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Dopamine D 2 Receptor Isoforms Expressed in AtT20 Cells Differentially Couple to G Proteins to Acutely Inhibit High Voltage‐Activated Calcium Channels
Author(s) -
Wolfe Shannyn E.,
Morris Stephen J.
Publication year - 1999
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1999.0732375.x
Subject(s) - gene isoform , receptor , g protein , biology , dopamine , adenylyl cyclase , agonist , gs alpha subunit , g protein coupled receptor , microbiology and biotechnology , biochemistry , biophysics , neuroscience , gene
: The dopamine D 2 receptor belongs to the serpentine superfamily of receptors, which have seven transmembrane segments and activate G proteins. D 2 receptors are known to be linked, through Gα o ‐ and Gα i ‐containing G proteins, to several signaling pathways in neuronal and secretory cells, including inhibition of adenylyl cyclase and high voltage‐activated Ca 2+ channels (HVA‐CCs). The dopamine D 2 receptor exists in two alternatively spliced isoforms, “long” and “short” (D 2L and D 2S , respectively), which have identical ligand binding sites but differ by 29 amino acids in the third intracellular loop, the proposed site for G protein interaction. This has led to the speculation that the two isoforms may interact with different G proteins. We have transfected the AtT20 cell line with either D 2L (KCL line) or D 2S (KCS line) to facilitate experimentation on the individual isoforms. Both lines show dopamine agonist‐dependent inhibition of Q‐type HVA‐CCs. We combined G protein antisense knock‐down studies with multiwavelength fluorescence video microscopy to measure changes in HVA‐CC inhibition to investigate the possibility of differential G protein coupling to this inhibition. The initial, rapid, K + depolarization‐induced increase in intracellular Ca 2+ concentration is due to influx through HVA‐CCs. Our studies reveal that both D 2 isoforms couple to Gα o to partially inhibit this influx. However, D 2L also couples to Gα 13 , whereas D 2S couples to Gα 12 . These data support the hypothesis of differential coupling of D 2 receptor isoforms to G proteins.