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

• Published in: Molecular pharmacology 2006-07, Vol.70 (1), p.90-100
• Main Authors: Partridge, John G, Puhl, 3rd, Henry L, Ikeda, Stephen R
• Format: Article
• Language: English
• Subjects: Adrenergic alpha-2 Receptor Agonists; Adrenergic alpha-Agonists - pharmacology; Animals; Blotting, Western; Calcium Channels, N-Type - physiology; Carrier Proteins - genetics; Carrier Proteins - metabolism; Carrier Proteins - physiology; Cell Line; Cells, Cultured; Eye Proteins - genetics; Eye Proteins - metabolism; Eye Proteins - physiology; Green Fluorescent Proteins - genetics; Green Fluorescent Proteins - metabolism; GTP-Binding Protein Regulators - genetics; GTP-Binding Protein Regulators - metabolism; GTP-Binding Protein Regulators - physiology; Humans; Male; Membrane Potentials - drug effects; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - metabolism; Nerve Tissue Proteins - physiology; Norepinephrine - pharmacology; Patch-Clamp Techniques; Phosphoproteins - genetics; Phosphoproteins - metabolism; Phosphoproteins - physiology; Rats; Receptors, Adrenergic, alpha-2 - physiology; Receptors, G-Protein-Coupled - physiology; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Superior Cervical Ganglion - cytology; Superior Cervical Ganglion - drug effects; Superior Cervical Ganglion - physiology; Time Factors
• ISSN: 0026-895X; 1521-0111
• DOI: 10.1124/mol.105.021394

Phosducin (PDC) has been shown in structural and biochemical experiments to bind the Gβγ subunit of heterotrimeric G-proteins. A proposed function of PDC and phosducin-like protein (PDCL) is the sequestration of “free” Gβγ from the plasma membrane, thereby terminating signaling by Gβγ. The functional impact of heterologously expressed PDC and PDCL on N-type calcium channel (Ca V 2.2) 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 Gβγ-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 Gβγ sequestering proteins that abolish the short-term inhibition of Ca 2+ channels, PDC and PDCL require prolonged agonist exposure before effects on modulation are realized.