Light-induced reduction of cytoplasmic free calcium in retinal rod outer segment

Yau, King Wai; Nakatani, Keigo

doi:10.1038/313579a0

Cited by 354 publications

(209 citation statements)

References 28 publications

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“…Since Ca2+ levels in ROSs reflect recent light signaling, and neuronal adenylyl cyclase is commonly regulated by Ca2+/calmodulin, the possibility that ROS adenylyl cyclase might be regulated by Ca2+ was tested. In bovine ROS preparations in which soluble components are retained, adenylyl cyclase activity exhibited a striking dependence on free [Ca2+] over its physiological range (7,(23)(24)(25) in ROS cytosol (Fig. 2).…”

Section: Methodsmentioning

confidence: 99%

Regulation of phosducin phosphorylation in retinal rods by Ca2+/calmodulin-dependent adenylyl cyclase.

Willardson

Wilkins

Yoshida

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

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The phosphoprotein phosducin (Pd) regulates many guanine nucleotide binding protein (G protein)-linked signaling pathways. In visual signal transduction, unphosphorylated Pd blocks the interaction of light-activated rhodopsin with its G protein (Gt) by binding to the fry subunits of Gt and preventing their association with the Gta subunit. When Pd is phosphorylated by cAMP-dependent protein kinase, it no longer inhibits Gt subunit interactions.Thus, factors that determine the phosphorylation state of Pd in rod outer segments are important in controlling the number of Gts available for activation by rhodopsin. The cyclic nucleotide dependencies of the rate of Pd phosphorylation by endogenous cAMP-dependent protein kinase suggest that cAMP, and not cGMP, controls Pd phosphorylation. The synthesis of cAMP by adenylyl cyclase in rod outer segment preparations was found to be dependent on Ca2+ and calmodulin. The Ca2+ dependence was within the physiological range of Ca2+ concentrations in rods (K./2 = 230 + 9 nM) and was highly cooperative (napp = 3.6 + 0.5). Through its effect on adenylyl cyclase and cAMP-dependent protein kinase, physiologically high Ca2+ (1100 nM) was found to increase the rate of Pd phosphorylation 3-fold compared to the rate of phosphorylation at physiologically low Ca2+ (8 nM). No evidence for Pd phosphorylation by other Ca2+-dependent kinases was found. These results suggest that Ca2+ can regulate the light response at the level of Gt activation through its effect on the phosphorylation state of Pd.

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Section: Methodsmentioning

confidence: 99%

Regulation of phosducin phosphorylation in retinal rods by Ca2+/calmodulin-dependent adenylyl cyclase.

Willardson

Wilkins

Yoshida

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

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“…In addition the channels' closure is accompanied by a decrease in the cytoplasmic free [Ca 2÷] [2], which in turn controis the cell recovery by modulating the activity of guanylate cyclase [3~]. Another point of Ca 2÷ action upon the process recovery is believed to be rhodopsin phosphorylation [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Calcium‐sensitive control of rhodopsin phosphorylation in the reconstituted system consisting of photoreceptor membranes, rhodopsin kinase and recoverin

1994

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Rhodopsin phosphorylation in the reconstituted system consisting of urea-washed photoreceptor membranes, rhodopsin kinase and recoverin is regulated by Ca2+: the process takes place at low [Ca 2÷] but is suppressed at high [Ca2+]. In the absence of recoverin, rhodopsin kinase is active irrespective of the cation concentration used. Hence, recoverin is an inhibitor (at high [Ca2+]) but not an activator of rhodopsin kinase. Based jointly on these data obtained on the reconstituted system and on our preceding experiments on rod outer segments suspension, one may conclude that (i) the function of recoverin in retina rod cells is the Ca2+-sensitive control of rhodopsin phosphorylation and (ii) the presence of recoverin is essential and sufficient to provide rhodopsin kinase with the Ca 2÷ sensitivity.

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“…Ca ~+ entry in the dark provides negative feedback control of cGMP synthesis (LoUey and Racz, 1982;Pepe, Panfoli, and Cugnoli, 1986;Hodgkin and Nunn, 1988;Koch and Stryer, 1988;Dizhoor, Ray, Kumar, Niemi, Spencer, Brolley, Walsh, Philipov, Hurley, and Stryer, 1991). A light-induced drop in internal Ca 2+ concentration (Yau and Nakatani, 1985;McNaughton, Cervetto, and Nunn, 1986) is important for the recovery of the light response and for light adaptation (Matthews, Murphy, Fain, and Lamb, 1988;Nakatani and Yau, 1988b).…”

Section: Introductionmentioning

confidence: 99%

Interactions between divalent cations and the gating machinery of cyclic GMP-activated channels in salamander retinal rods.

Karpen

Brown

Stryer

et al. 1993

The Journal of General Physiology

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The effects of divalent cations on the gating of the cGMP-activated channel, and the effects of gating on the movement of divalent cations in and out of the channel's pore were studied by recording macroscopic currents in excised membrane patches from salamander retinal rods. The fractional block of cGMPactivated Na + currents by internal and external Mg 2+ as well as internal Ca ~+ was nearly independent ofcGMP concentration. This indicates that Mg 2÷ and Ca ~÷ bind with similar affinity to open and closed states of the channel. In contrast, the efficiency of block by internal Cd 2÷ or Zn 2÷ increased in proportion to the fraction of open channels, indicating that these ions preferentially occupy open channels. The kinetics of block by internal Ni 2+, which competes with Mg z÷ but blocks more slowly, were found to be unaffected by the fraction of channels open. External Ni z÷, however, blocked and unblocked much more rapidly when channels were mostly open. This suggests that within the pore a gate is located between the binding site(s) for ions and the extraceUular mouth of the channel. Micromolar concentrations of the transition metal divalent cations Ni 2÷, Cd 2+, Zn ~+, and Mn 2÷ applied to the cytoplasmic surface of a patch potentiated the response to subsaturating concentrations of cGMP without affecting the maximum current induced by saturating cGMP. The concentration of cGMP that opened half the channels was often lowered by a factor of three or more. Potentiation persisted after the experimental chamber was washed with divalent-free solution and fresh cGMP was applied, indicating that it does not result from an interaction between divalent cations and cGMP in solution; 1 mM EDTA or isotonic MgCl~ reversed potentiation. Voltage-jump experiments suggest that potentiation results from an increase in the rate of cGMP binding. Lowering the ionic strength of the bathing solution enhanced potentiation, suggesting that it involves electrostatic interactions. The strong electrostatic effect on cGMP binding and absence of effect on ion permeation through open channels implies that the cGMP binding sites on the channel are well separated from the permeation pathway.Address reprint requests to Dr.

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Light-induced reduction of cytoplasmic free calcium in retinal rod outer segment

Cited by 354 publications

References 28 publications

Regulation of phosducin phosphorylation in retinal rods by Ca2+/calmodulin-dependent adenylyl cyclase.

Regulation of phosducin phosphorylation in retinal rods by Ca2+/calmodulin-dependent adenylyl cyclase.

Calcium‐sensitive control of rhodopsin phosphorylation in the reconstituted system consisting of photoreceptor membranes, rhodopsin kinase and recoverin

Interactions between divalent cations and the gating machinery of cyclic GMP-activated channels in salamander retinal rods.

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