Differential signaling of dopamine-D2S and -D2L receptors to inhibit ERK1/2 phosphorylation.
Although they have distinct functions, the signaling of dopamine-D(2) receptor short and long isoforms (D(2)S and D(2)L) is virtually identical. We compared inhibitory regulation of extracellular signal-regulated kinases (ERK1/2) in GH4 pituitary cells separately transfected with these isoforms. Activation of rat or human dopamine-D(2)S, muscarinic or somatostatin receptors inhibited thyrotropin-releasing hormone-induced ERK1/2 phosphorylation, while the D(2)L receptor failed to inhibit this response. In order to address the structural basis for the differential signaling of D(2)S and D(2)L receptors, we examined the D(2)L-SS mutant, in which a protein kinase C (PKC) pseudosubstrate site that is present in the D(2)L but not D(2)S receptor was converted to a consensus PKC site. In transfected GH4 cells, the D(2)L-SS mutant inhibited thyrotropin-releasing hormone-induced ERK1/2 phosphorylation almost as strongly as the D(2)S receptor. A D(2)S-triple mutant that eliminates PKC sites involved in D(2)S receptor desensitization also inhibited ERK1/2 activation. Similarly, in striatal cultures, the D(2)-selective agonist quinpirole inhibited potassium-stimulated ERK1/2 phosphorylation, indicating the presence of this pathway in neurons. In conclusion, the D(2)S and D(2)L receptors differ in inhibitory signaling to ERK1/2 due to specific residues in the D(2)L receptor alternatively spliced domain, which may account for differences in their function in vivo.
Van-Ham
Irit Itzhaki
II
Departments of Medicine and Cellular and Molecular Medicine, and Ottawa Health Research Institute (Neuroscience), University of Ottawa, Ottawa, Ontario, Canada.
Banihashemi
Behzad
B
Departments of Medicine and Cellular and Molecular Medicine, and Ottawa Health Research Institute (Neuroscience), University of Ottawa, Ottawa, Ontario, Canada.
Wilson
Ariel M
AM
Departments of Medicine and Cellular and Molecular Medicine, and Ottawa Health Research Institute (Neuroscience), University of Ottawa, Ottawa, Ontario, Canada.
Jacobsen
Kirsten X
KX
Departments of Medicine and Cellular and Molecular Medicine, and Ottawa Health Research Institute (Neuroscience), University of Ottawa, Ottawa, Ontario, Canada.
Czesak
Margaret
M
Departments of Medicine and Cellular and Molecular Medicine, and Ottawa Health Research Institute (Neuroscience), University of Ottawa, Ottawa, Ontario, Canada.
Albert
Paul R
PR
Departments of Medicine and Cellular and Molecular Medicine, and Ottawa Health Research Institute (Neuroscience), University of Ottawa, Ottawa, Ontario, Canada.
D017398:Alternative Splicing / Q000235:genetics; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003342:Corpus Striatum / Q000378:metabolism; D004298:Dopamine / Q000378:metabolism*; D018491:Dopamine Agonists / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism*; D006801:Humans; D009154:Mutation / Q000235:genetics; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D010902:Pituitary Gland / Q000378:metabolism; D020033:Protein Isoforms / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D011493:Protein Kinase C / Q000737:chemistry; D017434:Protein Structure, Tertiary / Q000235:genetics; D051381:Rats; D017448:Receptors, Dopamine D2 / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism / Q000494:pharmacology
D018491:Dopamine Agonists; D020033:Protein Isoforms; D017448:Receptors, Dopamine D2; C113776:dopamine D2L receptor; D013973:Thyrotropin-Releasing Hormone; D011493:Protein Kinase C; D048049:Extracellular Signal-Regulated MAP Kinases; D004298:Dopamine