Interaction of the alpha(1B)-adrenergic receptor with gC1q-R, a multifunctional protein.
gC1q-R, a multifunctional protein, was found to bind with the carboxyl-terminal cytoplasmic domain of the alpha(1B)-adrenergic receptor (173 amino acids, amino acids 344-516) in a yeast two-hybrid screen of a cDNA library prepared from the rat liver. In a series of studies with deletion mutants in this region, the ten arginine-rich amino acids (amino acids 369-378) were identified as the site of interaction. The interaction was confirmed by specific co-immunoprecipitation of gC1q-R with full-length alpha(1B)-adrenergic receptors expressed on transfected COS-7 cells, as well as by fluorescence confocal laser scanning microscopy, which showed co-localization of these proteins in intact cells. Interestingly, the alpha(1B)-adrenergic receptors were exclusively localized to the region of the plasma membrane in COS-7 cells that expressed the alpha(1B)-adrenergic receptor alone, whereas gC1q-R was localized in the cytoplasm in COS-7 cells that expressed gC1q-R alone; however, in cells that co-expressed alpha(1B)-adrenergic receptors and gC1q-R, most of the alpha(1B)-adrenergic receptors were co-localized with gC1q-R in the intracellular region, and a remarkable down-regulation of receptor expression was observed. These observations suggest a new role for the previously identified complement regulatory molecule, gC1q-R, in regulating the cellular localization and expression of the alpha(1B)-adrenergic receptors.
Xu
Z
Z
Department of Molecular, Cell Pharmacology, National Children's Medical Research Center, Taishido 3-35-31, Setagaya-ku, Tokyo, 154-1809 Japan.
Hirasawa
A
A
Shinoura
H
H
Tsujimoto
G
G
D000818:Animals; D019556:COS Cells; D003167:Complement Activation; D018960:Hyaluronan Receptors; D008562:Membrane Glycoproteins / Q000378:metabolism; D024101:Mitochondrial Proteins; D009154:Mutation; D011485:Protein Binding; D051381:Rats; D011942:Receptors, Adrenergic, alpha / Q000235:genetics / Q000378:metabolism*; D011951:Receptors, Complement / Q000378:metabolism*; D012441:Saccharomyces cerevisiae; D014162:Transfection
C490195:C1qbp protein, rat; D018960:Hyaluronan Receptors; D008562:Membrane Glycoproteins; D024101:Mitochondrial Proteins; D011942:Receptors, Adrenergic, alpha; D011951:Receptors, Complement; C032402:complement 1q receptor