Phototransduction in the microvillar visual cell of Limulus: Electrophysiology and biochemistry

Becker, Ursula; Nuske, Joachim H.; Stieve, H.

doi:10.1016/0278-4327(88)90027-2

Cited by 5 publications

(2 citation statements)

References 113 publications

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“…4. (For more detailed models see Becker et al (1988) and Payne et al (1988).) The active metarhodopsin presumably binds specific G-proteins.…”

Section: Enzyme Cascadementioning

confidence: 99%

Biophysical processes in invertebrate photoreceptors: recent progress and a critical overview based on Limulus photoreceptors

Nagy

1991

Quart. Rev. Biophys.

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Limulus ventral nerve photoreceptor, a classical preparation for the study the phototransduction in invertebrate eyes, seems to have a very complex mechanism to transform light energy into a physiological signal. Although the main function of the photoreceptor is to change the membrane conductance according to the illumination, the cell has voltage-activated conductances as well. The voltage-gated conductances are matched to the light-activated ones in the sense that they make the function of the cell more efficient. The complex mechanism of phototransduction and the presence of four different voltage-gated conductance in Limulus ventral nerve photoreceptors indicate that these cells are far less differentiated than the photoreceptor cells of vertebrates. Indications accumulated in recent years support the view that the ventral photoreceptor of Limulus has different light-activated macroscopic current components, ion channels and terminal transmitters. After conclusions from macroscopic current measurements (Payne, 1986; Payne et al. 1986 a, b), direct evidence was presented by single-channel (Nagy & Stieve, 1990 a, b; Nagy, 1990 a, b) and macroscopic current measurements (Deckert et al. 1991 a, b) for three different light-activated conductances. It has been shown that two of these conductances are stimulated by two different excitation mechanisms. The two mechanisms, having different kinetics, release probably two different transmitters. One of them might be the cGMP (Johnson et al. 1986), the other one the calcium ion (Payne et al. 1986 a, b). However, the biochemical processes which link the rhodopsin molecules and the ion channels are not known. The unknown chemical details of the phototransduction result in a delay for the mathematical description of the biophysical mechanisms. More biochemical details are known about the adaptation mechanism. It was found that inositol 1,4,5-trisphosphate is a messenger for the release of calcium ions from the intracellular stores and that calcium ions are the messengers for adaptation (Payne et al. 1986 b; Payne & Fein, 1987). Concerning the mechanism of calcium release, it was revealed that a negative feedback acts on the enzyme cascade to regulate the internal calcium level and to protect the stores against complete emptying (Payne et al. 1988, 1990). Calcium ions also play an important role in the excitation mechanism. (a) In [Ca2+]i-depleted cells the light-induced current was increased after intracellular Ca2+ injection, suggesting that calcium is necessary for the transduction mechanism (Bolsover & Brown, 1985).(ABSTRACT TRUNCATED AT 400 WORDS)

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“…4. (For more detailed models see Becker et al (1988) and Payne et al (1988).) The active metarhodopsin presumably binds specific G-proteins.…”

Section: Enzyme Cascadementioning

confidence: 99%

Biophysical processes in invertebrate photoreceptors: recent progress and a critical overview based on Limulus photoreceptors

Nagy

1991

Quart. Rev. Biophys.

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“…In Limulus ventral nerve photoreceptors a conformational change of a rhodopsin molecule, caused by absorption of a photon, triggers an enzmye cascade resulting in an increase in the concentration of a putative intracellular transmitter (Cone 1973;Becker et al 1988;Stieve 1989). Transmitter molecules bind to channel proteins, increase the open probability and depolarize the cell.…”

Section: Introductionmentioning

confidence: 99%

Light-activated single channel currents in Limulus ventral nerve photoreceptors

Nagy

Stieve

1990

Eur Biophys J

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Light-activated single channel currents were measured in Limulus ventral photoreceptors in the cellattached configuration at 14°C. The results show three channel types with conductances of 6.2, 10.4 and 28.7 pS. The most active channels have the 10 pS conductance; the open time histograms of these channels could be best fitted by the sum of two exponentials with time constants (and weights) of 0.58 ms (0.78) and 4.32 ms (0.22), suggesting two populations of channels or two open states. The mean open time was 1.38 ms.The open time histogram of the channels with the 29 pS conductance could be best fitted by a single exponential with a time constant of 3.35 ms. First latencies of the 10 pS channels were between 40 and 280 ms but those of the 29 pS conductance channels were > 300 ms. These findings suggest that the two channel types are gated by two different intracellular transmitters or mechanisms.

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Microvillar Photoreceptor Cells of Invertebrates

Stieve

1990

Sensory Transduction

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Phototransduction in the microvillar visual cell of Limulus: Electrophysiology and biochemistry

Cited by 5 publications

References 113 publications

Biophysical processes in invertebrate photoreceptors: recent progress and a critical overview based on Limulus photoreceptors

Biophysical processes in invertebrate photoreceptors: recent progress and a critical overview based on Limulus photoreceptors

Light-activated single channel currents in Limulus ventral nerve photoreceptors

Microvillar Photoreceptor Cells of Invertebrates

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