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Calcium Mobilisation (calcium + mobilisation)
Selected AbstractsIdentification and characterisation of GPR100 as a novel human G-protein-coupled bradykinin receptorBRITISH JOURNAL OF PHARMACOLOGY, Issue 5 2003Katrin Boels G-protein-coupled receptor 100 (GPR100) was discovered by searching the human genome database for novel G-protein-coupled peptide receptors. Full-length GPR100 was amplified from a cDNA library of the neuroendocrine cell line BON, which is derived from a human pancreas carcinoid. The open-reading frame, present on a single exon, coded for a protein of 374 amino acids with highest sequence identity (43%) to the human orphan somatostatin- and angiotensin-like peptide receptor. The analysis of chromosomal localisation mapped the GPR100 gene to chromosome 1q21.2,q21.3. The stable expression of GPR100 in Chinese hamster ovary cells together with aequorin as calcium sensor and the promiscuous G-protein subunit ,16 as signal transducer revealed bradykinin and kallidin as effectors to elicit a calcium response. Dose,response curves yielded EC50 values for both ligands in the low nanomolar range, while the respective analogues without arginine at the carboxy-terminus were inactive. Calcium mobilisation was inhibited by the phospholipase C blocker U73122, but not by pertussis toxin, suggesting the involvement of the G-protein subunit ,q and not ,i or ,o in signal transduction. In line with the main function of kinins as peripheral hormones, we found that GPR100 was expressed predominantly in tissues like pancreas, heart, skeletal muscle, salivary gland, bladder, kidney, liver, placenta, stomach, jejunum, thyroid gland, ovary, and bone marrow, but smaller amounts were also detected in the brain and in cell lines derived from tumours of various origins. British Journal of Pharmacology (2003) 140, 932,938. doi:10.1038/sj.bjp.0705521 [source] Discovery and recognition of purine receptor subtypes on plateletsDRUG DEVELOPMENT RESEARCH, Issue 1-2 2001Susanna M.O. HouraniArticle first published online: 9 MAY 200 Abstract The effects of purines on platelets have been known since the 1960s, when Born demonstrated aggregation induced by ADP and its inhibition by adenosine and by ATP. The inhibition by adenosine is not specific for ADP, and adenosine acts at a separate receptor to stimulate adenylate cyclase, which has an inhibitory effect on platelet function. Studies using selective agonists and antagonists have shown that the platelet receptor is of the A2A subtype and this has been confirmed using A2A knockout mice. The situation with ADP is more complex, and there has been controversy about the number of ADP receptors on platelets. ADP causes shape change, aggregation, mobilisation of calcium from intracellular stores, rapid calcium influx, and inhibition of adenylate cyclase, and the relationship between these is becoming clearer. Two cloned P2 receptors have been detected on platelets, P2X1 and P2Y1, and a third P2Y receptor is thought to exist. The P2X1 receptor is responsible for the rapid calcium influx and can be activated by ATP as well as by ADP, but is likely to be desensitised under normal experimental conditions and its pathophysiological role is uncertain. The P2Y1 receptor is responsible for calcium mobilisation, shape change, and the initiation of aggregation, and these responses are abolished in P2Y1 knockout mice, while the other P2Y receptor is responsible for inhibition of adenylate cyclase and is required for full aggregation. ATP is a competitive antagonist at both these P2Y receptors, while some nucleotide analogues can discriminate between them. Drug Dev. Res. 52:140,149, 2001. © 2001 Wiley-Liss, Inc. [source] Nuclear targeting of a midregion PTHrP fragment is necessary for stimulating growth in breast cancer cellsINTERNATIONAL JOURNAL OF CANCER, Issue 1 2006Rajendra Kumari Abstract Parathyroid-hormone related protein (PTHrP) is the primary factor in humoral hypercalcemia of malignancy and is highly secreted by breast cancers. The pro-hormone undergoes post-translational processing and cleavage to give rise to mature secretory peptides, one of which is midregion PTHrP (38-94/95/101) containing a nuclear localisation sequence (NLS) in amino acids (87-106). The current study investigates whether the NLS in midregion PTHrP is important in breast cancer growth. PTHrP-(67-101), a midregion PTHrP fragment containing NLS-(87-101) significantly increased growth of MCF-7 and MDA-MB231 cells (126.3 and 121.3% of control respectively in serum conditions), independent of PTHR1 whereas PTHrP-(67-86), which lacks the NLS did not. Fluorescent-labelled PTHrP-(67-101) translocated to the nucleus, whereas PTHrP-(67-86) remained cytosolic and a scrambled(+NLS) peptide was not internalised. In comparison, no growth influence or uptake was seen in non-tumour breast cells (Hs578Bst). Increases in intracellular calcium mobilisation were observed in breast cancer cells stimulated with both PTHrP-(67-101) and PTHrP-(67-86) (EC50 of 3.2 pM and 2.2 pM respectively for MCF-7 cells), whereas inositide turnover was not detected. Both nuclear uptake and calcium signalling were attenuated in the presence of EGTA, but not with U73122 or N-terminal PTHrP peptides. Our studies indicate that the NLS-containing midregion PTHrP peptide is dependent on both internalisation and nuclear translocation to induce growth in breast cancer cells. These findings highlight the importance of midregion PTHrP and its receptor in breast cancer growth and may provide potential targets for future therapeutic intervention. © 2006 Wiley-Liss, Inc. [source] Tetraamine-Derived Bifunctional Chelators for Technetium-99m Labelling: Synthesis, Bioconjugation and Evaluation as Targeted SPECT Imaging Probes for GRP-Receptor-Positive Tumours,CHEMISTRY - A EUROPEAN JOURNAL, Issue 7 2010Keelara Abiraj Dr. Abstract Owing to its optimal nuclear properties, ready availability, low cost and favourable dosimetry, 99mTc continues to be the ideal radioisotope for medical-imaging applications. Bifunctional chelators based on a tetraamine framework exhibit facile complexation with Tc(V)O2 to form monocationic species with high in vivo stability and significant hydrophilicity, which leads to favourable pharmacokinetics. The synthesis of a series of 1,4,8,11-tetraazaundecane derivatives (01,06) containing different functional groups at the 6-position for the conjugation of biomolecules and subsequent labelling with 99mTc is described herein. The chelator 01 was used as a starting material for the facile synthesis of chelators functionalised with OH (02), N3 (04) and O -succinyl ester (05) groups. A straightforward and easy synthesis of carboxyl-functionalised tetraamine-based chelator 06 was achieved by using inexpensive and commercially available starting materials. Conjugation of 06 to a potent bombesin-antagonist peptide and subsequent labelling with 99mTc afforded the radiotracer 99mTc-N4-BB-ANT, with radiolabelling yields of >97,% at a specific activity of 37,GBq,,mol,1. An IC50 value of (3.7±1.3),nM was obtained, which confirmed the high affinity of the conjugate to the gastrin-releasing-peptide receptor (GRPr). Immunofluorescence and calcium mobilisation assays confirmed the strong antagonist properties of the conjugate. In vivo pharmacokinetic studies of 99mTc-N4-BB-ANT showed high and specific uptake in PC3 xenografts and in other GRPr-positive organs. The tumour uptake was (22.5±2.6),% injected activity per gram (%,IA,g,1) at 1,h post injection (p.i.). and increased to (29.9±4.0),%,IA,g,1 at 4,h p.i. The SPECT/computed tomography (CT) images showed high tumour uptake, clear background and negligible radioactivity in the abdomen. The promising preclinical results of 99mTc-N4-BB-ANT warrant its potential candidature for clinical translation. [source] | ||||||||||