Galanin receptors in human hypothalamus: biochemical and structural analysis.
Galanin receptors have been characterized in normal human hypothalamus using 125I-galanin binding assays. Competition experiments of porcine 125I-galanin binding to human hypothalamic membranes with native human, porcine and rat galanin (10(-11) M to 10(-8) M) gave comparable results with IC50 close to 0.1 nM. Scatchard analysis indicated one type of high affinity binding sites (Kd = 0.11 nM) with a capacity of 460 fmol/mg protein. Galanin-(1-15) and galanin-(2-29) inhibited tracer binding (IC50 = 1.5 nM), galanin-(3-29) and galanin-(10-29) being inactive. The galanin receptor antagonist, galantide, 10(-14) M to 10(-8) M, also strongly displaced binding of 125I-galanin to the human receptor (IC50 close to 0.15 nM). Guanine nucleotides (from 10(-8) M to 10(-4) M) decreased tracer binding to human membranes by increasing the dissociation of the galanin-receptor complexes. Structural analysis by covalent labelling indicated that the human galanin receptor behaves as a monomeric protein with a molecular mass of 54,000 daltons.
Lorinet
A M
AM
Laboratoire de Biologie et Physiologie des Cellules Digestives, Institut National de la Santé et de la Recherche Médicale, Paris, France.
Javoy-Agid
F
F
Laburthe
M
M
Amiranoff
B
B
D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D001665:Binding Sites; D001667:Binding, Competitive; D003198:Computer Simulation; D005260:Female; D019004:Galanin / Q000031:analogs & derivatives; D006150:Guanine Nucleotides / Q000494:pharmacology; D006801:Humans; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D007457:Iodine Radioisotopes; D008297:Male; D008970:Molecular Weight; D010446:Peptide Fragments / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D011869:Radioligand Assay; D051381:Rats; D044088:Receptors, Galanin; D011964:Receptors, Gastrointestinal Hormone / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D013373:Substance P / Q000031:analogs & derivatives*; D013552:Swine
D006150:Guanine Nucleotides; D007457:Iodine Radioisotopes; D010446:Peptide Fragments; D010455:Peptides; D044088:Receptors, Galanin; D011964:Receptors, Gastrointestinal Hormone; C074975:galantide; D013373:Substance P; D019004:Galanin