Article,

Expression of phosducin in a phosducin-negative cell line reveals functions of a Gbetagamma-binding protein

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J Biol Chem, 271 (37): 22546-51 (September 1996)Schulz, K Danner, S Bauer, P Schroder, S Lohse, M J Research Support, Non-U.S. Gov't United states The Journal of biological chemistry J Biol Chem. 1996 Sep 13;271(37):22546-51..

Abstract

Phosducin is a member of the large group of proteins that bind to G-protein betagamma-subunits (Gbetagamma) and whose biological functions are often unknown. Human A431 cells do not contain detectable amounts of phosducin. We generated A431 cells expressing phosducin at a level of approximately 1 pmol/mg of cytosolic protein, which is approximately 10% of the phosducin level in brain. cAMP accumulation in response to beta2-adrenergic receptor agonists was enhanced at early times in phosducin-expressing cells, but reached a lower plateau than in control cells. Permeabilization of the cells with digitonin did not change this pattern, but allowed the introduction of specific inhibitors: antibodies to phosducin abolished all differences between the two cell lines. Inhibitors of the beta-adrenergic receptor kinase abolished the differences at early time points. An almost complete loss of beta2-adrenergic receptor desensitization in the phosducin-expressing cells was also observed when intact cells were desensitized and receptor function was then determined in membrane preparations. Inhibition of protein kinase A accentuated the effects of phosducin, suggesting that also in vivo phosducin is regulated by this kinase. These data indicate that phosducin affects G-protein-mediated signaling in at least two ways: it dampens the overall responsiveness, and it impairs the rapid desensitization mediated by the beta-adrenergic receptor kinase.

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