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First published on April 11, 2006; DOI: 10.1124/mol.105.021394

0026-895X/06/7001-90-100$20.00
Mol Pharmacol 70:90-100, 2006

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Phosducin and Phosducin-like Protein Attenuate G-Protein-Coupled Receptor-Mediated Inhibition of Voltage-Gated Calcium Channels in Rat Sympathetic Neurons

John G. Partridge1, Henry L. Puhl, III, and Stephen R. Ikeda

Laboratory of Molecular Physiology, Section on Transmitter Signaling, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland

Phosducin (PDC) has been shown in structural and biochemical experiments to bind the Gbeta{gamma} subunit of heterotrimeric G-proteins. A proposed function of PDC and phosducin-like protein (PDCL) is the sequestration of "free" Gbeta{gamma} from the plasma membrane, thereby terminating signaling by Gbeta{gamma}. The functional impact of heterologously expressed PDC and PDCL on N-type calcium channel (CaV2.2) modulation was examined in sympathetic neurons, isolated from rat superior cervical ganglia, using whole-cell voltage clamp. Expression of PDC and PDCL attenuated voltage-dependent inhibition of N-type calcium channels, a Gbeta{gamma}-dependent process, in a time-dependent fashion. Calcium current inhibition after short-term exposure to norepinephrine was minimally altered by PDC or PDCL expression. However, in the continued presence of norepinephrine, PDC or PDCL relieved calcium channel inhibition compared with control neurons. We observed similar results after activation of heterologously expressed metabotropic glutamate receptors with 100 µM L-glutamate. Neurons expressing PDC or PDCL maintained suppression of inhibition after re-exposure to agonist. Unlike other Gbeta{gamma} sequestering proteins that abolish the short-term inhibition of Ca2+ channels, PDC and PDCL require prolonged agonist exposure before effects on modulation are realized.

Received December 1, 2005; accepted April 11, 2006

Address correspondence to: Dr. Stephen R Ikeda, Laboratory of Molecular Physiology, NIH/NIAAA/DICBR, 5625 Fishers Lane, Room TS11A, MSC 9411, Bethesda, MD 20892-9411. E-mail: sikeda{at}mail.nih.gov




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C. M. Krispel, M. Sokolov, Y.-M. Chen, H. Song, R. Herrmann, V. Y. Arshavsky, and M. E. Burns
Phosducin Regulates the Expression of Transducin {beta}{gamma} Subunits in Rod Photoreceptors and Does Not Contribute to Phototransduction Adaptation
J. Gen. Physiol., August 27, 2007; 130(3): 303 - 312.
[Abstract] [Full Text] [PDF]


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