title: Characterization of binding sites for N-Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2) in rat brain.
abstract: Binding sites for N-Tyr-Pro-Leu-Gly-NH2 (Tyr-MIF-1), a novel peptide structurally related but immunoreactively different from Pro-Leu-Gly-NH2 (MIF-1), were investigated. The presence of Tyr-MIF-1-like material in brain tissue has previously been demonstrated by RIA and its levels were shown to vary with the diurnal cycle and after pinealectomy. We now demonstrate a high affinity binding site in rat brain that is saturable and specific for Tyr-MIF-1. Crude P2 synaptosomal fractions from rat brains were incubated with 125I-Tyr-MIF-1 in the presence or absence of 10 microM unlabeled Tyr-MIF-1 (nonspecific binding). Binding reached equilibrium at 30-40 min at 23 degrees C and at about 4 hr on ice, after which it was relatively stable for at least 18 hr. None of the other peptides (including MIF-1) or amino acid residues tested were found to effectively compete for 125I-Tyr-MIF-1 binding. Binding was linear with protein from 280 micrograms to at least 1.1 mg protein per tube. Scatchard analysis of the striatum-thalamus revealed the presence of binding sites with an apparent Kp of 91 nM and maximum number of sites in the range of 45 fmol/mg tissue. Analysis of several brain areas revealed a differential distribution of the binding sites with relatively high concentrations in cortex, striatum, and amygdala and low concentrations in pons-medulla. Together with the previously published RIA results, the demonstration of a receptor for Tyr-Pro-Leu-Gly-NH2 supports the concept of the presence of this novel peptide and its receptor in the brain.
mesh_terms: D000679:Amygdala / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D001921:Brain / Q000378:metabolism*; D001933:Brain Stem / Q000378:metabolism; D002531:Cerebellum / Q000378:metabolism; D002540:Cerebral Cortex / Q000378:metabolism; D003342:Corpus Striatum / Q000378:metabolism; D006624:Hippocampus / Q000378:metabolism; D007700:Kinetics; D009075:MSH Release-Inhibiting Hormone / Q000031:analogs & derivatives* / Q000378:metabolism*; D008297:Male; D008636:Mesencephalon / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018017:Receptors, Pituitary Hormone-Regulating Hormone; D013788:Thalamus / Q000378:metabolism
chemical_list: C037078:MSH release inhibiting hormone receptor; D011956:Receptors, Cell Surface; D018017:Receptors, Pituitary Hormone-Regulating Hormone; C036930:tyrosyl-prolyl-leucyl-glycinamide; D009075:MSH Release-Inhibiting Hormone