Phosducin and phosducin-like protein attenuate G-protein-coupled receptor-mediated inhibition of voltage-gated calcium channels in rat sympathetic neurons.
Phosducin (PDC) has been shown in structural and biochemical experiments to bind the Gbetagamma subunit of heterotrimeric G-proteins. A proposed function of PDC and phosducin-like protein (PDCL) is the sequestration of "free" Gbetagamma from the plasma membrane, thereby terminating signaling by Gbetagamma. 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 Gbetagamma-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 microM L-glutamate. Neurons expressing PDC or PDCL maintained suppression of inhibition after re-exposure to agonist. Unlike other Gbetagamma sequestering proteins that abolish the short-term inhibition of Ca2+ channels, PDC and PDCL require prolonged agonist exposure before effects on modulation are realized.
Partridge
John G
JG
Laboratory of Molecular Physiology, NIH/NIAAA/DICBR, 5625 Fishers Lane, Room TS11A, MSC 9411, Bethesda, MD 20892-9411, USA.
Puhl
Henry L
HL
Ikeda
Stephen R
SR
D058647:Adrenergic alpha-2 Receptor Agonists; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D020864:Calcium Channels, N-Type / Q000502:physiology*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002460:Cell Line; D002478:Cells, Cultured; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D020555:GTP-Binding Protein Regulators / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D018832:Molecular Chaperones; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D018341:Receptors, Adrenergic, alpha-2 / Q000502:physiology; D043562:Receptors, G-Protein-Coupled / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017783:Superior Cervical Ganglion / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
D058647:Adrenergic alpha-2 Receptor Agonists; D000316:Adrenergic alpha-Agonists; C503279:Cacna1b protein, rat; D020864:Calcium Channels, N-Type; D002352:Carrier Proteins; D005136:Eye Proteins; D020555:GTP-Binding Protein Regulators; D018832:Molecular Chaperones; D009419:Nerve Tissue Proteins; C098789:PDCL protein, human; C498320:Pdcl protein, rat; D010750:Phosphoproteins; D018341:Receptors, Adrenergic, alpha-2; D043562:Receptors, G-Protein-Coupled; D011993:Recombinant Fusion Proteins; C065631:phosducin; D049452:Green Fluorescent Proteins; D009638:Norepinephrine