Abstract
Protein phosphorylation is an important mechanism in the modulation of voltage-dependent ionic channels. In squid giant axons, the potassium delayed rectifier channel is modulated by an ATP-mediated phosphorylation mechanism, producing important changes in amplitude and kinetics of the outward current. The characteristics and biophysical basis for the phosphorylation effects have been extensively studied in this preparation using macroscopic, single-channel and gating current experiments. Phosphorylation produces a shift in the voltage dependence of all voltage-dependent parameters including open probability, slow inactivation, first latency, and gating charge transferred. The locus of the effect seems to be located in a fast 20 pS channel, with characteristics of delayed rectifier, but at least another channel is phosphorylated under our experimental conditions. These results are interpreted quantitatively with a mechanistic model that explains all the data. In this model the shift in voltage dependence is produced by electrostatic interactions between the transferred phosphate and the voltage sensor of the channel.
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Augustine, C. K., and Bezanilla, F. (1990). “Phosphorylation modulates potassium conductance and gating current of perfused giant axons of squid,”J. Gen. Physiol. 95, 245–272.
Bezanilla, F., and Vandeberg, C. (1990. “The cut-open axon technique,” inSquid as Experimental Animals. (Gilbert, D. L., Adelman, W. J., Jr., and Arnold J. M., eds.), Plenum Press, New York, pp. 153–159.
Bezanilla, F., Vergara, J., and Taylor, R. E. (1982). “Voltage clamping of excitable membranes,” inMethods of Experimental Physics (Ehrenstein, G., and Lecar, H., eds.), (Vol. 20, Academic Press, New York, pp. 445–511.
Bezanilla, F., Caputo, C., Dipolo, R., and Rojas, H. (1986). “Potassium conductance of the squid giant axon is modulated by ATP,”Proc. Nat. Acad. Sci. USA 83, 2743–2745.
Brown, A., and Birmbaumer, L. (1990). “Ionic channels and their regulation by G protein subunits,”Annu. Rev. Physiol. 52, 197–213.
Chabala, L. D. (1984). “The kinetics of recovery and development of potassium channel inactivation in perfused squid (Loligo pealei) giant axons,”J. Physiol. (London)356, 193–220.
Clay, J. R. (1989). “Slow inactivation and reactivation of the K+ channel in squid axons. A tail current analysis,”Biophys. J. 55, 407–414.
Cole, K. C., and Moore, J. W. (1960). “Potassium ion current in the squid giant axon: dynamic characteristic,”Biophys. J. 1, 1–14.
Grahame, D. C. (1947). “The electrical double layer and the theory of electrocapillarity,”Chem. Rev. 41, 441–501.
Hamill, O. P., Marty, A., Neher, E., Sakmann, B., and Sigworth, F. J. (1981). “Improved patch-clamp techniques for recording from cell and cell-free membrane patches,”Pflugers Arch. 391, 85–100.
Kaczmarek, L. R., and Levitan, I. B. (1987).The Biochemical Control of Neuronal Excitability, Oxford University Press.
Levitan, I. B. (1989). “Modulation of ion channels in neurons and other cells,”Annu. Rev. Neurosci. 11, 119–136.
Latorre, R., Oberhauser, A., Labarca, P., and Alvarez, O. (1989). “Varieties of calcium. Activated potassium channels,”Ann. Rev. Physiol. 51, 385–399.
Llano, I., Webb, C. K., and Bezanilla, F. (1988). “Potassium conductance of the squid giant axon: Single channel studies,”J. Gen. Physiol. 92, 179–196.
Perozo, E., and Bezanilla, F. (1989). “ATP-mediated K-channel phosphorylation in squid axons is further potentiated in the presence of GTP-γ-S,”Biophys. J. 55, 587a.
Perozo, E., and Bezanilla, F. (1990). “Phosphorylation effects voltage gating of K+ channel by electrostatic interactions,”Neuron 5, 685–690.
Perozo, E., and Bezanilla, F. (1991). “Kinetic and steady-state properties of slow inactivation of the delayed rectifier K+ channel,”Biophys. J. 59, 405a.
Perozo, E., Bezanilla, F., and Dipolo, R. (1989). “Modulation of K channels in dialyzed squid axons. ATP-mediated phosphorylation,J. Gen. Physiol. 93, 1195–1218.
Perozo, E., Vandenberg, C., Jong, D. S., and Bezanilla, F. (1991a). “Single channel studies of the phosphorylation of K+ channels in the squid giant axon. I. Steady-state conditions,”J. Gen. Physiol., in press.
Perozo, E., Jong, D. S., and Bezanilla, F. (1991b). “Single-channel studies of the phosphorylation of K+ channels in the squid giant axon. II. Nonstationary conditions,”J. Gen. Physiol., in press.
Schwarz, T. L., Tempel, B. L., Papazian, D. M., Jan, Y. N., and Yan, L. Y. (1988). “Multiple potassium-channel components are produced by alternative splicing at the Shaker locus in Drosophila,”Nature (London)331, 137–142.
Siegelbaum, S. A., Camardo, J. S., and Kandel, E. R. (1982). “Serotonin and cyclic AMP close single Kp channels inAplysia sensory neurons,”Nature (London)299, 413–417.
Stimers, J. R., Bezanilla, F., and Taylor, R. E. (1987). “Sodium channel gating current. Origin of the rising phase,”J. Gen. Physiol. 89, 521–540.
White, M. M., and Bezanilla, F. (1985). “Activation of squid axon K+ channels. Ionic and gating current studies,”J. Gen. Physiol. 85, 539–554.
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Perozo, E., Bezanilla, F. Phosphorylation of K+ channels in the squid giant axon. A mechanistic analysis. J Bioenerg Biomembr 23, 599–613 (1991). https://doi.org/10.1007/BF00785813
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DOI: https://doi.org/10.1007/BF00785813