Structural Basis for Antibody Discrimination between Two Hormones That Recognize the Parathyroid Hormone Receptor

Parathyroid hormone-related protein (PTHrP) plays a vital role in the embryonic development of the skeleton and other tissues. When it is produced in excess by cancers it can cause hypercalcemia, and its local production by breast cancer cells has been implicated in the pathogenesis of bone metastasis formation in that disease. Antibodies have been developed that neutralize the action of PTHrP through its receptor, parathyroid hormone receptor 1, without influencing parathyroid hormone action through the same receptor. Such neutralizing antibodies against PTHrP are therapeutically effective in animal models of the humoral hypercalcemia of malignancy and of bone metastasis formation. We have determined the crystal structure of the complex between PTHrP (residues 1–108) and a neutralizing monoclonal anti-PTHrP antibody that reveals the only point of contact is an α-helical structure extending from residues 14–29. Another striking feature is that the same residues that interact with the antibody also interact with parathyroid hormone receptor 1, showing that the antibody and the receptor binding site on the hormone closely overlap. The structure explains how the antibody discriminates between the two hormones and provides information that could be used in the development of novel agonists and antagonists of their common receptor.The discovery of parathyroid hormone (PTH)6 -related protein (PTHrP) as the cause of hypercalcemia in many patients with cancer provided new insights into the pathogenesis of the skeletal complications of malignancy (1). It revealed PTHrP as a previously unrecognized hormone, related in evolution to the calcium-regulating PTH, but important in the pathogenesis of the humoral hypercalcemia of malignancy, a syndrome in which hypercalcemia occurs without evident bone metastases. Whereas PTH consists of 84 amino acids, human PTHrP has three alternative splice products of 139, 141, and 173 residues. Apart from 8 of the first 13 residues of PTH and PTHrP being identical, there is no significant identity between these peptides (2). PTHrP actively promotes bone resorption, doing so in a manner identical to that of PTH by acting upon the receptor (PTH1R) it shares with PTH. The PTH1R is located on cells of the osteoblast lineage, which program the formation and activation of osteoclasts, and on cells of the kidney tubule, through which both PTHrP and PTH promote cyclic AMP and phosphorus excretion but reduce calcium excretion. Other actions of PTHrP that reflect those of PTH include the ability to relax vascular and other smooth muscle. This response may reflect a physiological function of PTHrP rather than of PTH and is consistent with PTHrP production and local action on smooth muscles at various sites (3).The first 34 amino acids of each hormone contain the full biological activities of both PTH and of PTHrP to activate the PTH1R (4). The sequences of PTHrP and PTH between residues 14 and 34 are interesting in that, although they are not homologous, nevertheless they appear to be critical for binding of each to the seven transmembrane G protein-coupled receptor, PTH1R (4). Within the first 34 amino acids of PTH and PTHrP two functional regions have been revealed based on structural and cross-linking studies (5–8). These studies have indicated that the C-terminal half of the first 34 residues of each hormone comprises the high affinity binding domain, interacting with the N-terminal portion of the extracellular domain of the receptor. The N-terminal half of each hormone activates the receptor through contact points on the extracellular loops and juxtamembrane regions (9).Despite their equal ability to activate through the PTH1R, it was clear from the earliest work, even with antibodies against peptides within the first 14 residues of PTHrP, that highly specific antibodies could be generated that discriminate between PTH and PTHrP (10). Likewise, polyclonal antibodies against PTHrP-(1–34) that neutralized its effects completely in vitro in promotion of cyclic AMP production in response to PTHrP without any detectable neutralizing effect on PTH were used to prevent and to treat hypercalcemia in nude mice bearing xenografts of PTHrP-secreting human cancers (11, 12). Similar results were obtained with a neutralizing mouse monoclonal antibody against PTHrP (13). Subsequently, after the finding that breast cancer metastases to bone were enriched in PTHrP production (14), Guise and Mundy (15) used an experimental model in nude mice in which human breast cancer cells grow as lytic deposits in bone after intracardiac injection and showed that PTHrP production by the cancers contributed to the process of tumor establishment and growth in bone by promoting osteoclast formation and bone resorption. Furthermore, the tumor establishment and growth in bone could be prevented by treating the mice with a monoclonal antibody against PTHrP (16) or with a bisphosphonate (17) to inhibit bone resorption.The efficacy of anti-PTHrP antibodies in treating both humoral-mediated hypercalcemia in cancer and bone metastasis formation and growth in mouse models raises the prospect of humanized forms of these antibodies being used as therapeutic agents in these diseases in human subjects, and preclinical data have been obtained in support of that (18, 19). With that in mind, the present project was undertaken in which we have made use of a monoclonal antibody prepared against human PTHrP (residues 1–34), which neutralizes the actions of PTHrP through PTH1R without any action against PTH. The antibody has been complexed with recombinant human PTHrP (residues 1–108) to generate crystals that have been used to analyze the three-dimensional structure with the aim of discovering the structural basis of neutralization of PTHrP action by the antibody.     

Non-targeted metabolite profiling in activated macrophage secretion

Periodontal diseases are inflammatory infectious diseases that affect the periodontal tissue. Macrophages play a central role in inflammatory conditions, leading to the destruction of tissues. Identifying the signaling molecules secreted by macrophages would be valuable to the study of these diseases. Here, we present non-targeted analysis using capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS) for the profiling of extracellular metabolites released during macrophage activation. Lipopolysaccharide (LPS)-induced activation of a mouse macrophage-like cell line RAW264.7 was used as a model system. Cells were treated without (control) or with LPS for 22?h and, after washing, were incubated for 1?h in phosphate-buffered saline. The accumulation of metabolites in the culture supernatant was monitored. LPS treatment significantly enhanced the accumulation of prostaglandins, tumor necrosis factor-??, nitric oxide and citrulline in the culture medium. RAW264.7 cells produced 46 metabolites and 66% of these showed significant changes (P?<?0.05) following cell activation. In particular, the production of leucine, hypoxanthine, choline, putrecine, N ₈-acetylspermidine, succinate, itaconate, and 4-methyl-2-oxopentanoate was significantly increased by cell activation (P?<?0.001). Significantly elevated production of lactate and glycine was also observed. Here, we present the first catalog of the up and down-regulation of the various metabolites secreted by macrophages following inflammatory activation.     

Socioeconomic Status Correlates with the Prevalence of Advanced Coronary Artery Disease in the United States

Background

Increasingly studies have identified socioeconomic factors adversely affecting healthcare outcomes for a multitude of diseases. To date, however, there has not been a study correlating socioeconomic details from nationwide databases on the prevalence of advanced coronary artery disease. We seek to identify whether socioeconomic factors contribute to advanced coronary artery disease prevalence in the United States.

Methods and Findings

State specific prevalence data was queried form the United States Nationwide Inpatient Sample for 2009. Patients undergoing percutaneous coronary angioplasty and coronary artery bypass graft were identified as principal procedures. Non-cardiac related procedures, lung lobectomy and hip replacement (partial and total) were identified and used as control groups. Information regarding prevalence was then merged with data from the Behavioral Risk Factor Surveillance System, the largest, on-going telephone health survey system tracking health conditions and risk behaviors in the United States. Pearson''s correlation coefficient was calculated for individual socioeconomic variables including employment status, level of education, and household income. Household income and education level were inversely correlated with the prevalence of percutaneous coronary angioplasty (−0.717; −0.787) and coronary artery bypass graft surgery (−0.541; −0.618). This phenomenon was not seen in the non-cardiac procedure control groups. In multiple linear regression analysis, socioeconomic factors were significant predictors of coronary artery bypass graft and percutaneous transluminal coronary angioplasty (p<0.001 and p = 0.005, respectively).

Conclusions

Socioeconomic status is related to the prevalence of advanced coronary artery disease as measured by the prevalence of percutaneous coronary angioplasty and coronary artery bypass graft surgery.     

Population genetic structure of the spotted seal Phoca largha along the Coast of Hokkaido,based on mitochondrial DNA sequences

Population genetic structure of the spotted seal, Phoca largha, along coastal regions of Hokkaido was investigated, using mitochondrial DNA (mtDNA) sequences. A 571-bp fragment of the mtDNA control region and adjacent threonine and proline transfer RNA genes was sequenced from 66 seals. We categorized all individuals into three groups considering sampling area and season: twenty-four seals from the Sea of Okhotsk in winter, 11 seals from the Sea of Okhotsk coast in fall, and 31 seals from the Sea of Japan coast in winter. From the 66 animals, 57 haplotypes were identified. Compared with the harbor seal sequence, all spotted seals examined shared two deletions in the control region, which distinguished between the two species. Forty-nine haplotypes were represented by a single individual, and haplotypes shared by more than two animals were generally restricted to same sampling-groups. Phylogenetic trees did not indicate clear geographic differences among the three groups. An Analysis of molecular variances (AMOVA) did not showed any significant population genetic structure in Hokkaido spotted seals (Phi(st )= -0.003). Our results showed a high level of diversity but no genetic structure, and did not deny the possibility that seals in the Okhotsk breeding concentration mainly stayed in the fall Okhotsk and also inhabited in the winter Sea of Japan.     

Reduction of methemoglobin via electron transfer from photoreduced flavin: restoration of O2-binding of concentrated hemoglobin solution coencapsulated in phospholipid vesicles

Ferric methemoglobin is reduced to its ferrous form by photoirradiation either by direct photoexcitation of the heme portion to induce electron transfer from the surrounding media (Sakai at al. (2000) Biochemistry 39, 14595-14602) or by an indirect electron transfer from a photochemically reduced electron mediator such as flavin. In this research, we studied the mechanism and optimal condition that facilitates photoreduction of flavin mononucleotide (FMN) to FMNH(2) by irradiation of visible light, and the succeeding reduction of concentrated metHb in phospholipid vesicles to restore its O(2) binding ability. Visible light irradiation (435 nm) of a metHb solution containing FMN and an electron donor such as EDTA showed a significantly fast reduction to ferrous Hb with a quantum yield (Phi) of 0.17, that is higher than the method of direct photoexcitation of heme (Phi = 0.006). Electron transfer from a donor molecule to metHb via FMN was completed within 30 ns. Native-PAGE and IEF electrophoresis indicated no chemical modification of the surface of the reduced Hb. Coencapsulation of concentrated Hb solution (35 g/dL) and the FMN/EDTA system in vesicles covered with a phospholipid bilayer membrane (Hb-vesicles, HbV, diameter: 250 nm) facilitated the metHb photoreduction even under aerobic conditions, and the reduced HbV restored the reversible O(2) binding property. A concentrated HbV suspension ([Hb] = 8 g/dL) was sandwiched with two glass plates to form a liquid layer with the thickness of about 10 microm (close to capillary diameter in tissue, 5 microm), and visible light irradiation (221 mW/cm(2)) completed 100% metHb photoreduction within 20 s. The photoreduced FMNH(2) reacted with O(2) to produce H(2)O(2), which was detected by the fluorescence measurement of the reaction of H(2)O(2) and p-nitrophenylacetic acid. However, the amount of H(2)O(2) generated during the photoreduction of HbV was significantly reduced in comparison with the homogeneous Hb solution, indicating that the photoreduced FMNH(2) was effectively consumed during the metHb reduction in a highly concentrated condition inside the HbV nanoparticles.     

Expression of the Xenopus GTP-binding protein gene Ran during embryogenesis

The Ran gene family encodes small GTP binding proteins that are associated with a variety of nuclear processes. We isolated a Xenopus Ran cDNA and analyzed the pattern of expression of this gene during embryogenesis. Ran is expressed maternally and later in the CNS, neural crest, mesenchyme, eyes, and otic vesicles. However, expression is not detected in the somites or the notochord. Received: 22 November 1999 / Accepted: 22 December 1999     

中国长管蚜亚科19种新纪录

我们在东北农林蚜虫区系考察中发现下述长管蚜亚科19种为我国首次纪录。 1.茜草叶无网蚜Acyrthosiphon rubifoliae(Shinji)此种名为一疑难名称(nomen dubium),我们采得此种与原记述特征相符。寄主:茜草*。分布:吉林(长白山);日本。 2.日本忍冬圆尾蚜Amphicercidus japonicus(Hori)寄主:莫罗氏忍冬、忍冬属植物*。分布:辽宁(沈阳);日本。 3.飞帘短尾蚜Brachycadus(Acaudus)cardui(L.)寄主:第一寄主李、榆叶梅*、樱桃李、乌荆子、杏、小樱桃、甜樱桃;第二寄主菊科、紫草科。     

Alteration of Immune Responses of Rabbits Infected with Bovine Immunodeficiency-Like Virus

Nine 3-month-old rabbits were inoculated with bovine immunodeficiency-like virus (BIV) to study the pathogenesis of BIV and alteration of the immune responses in experimentally infected rabbits. BIV proviral DNA and anti-BIV antibodies were detected from all rabbits inoculated with BIV-infected bovine embryo spleen (BESP) cells. Rabbits inoculated with spleen cells of the BIV-infected rabbit also converted to proviral DNA-positive and BIV-antibody-positive. The blastogenic responses to concanavalin A of peripheral blood mononuclear cells prepared from BIV-infected rabbits were not significantly different from those from uninfected controls at 2 and 4 months post-inoculation (PI). The humoral immune responses against bovine serum albumin (BSA) were depressed in two of four BIV-infected rabbits at 1 to 3 months PI. The antibody responses against sheep red blood cells (SRBCs) were significantly depressed in all BIV-infected rabbits at 2 to 4 months PI. BIV was rescued by cocultivation of spleen cells of infected rabbits with BESP cells. Distinct development of lymphoid follicle was observed in lymph nodes and spleens of uninfected rabbits which received BSA and SRBCs. In contrast, moderate lymphoid cell depletion was observed in BIV-infected rabbits which received the same immunogens.