CHARACTERIZATION OF FUNCTIONAL NEUROTENSIN RECEPTORS ON HUMAN-LYMPHOCYTES

Background. Neurotensin, a tridecapeptide, regulates gut motility, sec retion, and mucosal growth; an immunomodulatory role for neurotensin h as been postulated but not clearly defined. The purpose of this study was to determine whether neurotensin receptors (NTR) are present on pe ripheral blood lymphocytes (PBLs) and to characterize binding, functio nal, and molecular properties. Methods. Iodine 125 labeled-neurotensin binding was determined for both human PBLs and the T-cell lines, Molt -4 and Jurkat, by Scatchard analysis. To analyze functional capacity o f the NTR, PBLs were cultured in the presence of phytohemagglutinin (1 mu g/ml) with or without neurotensin and harvested at 48 hours after an 8-hour pulse of tritiated thymidine. For molecular analyses, RNA ex tracted from PBLs and T-cell lines was analyzed by either Northern hyb ridization with a labeled NTR cDNA or ribonuclease protection with an antisense human NTR probe. Results. Scatchard analyses of neurotensin binding to human PBLs and MOLT-4 showed two classes of binding sites w ith different affinities. Incubation of phytohemagglutinin-stimulated PBLs with neurotensin significantly enhanced proliferation. Northern h ybridization showed mRNA of the authentic NTR or a receptor subtype of close homology, in PBLs and the T-cell lines; ribonuclease protection analysis identified the authentic human NTR in the MOLT-4 cell line. Conclusions. Using a combination of molecular techniques and Scatchard analysis, we have demonstrated the presence of a cell surface NTR wit h a high affinity Sor neurotensin on human PBLs and the MOLT-4 cell li ne. The Junctional role of NTR has been established by enhanced neurot ensin and the immune system and suggest that neurotensin may play an i mportant regulatory role in gut mucosal immune responses in vivo.