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Investigation of the D 1 ‐D 2 dopamine receptor heteromer reveals a complex signaling mechanism not limited to G q protein activation
Author(s) -
Chun Lani Sunil,
Free R Benjamin,
Doyle Trevor B.,
Huang XiPing,
Sibley David R.
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.881.1
Subject(s) - chemistry , g protein coupled receptor , g protein , pertussis toxin , receptor , cholera toxin , biophysics , microbiology and biotechnology , biochemistry , stereochemistry , biology
The D 1 (D 1 R) and D 2 (D 2 R) dopamine receptors modulate cAMP levels via activation of G s/olf and G i/o proteins, but are also are proposed to form hetero‐oligomers that, when stimulated, initiate G q ‐mediated activation of phospholipase C (PLC) and Ca 2+ mobilization. In addition, the compound SKF83959 has been proposed to be a D 1 ‐D 2 heteromer‐selective agonist and has been used as a functional probe of the heteromer in vivo . We investigated several mechanistic and pharmacological aspects of the proposed D 1 ‐D 2 heteromer and showed that concurrent stimulation of the D 1 R and D 2 R were required to elicit Ca 2+ mobilization. Additionally, both the long and short isoforms of the D 2 R were able to form functional heteromers with the D 1 R. However, in contrast to previous reports, SKF83959 partially inhibited the D 1 ‐D 2 ‐mediated Ca 2+ response and non‐selectively exhibited high affinity for a variety of GPCRs. Finally, while overexpression of G αq did boost the D 1 ‐D 2 mediated Ca 2+ response, inhibiting the function of the G i or G s proteins, using pertussis toxin or cholera toxin, respectively, drastically reduced the Ca 2+ response, as did sequestration of G βγ subunits using catalytically inactive GRK2 mutants. These data indicate that the mechanism of D 1 ‐D 2 mediated Ca 2+ mobilization cannot be solely attributed to G q protein activation and that additional downstream, crosstalk pathways are involved. Supported by the NIH IRP.