Abstract
Cyclic nucleotide-gated (CNG) channels are crucial for phototransduction in vertebrate rod photoreceptors. The cGMP sensitivity of these channels is modulated by diffusible intracellular messengers, including Ca2+/calmodulin, contributing to negative feedback during sensory adaptation. Membrane-associated protein tyrosine kinases and phosphatases also modulate rod CNG channels, but whether this results from direct changes in the phosphorylation state of the channel protein has been unclear. Here, we show that bovine rod CNG channel α-subunits (bRET) contain a tyrosine phosphorylation site crucial for modulation. bRET channels expressed in Xenopus oocytes exhibit modulation, whereas rat olfactory CNG channels (rOLF) do not. Chimeric channels reveal that differences in the C terminus, containing the cyclic nucleotide-binding domain, account for this difference. One specific tyrosine in bRET (Y498) appears to be crucial; replacement of this tyrosine in bRET curtails modulation, whereas installation into rOLF confers modulability. As the channel becomes dephosphorylated, there is an increase in the rate of spontaneous openings in the absence of ligand, indicating that changes in the phosphorylation state affect the allosteric gating equilibrium. Moreover, we find that dephosphorylation, which favors channel opening, requires open channels, whereas phosphorylation, which promotes channel dosing, requires closed channels. Hence, modulation by changes in tyrosine phosphorylation is activity-dependent and may constitute a positive feedback mechanism, contrasting with negative feedback systems underlying adaptation.
| Original language | English |
|---|---|
| Pages (from-to) | 4786-4795 |
| Number of pages | 10 |
| Journal | Journal of Neuroscience |
| Volume | 19 |
| Issue number | 12 |
| State | Published - Jun 15 1999 |
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Keywords
- Cyclic GMP
- Phosphorylation
- Phototransduction
- Protein kinase
- Rod photoreceptor
- Tyrosine kinase
ASJC Scopus subject areas
- Neuroscience(all)
Cite this
Activity-dependent modulation of rod photoreceptor cyclic nucleotide- gated channels mediated by phosphorylation of a specific tyrosine residue. / Molokanova, Elena; Maddox, Floyd; Luetje, Charles W; Kramer, Richard H.
In: Journal of Neuroscience, Vol. 19, No. 12, 15.06.1999, p. 4786-4795.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Activity-dependent modulation of rod photoreceptor cyclic nucleotide- gated channels mediated by phosphorylation of a specific tyrosine residue
AU - Molokanova, Elena
AU - Maddox, Floyd
AU - Luetje, Charles W
AU - Kramer, Richard H.
PY - 1999/6/15
Y1 - 1999/6/15
N2 - Cyclic nucleotide-gated (CNG) channels are crucial for phototransduction in vertebrate rod photoreceptors. The cGMP sensitivity of these channels is modulated by diffusible intracellular messengers, including Ca2+/calmodulin, contributing to negative feedback during sensory adaptation. Membrane-associated protein tyrosine kinases and phosphatases also modulate rod CNG channels, but whether this results from direct changes in the phosphorylation state of the channel protein has been unclear. Here, we show that bovine rod CNG channel α-subunits (bRET) contain a tyrosine phosphorylation site crucial for modulation. bRET channels expressed in Xenopus oocytes exhibit modulation, whereas rat olfactory CNG channels (rOLF) do not. Chimeric channels reveal that differences in the C terminus, containing the cyclic nucleotide-binding domain, account for this difference. One specific tyrosine in bRET (Y498) appears to be crucial; replacement of this tyrosine in bRET curtails modulation, whereas installation into rOLF confers modulability. As the channel becomes dephosphorylated, there is an increase in the rate of spontaneous openings in the absence of ligand, indicating that changes in the phosphorylation state affect the allosteric gating equilibrium. Moreover, we find that dephosphorylation, which favors channel opening, requires open channels, whereas phosphorylation, which promotes channel dosing, requires closed channels. Hence, modulation by changes in tyrosine phosphorylation is activity-dependent and may constitute a positive feedback mechanism, contrasting with negative feedback systems underlying adaptation.
AB - Cyclic nucleotide-gated (CNG) channels are crucial for phototransduction in vertebrate rod photoreceptors. The cGMP sensitivity of these channels is modulated by diffusible intracellular messengers, including Ca2+/calmodulin, contributing to negative feedback during sensory adaptation. Membrane-associated protein tyrosine kinases and phosphatases also modulate rod CNG channels, but whether this results from direct changes in the phosphorylation state of the channel protein has been unclear. Here, we show that bovine rod CNG channel α-subunits (bRET) contain a tyrosine phosphorylation site crucial for modulation. bRET channels expressed in Xenopus oocytes exhibit modulation, whereas rat olfactory CNG channels (rOLF) do not. Chimeric channels reveal that differences in the C terminus, containing the cyclic nucleotide-binding domain, account for this difference. One specific tyrosine in bRET (Y498) appears to be crucial; replacement of this tyrosine in bRET curtails modulation, whereas installation into rOLF confers modulability. As the channel becomes dephosphorylated, there is an increase in the rate of spontaneous openings in the absence of ligand, indicating that changes in the phosphorylation state affect the allosteric gating equilibrium. Moreover, we find that dephosphorylation, which favors channel opening, requires open channels, whereas phosphorylation, which promotes channel dosing, requires closed channels. Hence, modulation by changes in tyrosine phosphorylation is activity-dependent and may constitute a positive feedback mechanism, contrasting with negative feedback systems underlying adaptation.
KW - Cyclic GMP
KW - Phosphorylation
KW - Phototransduction
KW - Protein kinase
KW - Rod photoreceptor
KW - Tyrosine kinase
UR - http://www.scopus.com/inward/record.url?scp=0033564047&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0033564047&partnerID=8YFLogxK
M3 - Article
C2 - 10366613
AN - SCOPUS:0033564047
VL - 19
SP - 4786
EP - 4795
JO - Journal of Neuroscience
JF - Journal of Neuroscience
SN - 0270-6474
IS - 12
ER -