Calcium channels in the somatic membrane of the rat dorsal root ganglion neurons, effect of cAMP

Fedulova, S. A.; Kostyuk, P. G.; Veselovsky, N.S.

doi:10.1016/0006-8993(81)90457-1

Cited by 76 publications

(32 citation statements)

References 7 publications

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“…These effects are mimicked by intracellular injection of cAMP (5,6) or of the catalytic subunit of cAMP-dependent protein kinase (7,8), in agreement with the proposal that cAMP-dependent protein phosphorylation is the final step in the regulatory pathway. In the nervous system, intracellularly perfused molluscan neurons lose their voltage-sensitive calcium current unless ATP, Mg2 , and cAMP or the catalytic subunit of cAMP-dependent protein kinase are included in the perfusate (9,10), and similar requirements for maintenance of calcium currents are observed in dorsal root ganglion neurons (11). These results suggest that modulation of calcium channel properties by a regulatory pathway involving cAMP-dependent protein phosphorylation may be a common property of these ionic channels in different tissues.…”

mentioning

confidence: 65%

“…Physiological evidence suggests that phosphorylation by the catalytic subunit of cAMP-dependent protein kinase modulates calcium channel function in a number of cell types (3)(4)(5)(6)(7)(8)(9)(10)(11). The most direct mechanism for such regulation would be phosphorylation of a polypeptide component of the channel that can regulate channel activity.…”

Section: Discussionmentioning

confidence: 99%

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Phosphorylation of the calcium antagonist receptor of the voltage-sensitive calcium channel by cAMP-dependent protein kinase.

Curtis¹,

Catterall²

1985

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

236

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Physiological studies indicate that voltagesensitive calcium channels'are regulated by cAMP and protein phosphorylation. The calcium antagonist receptor of the voltage-sensitive' calcium channel from transverse-tubule membranes consists of three subunits, designated a, (, and y. The catalytic subunit of cAMP-dependent protein kinase phosphorylates both the a and .3 subunits of the purified receptor at a rate and extent that suggests they are potential physiological substrates of this enzyme. The phosphorylation of the a and P subunits in transverse-tubule membranes was analyzed by two-dimensional gel electrophoresis. In intact transversetubule membranes, the a subunit is not significantly phosphorylated. However, the p subunit, identified by its Mr, pI, and binding to wheat germ agglutiniq-Sepharose, was one of the substrates selectively phospoorylated by cAMP-dependent protein kinase in transverse-tubule membranes. These results suggest that cAMP-dependent phosphorylation of the (3 subunit of the calcium antagonist receptor may be an important regulatory mechanism for calcium channel function.Voltage-sensitive calcium channels mediate calcium-dependent depolarization of excitable cells, cause increased cytosolic calcium concentration in response to membrane depolarization, and initiate excitation-contraction and excitation-secretion coupling (1, 2). Several lines of evidence indicate that the activity of calcium channels is modulated directly or indirectly by cAMP-dependent protein phosphorylation. In the heart, the positive inotropic and chronotropic effects of norepinephrine and other f-adrenergic agonists are due to increased inward calcium current during the plateau phase of the cardiac action potential (3,4). These effects are mimicked by intracellular injection of cAMP (5,6) or of the catalytic subunit of cAMP-dependent protein kinase (7,8) Preparation of T-Tubule Membranes. T-tubule membranes (15) and the purified calcium antagonist receptor were prepared from rabbit fast muscle as previously described (17), with the protease inhibitors phenylmethylsulfonyl fluoride (1 mM), pepstatin A (1 puM), 1,10-phenanthroline (1 mM), iodoacetamide (1 mM), antipain (1 ug/ml), and leupeptin (1 jig/ml) present in all solutions. Protein concentrations were determined by the dye-binding assay of Bradford (20).Phosphorylation Assay. The standard reaction mixture containing 0.5-5.0 pmol of calcium antagonist receptor (membrane-bound, solubilized, or purified), 6 mM MgCl2, 6 mM EGTA, 2 ug of the catalytic subunit of cAMP-dependent protein kinase, and 0.06 ;LM [y-32P]ATP (2.9 x 103 cpm/fmol) in a final volume of 120'pl. The reaction was initiated by the addition of catalytic subunit, and samples were incubated for 10 min at 370C, unless otherwise stated. The reaction was stopped by addition of 90 Al of 100 uM EDTA, samples were cooled to 40C, and unbound 32p was removed by centrifugation through a 2-ml Sephadex G-50 column (21). Samples then were immediately processed for polyacrylamide gel electrophoresis.

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mentioning

confidence: 65%

Section: Discussionmentioning

confidence: 99%

Phosphorylation of the calcium antagonist receptor of the voltage-sensitive calcium channel by cAMP-dependent protein kinase.

Curtis¹,

Catterall²

1985

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

236

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“…This washout of FD channels is slowed by adding 3 mM MgATP and 40 AM GTP to the internal solution . There is evidence that a shift toward dephosphorylation caused by the decrease in the activity of cAMPdependent protein kinase is a contributing factor in the loss of functional Ca channels in perfused neurons (Fedulova et al, 1981(Fedulova et al, , 1985Doroshenko et al, 1982Doroshenko et al, , 1984 ; see also Levitan, 1985). Furthermore, prevention of the washout of unitary Ca channel currents in isolated membrane patches from GH3 cells by phosphorylating agents has been recently reported (D .…”

Section: Washout Of Ca Channels and Shift In Their Activation Curvementioning

confidence: 99%

“…It is well known that Ca currents are not stable cells internally dialyzed with simple saline solutions because they tend to disappear after the start of cell perfusion (Fedulova et al ., 1981 ;Byerly and Hagiwara, 1982 ;Fenwick et al, 1982 ;Doroshenko et al, 1982 ;Byerly and Moody, 1984) . As in GH3 cells (C .…”

Section: Changes In Ca Channel Activity During Intracellular Dialysismentioning

confidence: 99%

“…The loss of functional Ca channels in perfused neurons seems to be a consequence of dephosphorylation of a regulatory site associated with the channel caused by the decrease in the activity of cAMP-dependent protein kinase after the washout of CAMP and ATP during intracellular dialysis (for recent reviews, see Kostyuk, 1984, andLevitan, 1985) . The intracellular addition of phosphorylating agents (several combinations of ATP, Mg, cAMP, and the catalytic subunit of the CAMP-dependent protein kinase) slows down the loss of Ca channels and can even restore Ca channel activity to its initial level (Fedulova et al, 1981(Fedulova et al, , 1985Doroshenko et al, 1982Doroshenko et al, , 1984Forscher and Oxford, 1985). Fig.…”

Section: Changes In Ca Channel Activity During Intracellular Dialysismentioning

confidence: 99%

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Calcium channel currents in pars intermedia cells of the rat pituitary gland. Kinetic properties and washout during intracellular dialysis.

Cota¹

1986

The Journal of General Physiology

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Ca channel currents to primary cultured pars intermedia cells were studied using whole-cell recording with patch pipettes. Experiments were carried out at 18-21°C in cells internally dialyzed with K-free, EGTA-containing solutions and in the presence of 10 mM Ca or 10 mM Ba in the external solution . Ca and Ba currents depended on the activity of two main populations of channels, SD and FD . With Ca as the charge carrier, these two populations differed in their closing time constants at -80 mV (SD, 1 .8 ms; FD, 110 jus), apparent activation levels (SD, -40 mV ; FD, -5 mV), half-maximal activation levels (SD, +5 to +10 mV ; FD, +20 to +25 mV), half-times of activation at +20 mV (SD, 2.5-3 .5 ms ; FD, 1 .0-1 .3 ms), and time courses of inactivation (SD, fast ; FD, slow). Functional FD channels were almost completely'lost within 20-25 min of breaking into a cell, whereas SD channels retained most of their functional activity . In addition, the conductance-voltage curve for FD channels shifted^-15 mV toward more negative membrane potentials within 11-14 min under whole-cell recording. At that time, 60-70% of the FD channel maximum conductance was lost . However, the conductance-voltage curve for SD channels shifted <5 mV within 25 min. The addition of 3 mM MgATP and 40 ,.M GTP to the internal solution slowed down the loss of FD channels and prevented the shift in their activation curve. It was also found that the amplitude of the current carried by FD channels tends to increase as a function of the age of the culture, with no obvious changes in the kinetic properties of the channels or in SD channel activity .

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Calcium channels and calcium channel antagonists

Greenberg

1987

Annals of Neurology

135

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Changes in free intracellular Ca2+ levels provide signals that allow nerve and muscle cells to respond to a host of external stimuli. A major mechanism for elevating the level of intracellular Ca2+ is the influx of extracellular Ca2+ through voltage-dependent channels in the cell membrane. Recent research has yielded new insights into the physiological properties, molecular structure, biochemical regulation, and functional heterogeneity of voltage-dependent Ca2+ channels. In addition, Ca2+ channel antagonist drugs have been developed that are valuable both as probes of channel structure and function and as therapeutic agents. Preliminary evidence suggests that these drugs may be useful in the treatment of diverse neurological disorders, including headache, subarachnoid hemorrhage, stroke, and epilepsy.

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Calcium channels in the somatic membrane of the rat dorsal root ganglion neurons, effect of cAMP

Cited by 76 publications

References 7 publications

Phosphorylation of the calcium antagonist receptor of the voltage-sensitive calcium channel by cAMP-dependent protein kinase.

Phosphorylation of the calcium antagonist receptor of the voltage-sensitive calcium channel by cAMP-dependent protein kinase.

Calcium channel currents in pars intermedia cells of the rat pituitary gland. Kinetic properties and washout during intracellular dialysis.

Calcium channels and calcium channel antagonists

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