRNA was abundant in GC of antral and atretic follicles, and was expressed at low levels in the thecal and interstitial compartments. IGF-binding protein (IGFBP) 1 mRNA was not detected, but IGFBPs 2-5 mRNAs each demonstrated a unique ovarian distribution. IGFBP2 mRNA was abundant in GC and thecal cells at all stages of development. IGFBP3 mRNA was detected only in the endothelium of ovarian blood vessels. IGFBP4 mRNA was also localized in endothelium, but in addition was present in stromal connective tissue and in GC of the one Graafian follicle detected in this study, but not consistently in atretic follicles. IGFBP5 mRNA was expressed by luminal or cumulus GC in virtually all follicles and was highly abundant in stromal interstitial cells of the mature ovary.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of tetrahydroberberine on ischemic and reperfused myocardium in rats

The effects of tetrahydroberberine (THB) on ischemic and reperfused myocardium were studied in comparison with verapamil (Ver). In anesthetized rats, THB and its analogues, l-THP and l-SPD, reduced the infarct size after 4 h of left anterior descending coronary artery (LAD) ligation. In Langendorff hearts, in common with Ver, THB 1 and 10 mumol.L-1 markedly decreased the incidences of ventricular tachycardia (VT) and ventricular fibrillation (VF) in the reperfusion period. The malondialdehyde content and xanthine oxidase activity were also decreased in global ischemic-reperfused hearts pretreated with THB (P < 0.01, or P < 0.05). It suggested that THB could protect the myocardium from ischemic and reperfusion injury.

Placental glucose transporter gene expression and metabolism in the rat

In situ hybridization was used to evaluate patterns of gene expression for glucose transporters 1-4 (GT1-4) in the rat uteroplacenta from the time of implantation through term, and in vivo regional placental glucose metabolism was measured by 14C-labeled 2-deoxyglucose uptake. GT1 mRNA was highly abundant and GT3 was barely detected in the postimplantation decidual reaction. GT1 and 3 mRNAs were colocalized in the labyrinthine syncitiotrophoblast layer of the chorioallantoic placenta, which forms the membranous barrier between maternal and fetal circulations. The level of labyrinthine GT3 mRNA showed no change from midgestation through term; however, the volume of the labyrinth and hence total GT 3 gene expression increased greatly during this period. Labyrinthine GT1 mRNA levels, in contrast, showed significant diminution near term. GT1 mRNA was also localized in the placental growth plate, or junctional zone, where it was most abundant during the period of rapid placental growth and was decreased at term. Placental glucose metabolism, as reflected by steady-state 2-deoxyglucose uptake, was highest in the junctional zone during the rapid growth phase during midgestation, and decreased significantly at term, in parallel with GT1 gene expression. These findings suggest that GT1 is responsible for supplying glucose for use as a placental fuel and that GT3 is important for glucose transfer to the embryo.

Mutations in the codon for a conserved arginine-1563 in the COL4A5 collagen gene in Alport syndrome

We have screened 110 unrelated Alport syndrome kindreds for mutations in the exon 48 region of the COL4A5 collagen gene. Denaturing gradient gel electrophoresis (DGGE) of the PCR-amplified region of exon 48 revealed sequence variants in DNA from affected males and carriers of three unrelated kindreds. All three kindreds have classical Alport syndrome of the juvenile type. DNA-sequencing analyses demonstrated two different single base changes in the codon for arginine-1563 located in exon 48. In Utah kindred 2103, there was a substitution of C by T resulting in the change of the CGA codon for arginine to the translation stop codon TGA. In Utah kindred 2123 and in the Danish kindred A13, there was a C-->T mutation in the noncoding strand changing the same codon to CAA for glutamine. Both mutations were confirmed by allele-specific hybridization on PCR-amplified DNA from other family members.

A system for monitoring temperature distribution in bed and its application to the assessment of body movement

For the assessment of body movements during sleep, a system for monitoring the temperature in bed was developed. The system consists of 16 temperature sensors and a data logger with a memory card. Fifteen of the temperature sensors were arranged in line 6 cm apart on a flat cable. The temperatures at these 15 points in the bed, and the room temperature measured by the additional sensor, were stored on the memory card at predetermined intervals. The data were transferred into a microcomputer and analysed. Changes in posture and body movement were recognizable from the changes in the temperature profile, and well visualized using a three-dimensional display of the successive temperature profiles in the bed. The time of body movement was estimated from the derivative of the temperature profile. Comparison between this estimation and the video recording showed good agreement. The linear arrangement of the sensors provides a high-resolution temperature profile during sleep.

COL4A5 splice site mutation and alpha 5(IV) collagen mRNA in Alport syndrome

Mutations affecting the COL4A5 gene encoding the alpha 5 chain of type IV collagen, are involved in the pathogenesis of X-linked Alport syndrome. We used denaturing gradient gel electrophoresis (DGGE) to screen PCR amplified exons of COL4A5 for point mutations in a set of 18 Alport patients previously characterized by Southern blotting. One sequence variant was identified in the exon 38 region of a male Alport patient. Sequence analysis revealed a G to C transversion in the 5' intron splice donor site downstream from exon 38 (GT to CT). To determine the effect of the mutation on mRNA splicing, alpha 5(IV) cDNA was generated from total RNA of peripheral blood lymphocytes. Subsequent cDNA PCR yielded a product 81 base pairs shorter in the affected Alport patient, compared to normal controls. The absence of exon 38 from the alpha 5(IV) cDNA was confirmed by sequence analysis. The results demonstrated that the mutation leads to skipping of exon 38 in the processing of alpha 5(IV) pre-mRNA. The shortened transcript lacked 27 codons encoding a Gly-X-Y-repeat sequence with a preserved reading frame, enabling the translation of codons further downstream. Clinically, the patient presented with juvenile onset Alport syndrome, end-stage renal failure, and deafness. He had no ocular lesions. Typical ultrastructural changes of the glomerular basement membrane (GBM) were shown on electron microscopy. The patient developed anti-GBM antibodies after renal transplantation, however, renal function deteriorated only moderately.

CD4-independent binding of HIV-1 to the B lymphocyte receptor CR2 (CD21) in the presence of complement and antibody

Complement and antibody contribute to infection-enhancement and possible expanded cellular tropism of HIV-1 in vitro through a process requiring complement receptors. Until now, however, the ability of HIV-1 to bind complement receptors has not been documented or characterized. We investigated whether antibody and complement permitted HIV-1 to bind to the B lymphocyte receptor, CR2 (CD21), in an effort to learn more about infection-enhancement, and also because CR2 can mediate B cell proliferation and antigen localization in lymphoid organs in other systems. HIV-1 incubated with antibody and fresh human serum as a source of complement bound approximately 10-fold greater to cells expressing CR2 than to HIV-1-permissive cells lacking this receptor. A similar effect was observed using cells which expressed CR2 but no CD4. This binding was minimal in heat-inactivated and C3-deficient sera, and was significantly reduced by the anti-CR2 MoAb, OKB7, but not by the anti-CD4 MoAb, OKT4a. Thus, complement and antibody acted in concert to facilitate the binding of HIV-1 to CR2 independently of CD4. CD4-independent binding of HIV-1 to CR2 was not sufficient to produce infection in Raji-3 cells. Titres of antibodies mediating CR2 binding correlated with antibody titres as measured by immunofluorescence (P < 0.01) and infection-enhancement (P < 0.05) but were discordant with titres of neutralizing antibodies, a result consistent with the utilization of CR2 for enhanced infection of cells. The ability of complement and antibody to facilitate the binding of HIV-1 to CR2 in the absence of CD4 provides new insights into mechanisms of HIV-1-induced immunopathogenesis and infection-enhancement.

CECIL: a database for storing and retrieving clinical and molecular information on patients with Alport syndrome

CECIL is a database that stores clinical and molecular information on patients with Alport syndrome. The clinical component of CECIL is specific to Alport syndrome; the component that stores and manipulates molecular data can be used for any disease caused by a gene mutation, such as cystic fibrosis. While offering the ability to retrieve patient data through compound Boolean queries, CECIL also offers the ability to manipulate sequence information in various ways. In particular, CECIL can perform an augmented sequence alignment of an abnormal (patient) DNA sequence with a reference sequence. CECIL is currently being used by members of the International Alport Syndrome consortium. We describe CECIL's features and discuss the design decisions made in generalizing CECIL's architecture.

Fibroblast growth factor inhibits proliferation of a highly tumorigenic insulin-independent teratoma-derived cell line

The present paper examines the effect of basic fibroblast growth factor (bFGF) on the proliferation of teratoma-derived cell lines having increased tumorigenic properties isolated from the non-tumorigenic adipogenic cell line 1246. Although FGF is a mitogen for the non tumorigenic 1246 cells and for the moderately tumorigenic 1246-3A cells derived from the 1246 cells, bFGF inhibits the proliferation and DNA synthesis of the highly tumorigenic PC cells starting at concentration as low as 30 pg/ml. The inhibitory effect of FGF on PC cell growth is irreversible as demonstrated by the inability of the cells to resume proliferation once FGF is removed from the culture medium. Comparison of 125I-bFGF binding to the three cell lines was performed. Based on the Scatchard analysis of the binding data, PC cells display only low affinity class of FGF binding sites whereas 1246 and 1246-3A cells presented also high affinity binding sites. The inhibitory effect of FGF on PC cells did not go through activation of a PKC mediated pathway, which is also known to inhibit PC cell proliferation, since FGF inhibition of PC cell growth was still apparent after PKC down regulation. FGF was still able to transiently stimulate the expression of mRNA for early growth associated genes as demonstrated by c-myc and c-fos expression, although it inhibited cell proliferation on PC cells. Our data demonstrate that the highly tumorigenic teratoma cells acquire an inhibitory response for a factor which is growth stimulatory to non-tumorigenic and moderately tumorigenic cells from which they are derived.

Molecular genetics of Alport syndrome

Alport syndrome is a progressive hereditary kidney disease characterized by hematuria, sensorineural hearing loss and ocular lesions with structural defects in the glomerular basement membrane (GBM). The gene frequency has been estimated to be 1:5000. The disease is primarily X chromosome-linked, but autosomal forms have also been reported. The X-linked form has been shown to be caused by mutations in a recently identified alpha 5(IV) collagen chain gene (COL4A5). We have isolated cDNA clones for providing the entire primary structure of the human alpha 5(IV) chain. The gene has been located to the Xq22 region. Using antibodies against synthetic peptides, the alpha 5(IV) chain was shown to be located in the kidney only in the glomerular basement membrane. Thus far, the exon-intron structure has been determined for a large portion of the gene which probably has a size of over 200 kb. Numerous different mutations have been identified in the COL4A5 gene. The mutations include single base mutations, large deletions and other major rearrangements such as inversion and duplication. The consequences of the mutations observed can be considered sufficient to cause structural and functional defects in the type IV collagen molecule and, therefore, also the GBM network. This, in turn can explain the disruption of the GBM and hematuria occurring in these Alport patients. Alport syndrome is the first genetic basement membrane and kidney disease whose gene has been cloned. These recent results have enabled the development of antibodies and DNA probes for accurate diagnosis of Alport syndrome.

FGF inactivates myogenic helix-loop-helix proteins through phosphorylation of a conserved protein kinase C site in their DNA-binding domains

Myogenin belongs to a family of myogenic helix-loop-helix (HLH) proteins that activate muscle transcription through binding to a conserved DNA sequence associated with numerous muscle-specific genes. Fibroblast growth factor (FGF) inhibits myogenesis by inactivating myogenic HLH proteins. We show that activated protein kinase C (PKC) can substitute for FGF and inhibit transcriptional activity of myogenic HLH proteins. In transfected cells, FGF induces phosphorylation of a conserved site in the DNA-binding domain of myogenin. This site is phosphorylated by PKC in vivo and in vitro and mediates repression of the myogenic program through a loss in DNA binding activity. A myogenin mutant lacking the PKC phosphorylation site is not repressed by FGF, confirming this site as a molecular target for FGF-dependent repression of muscle transcription. These results establish a direct link between the signal transduction pathways that inhibit myogenesis and the transcription factors directly activating muscle-specific genes.

Alport syndrome: a genetic study of 31 families

Thirty one families with Alport syndrome including 3 families with associated syndromes were studied. The location of the COL4A5 gene, responsible for the Alport syndrome, was determined by linkage analysis with eight probes of the Xq arm and by a radiation hybrid panel. Concordant data indicated the localization of the Alport gene between DXS17 and DXS11. Four deletions and one single base mutation of the COL4A5 gene were detected. Homogeneity tests failed to show any evidence of genetic heterogeneity superimposed on clinical heterogeneity for ophthalmic signs and end-stage renal disease age.

Deletions of the COL4A5 gene in patients with Alport syndrome

Mutations in the COL4A5 gene encoding the alpha 5 chain of type IV collagen have been found in linkage with X-chromosomal Alport syndrome (AS). To identify COL4A5 mutations in patients from Germany with clinically defined AS, DNA from 20 unrelated patients was analyzed by conventional Southern blotting. By using full length alpha 5(IV) cDNA probes, large COL4A5 deletions could be detected in two patients. In one case, a 34 kb deletion affecting the 14 most 3' exons of the gene was observed. The second patient harbored a complete COL4A5 deletion. In both cases, functional alpha 5(IV) mRNA was unlikely to be present. Clinically, both patients developed end-stage renal failure before age 30. Furthermore, they had characteristic retinal flecks, and sensorineural hearing loss with typical changes on the audiogram. The patient with the complete deletion of COL4A5 lost the renal allograft due to an anti-GBM mediated glomerulonephritis.