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Specific residues of the 5‐HT1A receptor second and third intracellular domain C‐terminal determine Gβγ or Gαi coupling specificity, respectively
Author(s) -
Kushwaha Neena,
Harwood Shan C,
Wilson Ariel M,
Albert Paul R
Publication year - 2006
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.20.5.a918-c
Subject(s) - intracellular , mutant , receptor , signal transduction , coupling (piping) , chemistry , biophysics , microbiology and biotechnology , residue (chemistry) , biology , stereochemistry , biochemistry , gene , materials science , metallurgy
To address their role in 5‐HT1A receptor–G protein coupling, over sixty random point mutant 5‐HT1A receptors in the second intracellular loop C‐terminal domain (Ci2) ( 143 DYVNKRTPRR 152 ) were generated and most retained agonist binding. Mutants were tested for Gβγ signaling to ACII or PLC, and Gαi coupling. Most Ci2 mutations blocked 5‐HT1A signaling to Gβγ, but several also affected Gαi signaling. Ci2 residues K147, R148/151/152 and P150 were essential for coupling, consistent with an obligatory structural role. Polar residues (T149, N146) were required for Gβγ but not Gαi coupling, suggesting a selective interface with Gβγ. The Y144 residue directed specificity for both Gβγ and Gαi pathways and is predicted to form hydrogen bonds with D133/R134 (Ni2 DRY motif) and E340 (Ci3) to stabilize the G‐protein coupling domain. Consistent with a primary role of Ci3 in Gαi coupling, E340 mutants preferentially abrogated Gαi signaling, but one mutant partly blocked Gβγ signaling as well. Thus, the 5‐HT1A receptor Ci2 domain determines Gβγ specificity and stabilizes Gαi‐mediated signaling, while the Ci3 domain primarily directs Gαi coupling and stabilizes Gβγ coupling. Supported by CIHR.