Extracellular
nucleotides exert a variety of
biological actions through different subtypes of P2 receptors. Here we characterized in the human
neuroblastoma SH-SY5Y cells the simultaneous presence of various P2 receptors, belonging to the P2X ionotropic and P2Y metabotropic families. Western blot analysis detected the P2X1,2,4,5,6,7 and P2Y1,2,4,6, but not the P2X3 and P2Y12 receptors. We then investigated which
biological effects were mediated by the P2Y4 subtype and its physiological
pyrimidine agonist
UTP. We found that neuronal differentiation of the SH-SY5Y cells with dibutiryl-cAMP increased the expression of the P2Y4
protein and that
UTP itself was able to positively interfere with neuritogenesis. Moreover, transient transfection and activation of P2Y4 also facilitated neuritogenesis in SH-SY5Y cells, as detected by morphological phase contrast analysis and confocal examination of
neurofilament proteins NFL. This was concurrent with increased transcription of immediate-early genes linked to differentiation such as cdk-5 and NeuroD6, and activity of
AP-1 transcription family members such as c-fos, fos-B, and jun-D. Nevertheless, a prolonged activation of the
P2Y4 receptor by
UTP also induced cell death, both in naive, differentiated, and P2Y4-transfected SH-SY5Y cells, as measured by direct count of intact nuclei and cytofluorimetric analysis of damaged
DNA. Taken together, our data indicate that the high expression and activation of the
P2Y4 receptor participates in the neuronal differentiation and commitment to death of SH-SY5Y cells.