title: PI3K/Akt signaling pathway triggers P2X7 receptor expression as a pro-survival factor of neuroblastoma cells under limiting growth conditions.
abstract: The expression of purinergic P2X7 receptor (P2X7R) in neuroblastoma cells is associated to accelerated growth rate, angiogenesis, metastasis and poor prognosis. Noticeably, P2X7R allows the survival of neuroblastoma cells under restrictive conditions, including serum and glucose deprivation. Previously we identified specificity protein 1 (Sp1) as the main factor involved in the transcriptional regulation of P2rx7 gene, reporting that serum withdrawal triggers the expression of P2X7R in Neuro-2a (N2a) neuroblastoma cell line. Here we demonstrate that PI3K/Akt pathway is crucial for the upregulation of P2X7R expression in serum-deprived neuroblastoma cells, circumstance that facilitates cell proliferation in the absence of trophic support. The effect exerted by PI3K/Akt is independent of both mTOR and GSK3, but requires the activation of EGF receptor (EGFR). Nuclear levels of Sp1 are strongly reduced by inhibition of PI3K/Akt pathway, and blockade of Sp1-dependent transcription with mithramycin A prevents upregulation of P2rx7 gene expression following serum withdrawal. Furthermore, atypical PKCζ plays a key role in the regulation of P2X7R expression by preventing phosphorylation and, consequently, activation of Akt. Altogether, these data indicate that activation of EGFR enhanced the expression of P2X7R in neuroblastoma cells lacking trophic support, being PI3K/Akt/PKCζ signaling pathway and Sp1 mediating this pro-survival outcome.
authors.affiliation: Departamento de Bioquímica y Biología Molecular IV, Facultad de Veterinaria, Universidad Complutense de Madrid, 28040 Madrid, Spain.|Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, Madrid, Spain.
authors.forename: Rosa
authors.initials: R
authors.lastname: Gómez-Villafuertes
authors.affiliation: Departamento de Bioquímica y Biología Molecular IV, Facultad de Veterinaria, Universidad Complutense de Madrid, 28040 Madrid, Spain.|Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, Madrid, Spain.
authors.forename: Paula
authors.initials: P
authors.lastname: García-Huerta
authors.affiliation: Departamento de Bioquímica y Biología Molecular IV, Facultad de Veterinaria, Universidad Complutense de Madrid, 28040 Madrid, Spain.|Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, Madrid, Spain.
authors.forename: Juan Ignacio
authors.initials: JI
authors.lastname: Díaz-Hernández
authors.affiliation: Departamento de Bioquímica y Biología Molecular IV, Facultad de Veterinaria, Universidad Complutense de Madrid, 28040 Madrid, Spain.|Instituto de Investigación Sanitaria del Hospital Clínico San Carlos, Madrid, Spain.
authors.forename: M Teresa
authors.initials: MT
authors.lastname: Miras-Portugal
mesh_terms: D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000235:genetics; D066246:ErbB Receptors / Q000096:biosynthesis / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007527:Isoenzymes / Q000235:genetics*; D009362:Neoplasm Metastasis; D009389:Neovascularization, Pathologic / Q000235:genetics* / Q000473:pathology; D009447:Neuroblastoma / Q000235:genetics* / Q000473:pathology; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics; D011379:Prognosis; D011493:Protein Kinase C / Q000235:genetics*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics; D058486:Receptors, Purinergic P2X7 / Q000096:biosynthesis* / Q000235:genetics; D044967:Serum / Q000737:chemistry; D016329:Sp1 Transcription Factor / Q000235:genetics; D000099293:Protein Kinase C-lambda
chemical_list: D066246:ErbB Receptors; D007527:Isoenzymes; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C; D051057:Proto-Oncogene Proteins c-akt; D058486:Receptors, Purinergic P2X7; D016329:Sp1 Transcription Factor; D000099293:Protein Kinase C-lambda; C546468:P2RX7 protein, human; C108209:SP1 protein, human; C512478:EGFR protein, human