title: The Internalization of Neurotensin by the Low-Affinity Neurotensin Receptors (NTSR2 and vNTSR2) Activates ERK 1/2 in Glioma Cells and Allows Neurotensin-Polyplex Transfection of tGAS1.
abstract: Glioblastoma is the most malignant primary brain tumor and is very resistant to treatment; hence, it has a poor prognosis. Neurotensin receptor type 1 (NTSR1) plays a key role in cancer malignancy and has potential therapeutic applications. However, the presence and function of neurotensin (NTS) receptors in glioblastoma is not clearly established. RT-PCR assays showed that healthy (non-tumor) astroglial cells and C6 glioma cells express NTSR2 and its isoform (vNTSR2) rather than NTSR1. In glioma cells, NTS promotes the phosphorylation of extracellular signal-regulated kinases 1/2 (ERK 1/2), an effect that was completely abolished by blocking the internalization of the NTS/NTSR complex. We demonstrated pharmacologically that the internalization is dependent on the activation of NTSR2 receptors and it was prevented by levocabastine, a NTSR2 receptor antagonist. The internalization of NTSR2 and vNTSR2 was further demonstrated by its ability to mediate gene transfer (transfection) via the NTS-polyplex system. Expression of reporter transgenes and of the pro-apoptotic soluble form of growth arrest specific 1 (tGAS1) was observed in glioma cells. A significant reduction on the viability of C6 cells was determined when tGAS1 was transfected into glioma cells. Conversely, astroglial cells could neither internalize NTS nor activate ERK 1/2 and could not be transfected by the NTS-polyplex. These results demonstrate that the internalization process of NTSR2 receptors is a key regulator necessary to trigger the activation of the ERK 1/2. Our data support a new internalization pathway in glioma C6 cells that involve NTSR2/vNTSR2, which can be used to selectively transfer therapeutic genes using the NTS-polyplex system.
authors.affiliation: Departamento de Fisiología, Biofísica y Neurociencias, Centro de Investigación y de Estudios Avanzados del IPN, Av. IPN # 2508, 07360, Mexico, DF, Mexico.
authors.forename: Alberto E
authors.initials: AE
authors.lastname: Ayala-Sarmiento
authors.forename: Daniel
authors.initials: D
authors.lastname: Martinez-Fong
authors.forename: José
authors.initials: J
authors.lastname: Segovia
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D016466:CHO Cells; D018797:Cell Cycle Proteins / Q000235:genetics*; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D004705:Endocytosis / Q000235:genetics; D058851:GPI-Linked Proteins / Q000235:genetics; D005910:Glioma / Q000378:metabolism* / Q000473:pathology; D020935:MAP Kinase Signaling System / Q000502:physiology; D051379:Mice; D053758:Nanoparticles / Q000378:metabolism; D009496:Neurotensin / Q000378:metabolism*; D011108:Polymers; D011485:Protein Binding; D020033:Protein Isoforms / Q000378:metabolism; D051381:Rats; D018028:Receptors, Neurotensin / Q000378:metabolism*; D014162:Transfection / Q000379:methods
chemical_list: D018797:Cell Cycle Proteins; D058851:GPI-Linked Proteins; C501181:Gas1 protein, rat; C099727:Ntsr2 protein, rat; D011108:Polymers; D020033:Protein Isoforms; D018028:Receptors, Neurotensin; D009496:Neurotensin