Staurosporine differentiation of NPFF2 receptor-transfected SH-SY5Y neuroblastoma cells induces selectivity of NPFF activity towards opioid receptors

Activation of the NPFF2 receptor reduces the inhibitory effect of opioids on the N-type Ca2+ channel. Although this anti-opioid effect is specific for opioid receptors in neurons and tissues, it also affects NPY Y2 and α2-adrenoreceptors in undifferentiated SH-SY5Y cells stably expressing the NPFF2 receptor. To test whether this difference could be due to the immaturity of these cells, they were differentiated to a noradrenergic neuronal phenotype with staurosporine. The differentiated cells ceased to divide and grew long, thin neurites. The inhibition of the depolarization-triggered Ca2+ transient by activation of Gi-coupled receptors was either unaffected (μ-opioid), increased (NPY), reduced (NPFF2) or lost (α2-adrenoreceptors). Following a 20 min incubation with 1DMe, the effect of DAMGO was reduced, as in undifferentiated cells, but the effect of NPY was no longer affected. Staurosporine differentiation did not modify the coupling of the μ-opioid and NPFF2 receptors to the Gi/o proteins. We suggest that the specificity of the effect of NPFF may not reside in the molecular mechanism of its anti-opioid activity itself but in the organization of receptors within the membrane.