Calcitonin receptor

FIGURE 2.2 Binding and dose-response curves for human calcitonin on human calcitonin receptors type 2. (a) Dose-response curves for microphysiometry responses to human calcitonin in HEK cells (open circles) and binding in membranes from HEK cells (displacement of [,25I]-human calcitonin). Data from [1]. (b) Regression of microphysiometry responses to human calcitonin (ordinates) upon human calcitonin fractional receptor occupancy (abscissae). Dotted line shows a direct correlation between receptor occupancy and cellular response. 

FIGURE 3.11 Constitutive activity in melanophores expressing hCTR2 receptor, (a) Basal melanophore activity, (b) Effect of transfection with human cDNA for human calcitonin receptors (16 j-ig/ml). (c) Concentration response curve for cDNA for human calcitonin receptors (abscissae as log scale) and constitutive activity. Data redrawn from [27]. 

Chen, W.-J., Armour, S., Way, J., Chen, G., Watson, C., Irving, P., Cobb, J., Kadwell, S., Beaumont, K., Rimele, T., and Kenakin, T. P. (1997). Expression cloning and receptor pharmacology of human calcitonin receptors from MCF-7 cells and their relationship to amylin receptors. Mol. Pharmacol. 52 1164-1175. 

FIGURE 5.4 Microphysiometry responses of HEK 293 cells transfected with human calcitonin receptor, (a) Use of microphysiometry to detect receptor expression. Before transfection with human calcitonin receptor cDNA, HEK cells do not respond to human calcitonin. After transfection, calcitonin produces a metabolic response, thereby indicating successful membrane expression of receptors, (b) Cumulative concentration-response curve to human calcitonin shown in real time. Calcitonin added at the arrows in concentrations of 0.01, 0.1, 1.10, and lOOnM. Dose-response curve for the effects seen in panel B. 

FIGURE 5.6 Calcitonin receptor responses, (a) Real-time melanin dispersion (reduced light transmittance) caused by agonist activation (with human calcitonin) of transfected human calcitonin receptors type II in melanophores. Responses to 0.1 nM (filled circles) and lOnM (open circles) human calcitonin, (c) Dose-response curves to calcitonin in melanophores (open circles) and HEK 293 cells, indicating calcium transient responses (filled circles). 

FIGURE 5.11 Microphysiometry responses to 1 nM human calcitonin, (a) Responses obtained from HEK 293 cells stably transfected with low levels of human calcitonin receptor (68 pM/mg protein). Response is sustained, (b) Response from HEK 293 cells stably transfected with high levels of receptor (30,000 pM/mg protein). Data redrawn from [8],... 

Armour, S. L., Foord, S., Kenakin, T., and Chen, W.-J. (1999). Pharmacological characterization of receptor-activity-modifying proteins (RAMPs) and the human calcitonin receptor. J. Pharmacol. Toxicol. Meth. 42 217—224. 

FIGURE 11.2 Paired experimental data. Values of constitutive calcitonin receptor activity [1 -(Tr/Tj) units] in transiently transfected melanophores. Five separate experiments are shown. Points to the left indicate the basal level of constitutive activity before (filled circles) and after (open circles) addition of 100 nM AC512 (calcitonin receptor inverse agonist). Lines join values for each individual experiment. Points to the right are the mean values for constitutive activity in control (filled circles) and after AC512 (open circles) for all five experiments (bars represent standard errors of the mean). Data shown in Table 11.3. 

Paired t-tests Changes in constitutive calcitonin receptor responses with 100 nM AC512. 

As can be seen from the analysis in Table 11.3, the paired t-test indicates that the effect of AC512 on the constitutive activity is significant at the 99% level of confidence (p<0.01 and AC512 is an inverse agonist and does decrease the constitutive receptor activity of calcitonin receptors). 

Differences in constitutive calcitonin receptor activity in four separate receptor transfection experiments (xj to x ). Four readings of activity taken for each transfection. 

FIGURE 11.3 One-way ANOVA (analysis of variance). One-way analysis of variance of basal rates of metabolism in melanophores (as measured by spontaneous dispersion of pigment due to G,.-protein activation) for four experiments. Cells were transiently transfected with cDNA for human calcitonin receptor (8 j-ig/ml) on four separate occasions to induce constitutive receptor activity. The means of the four basal readings for the cells for each experiment (see Table 11.4) are shown in the histogram (with standard errors). The one-way analysis of variance is used to determine whether there is a significant effect of test occasion (any one of the four experiments is different with respect to level of constitutive activity). 

Kim MS, Day CJ, Selinger Cl, Magno CL, Stephens SR, Morrison NA. MCP-1-induced human osteoclast-like cells are tartrate-resistant acid phosphatase, NFATcl, and calcitonin receptor-positive but require receptor activator of NFkap-paB ligand for bone resorption. J Biol Chem 2006 281(2) 1274-1285. 

Reported applications of BSOCOES include studying the polypeptide antigens on lymphocyte cell surfaces (Zarling et al., 1980), crosslinking labeled (3-endorphin to its opioid receptors (Howard et al., 1985), and isolation and characterization of calcitonin receptors in rat kidney (Bouizar et al., 1986). 

Bouizar, Z., Fouchereau-Person, M., Taboulet, J., Moukhtar, M.S., and Milhaud, G. (1986) Purification and characterization of calcitonin receptors in rat kidney membranes by covalent cross-linking techniques. Eur. J. Biochem. 155, 141-147. 

Calcitonin lowers serum Ca2+ and Pi levels, primarily by inhibiting the process of bone resorption, but also by decreasing resorption of Pi and Ca2+ in the kidney. Calcitonin receptors are predictably found primarily on bone cells (osteoclasts) and renal cells, and generation of cAMP via adenylate cyclase activation plays a prominent role in hormone signal transduction. 

Cohen, D. P., Thaw, C. N., Varma, A., Gershengorn, M. C., and Nussenzveig, D. R. (1997) Human calcitonin receptors exhibit agonist-independent (constitutive) signaling activity. Endocrinology 138, 1400-1405. 

Calcitonin (Miacalcin, Miacalcin Nasal Spray) is a synthetic 32-amino acid polypeptide that is identical to salmon calcitonin. Salmon calcitonin is more potent than human calcitonin because of its higher affinity for the human calcitonin receptor and its slower metabolic clearance. Administration is by subcutaneous or intramuscular injection or by nasal spray. The absorption of the nasal form is slower than that of the parenteral routes. 

The diverse actions of AM are mediated by the 7-transmembrane G protein-coupled calcitonin receptor-like receptor (CRLR) which coassembles with subtypes 2 and 3 of a family of receptor-activity-modifying proteins (RAMPs), thus forming a receptor-coreceptor system. Binding of AM to CRLR activates Gs and triggers cAMP formation in vascular smooth muscle cells, and increases nitric oxide production in endothelial cells. Other signaling pathways are also involved. 

Poyner DR et al International Union of Pharmacology. XXXII. The mammalian calcitonin gene-related peptides, adrenomedullin, amylin, and calcitonin receptors. Pharmacol Rev 2002 54 233. [PMID 12037140]... 

McLatchie L. M., Fraser N. J., Main M. J., Wise A., Brown J., Thompson N., Solari R., Lee M. G. and Foord S. M. (1998) RAMPs regulate the transport and ligand specificity of the calcitonin-receptor-like receptor. Nature 393, 333-339. 

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