Characterization of a putative calcitonin receptor in IMR 32 human neuroblastoma cells.
In this study we characterized calcitonin (CT) receptors in human neuroblastoma IMR 32 cells. Saturation binding assays indicated that [125I]-human CT bound with high affinity to IMR 32 cell membranes (K(d) = 253.6 pM; Bmax = 3.84 fmol/ mg protein). In competition binding studies, human adrenomedullin displayed high affinity for these sites (IC50 = 30 nM) whereas human alpha calcitonin-gene related peptide (alphaCGRP; IC50 = 145 nM) and human amylin (IC50 = 415 nM) showed lower affinity. These peptides increased cAMP levels in viable cells; the relative potencies were: human CT > human adrenomedullin > human cCGRP > or = human amylin. The expression of mRNA coding for the published sequences of the human calcitonin receptor and of the human calcitonin receptor-like receptorwas evaluated by reverse transcriptase-polymerase chain reaction. Electrophoretic analysis did not confirm the occurrence of mRNA coding for the above mentioned receptors in these cells. This study suggests the presence of a novel, putative CT receptor in IMR 32 cells.
Spampinato
S
S
Department of Pharmacology, University of Bologna, Italy. spampi@biocfarm.unibo.it
Falcucci
B
B
Cacciaguerra
S
S
Campana
G
G
Murari
G
G
D053607:Adrenomedullin; D000682:Amyloid / Q000378:metabolism*; D001667:Binding, Competitive; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism*; D006801:Humans; D058228:Islet Amyloid Polypeptide; D009447:Neuroblastoma / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism*; D018003:Receptors, Calcitonin / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000682:Amyloid; D058228:Islet Amyloid Polypeptide; D010455:Peptides; D018003:Receptors, Calcitonin; D053607:Adrenomedullin; D000242:Cyclic AMP; D015740:Calcitonin Gene-Related Peptide