Rectification of CGMP-activated Channels Induced by Phosphorylation in Dogfish Retinal 'on' Bipolar Cells
Overview
Authors
Affiliations
1. Whole-cell current responses to brief flashes were obtained from voltage-clamped 'on' bipolar cells in dark-adapted dogfish retinal slices. When internal Ca2+ was buffered to low levels, the current-voltage (I-V) relation of their flash responses was linear, with a reversal potential near 0 mV. 2. On elevating internal Ca2+ the light-dependent I-V relation showed outward rectification, such that the current response to a flash decreased e-fold for a hyperpolarization of 22 mV. 3. Inclusion of a CaMKII inhibitory peptide in the patch-pipette solution removed the rectification even in the presence of 50 microM Ca2+. 4. These results are consistent with CaMKII phosphorylation of cGMP-activated channels leading to a voltage-dependent reduction in conductance (outward rectification) and a reduced light response. The voltage-dependent property suggests that phosphorylation creates an energy barrier near the outer part of the channel, reducing the flow principally of monovalent cations. 5. This is the first reported instance of CaMKII phosphorylation acting to change the electrical characteristics of a membrane channel from linear to rectifying. 6. Ca2+-dependent desensitization by background light and channel rectification may underlie the change in centre-surround organization of the visual system with light adaptation.
Activation mechanism of a neuromodulator-gated pacemaker ionic current.
Gray M, Daudelin D, Golowasch J J Neurophysiol. 2017; 118(1):595-609.
PMID: 28446585 PMC: 5511868. DOI: 10.1152/jn.00743.2016.
Voltage Dependence of a Neuromodulator-Activated Ionic Current.
Gray M, Golowasch J eNeuro. 2016; 3(2).
PMID: 27257619 PMC: 4874538. DOI: 10.1523/ENEURO.0038-16.2016.
Regulation of ON bipolar cell activity.
Snellman J, Kaur T, Shen Y, Nawy S Prog Retin Eye Res. 2008; 27(4):450-63.
PMID: 18524666 PMC: 2632956. DOI: 10.1016/j.preteyeres.2008.03.003.
Schein S, Ahmad K Biophys J. 2006; 91(9):3257-67.
PMID: 16920838 PMC: 1614493. DOI: 10.1529/biophysj.106.091744.
Modulation by brain natriuretic peptide of GABA receptors on rat retinal ON-type bipolar cells.
Yu Y, Cao L, Yang X J Neurosci. 2006; 26(2):696-707.
PMID: 16407567 PMC: 6674405. DOI: 10.1523/JNEUROSCI.3653-05.2006.