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D 2L , D 2S , and D 3 dopamine receptors stably transfected into NG108‐15 cells couple to a voltage‐dependent potassium current via distinct G protein mechanisms
Author(s) -
Liu LiXin,
Monsma Frederick J.,
Sibley David R.,
Chiodo Louis A.
Publication year - 1996
Publication title -
synapse
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.809
H-Index - 106
eISSN - 1098-2396
pISSN - 0887-4476
DOI - 10.1002/(sici)1098-2396(199610)24:2<156::aid-syn7>3.0.co;2-e
Subject(s) - receptor , dopamine receptor d2 , signal transduction , biology , pertussis toxin , microbiology and biotechnology , g protein , dopamine receptor , 5 ht5a receptor , chemistry , biochemistry
The D 2 ‐like dopamine (DA) receptor family has continued to expand and now includes the D 2 ‐short (D 2S ) and D 2 ‐long (D 2L ) receptor isoforms and the D 3 and D 4 receptors. The D 2 receptor isoforms differ in length by 29 amino acids within the third cytoplasmic loop, a region of the receptor believed to be important for G protein coupling. This observation has led to the hypothesis that the two isoforms of the D 2 receptor may utilize different signal transduction pathways when present in the same cell. The D 2 and D 3 receptors, although mostly different, show some common amino acid sequences within the third cytoplasmic loop. Thus, it is possible that the D 2 and D 3 receptors may employ similar signal transduction pathways. To test these hypotheses directly, NG108‐15 neuroblastoma‐glioma hybrid cells were stably transfected to express either the D 2S , D 2L , or D 3 DA receptors. All transfected but not untransfected NG108‐15 cells demonstrated a dose‐dependent reduction in the peak whole‐cell potassium (K + ) current in response to receptor activation by DA or the DA receptor agonists quinpirole (QUIN) and apomorphine (APO). The modulation of K + current by D 2S receptor stimulation was prevented by pretreatment of the cells with cholera toxin (20 μg/ml for 18 h), whereas pertussis toxin pretreatment (500 ng/ml for 4 h) completely blocked the effects of D 2L and D 3 receptor activation. These observations suggest that the signal transduction mechanisms involved in coupling the two isoforms of the D 2 receptor to the K + current are different, whereas the D 2L and D 3 receptor coupling mechanisms may be similar. In direct support of this hypothesis, it was observed that the intracellular application of a polyclonal antibody that is specific for the G 0α subunit completely blocked the ability of D 2L and D 3 receptors to modulate outward K + currents. In contrast, the D 2S ‐mediated modulation of K + currents was blocked by intracellular application of an antibody recognizing G Sα but not G 0α . These findings demonstrate that D 2S and D 2L receptors are able to couple to a common effector in a cell via two G protein pathways. © 1996 Wiley‐Liss, Inc.