Expression of functional Y1 receptors for neuropeptide Y in human Ewing's sarcoma cell lines

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Abstract
In the human Ewing's sarcoma cell line WE-68, saturation analysis using3H-labelled neuropeptide Y ([3H]NPY) as the radioligand disclosed a homogeneous population of binding sites with a dissociation constant (K d ) of 4.5 nM and maximal binding capacity (B max) of 712 fmol/mg cell protein. Besides the WE-68 cell line, ten other human Ewing's sarcoma cell lines (FM-62, HS-80, HT-78, HT-M1-78, NT-68, RM-82, RS-63, VH-64, WE-M1-68, WE-M2-68) were also found to display NPY receptors withK d varying from 3.5 nM to 10.7 nM andB max=247−3744 fmol/mg cell protein. NPY, its natural analogues and the Y1-receptor-specific peptide ligand [Leu31, Pro34]NPY inhibited [3H]NPY binding in the potency order: [Leu31,Pro34]NPY≧human NPY≧peptide YY (PYY)>> salmon pancreatic polypeptide (PP) > human PP>porcine NPY13–36≫NPY22–36. In the Ewing's sarcoma cell lines NPY provoked inhibition of forskolin-stimulated cyclic AMP formation by up to 98%. Pertussis toxin alleviated the cyclic-AMP-inhibitory response to NPY. In isolated Ewing's sarcoma plasma membranes pertussis toxin [32P]ADP-ribosylated a 41-kDa protein. The ability of NPY and analogues to inhibit cyclic AMP accumulation paralleled their potencies in displacing radioligand binding. By contrast, a cell line derived from an atypical form of Ewing's sarcoma did not express specific and functional NPY receptors. These results demonstrate that conventional Ewing's sarcoma cells possess Gi-potein-coupled NPY receptors of the Y1 type, which upon interaction with NPY, PYY, and PP mediate inhibition of cyclic AMP generation.