Colocalization of neurotensin receptors and of the neurotensin-degrading enzyme endopeptidase 24-16 in primary cultures of neurons.
This paper compares the localization of neurotensin receptors and of endopeptidase 24-16, a peptidase likely involved in the inactivation of neurotensin in primary cultures of neurons. Neurotensin binding sites were radiolabeled with 125I-Tyr3-neurotensin, whereas endopeptidase 24-16 was stained by immunohistochemical techniques using a monospecific polyclonal antibody. Endopeptidase 24-16 is present in 80-85% of the nondifferentiated neurons. The proportion of immunoreactive neurons decreased during maturation to reach 35-40% after 4-8 d of culture. By contrast, neurotensin receptors were not detectable in nondifferentiated cells and appear during maturation. Specific 125I-Tyr3-neurotensin labeling is maximal after 4 d of culture and is located on about 10% of differentiated neurons. Double-labeling experiments show that about 90% of cortical, hypothalamic, and mesencephalic neurons bearing the neurotensin receptor also contained endopeptidase 24-16, supporting the hypothesis that one of the functions of endopeptidase 24-16 is the physiological inactivation of neurotensin. However, the presence of endopeptidase 24-16 on numerous neurons that do not contain neurotensin receptors also suggests that the enzyme could be involved in the degradation and/or maturation of other neuropeptides.
Chabry
J
J
Institut de Pharmacologie Moléculaire et Cellulaire Centre National de la Recherche Scientifique, Valbonne, France.
Checler
F
F
Vincent
J P
JP
Mazella
J
J
D000818:Animals; D001921:Brain / Q000378:metabolism; D002454:Cell Differentiation; D002478:Cells, Cultured; D007457:Iodine Radioisotopes; D008666:Metalloendopeptidases / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D007470:Monoiodotyrosine / Q000378:metabolism; D009474:Neurons / Q000201:enzymology / Q000378:metabolism*; D009479:Neuropeptides / Q000378:metabolism; D009496:Neurotensin / Q000378:metabolism*; D018028:Receptors, Neurotensin; D017981:Receptors, Neurotransmitter / Q000378:metabolism*
D007457:Iodine Radioisotopes; D009479:Neuropeptides; D018028:Receptors, Neurotensin; D017981:Receptors, Neurotransmitter; D009496:Neurotensin; D008666:Metalloendopeptidases; C062316:neurolysin; D007470:Monoiodotyrosine