Differential modulation of nucleoside transport types in neuroblastoma cells by protein kinase activation.
Nucleoside transport regulation in undifferentiated Neuro-2A cells has been studied and found to include Na+-dependent adenosine transport and facilitated diffusion adenosine transport. The latter corresponded to nitrobenzylthioinosine-sensitive nucleoside transport. Short-term treatment of Neuro-2A cells with physiologically relevant signals only modulated the facilitated diffusion component. The stimulation of undifferentiated cells with forskolin or other activators of the protein kinase A pathway, decreased NBTI-sensitive adenosine transport. Treatment of cells with an inactive analogue of forskolin, 1,9-dideoxi-forskolin, had no effect on NBTI-sensitive nucleoside transport. Therefore, the inhibition of protein kinase A activity by pre-incubation with H-89 or the cAMP antagonist, Rp-8-Br-cAMPS, completely prevented the inhibitory effect of forskolin. Similarly, the activation of protein kinase C with phorbol 12,13-dibutyrate (PDBu) and the calcium ionophore A-23187 decreased NBTI-sensitive adenosine transport. The effect of PDBu was reversed by pre-incubation of cells with staurosporine. Maximal transport inhibition was obtained by the simultaneous stimulation of cells with a phorbol ester and A-23187 or a phorbol ester and forskolin. The modulation of NBTI-sensitive nucleoside transport corresponded to changes in specific [3H]NBTI binding to Neuro-2A cells. Maximal inhibition correlated well with a maximal enhancement of cAMP production. However, the Na+-dependent adenosine transport in Neuro-2A cells was not modulated by any of these signals.
Sen
R P
RP
Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain.
Delicado
E G
EG
Miras-Portugal
M T
MT
D000241:Adenosine / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D001692:Biological Transport; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004789:Enzyme Activation; D051379:Mice; D009447:Neuroblastoma / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D011493:Protein Kinase C / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism; D013868:Thioinosine / Q000031:analogs & derivatives / Q000378:metabolism; D014316:Tritium; D014407:Tumor Cells, Cultured
D014316:Tritium; D005576:Colforsin; D013868:Thioinosine; D012964:Sodium; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; C001789:4-nitrobenzylthioinosine; D000241:Adenosine