Neurotensin: specific binding to synaptic membranes from rat brain.

Abstract

The binding of neurotensin to synaptic membranes from rat brain was studied at 24°with the use of [3HJ neurotensin. The binding was found to be highly specific, saturable, and reversible. Values for KD of 2 nM and 0.9 nM were derived from equilibrium and kinetic experiments, respectively. Virtually no degradation of neurotensin was observed in the incubation medium after exposure to synaptic membranes under the conditions of the binding studies. Competitive inhibition of [3Hlneurotensin binding by partial sequences of neurotensin revealed that the addition of the residue arginine-8 to the neurotensin(9-13)pentapeptide increases about 500-fold the relative binding potency, whereas the remaining portion of the NH2-terminal region is mainly responsible for full pharmacological potency; the COOH-terminal leucyl residue is essential for bin ing.

Apamin as a selective blocker of the calcium-dependent potassium channel in neuroblastoma cells: voltage-clamp and biochemical characterization of the toxin receptor.

“…However the most active compound in preventing '2I-apamin association to its receptor is neurotensin. This neuropeptide of 13 amino acids has two contiguous arginines in its active site (22).t Other charged molecules like verapamil also interfere with '"I-apamin binding to the neuroblastoma membrane.…”

Cloning and expression of a complementary DNA encoding a high affinity human neurotensin receptor

“…Fig. 4 with an order of potency identical to the neurotensin receptor expressed in the HT29 cell line [6] and other tissues [14]: (i) neurotensin is the most potent competitor, followed by neuromedin N and SR 48692; (ii) the apparent half maximal concentrations for an inhibition (IC,,) derived from the competition curves were 0.3, 2.6 and 38 nM, respectively; and (iii) levocabastine, an anti-histamine agent described as a ligand for the low affinity neurotensin binding site [22] does not compete (using concentrations up to 10 PM) with "SI-labeled [monoiodo-Tyr3] neurotensin for the binding to COS cells, demonstrating that the transfected cDNA encodes a high affinity NTR.…”

“…The biochemical and pharmacological properties of these binding sites have been extensively studied using mammalian brain homogenates as well as membrane preparations from neuronal and certain non-neuronal cell lines [5,6]. It has been shown that the interaction with these receptors modulates intracellular levels of cGMP, CAMP and inositol phosphates [7,8].…”

Neurotensin stimulates inositol trisphosphate-mediated calcium mobilization but not protein kinase C activation in HT29 cells. Involvement of a G-protein

“…5, Table 4). [6,20] and that receptor occupancy leads to inositol phosphate formation [6]. The present work was designed variations using the fluorescent indicator quin 2 [9] showed that neurotensin (0.…”