-
[show abstract]
[hide abstract]
ABSTRACT: Growth hormone (GH) is widely prescribed for children with short stature across a range of growth disorders. We describe the variability of responses seen in conditions approved for GH therapy. Although responses in different growth disorders are satisfactory, evidence is increasing for an unacceptably high rate of poor or unsatisfactory response (i.e., not leading to significant catch-up growth) in terms of change in height standard deviation score and height velocity. Consequently, there is a need to define a poor response and to prevent or correct it by optimizing treatment regimens. This review discusses the optimal investigation of the child who is a candidate for GH therapy so that a diagnosis-based guide to therapy and dosage can be made. The relevant parameters in the evaluation of growth response are described together with the definitions of a poor response.
Indian journal of endocrinology and metabolism. 12/2012; 16(Suppl 2):S178-84.
-
[show abstract]
[hide abstract]
ABSTRACT: Growth hormone (GH) is widely prescribed for children with short stature across a range of growth disorders. Recombinant human (rh) insulin-like growth factor-1 (rhIGF-1) therapy is approved for severe primary IGF-I deficiency - a state of severe GH resistance. Evidence is increasing for an unacceptably high rate of poor or unsatisfactory response to growth-promoting therapy (i.e. not leading to significant catch up growth) in terms of change in height standard deviation score (SDS) and height velocity (HV) in many approved indications. Consequently, there is a need to define poor response and to prevent or correct it by optimizing treatment regimens within accepted guidelines. Recognition of a poor response is an indication for action by the treating physician, either to modify the therapy or to review the primary diagnosis leading either to discontinuation or change of therapy. This review discusses the optimal investigation of the child who is a candidate for GH or IGF-1 therapy so that a diagnosis-based choice of therapy and dosage can be made. The relevant parameters in the evaluation of growth response are described together with the definitions of poor response. Prevention of poor response is addressed by discussion of strategy for first-year management with GH and IGF-1. Adherence to therapy is reviewed as is the recommended action following the identification of the poorly responding patient. The awareness, recognition and management of poor response to growth-promoting therapy will lead to better patient care, greater cost-effectiveness and increased opportunities for clinical benefit.
Clinical Endocrinology 04/2012; 77(2):169-81. · 3.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Growth hormone insensitivity syndrome (GHIS) is caused by a defective growth hormone receptor (GHR) and is associated with insulin-like growth factor-I (IGF-I) deficiency, severely short stature and, from adolescence, fasting hyperglycemia and obesity. We studied the effects of treatment with IGF-I in either a 1:1 molar complex with IGFBP-3 (IGF-I/BP-3-Tx) or with IGF-I alone (IGF-I-Tx) on metabolism and linear growth.
Two brothers, compound heterozygous for a GHR gene defect, were studied. After 8 months without treatment, we examined the short- and long-term effects of IGF-I/BP-3-Tx and, subsequently, IGF-I-Tx on 12-hour overnight levels of IGF-I, GH, insulin, IGFBP-1, insulin sensitivity by hyperinsulinemic euglycemic clamp, body composition by dual-energy X-ray absorptiometry and linear growth.
Mean overnight levels of insulin decreased and IGFBP-1, a measure of hepatic insulin sensitivity, increased on both regimens, but was more pronounced on IGF-I-Tx. Insulin sensitivity by clamp showed no consistent changes. Lean body mass increased and abdominal fat mass decreased in both subjects on IGF-I-Tx. However, the changes were inconsistent during IGF-I/BP-3-Tx. Height velocity was low without treatment, increased slightly on IGF-I/BP-3-Tx and doubled on IGF-I-Tx.
Both modalities of IGF-I improved determinants of hepatic insulin sensitivity, body composition and linear growth rate; however, IGF-I alone seemed to be more efficient.
Hormone Research in Paediatrics 09/2011; 76(5):355-66.
-
[show abstract]
[hide abstract]
ABSTRACT: Therapeutic immunization of HIV-1-infected individuals with or without anti-retroviral therapy is a new promising disease prevention. To induce a new cytotoxic T(CD8) lymphocyte (CTL) immunity during chronic HIV-1 infection 15 infrequently targeted but conserved HLA-supertype binding CTL epitopes from Gag, Pol, Nef, Env, Vpu and Vif were identified. The 15 T(CD8) and three T(CD4) helper peptides were GMP synthesised and formulated with a new adjuvant CAF01 which is a synthetic two-component liposomic adjuvant comprising the quaternary ammonium dimethyl-dioctadecyl-ammonium (DDA) and the immune modulator trehalose 6,6'-dibehenate (TDB). Using IFN-γ ELISPOT assay, T-cell immune induction by the vaccine was found to both CD4 and CD8 T-cell restricted peptides in HLA-A2 transgenic mice. Comprehensive toxicity studies of the CAF01 adjuvant-alone and together with different vaccines showed that CAF01 when tested at human dose levels was safe and well tolerated with only local inflammation at the site of injection and no systemic reactions. No pharmacological safety issues were observed in Beagle dogs. The HIV-1 vaccine toxicity study in the Göttingen Minipig(®) showed no systemic toxicity from five repetitive i.m. injections, each with a 2-week interval, of either the 18 HIV-1 peptide antigen solution (AFO18) or the AFO18-CAF01, in which the 18 HIV-1 peptides were formulated with the CAF01 adjuvant. Distinct inflammatory responses were observed in the injected muscles of the AFO18-CAF01 vaccine treated animals as a result of the immune stimulating effect of the adjuvant on the vaccine. The results of the toxicity studies provide optimism for phase I clinical trials evaluating the therapeutic HIV-1 T-cell vaccination approach using multiple subdominant minimal epitope peptides applying the novel cationic adjuvant CAF01.
Vaccine 07/2011; 29(40):7067-74. · 3.77 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Insulin glargine offers sustained insulin delivery for 24 h. Change to glargine treatment consistently results in lower fasting glucose and fewer hypoglycemic episodes in children with type 1 diabetes compared to continuation of NPH, although glargine has not been shown to improve HbA1c in randomized trials. Studies comparing glargine and NPH in multiple injection therapy in children treated from diagnosis of type 1 diabetes are lacking.
HbA1c and insulin requirement were compared in a retrospective study of children (7-17 yr of age) with type 1 diabetes treated from diagnosis with basal insulin glargine (n = 49) or NPH (n = 49) in a multiple injection therapy (MIT) regimen with a rapid-acting insulin analogue. Patients were followed every third month for 1 yr. HbA1c, insulin dose, and weight data were retrieved.
HbA1c (mean ± SD) was lower at 3-5 months (5.5 ± 0.89 vs. 6.2 ± 0.89%, p < 0.05) and 6-9 months (5.6 ± 1.14 vs. 6.6 ± 0.99%; p < 0.001) in glargine treated. After 12 months, HbA1c was significantly lower in glargine treated (6.3 ± 1.56 vs. 7.1 ± 1.28; p < 0.01). Reported total insulin doses were similar at nadir (0.5 U/kg BW × 24 h), but significantly lower at 12 months in glargine treated (0.64 ± 0.23 vs. 0.86 ± 0.3 U/kg BW × 24 h; p < 0.001).
HbA1c 1 yr from diagnosis was lower in children treated with glargine from start as compared with those on NPH. This observation should be viewed in the light of a significantly lower dose of total daily insulin in the glargine group.
Pediatric Diabetes 03/2011; 12(5):501-5. · 2.16 Impact Factor
-
Jaap T van Dissel,
Darius Soonawala,
Simone A Joosten,
Corine Prins,
Sandra M Arend, Peter Bang,
Pernille Nyholm Tingskov,
Karen Lingnau,
Jan Nouta,
Søren T Hoff,
Ida Rosenkrands,
Ingrid Kromann,
Tom H M Ottenhoff,
T Mark Doherty,
Peter Andersen
[show abstract]
[hide abstract]
ABSTRACT: New TB vaccines are urgently needed because of the apparent lack of effect of the BCG vaccine on rates of adult contagious pulmonary tuberculosis and the risk of disseminated BCG disease in immunocompromised individuals. Since BCG appears to protect children, the primary target for vaccine development is a booster vaccine for adults but such vaccines ideally need to be able to efficiently prime mycobacterially naïve individuals as well as boost individuals previously vaccinated with BCG and those latently infected with TB. Protective immunity against Mycobacterium tuberculosis depends mainly on the generation of a Th1-type cellular immune response characterized by interferon-gamma (IFN-γ) production. In the present study, we monitored safety and IFN-γ responses in healthy BCG-vaccinated and prior or latently TB-infected individuals receiving a novel vaccine composed of the fusion protein Ag85B-ESAT-6 combined with the adjuvant IC31(®), administered at 0 and 2 months. Vaccination caused few local or systemic adverse effects besides transient soreness at the injection site, but it elicited strong antigen-specific T cell responses against Ag85B-ESAT-6 and both the Ag85B and ESAT-6 components, that could be augmented by second vaccination. The strong responses persisted through 32 weeks of follow-up, indicating the induction of a persistent memory response in the vaccine recipients.
Vaccine 01/2011; 29(11):2100-9. · 3.77 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Tuberculosis (TB) remains a major killer worldwide. The only available TB-vaccine, the nearly century-old Mycobacterium bovis BCG, has had only a limited effect on TB incidence. Therefore, developing new TB vaccines is a key priority, and the first new generation TB vaccines are now being tested in clinical trials. Here we describe the development and first testing in humans of a novel, wholly synthetic TB subunit vaccine. This vaccine has proven safe and highly immunogenic in all species in which it was tested, including mice, guinea pigs, non-human primates and humans. Most encouragingly, following vaccination in humans, strong IFN-γ responses persisted through at least 2½ years of follow-up, indicating induction of a substantial memory response by this new TB vaccine. These findings encourage further preclinical and clinical studies with TB subunit vaccines and cellular immunity-stimulating new adjuvants.
Human vaccines 12/2010; 6(12):1007-15. · 3.58 Impact Factor
-
Olga V Fofanova-Gambetti,
Vivian Hwa,
Jan M Wit,
Horacio M Domene,
Jesús Argente, Peter Bang,
Wolfgang Högler,
Susan Kirsch,
Catherine Pihoker,
Harvey K Chiu,
Laurie Cohen,
Christina Jacobsen,
Hector G Jasper,
Gabriele Haeusler,
Angel Campos-Barros,
Elena Gallego-Gómez,
Ricardo Gracia-Bouthelier,
Hermine A van Duyvenvoorde,
Jesús Pozo,
Ron G Rosenfeld
[show abstract]
[hide abstract]
ABSTRACT: To date, 16 IGFALS mutations in 21 patients with acid-labile subunit (ALS) deficiency have been reported. The impact of heterozygosity for IGFALS mutations on growth is unknown.
The study evaluates the impact of heterozygous expression of IGFALS mutations on phenotype based on data collected by the International ALS Consortium.
Patient information was derived from the IGFALS Registry, which includes patients with IGFALS mutations and family members who were either heterozygous carriers or homozygous wild-type. Within each family, the effect of IGFALS mutations on stature was analyzed as follows: 1) effect of two mutant alleles (2ALS) vs. wild-type (WT); 2) effect of two mutant alleles vs. one mutant allele (1ALS); and 3) effect of one mutant allele vs. wild-type. The differences in height sd score (HtSDS) were then pooled and evaluated.
Mean HtSDS in 2ALS was -2.31 +/- 0.87 (less than -2 SDS in 62%); in 1ALS, -0.83 +/- 1.34 (less than -2 SDS in 26%); and in WT, -1.02 +/- 1.04 (less than -2 SDS in 12.5%). When analyses were performed within individual families and pooled, the difference in mean HtSDS between 2ALS and WT was -1.93 +/- 0.79; between 1ALS and WT, -0.90 +/- 1.53; and between 2ALS and 1ALS, -1.48 +/- 0.83.
Heterozygosity for IGFALS mutations results in approximately 1.0 SD height loss in comparison with wild type, whereas homozygosity or compound heterozygosity gives a further loss of 1.0 to 1.5 SD, suggestive of a gene-dose effect. Further studies involving a larger cohort are needed to evaluate the impact of heterozygous IGFALS mutations not only on auxology, but also on other aspects of the GH/IGF system.
The Journal of clinical endocrinology and metabolism 09/2010; 95(9):4184-91. · 6.50 Impact Factor
-
Jaap T van Dissel,
Sandra M Arend,
Corine Prins, Peter Bang,
Pernille Nyholm Tingskov,
Karen Lingnau,
Jan Nouta,
Michèl R Klein,
Ida Rosenkrands,
Tom H M Ottenhoff,
Ingrid Kromann,
T Mark Doherty,
Peter Andersen
[show abstract]
[hide abstract]
ABSTRACT: Though widely used, the BCG vaccine has had little apparent effect on rates of adult pulmonary tuberculosis. Moreover, the risk of disseminated BCG disease in immunocompromised individuals means that improved TB vaccines ideally need to be able to efficiently prime mycobacterially-naïve individuals as well as boost individuals previously vaccinated with BCG. Protective immunity against Mycobacterium tuberculosis is thought to depend on the generation of a Th1-type cellular immune response characterized by interferon-gamma (IFN-gamma) production. In the present study, we monitored safety and IFN-gamma responses in healthy TB-naïve humans receiving an entirely novel vaccine, composed of the fusion protein Ag85B-ESAT-6, administered at 0 and 2 months either as recombinant protein alone or combined with two concentrations of the novel adjuvant IC31. Vaccination did not cause local or systemic adverse effects besides transient soreness at the injection site, but it elicited strong antigen-specific T cell responses against H1 and both the Ag85B and the ESAT-6 components. These strong responses persisted through 2.5 years of follow-up, indicating the induction of a substantial memory response in the vaccine recipients.
Vaccine 03/2010; 28(20):3571-81. · 3.77 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: With the availability of recombinant human (rh) IGF-I as a new therapeutic agent, the criteria for diagnosis and strategies for management of growth deficiencies continue to evolve. This supplement provides a clinical update on molecular, therapeutic, and metabolic aspects of the management of short stature associated with insulin-like growth factor-I deficiency (IGFD). Several distinct, single-gene defects associated with primary IGFD now have been identified. The first section of this supplement focuses on selecting certain patients for specific genetic testing of the GH/IGF-I axis, based on previously obtained clinical and biochemical assessments. Management of short stature in children responding poorly to rhGH and definitions of a good and poor response are discussed in the next section. In addition, the authors further address different methods to help practicing clinicians predict and assess GH response, review the effect of rhGH on final adult height, and discuss the role IGF-I may have in the therapeutic approach to short stature. Finally, the metabolic aspects related to the treatment of short stature are discussed in the third part of this supplement.
Pediatric endocrinology reviews: PER 02/2010; 7 Suppl 1:154-71.
-
Yasir A W Skeiky,
Jes Dietrich,
Todd M Lasco,
Katherine Stagliano,
Veerabadran Dheenadhayalan,
Margaret Ann Goetz,
Luis Cantarero,
Randall J Basaraba, Peter Bang,
Ingrid Kromann,
J Bruce McMclain,
Jerald C Sadoff,
Peter Andersen
[show abstract]
[hide abstract]
ABSTRACT: Despite the extensive success with the introduction of M. bovis Bacille Calmette-Guérin (BCG), tuberculosis (TB) remains a major global epidemic infecting between 8 and 9 million people annually with an estimated 1.7 million deaths each year. However, because of its demonstrated effectiveness against some of the most severe forms of childhood TB, it is now realized that BCG vaccination of newborns is unlikely to be replaced. Therefore, BCG or an improved BCG will continue to be used as a prime TB vaccine and there is a need to develop effective boost vaccines that would enhance and prolong the protective immunity induced by BCG prime immunization. We report on a heterologous booster approach using two highly immunogenic TB antigens comprising Ag85B and TB10.4 (HyVac4) delivered as a fusion molecule and formulated in the proprietary adjuvant IC31. This vaccine was found to be immunogenic and demonstrated greater protection in the more stringent guinea pig model of pulmonary tuberculosis than BCG alone when used in a prime/boost regimen. Significant difference in lung involvement was observed for all animals in the HyVac4 boosted group compared to BCG alone regardless of time to death or sacrifice. A vaccine toxicology study of the HyVac4:IC31 regimen was performed and it was judged safe to advance the vaccine into clinical trials. Therefore, all non-clinical data supports the suitability of HyVac4 as a safe, immunogenic, and effective vaccination in a prime-boost regimen with BCG.
Vaccine 11/2009; 28(4):1084-93. · 3.77 Impact Factor
-
Pediatric endocrinology reviews: PER 05/2008; 5 Suppl 3:862-8.
-
Peter Bang
Pediatric endocrinology reviews: PER 05/2008; 5 Suppl 3:841-6.
-
[show abstract]
[hide abstract]
ABSTRACT: Mannan-binding lectin (MBL) is a member of the innate immune system, and MBL-deficiency affects 10-15% of Caucasians. With development of a plasma-derived MBL, substitution has become a therapeutic option in diseases associated with MBL insufficiency. The pharmacokinetics of injected MBL is weakly described, particularly in patients with infectious diseases. The pharmacokinetic profile of MBL following administration of 0.08 mg/kg to 20 healthy MBL-deficient volunteers and 0.2 mg/kg to 2 patients with Staphylococcus aureus septicaemia was established. In the volunteers, the maximal concentration was 2849 microg/l; the mean half-life (T(1/2)) was 69.6 h (14.6-114.9 h). The normalized clearance was 9x10(-6) l/minxkg, and the mean residence time was 82 h. In the patients the serum-MBL versus time curves were similar to those in the volunteers, and T(1/2) values were 36 and 40 h. In conclusion, MBL is distributed into a median volume of 3.4 l similar to the plasma volume, and the elimination in septicaemic patients was within the range of the controls. Due to the large individual variation in T(1/2), we recommend that MBL therapy, with respect to dose and infusion intervals, is based on the chosen therapeutic target (> or =1000 microg/l) and MBL serum determinations following the first infusion.
Scandinavian Journal of Infectious Diseases 02/2008; 40(1):44-8. · 1.72 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Calpains are cytoplasmic Ca(2+)-regulated cysteine proteases that may regulate insulin-like growth factor (IGF)-independent actions of insulin-like growth factor binding proteins (IGFBPs) through IGFBP proteolysis. In this study, [(125)I]-labeled IGFBP-2 and -3, but not IGFBP-1, were proteolyzed by Ca(2+)-activated m-calpain in vitro. Degradation of higher concentrations of the recombinant proteins IGFBP-2 and -3 by m-calpain was dose-dependent, but was terminated within 20 min by autolysis. By subjecting proteolytic fragments to N-terminal amino acid sequence analysis, the primary cleavage sites in IGFBP-2 and -3 were localized to the non-conserved central linker regions. Using the biosensor technique, in vitro binding of m-calpain to IGFBP-3 was demonstrated to be a Ca(2+)-dependent reaction with a rapid on/off rate.
Biological Chemistry 09/2007; 388(8):859-63. · 2.96 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We sought to test the hypothesis that start of insulin glargine with sustained nightly insulin action results in changes in circulating concentrations of IGF-I and IGF binding proteins (IGFBPs) in adolescents with type 1 diabetes-changes that may support improvement of A1C.
Twelve pubertal adolescents with type 1 diabetes and initially on NPH insulin were studied during 12 weeks of intensified treatment with glargine.
Subnormal IGF-I SD scores on NPH (-1.8 +/- 0.4) rapidly increased and remained 54 +/- 9% elevated (P < 0.001) after 12 weeks on glargine. A1C decreased from 8.3 +/- 0.6% to a nadir of 6.9 +/- 0.3% (P = 0.002) at 6 weeks and correlated with changes in IGF-I (r = -0.64, P < 0.05). The increase in IGF-I did not suppress the mean overnight growth hormone (GH) secretion at 6 weeks. The mean overnight IGFBP-1 levels decreased (P = 0.035), supporting the hypothesis that the nightly hepatic insulin action was increased. Circulating IGF-I increased in the absence of changes in both GH secretion and GH receptor numbers (assessed by growth hormone binding protein), indicating that postreceptor mechanisms are involved. IGFBP-3 proteolysis was decreased.
Increased hepatic insulin action after start of glargine was evident from a decrease in night time IGFBP-1 concentrations. This may improve GH postreceptor signaling, resulting in increased circulating IGF-I. We suggest that even in the absence of changes in GH, increased IGF-I and decreased IGFBP-1 support the improvement of metabolic control.
Diabetes care 07/2007; 30(6):1357-63. · 8.09 Impact Factor
-
Pediatric endocrinology reviews: PER 06/2007; 4 Suppl 2:252-71.
-
[show abstract]
[hide abstract]
ABSTRACT: Circulating insulin-like growth factor-binding protein 1 (IGFBP-1) normally has a close inverse relationship to insulin secretion, which results in a characteristic diurnal variation. However, in type 2 diabetes the correlation with insulin may be lost and IGFBP-1 concentrations relatively increased. The aim of this study was to determine the effect of nutritional deprivation on the diurnal patterns of IGFBP-1 regulation in type 2 diabetes mellitus. After a baseline assessment period, food intake was reduced over 48 hours to 627.6 kJ/d (150 kcal/d) for 72 hours and increased again over 24 hours to baseline (refeeding). Blood samples were taken at 2-hour intervals, for 24 hours in the baseline period, 48 hours during nutritional deprivation, and 24 hours during refeeding. Six individuals with type 2 diabetes were compared with 2 groups that were selected for normal fasting glucose and insulin levels and comprised 6 obese and 6 lean subjects. During energy (caloric) restriction, fasting insulin levels decreased to a similar extent in each study group. At baseline, IGFBP-1 concentrations were similar in each of the study groups and at the end of the period of energy (caloric) restriction the 6:00 AM fasting levels had increased by 144% in the obese control group and by 245% in the lean individuals (each P < .001). In the patients with type 2 diabetes there was a blunted increase in IGFBP-1 concentrations with nutritional deprivation by 33% compared with baseline. During refeeding after nutritional deprivation the IGFBP-1 response to insulin was restored in the individuals with diabetes. In conclusion, patients with type 2 diabetes mellitus have altered IGFBP-1 regulation, relating to impaired hepatic insulin sensitivity, which improves after a period of energy (caloric) restriction.
Metabolism 04/2005; 54(3):275-80. · 2.66 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The cytokine IL-1alpha is produced constitutively by the intact testis, but its function in this organ remains largely unknown. In this study we examined cooperation between IL-1alpha and GH and IGFs with regard to stimulation of steroidogenesis by Leydig cells from 40-d-old rats in vitro. IL-1alpha alone stimulated testosterone (T) and dihydrotestosterone (DHT) production. GH, IGF-I, or IGF-II alone was without effect on T production, but they were found to elevate DHT release, albeit without an obvious dose-response effect. Costimulation with IL-1alpha and GH or with IL-1alpha and IGF-I or IGF-II elevated the rate of steroidogenesis (both T and DHT) above that observed with IL-1alpha alone. GH was found to increase the level of IGF-I in the cultured Leydig cells, an effect that was potentiated by IL-1alpha. The costimulatory effect of GH on steroidogenesis was abolished by treatment with picropodophyllin, a specific inhibitor of the IGF-I receptor, indicating that the action of GH is mediated via IGF-I. Moreover, cells costimulated with IL-1alpha and GH exhibited a marked decrease in the level of intact IGF-binding protein-3 in the culture medium due to the induction of proteolytic activity toward this binding protein. In contrast, secretion of IGF-binding protein-2 was increased by such costimulation. These findings suggest that the stimulation of steroidogenesis in Leydig cells evoked by GH and IGFs requires cooperation with IL-1alpha. This cooperation may play an important role in connection with postnatal Leydig cell maturation and steroidogenesis.
Endocrinology 02/2005; 146(1):221-30. · 4.46 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Insulin-like growth factor binding protein-3 (IGFBP-3) is well established as a growth-inhibitory, apoptosis-inducing secreted molecule that acts via insulin-like growth factor (IGF)-independent as well as IGF-dependent pathways. Nuclear localization of IGFBP-3 has been observed and nuclear binding partners for IGFBP-3 demonstrated. However, little is known about the mechanism of IGFBP-3 internalization. We hypothesized that IGFBP-3 is first secreted then taken up again into cells and that its internalization could occur via binding to transferrin or caveolin. Incubation of cells with an IGFBP-3-neutralizing antibody demonstrated that nuclear translocation of endogenous IGFBP-3 requires IGFBP-3 secretion and re-uptake. Nuclear localization of exogenously added IGFBP-3 was rapid, occurring within 15 min, inhibited by co-incubation and extracellular sequestration with IGF-I, and dependent on the transferrin-binding C-terminal peptide region of IGFBP-3. Co-immunoprecipitation assays confirmed that IGFBP-3 binds transferrin but not directly to the transferrin receptor (TfR1); however, transferrin binds TfR1 and a ternary complex is formed. Specific binding to caveolin scaffolding docking sequence was confirmed utilizing radiolabeled IGFBP-3. Blocking TfR1-mediated endocytosis prevents both endogenous and exogenous IGFBP-3 re-uptake and inhibitors of caveolae formation also retard IGFBP-3 nuclear entry. Co-treatment with anti-transferrin receptor antibody and cholesterol depletion agents completely abolished endogenous and exogenous IGFBP-3 uptake. Suppression of IGFBP-3 internalization by TfR1 blockade inhibited IGFBP-3-induced apoptosis. Together, these data indicate that the actions of IGFBP-3 are mediated by internalization via distinct endocytic pathways.
Journal of Biological Chemistry 02/2004; 279(1):469-76. · 4.77 Impact Factor
