Advantages of heterologous expression of human D2long dopamine receptors in human neuroblastoma SH-SY5Y over human embryonic kidney 293 cells

1 The human D2long dopamine receptor when expressed heterologously in a human neuronal cell line. SH-SY5Y, produced more robust functional signals than when expressed in a human embryonic kidney cell line, HEK293. Quinpirole (agonist)-induced GTP gamma(35)S binding and high affinity sites were 3-4 fold greater in SH-SY5Y than in HEK293 cells. 2 N-type Ca2+ channel currents present in SH-SY5Y cells, but nor HEK293 cells, were inhibited potently by quinpirole with a half-maximal inhibitory concentration of 0.15 +/- 0.03 nM. Inhibition of adenylyl cyclases by agonists. on the other hand, was of similar potency and efficacy in the two cell lines. 3 GTP gamma(35)S-Bound G alpha subunits from quinpirole-activated and solubilized membranes were monitored upon Immobilization with various G alpha-specific antibodies. G alpha(i) and G alpha(o) subunits were highly labelled with GTP gamma(35)S in SH-SY5Y cells, but only G alpha(i) subunits were labelled in HEK293 cells. The additional G(o) coupling in SH-SY5Y cells could arise, at least in part, from the presence of G(o) coupled-effecters. such as the N-type Ca2+ channel, and may contribute to robust agonist-induced GTP gamma(35)S binding, which is a reliable means for measuring ligand intrinsic efficacy. 4 It appears that expression of neuronal G protein-coupled receptors in neuronal environments could reveal additional functional characteristics that are absent in non-neuronal cell lints. This appears to be due to, at least In part, to the presence of neuron-specific effectors. These findings underscore the importance of the cellular environment in which drug actions are examined, particularly in the face of intensive efforts to develop drugs for G protein-coupled receptors of various origins.