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PubMed1998

Value of abdominal sonography in the assessment of children with abdominal pain.

PURPOSE: We retrospectively evaluated the usefulness of sonography in the diagnostic assessment of children with abdominal pain. METHODS: From July 1988 to October 1996, 676 children who had abdominal pain and were referred for sonography underwent abdominal and pelvic sonographic examination. Of these, 644 children had recurrent abdominal pain (RAP) and 32 children had acute or subacute abdominal pain (ASAP). The mean ages and relative risks of underlying abnormalities were calculated for children with RAP and ASAP. RESULTS: Abdominal abnormalities were sonographically detected in 10 children with RAP (2%), a significantly lower incidence than in children with ASAP (56%, p < 0.0001), with a relative risk of 0.028 (95% CI, 0.014-0.055). In the RAP group, an underlying abnormality was more likely (p < 0.001) to be sonographically detected in children who had atypical clinical features (5 of 46%; 11%) than in those with typical clinical features (5 of 598; 1%), with a relative risk of 12.94 (95% CI, 3.90-43.30). Children with RAP were found to have hydronephrosis (3), urinary cystitis (2), duplex kidney (1), hypoplastic low-lying kidney (1), choledochal cyst (1), ovarian teratoma (1), and gross gaseous distention with fecal masses (1). Children with ASAP had urinary cystitis (4), intussusception (2), appendicitis (2), appendiceal abscess (1), perforated gut with ascites (1), gut duplication (1), thickened gut wall with fluid from severe gastroenteritis (1), gross gaseous distention with fecal masses (1), hepatosplenomegaly (1), cholecystitis (1), gross hydronephrosis (1), Wilms' tumor (1), and abdominal neuroblastoma (1). CONCLUSIONS: Abdominal sonography is useful in children with ASAP. Although an underlying abnormality was rarely found in children with RAP, children who have RAP with atypical clinical features should have sonographic screening. If no abnormalities are found, the normal sonograms may be reassuring to parents.

Abdomen, Acute↗

PubMed2002

Differential gene expression in response to copper in Acidithiobacillus ferrooxidans analyzed by RNA arbitrarily primed polymerase chain reaction.

Acidithiobacillus ferrooxidans is a chemoautotrophic bacterium that plays an important role in metal bioleaching processes. Despite the high level of tolerance to heavy metals shown by A. ferrooxidans, the genetic basis of copper resistance in this species remains unknown. We investigated the gene expression in response to copper in A. ferrooxidans LR using RNA arbitrarily primed polymerase chain reaction (RAP-PCR). One hundred and four differentially expressed genes were identified using eight arbitrary primers. Differential gene expression was confirmed by DNA slot blot hybridization, and approximately 70% of the RAP-PCR products were positive. The RAP-PCR products that presented the highest levels of induction or repression were cloned, sequenced and the sequences were compared with those in databases using the BLAST search algorithm. Seventeen sequences were obtained. The RAP-PCR product with the highest induction ratio showed similarity with the A. ferrooxidans cytochrome c. A high similarity with the thiamin biosynthesis gene thiC from Caulobacter crescentus was observed for another RAP-PCR product induced by copper. An RAP-PCR product repressed by copper showed significant similarity with the carboxysome operon that includes the ribulose-1,5-bisphosphate carboxylase/oxygenase complex from A. ferrooxidans and another copper-repressed product was significantly similar to the XyIN outer membrane protein from Pseudomonas putida. Finally, RAP-PCR products of unknown similarities were also present.

Base Sequence↗

PubMed2001

Role of apolipoprotein E receptors in regulating the differential in vivo neurotrophic effects of apolipoprotein E.

Apolipoprotein E (apoE) is known to bind to at least five receptors, including the low-density lipoprotein (LDL) receptor-related protein (LRP), very low density LDL receptor (VLDL-R), LDL-R, apoE receptor 2 (apoER2), and megalin/gp330. In this context, the main objective of the present study was to better understand the contributions of LRP and LDL-R to the in vivo neurotrophic effects of apoE. For this purpose, apoE-deficient and receptor-associated protein (RAP)-deficient mice were infused with recombinant apoE3, RAP, or saline. Infusion of apoE3 into apoE-deficient mice resulted in amelioration of degenerative alterations of pyramidal neurons, but had no effect on somatostatin-producing interneurons. In contrast, infusion of apoE3 into RAP-deficient mice resulted in amelioration of degenerative alterations of somatostatin-producing interneurons. LRP and LDL-R levels were significantly reduced in RAP-deficient mice, but significantly increased in the apoE-deficient mice. In contrast, levels of apoE were reduced in the RAP-deficient mice compared to wildtype controls, suggesting that neurotrophic effects of apoE3 in the RAP-deficient mice were related to a combined deficit in endogenous apoE and selected apoE receptors. Furthermore, in apoE-deficient mice, infusion of apoE3 had a neurotrophic effect on somatostatin-producing interneurons only when combined with RAP, suggesting that increased expression of apoE receptors in apoE-deficient mice prevented apoE from rescuing somatostatin-producing neurons. This study supports the contention that some of the in vivo neurotrophic effects of apoE are mediated by LRP and LDL-R and that a critical balance between levels of apoE and its receptors is necessary for the differential neurotrophic effects to appear.

Animals↗

PubMed2002

Use of resistance-area product derived from Doppler MCA velocity to estimate the range of active cerebrovascular regulation.

The purpose of the present study was to explore the development of a method to estimate the range of active cerebrovascular regulation using resistance-area product (RAP) derived from transcranial Doppler ultrasound recordings of middle cerebral artery blood velocity (MCAV) obtained before and after physiologic challenge. Intracranial pressure (ICP), arterial blood pressure (ABP), and MCAV were monitored on 9 patients before and after challenges with either Noradrenlin or CO2 inhalation. One patient was monitored at 24, 48, 72, and 96 hrs. For each cardiac cycle a value of RAP was computed from the inverse of the slope of the regression line of paired values of aligned MCAV and ABP recordings. Mean values of percent change of difference of RAP (% delta RAP) versus change of cerebral perfusion pressure (CPP) were computed. Theoretical values of % delta RAP were derived from reported lab values of percent change diameter of arterioles versus ABP. Of the nine patients, 22% (2/9) demonstrated either impaired dilation and/or constriction. Furthermore, the correlation between theoretical and experimental values of % delta RAP and CPP (n = 34) was strong (r = .86, p < .005). The serially-monitored patient failed to dilate during all CO2 challenges and to fully constrict to the Noradrenlin challenge at 72 hrs. % delta RAP associated with corresponding changes of CPP may have value as a clinical method to estimate the range of active cerebrovascular regulation.

Adolescent↗

PubMed1995

Helicobacter pylori, hypergastrinaemia, and recurrent abdominal pain in children.

The association between Helicobacter pylori and recurrent abdominal pain (RAP) is controversial. In this cross-sectional study, the authors aim to determine whether hypergastrinaemia causes RAP in children with H pylori gastritis. In 439 children age 4 to 13 years (mean 7.3 years) attending for nongastrointestinal day-case surgery, anti-Helicobacter immunoglobulin G (IgG) was identified in serum by an enzyme-linked immunosorbent assay (ELISA) method validated in children and fasting plasma gastrin was measured. A history of RAP was sought. One hundred twenty-seven children (29%) tested seropositive for H pylori. Fifty-one seronegative children (16.3%) and 22 seropositive children (17.3%) gave a history of RAP. The mean fasting gastrin in seronegative children was 52 ng/L compared with 117 ng/L in seropositive children (P < .001). The mean fasting gastrin in seropositive children with RAP (124 ng/L) was not significantly different from that of seropositive children without RAP (115 ng/L). The high prevalence of H pylori seropositivity in this study is at variance with other reported paediatric data from the developed world. No association between childhood H pylori gastritis, hypergastrinaemia, and RAP was found. In children with H pylori gastritis, the increase in circulating gastrin (mean 140% increase) is greater than that seen in adults (50% increase).

Abdominal Pain↗

PubMed1995

The secretary pathway of plasmodium falciparum regulates transport of p82/RAP1 to the rhoptries.

The rhoptries of Plasmodium falciparum are formed during a restricted period in the asexual erythrocytic cycle. The steps required for rhoptry biogenesis and the pathway for targeting proteins to the rhoptries have not been elucidated. Using the maturation of the Rhoptry-Associated Protein 1 (RAP-1) gene product to study these steps, it is reported here that a secretory pathway controls transport of protein complexes containing RAP-1 products to the rhoptries. Both brefeldin A (BFA) and low temperature reversibly block the processing of an 86-kDa precursor (Pr86) to the mature 82-kDa RAP-1 product (p82). Furthermore, the points of action of BFA and low temperature appear to overlap since their sequential application reversibly prevents Pr86 processing. Treatment of intact cells with N-ethylmaleimide, which prevents the fusion of transport vesicles with Golgi membranes in other eukaryotic cells, irreversibly blocks processing of Pr86. The role of the secretory pathway in targeting p82 protein complexes to the rhoptries product of RAP-1. These in vitro results also reveal that the RAP-1 product contains a cleavable N-terminal signal peptide and appears to be initially synthesized as an 84-kDa protein. The above data indicate that transport of p82 to the rhoptries is regulated by the secretory pathway and that the RAP-1 primary translation product differs in apparent molecular weight from the in vivo precursor Pr86. Our results suggest that rhoptry biogenesis is controlled in part by the secretory pathway and that the RAP-1 gene product acquires a previously undetected protein modification during its maturation.

Animals↗

PubMed1991

Pancreatectomy, amino acids and glucagon: effect on canine renal autoregulation.

Using pancreactectomized (PX) dogs, we recently suggested the importance of glucagon in modulating amino acid-induced increases in renal blood flow (RBF) and glomerular filtration rate (GFR). We have now ascertained whether glucagon's modulatory effect is associated with an impairment in renal autoregulation. As renal arterial pressure (RAP) was reduced to 70 mmHg (the lower limit of the autoregulatory range) in both sham-operated control (C) and PX control dogs, RBF and GFR remained at values that were greater than 90% of their respective controls. In control dogs infused with amino acids (0.051 mmol/kg per min, i.v.), RBF and GFR rose by 26 and 27%, respectively, at baseline RAP. As RAP was reduced to 70 mmHg, RBF and GFR fell by 25 and 37%, respectively. In PX dogs infused with either amino acids or glucagon (0.86 pmol/kg per min, i.v.) alone, RBF and GFR did not increase appreciably at baseline RAP. As RAP was reduced to 70 mmHg in these dogs, RBF and GFR remained at values that were greater than 90% of their respective controls. Yet, in PX dogs infused simultaneously with amino acids and glucagon, RBF and GFR rose by 22 and 24%, respectively, at baseline RAP. Moreover, as RAP was reduced to 70 mmHg, RBF and GFR fell by 22 and 31%, respectively. These data suggest that the ability of glucagon to modulate the renal hemodynamic response to amino acid infusion involves an impairment in renal autoregulation.

Amino Acids↗

PubMed1995

Inter- and intra-rater agreement of the Rehabilitation Activities Profile.

The objective of the study was to determine the inter- and intra-rater agreement of the Rehabilitation Activities Profile (RAP). The RAP is an assessment method that covers the domains of communication, mobility, personal care, occupation and relationships. Each domain consists of items which are further divided in sub-items for in-depth analysis. The RAP allows quantification of the severity of disabilities, handicaps and perceived problems of a patient with regard to the items and sub-items. For this purpose ordinal 4-point Likert scales were constructed. The RAP can be used for goal setting and evaluation of rehabilitation. Because of the broad intended use of the RAP and its construction, a special design for the reliability study was needed. The study was carried out in 5 rehabilitation facilities with the participation of various professions. The items and sub-items of the RAP were divided over these professions according to their expertise. Pairs of interviewers were formed that questioned a patient. For the determination of inter- and intra-rater agreement each pair of interviewers was allowed to question a patient only once. To establish the intra-rater agreement, video recordings were made during the interviews. The median (weighted) kappa value and percentage of agreement about the severity grading of a disability or handicap for all items and sub-items exceeded 0.84 and 81%, respectively, with regard to the inter- and intra-rater agreement. For the severity grading of perceived problems these values were 0.91 and 86%. The interpretation of kappa was hindered by two paradoxes recently described in the literature. The paradox "high agreement but low kappa" manifested itself in particular. It is concluded that inter- and intra-rater agreement of the RAP can be considered to be good to very good.

Activities of Daily Living↗

PubMed1998

The carboxy-terminal domain of the receptor-associated protein binds to the Vps10p domain of sortilin.

Binding of the receptor-associated protein (RAP) to the newly identified putative sorting receptor, sortilin, was analyzed by surface plasmon resonance analysis of recombinant RAP and sortilin domains and compared with binding to megalin and low density lipoprotein receptor-related protein (LRP). The data show that the RAP-binding site in sortilin is localized in the cysteine-rich lumenal part homologous to yeast vacuolar protein-sorting 10 protein (Vps10p), and the sortilin-binding site in RAP is localized in the carboxy-terminal domain III of the three homologous domains in RAP. Whereas sortilin bound only RAP domain III, megalin and LRP bound all RAP domains with the functional affinity order: domain III >domain I > domain II.

Adaptor Proteins, Vesicular Transport↗

PubMed1998

Recurrent abdominal pain: a potential precursor of irritable bowel syndrome in adolescents and young adults.

OBJECTIVES: To assess symptoms of irritable bowel syndrome (IBS) in patients with recurrent abdominal pain (RAP) 5 years after their initial evaluation, to identify the relation of IBS symptoms to functional disability and health service use, and to determine the extent to which IBS symptoms are associated with life stress and poor psychosocial adjustment. METHODS: Patients with RAP (n = 76) and control subjects (n = 49) completed a telephone interview; measures included the Bowel Disease Questionnaire, the Functional Disability Inventory, the Life Events Questionnaire, the Family Inventory of Life Events, the Center for Epidemiological Studies Depression Scale, the Self-Perception Profile for Adolescents, and the Health Resources Inventory. RESULTS: Five years after the initial evaluation, patients with RAP reported significantly more episodes of abdominal pain than did control subjects, as well as significantly higher levels of functional disability, school absence, and clinic visits for abdominal distress. Female patients with RAP were more likely than female control subjects to meet the Manning criteria for IBS. Among patients with RAP, higher levels of IBS symptoms were associated with significantly greater functional disability, more clinic visits, more life stress, higher levels of depression, and lower academic and social competence. CONCLUSION: Female patients with a history of RAP may be at increased risk of IBS during adolescence and young adulthood. Among adolescents and young adults with a history of RAP, IBS symptoms are likely to be associated with high levels of disability and health service use.

Abdominal Pain↗

PubMed1998

Analysis of the processing of Plasmodium falciparum rhoptry-associated protein 1 and localization of Pr86 to schizont rhoptries and p67 to free merozoites.

The processing and localization of Plasmodium falciparum rhoptry-associated protein 1 (RAP-1) products were examined using polyclonal and monoclonal antibodies raised to a recombinant protein containing residues 1-294 of RAP-1. Immunoblot and epitope mapping results with antibodies that selectively bound epitopes in the RAP-1 products Pr86, p82, and p67 showed that p82 and p67 are formed from Pr86 by progressive removal of epitopes from the amino-terminus of the RAP-1 coding sequence. The capacity of Pr86 to form complexes was revealed after size fractionation of parasite proteins radiolabeled in the presence of brefeldin A to prevent processing of Pr86. Fractions containing complexed Pr86 also contained the RAP-2 product p39 and the RAP-3 product p37, suggesting that Pr86, p39 and p37 may form complexes similar to complexes previously reported for p82 and p67 with p39 or p37. Immunofluorescence localization and immunoblot studies revealed that Pr86 is present in the rhoptries, but only transiently, and that it is not detected in segmenting schizonts or extracellular merozoites. p67 and p82, on the other hand, were shown to be major RAP-1 components in purified merozoites. Neither p67 nor p82 were relocalized from the intracellular rhoptries to the merozoite surface under conditions that promoted relocalization of the rhoptry protein PF83/apical membrane antigen 1. These results suggest that processing of Pr86 begins after Pr86 complexes are transported to the forming rhoptries and that two site-selective processing reactions occur in the rhoptries, a rapid cleavage of Pr86 to p82 and a delayed cleavage of p82 to p67. Since p67 is missing from ring-stage parasites (Howard et al., Am J Trop Med Hyg, 1984;33:1055 59), the present results indicate there is a narrow time during which p67 may play a role in merozoite invasion of erythrocytes.

Animals↗

PubMed2000

The 2.2-kb promoter of cartilage-derived retinoic acid-sensitive protein controls gene expression in cartilage and embryonic mammary buds of transgenic mice.

Cartilage-derived retinoic acid-sensitive protein (CD-RAP) is a secreted protein primarily expressed in chondrocytes. Pathologically, CD-RAP is detected in melanoma, chondrosarcoma and breast cancer. As an approach to define the transcriptional regulatory domains responsible for induction of chondrocyte activity in vivo, we generated transgenic mice harboring various fragments of the mouse CD-RAP promoter linked to the Escherichia coli beta-galactosidase gene. Analysis of the transgene expression pattern by X-gal staining indicates that 2251 bp of the CD-RAP 5'-flanking sequence generates beta-galactosidase activity in all cartilage in embryos and adult animals. In addition, we also detected transient X-gal staining in mammary gland primordium from day 11.5 to 15.5 of gestation. Histological examination revealed that the transgene is located in the chondrocytes of cartilage and the epithelial cells of mammary buds. The cartilage transgene expression pattern is consistent with that of endogenous CD-RAP gene expression. The presence of beta-galactosidase in the mammary buds led us to the demonstration of a unique pattern of transient endogenous expression of CD-RAP in the mammary bud. The finding of transient CD-RAP expression in mammary buds suggests that it may play a role in the organogenesis of mammary glands.

Animals↗

PubMed1986

Steroidogenic effect of atrial natriuretic factor in isolated mouse Leydig cells is mediated by cyclic GMP.

The effects of different atrial natriuretic peptides on cyclic GMP formation and steroidogenesis have been studied in Percoll-purified mouse Leydig cells. Rat atrial peptides rANP (rat atrial natriuretic peptide), rAP-I (rat atriopeptin I) and rAP-II (rat atriopeptin II), in the presence of a phosphodiesterase inhibitor, stimulated cyclic GMP formation in a concentration-dependent manner. In the presence of saturating concentrations of the peptides, a 400-600 fold stimulation of cyclic GMP accumulation was observed. Among the peptides, rAP-II appeared to be the most potent. ED50 values (concentration causing half-maximal effect) for rAP-II, rANP and rAP-I were 1 X 10(-9) M, 2 X 10(-9) M and 2 X 10(-8) M respectively. A parallel stimulation of cyclic GMP formation and testosterone production by the cells was observed after incubation of the cells with various concentrations of rAP-II. In the presence of a saturating concentration of rAP-II (2 X 10(-8) M), maximum stimulation of intracellular cyclic GMP content was obtained within 5 min of incubation. Testosterone production by mouse Leydig cells could be stimulated by 8-bromo cyclic GMP in a concentration-related manner. At a 10 mM concentration of the cyclic nucleotide, steroidogenesis was stimulated to a similar extent as that obtained with a saturating concentration of human chorionic gonadotrophin (5 ng/ml). On the basis of these results we conclude that cyclic GMP acts as a second messenger in atrial-peptide-stimulated steroidogenesis in mouse Leydig cells. The steroidogenic effect of atrial peptides appears to be species-specific, since none of these peptides stimulated testosterone production by purified Leydig cells of rats, though in these cells a 40-60-fold stimulation of cyclic GMP formation in response to each of the three peptides was observed. However, 8-bromo cyclic GMP could stimulate testosterone production in rat Leydig cells. Therefore we conclude that the lack of steroidogenic response in rat Leydig cells to atrial-natriuretic-factor-stimulation results from an insufficient formation of cyclic GMP in these cells. This species difference would appear to result from a lower guanylate cyclase activity in rat Leydig cells.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed2003

A clinical measure for the assessment of problem solving in brain-injured adults.

Rapid Assessment of Problem Solving (RAPS) is a clinical test of verbal problem-solving skills for brain-injured persons. This modification of F. A. Mosher and J. R. Hornsby's (1966) Twenty Questions Test (20Q) reduces the memory demands of the test for brain-injured clients. This article provides background on the 20Q Test and modifications made for RAPS. It describes RAPS materials, administration, and scoring procedures and reports RAPS results for 70 normal participants. Normal participants solved RAPS problems with an average of 5 questions. Questions were predominantly constraint seeking and focused on semantic categories or features. Normal participants also reflected substantial variability in their performance on RAPS. This appeared to be related to 2 metacognitive abilities associated with problem solving, planning, and shifting set. The performance of 3 chronic traumatically brain injured individuals is also described and compared to the normal sample to illustrate clinical applications of RAPS.

Adult↗

PubMed2001

Treatment of Helicobacter pylori in children with recurrent abdominal pain.

BACKGROUND: The role of Helicobacter pylori remains unclear in children with recurrent abdominal pain (RAP). In this study children with RAP were included in a double blind treatment study to elucidate whether symptoms disappear in children with a H. pylori infection and RAP, if the bacteria are eradicated. METHODS: Thirty-seven H. pylori-infected children aged 4.9-14.5 years (median 9.8 years) with RAP were included. H. pylori was identified by histology and culture. The children were treated with amoxicillin and metronidazole for 14 days. A re-endoscopy including biopsies for histology and culture was done at least one month after the end of treatment. Simple questions for symptoms were asked and blood for serology was repeated 3 and 6 months after the end of treatment. During the observation period the results of the re-endoscopy and the serology 3 and 6 months after the re-endoscopy were blinded for 23 patients and opened to 14 of the patients according to the choice of the families. RESULTS: The eradication rates were 81% (30/37) in the total group and 74% (17/23) in the blinded group. The IgG antibodies to H. pylori decreased significantly 3 (p =.03) as well as 6 months after end of treatment (p <.001) in children with successful eradication. The number of children with RAP decreased after examination and treatment and the well-being improved after 6 months in almost 95% of the children. However, no correlation was seen between eradication of H. pylori and disappearance of RAP, neither after 3 nor after 6 months' observation in the total group of patients (p =.94 and p =.90) or in the blinded group (p =.42 and p =.65). CONCLUSIONS: These results do not provide evidence for a causal relationship between RAP and H. pylori.

Abdominal Pain↗

PubMed1996

Receptor-associated protein and members of the low density lipoprotein receptor family share a common epitope. An extended model for the development of passive Heymann nephritis.

Heymann nephritis is an experimental rat model for human membranous glomerulonephritis. Two target antigens have been identified in the proximal tubule brush border of rat kidneys. One of them is megalin, a 600-kDa membrane protein that belongs to the family of low density lipoprotein receptor (LDLR)-related proteins. The other one is receptor-associated protein (RAP), a polypeptide of 40 kDa that associates with members of the LDLR family. Here we show that antibodies produced against recombinant human RAP strongly cross-react with the chicken oocyte receptor for very low density lipoprotein and vitellogenin (LR8), and with two other members of the LDLR family, LDLR-related protein and megalin. The interaction of this antibody with LR8 showed binding characteristics exactly as those demonstrated for the physiological ligands of this receptor, in that binding of the antibody: (i) is Ca2+-dependent; (ii) is abolished by unfolding of the cysteine-rich binding domain by reduction; and (iii) interferes with the binding of very low density lipoprotein and vitellogenin. Immunopurification of the LR8-specific subpopulation of the polyclonal antiserum yielded an IgG fraction strongly reacting with LR8 as well as with RAP. Using recombinant fragments of RAP and peptide mapping, the cross-reacting epitope(s) could be narrowed down to three short sequences (5-7 residues) in the COOH-terminal part of the protein. After immunization with RAP, anti-LR8 antibodies and anti-RAP antibodies arise simultaneously, indicating that the receptor-specific activity is not due to anti-idiotypic antibodies. These findings suggest the existence of a common epitope(s) on RAP and members of the LDL receptor family. Based on these results, we present an extended molecular model for the development of passive Heymann nephritis.

Animals↗

PubMed1999

The very low density lipoprotein receptor regulates urokinase receptor catabolism and breast cancer cell motility in vitro.

The very low density lipoprotein receptor (VLDLr) binds diverse ligands, including urokinase-type plasminogen activator (uPA) and uPA-plasminogen activator inhibitor-1 (PAI-1) complex. In this study, we characterized the effects of the VLDLr on the internalization, catabolism, and function of the uPA receptor (uPAR) in MCF-7 and MDA-MB-435 breast cancer cells. When challenged with uPA.PAI-1 complex, MDA-MB-435 cells internalized uPAR; this process was inhibited by 80% when the activity of the VLDLr was neutralized with receptor-associated protein (RAP). To determine whether internalized uPAR is degraded, we studied the catabolism of [35S]methionine-labeled uPAR. In the absence of exogenous agents, the uPAR catabolism t(1)/(2) was 8.2 h. uPA.PAI-1 complex accelerated uPAR catabolism (t(1)/(2) to 1.8 h), while RAP inhibited uPAR catabolism in the presence (t(1)/(2) of 7.8 h) and absence (t(1)/(2) of 16.9 h) of uPA.PAI-1 complex, demonstrating a critical role for the VLDLr. When MCF-7 cells were cultured in RAP, cell surface uPAR levels increased gradually, reaching a new steady-state in 3 days. The amount of uPA which accumulated in the medium also increased. Culturing in RAP for 3 days increased MCF-7 cell motility by 2.2 +/- 0.1-fold and by 4.4 +/- 0.3-fold when 1.0 nM uPA was added. The effects of RAP on MCF-7 cell motility were entirely abrogated by an antibody which binds uPA and prevents uPA binding to uPAR. MCF-7 cells that were cultured in RAP demonstrated increased levels of activated mitogen-activated protein kinases. Furthermore, the MEK inhibitor, PD098059, decreased the motility of RAP-treated cells without affecting control cultures. These studies suggest a model in which the VLDLr regulates autocrine uPAR-initiated signaling and thereby regulates cellular motility.

Breast Neoplasms↗

PubMed1999

An extrahepatic receptor-associated protein-sensitive mechanism is involved in the metabolism of triglyceride-rich lipoproteins.

We have used adenovirus-mediated gene transfer in mice to investigate low density lipoprotein receptor (LDLR) and LDLR-related protein (LRP)-independent mechanisms that control the metabolism of chylomicron and very low density lipoprotein (VLDL) remnants in vivo. Overexpression of receptor-associated protein (RAP) in mice that lack both LRP and LDLR (MX1cre(+)LRP(flox/flox)LDLR(-/-)) in their livers elicited a marked hypertriglyceridemia in addition to the pre-existing hypercholesterolemia in these animals, resulting in a shift in the distribution of plasma lipids from LDL-sized lipoproteins to large VLDL-sized particles. This dramatic increase in plasma lipids was not due to a RAP-mediated inhibition of a unknown hepatic high affinity binding site involved in lipoprotein metabolism, because no RAP binding could be detected in livers of MX1cre(+)LRP(flox/flox)LDLR(-/-) mice using both membrane binding studies and ligand blotting experiments. Remarkably, RAP overexpression also resulted in a 7-fold increase (from 13.6 to 95.6 ng/ml) of circulating, but largely inactive, lipoprotein lipase (LPL). In contrast, plasma hepatic lipase levels and activity were unaffected. In vitro studies showed that RAP binds to LPL with high affinity (K(d) = 5 nM) but does not affect its catalytic activity, in vitro or in vivo. Our findings suggest that an extrahepatic RAP-sensitive process that is independent of the LDLR or LRP is involved in metabolism of triglyceride-rich lipoproteins. There, RAP may affect the functional maturation of LPL, thus causing the accumulation of triglyceride-rich lipoproteins in the circulation.

Animals↗