The action of calcium on the electrical properties of squid axons

Frankenhaeuser, B.; Hodgkin, A. L.

doi:10.1113/jphysiol.1957.sp005808

Cited by 1,721 publications

(989 citation statements)

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“…3). This screening effect is well known for the extracellular leaflet of the membrane that affects activation of the voltagegated sodium channels 10,18 . Here, we can consider CatCh as a light-gated membrane In comparison to already available optogenetic tools, CatCh induces in neurons an increased light-sensitivity similar to the slow-mutants 13 or SFO's 6 but with much accelerated response kinetics owing to its increased Ca ++ -permeability and the consequences on neuronal excitability.…”

Section: Application To Hippocampal Neuronsmentioning

confidence: 97%

“…This may confer benefits in terms of more effective tissue recruitment with deeper-penetrating green light. We assign the dramatically enhanced light-sensitivity of CatCh-expressing neurons to an increased Ca ++ permeability, thereby transiently increasing the surface potential on the cytosolic membrane surface 10,11,18,19 (for an explanation of the Ca ++ effect on the surface potential see Supplementary Figure 3). During light excitation, CatCh serves as a membrane bound fast Ca ++ -source that temporarily increases the local intracellular surface-Ca ++ -concentration and neutralizes the negative membrane surface charges.…”

Section: Application To Hippocampal Neuronsmentioning

confidence: 99%

“…Here we chose a different approach: since it is known that a cell's inner membrane surface potential is strongly influenced by Ca ++ , modifying submembraneous intracellular Ca ++ levels will lead to depolarization of the membrane and in neurons to activation of voltage-gated Na + channels. Thus we hypothesized that the light-sensitivity of a neuron can be indirectly increased by elevating its inner membrane surface potential via Ca ++ -influx 10,11 . We created a ChR2 mutant with an enhanced Ca ++ -permeability, which we named CatCh, i.e.…”

Section: Introductionmentioning

confidence: 99%

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Ultra light-sensitive and fast neuronal activation with the Ca2+-permeable channelrhodopsin CatCh

et al. 2011

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Section: Application To Hippocampal Neuronsmentioning

confidence: 97%

Section: Application To Hippocampal Neuronsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Ultra light-sensitive and fast neuronal activation with the Ca2+-permeable channelrhodopsin CatCh

et al. 2011

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“…V 1/2 has been shown to depend on the existence of certain charged residues on the external surface of the channel protein (11)(12)(13), suggesting these charges contribute to an electric potential at the external surface (14)(15)(16). Metal ions were early recognized to alter the excitability of neurons by shifting the G(V) curve of ion channels along the voltage axis (17)(18)(19)(20). For certain metal ions most of this effect is likely to be caused by screening (i.e., damping the electric field by mobile charges rather than by bound charges) of the critical negative charges at the external surface of the channel protein, modifying 4 out at the voltage sensor (14,15,20).…”

Section: Introductionmentioning

confidence: 99%

Extracellular Linkers Completely Transplant the Voltage Dependence from Kv1.2 Ion Channels to Kv2.1

Elinder

Madeja

Zeberg

et al. 2016

Biophysical Journal

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The transmembrane voltage needed to open different voltage-gated K (Kv) channels differs by up to 50 mV from each other. In this study we test the hypothesis that the channels' voltage dependences to a large extent are set by charged amino-acid residues of the extracellular linkers of the Kv channels, which electrostatically affect the charged amino-acid residues of the voltage sensor S4. Extracellular cations shift the conductance-versus-voltage curve, G(V), by interfering with these extracellular charges. We have explored these issues by analyzing the effects of the divalent strontium ion (Sr 2þ ) on the voltage dependence of the G(V) curves of wild-type and chimeric Kv channels expressed in Xenopus oocytes, using the voltage-clamp technique. Out of seven Kv channels, Kv1.2 was found to be most sensitive to Sr 2þ (50 mM shifted G(V) by þ21.7 mV), and Kv2.1 to be the least sensitive (þ7.8 mV). Experiments on 25 chimeras, constructed from Kv1.2 and Kv2.1, showed that the large Sr 2þ -induced G(V) shift of Kv1.2 can be transferred to Kv2.1 by exchanging the extracellular linker between S3 and S4 (L3/4) in combination with either the extracellular linker between S5 and the pore (L5/P) or that between the pore and S6 (LP/6). The effects of the linker substitutions were nonadditive, suggesting specific structural interactions. The free energy of these interactions was~20 kJ/mol, suggesting involvement of hydrophobic interactions and/or hydrogen bonds. Using principles from double-layer theory we derived an approximate linear equation (relating the voltage shifts to altered ionic strength), which proved to well match experimental data, suggesting that Sr 2þ acts on these channels mainly by screening surface charges. Taken together, these results highlight the extracellular surface potential at the voltage sensor as an important determinant of the channels' voltage dependence, making the extracellular linkers essential targets for evolutionary selection.

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“…How can this be reconciled? We tentatively attribute this effect to the long estabished membrane stabilizing effect of Ca 2+ [18], while at lower [Ca 2+ ] o , the established labilizing effect of veratridine may cause channel activation [7,42]. Similarly, in chromaffin cells, high [Ca 2+ ] o entails reduced veratridine-induced [Ca 2+ ] i increase [31] and catecholamine release [10,12].…”

Section: Discussionmentioning

confidence: 80%