Insulation of the conduction pathway of muscle transverse tubule calcium channels from the surface charge of bilayer phospholipid.

Coronado, Roberto; Affolter, Hubert

doi:10.1085/jgp.87.6.933

Cited by 75 publications

(76 citation statements)

References 38 publications

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“…Fits with Gaussian distributions of the open and baseline levels gave the mean value of the open and baseline currents plus their standard deviations. Idealization of the open and closed events was obtained by setting the closed discriminator at two standard deviations above the baseline level and the open discriminator at two standard deviations below the open level (Coronado and Affolter, 1986). The idealized data, containing the duration of each open and closed event and the amplitude of each open event, were stored in an ASCII file.…”

Section: Single Channel Data Analysis and Curve Fittingmentioning

confidence: 99%

Block by ruthenium red of the ryanodine-activated calcium release channel of skeletal muscle.

1993

The Journal of General Physiology

101

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A B S T R A C T The effects of ruthenium red and the related compounds tetraamine palladium (4APd) and tetraamine platinum (4APt) were studied on the ryanodine activated Ca ~+ release channel reconstituted in planar bilayers with the immunoaffinity purified ryanodine receptor. Ruthenium red, applied at submicromolar concentrations to the myoplasmic side (c/s), induced an all-or-none flickery block of the ryanodine activated channel. The blocking effect was strongly voltage dependent, as large positive potentials that favored the movement of ruthenium red into the channel conduction pore produced stronger block. The half dissociation constants (Kd) for ruthenium red block of the 500 pS channel were 0.22, 0.38, and 0.62 p-M, at +100, +80, and +60 mV, respectively. Multiple ruthenium red molecules seemed to be involved in the inhibition, because a Hill coefficient of close to 2 was obtained from the dose response curve. The half dissociation constant of ruthenium red block of the lower conductance state of the ryanodine activated channel (250 pS) was higher (Kd = 0.82 p-M at + 100 mV), while the Hill coefficient remained approximately the same (nil ----2.7). Ruthenium red block of the channel was highly asymmetric, as tram ruthenium red produced a different blocking effect. The blocking and unblocking events (induced by c/s ruthenium red) can be resolved at the single channel level at a cutoff frequency of 2 kHz. The closing rate of the channel in the presence of ruthenium red increased linearly with ruthenium red concentration, and the unblocking rate of the channel was independent of ruthenium red concentrations. This suggests that ruthenium red block of the channel occurred via a simple blocking mechanism. The on-rate of ruthenium red binding to the channel was 1.32 x 109 M -I s -l, and the off-rate of ruthenium red binding was 0.75 x l0 s s -1 at +60 mV, in the presence of 200 nM ryanodine. The two related compounds, 4APd and 4APt, blocked the channel in a similar way to that of ruthenium red. These compounds inhibited the open channel with lower affinities (Kd = 170 p.M, 4APd; Kd = 656 p-M, 4APt), and had Hill coefficients of close to 1. The results suggest that ruthenium red block of the ryanodine receptor is due to binding to multiple sites located in the conduction pore of the channel.

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Section: Single Channel Data Analysis and Curve Fittingmentioning

confidence: 99%

Block by ruthenium red of the ryanodine-activated calcium release channel of skeletal muscle.

1993

The Journal of General Physiology

101

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“…Single Ca2+ channel currents recorded in Na' gradients and in the absence of divalent ions are larger and better resolved than those observed in a Ba2+ gradient (Coronado & Affolter, 1986;Coronado, 1987). Thus, we used Na+ gradients and we initially confirmed the nature of the channels recorded by measuring the effects of pharmacological agents.…”

Section: Characterization Of Dhp-sensitive Ca2+ Channels From T-tubulmentioning

confidence: 99%

The action of amyotrophic lateral sclerosis immunoglobulins on mammalian single skeletal muscle Ca2+ channels.

Magnelli

Sawada

Delbono

et al. 1993

The Journal of Physiology

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SUMMARY1. The planar phospholipid bilayer technique was used to study the T-tubule skeletal muscle dihydropyridine (DHP)-sensitive calcium (Ca2") channel. To improve the signal-to-noise ratio, Ca2" channel activity was recorded using both 800-50 and 500-50 mm NaCl gradients.2. Ca21 channels were characterized by their cation selectivity and pharmacological profile. The mean open time for channels identified by these techniques was increased by the DHP agonist Bay K 8644 (2 /LM), while it was decreased by the DHP antagonist nifedipine (5 /yM). Nifedipine also reduced Ca21 channel amplitude levels.3. Immunoglobulins G (IgG) from three amyotrophic lateral sclerosis (ALS) patients (n = 14 experiments), one myasthenia gravis (MG) patient (n = 3 experiments) and one healthy individual (n = 4 experiments), were tested on Ca21 channel activity at a final concentration of 3 mg/ml. 4. Channel mrean open time, mean closed time and time integral for the current were not modified by normal IgG (n = 4 experiments). Similarly, MG IgG did not reduce channel activity (n = 3 experiments).5. ALS IgG reduced the mean open time of DHP-sensitive Ca21 channel activity in twelve out of fourteen experiments. In addition, in five out of twelve experiments, ALS IgG stabilized the channel to a smaller amplitude level.6. ALS IgG reduced Ca21 channel activity in a side-selective fashion, probably corresponding to the external side of the channel.7. These results suggest that ALS IgG action on DHP-sensitive Ca2+ channels is not mediated by second messengers, thus favouring a direct mechanism for interaction with the DHP receptor complex.

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“…But the similarity of other channels that were found in the fused synaptic vesicles (Yakir & Rahamimoff, 1993 b) or in the fused synaptosomes (Edry-Schiller, Ginsburg & Rahamimoff, 1991;Edry-Schiller & Rahamimoff, 1993) to channels characterized in preparations that were not subjected to fusion procedures (Miller & Richard, 1990;Zagotta and Aldrich, 1990) One advantage of the fused preparation used here over other fusion procedures is that no foreign lipids are added. In some other methods, developed to study organelles too small for direct patch clamp recordings, foreign lipids were added; changes in the lipid composition of membranes are known to affect the behaviour of channels in some cases (Bell & Miller, 1984;Moczydlowski, Alvarez, Vergara & Latorre, 1985;Coronado & Affolter, 1986;Cukierman, Zinkand, French & Krueger, 1988).…”

Section: Discussionmentioning

confidence: 99%

The non‐specific ion channel in Torpedo ocellata fused synaptic vesicles.

Yakir

Rahamimoff

1995

The Journal of Physiology

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1. Synaptic vesicles were isolated and fused into large structures with a diameter of more than 20 #sm to characterize their ionic channels. The 'cell'-attached and inside-out configurations of the patch clamp technique were used. 2. Two types of ion channels were most frequently observed: a low conductance chloride channel and a high conductance non-specific channel. 3. The non-specific channel has a main conducting state and a substate. The main conducting state has a slope conductance of 246 + 15 pS (± S.E.M., n = 15), in the presence of different combinations of KCl and potassium glutamate. 4. From the reversal potentials of the current-voltage (I-V) relation, it was concluded that this channel conducts both Cl-and K+.5. The non-specific channel is highly voltage dependent: under steady-state voltages it has a high open probability near 0 mV and does not inactivate; when the membrane is hyperpolarized (pipette side more positive), the open probability decreases dramatically. 6. Voltage pulses showed that upon hyperpolarization (from holding potentials between -20 and +20 mV), the channels deactivated; when the membrane was stepped back to the holding potential, the channels reactivated rapidly. 7. In a number of experiments, when the pipette side was made more negative than the bath, the open probability also decreased. 8. Frequently, a substate with a conductance of about 44 + 4% (± S.E.M., n = 3) of the main state was detected. 9. We speculate that this non-specific ion channel may have different roles at the various stages of the life cycle of the synaptic vesicle. When the synaptic vesicle is an intracellular structure, it might help its transmitter-concentrating capacity by dissipating the polarization. After fusion with the surface membrane, it might constitute an additional conductance pathway, taking part in frequency modulation of synaptic transmission.

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Insulation of the conduction pathway of muscle transverse tubule calcium channels from the surface charge of bilayer phospholipid.

Cited by 75 publications

References 38 publications

Block by ruthenium red of the ryanodine-activated calcium release channel of skeletal muscle.

Block by ruthenium red of the ryanodine-activated calcium release channel of skeletal muscle.

The action of amyotrophic lateral sclerosis immunoglobulins on mammalian single skeletal muscle Ca2+ channels.

The non‐specific ion channel in Torpedo ocellata fused synaptic vesicles.

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