Differential effects of age on the pathways of calcium influx into nerve terminals

Martínez, Alberto; Vitórica, Javier; Bogónez, Elena; Satrústegui, Jorgina

doi:10.1016/0006-8993(87)91608-8

Cited by 39 publications

(11 citation statements)

References 36 publications

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“…Because calcium entry via [Ca2'],/[Na']i exchange may contribute to a large extent to K+-dependent 45Ca2+ uptake in Na+-loaded synaptosomes (Coutinho et al, 1984), the Na+ concentration of the incubation media was low (32 mM) and was not changed during depolarization. We have previously observed that at these Na' concentrations, synaptosomes from 3-and 24month-old rats may sustain membrane potentials close to those found in nerve cells (Martinez et al, 1987~). Figure 2A shows the voltage-dependent inactivation of synaptosomal calcium channels in 3-and 24-monthold rats.…”

Section: Effect Of Age On Voltage-and Calcium-dependent Inactivation mentioning

confidence: 60%

“…The comparison between the means of different groups of data was evaluated by Student's t test. Where indicated, data were fitted by an iterative nonlinear, unweighted, least squares program based on a modified Newton-Gauss algorithm, as in previous studies (Martinez et al, 1987~). Table 1 shows the effect of aging on the initial (5-s) depolarization-dependent calcium uptake in synaptosomes from 3-, 12-, and 24-month-old rats.…”

Section: Other Methodsmentioning

confidence: 99%

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Reduction of K⁺‐Stimulated ⁴⁵Ca²⁺ Influx in Synaptosomes with Age Involves Inactivating and Noninactivating Calcium Channels and Is Correlated with Temporal Modifications in Protein Dephosphorylation

Martínez‐Serrano

Bogónez

Vitórica

et al. 1989

Journal of Neurochemistry

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The voltage-dependent calcium uptake in rat brain synaptosomes was measured under conditions in which [Ca2+]o/[Na+]i exchange was minimized to characterize the voltage-sensitive calcium channels from rats of different ages. In solutions of CaCl2 concentrations of less than 500 microM, the initial (5-s) calcium uptake declined by approximately 20-50% in 12- and 24-month-old rats relative to 3-month-old adults. Depolarization of synaptosomes from 3-month-old rats in a calcium-free medium or in the presence of 0.5 mM CaCl2 led to an exponential decline of the calcium uptake rate after 20 s (voltage- or voltage-and-calcium-dependent inactivation) to approximately 66 and 34% of the initial value with a t1/2 of 1.6 or 0.7 s, respectively. The presence of 1 microM nifedipine resulted in a 15-25% reduction of 45Ca2+ uptake rates, which appeared to affect noninactivating calcium channels, but addition of the calcium channel agonist Bay K 8644 was without effect. In 24-month-old rats, inactivation of 45Ca2+ uptake in calcium-free media was nondetectable, and in the presence of 0.5 mM CaCl2, the rate and extent of inactivation were also much lower than in 3-month-old animals (the t1/2 was 0.9 s, and the calcium uptake rate at 20 s was 55% of its initial value). Moreover, the presence of 1 microM nifedipine was without effect on initial calcium uptake or inactivation in synaptosomes from 24-month-old rats. These results indicate that the decrease in calcium channel-mediated 45Ca2+ uptake involves an inhibition or block of both dihydropyridine-resistant and -sensitive calcium channels.(ABSTRACT TRUNCATED AT 250 WORDS)

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Section: Effect Of Age On Voltage-and Calcium-dependent Inactivation mentioning

confidence: 60%

Section: Other Methodsmentioning

confidence: 99%

Reduction of K⁺‐Stimulated ⁴⁵Ca²⁺ Influx in Synaptosomes with Age Involves Inactivating and Noninactivating Calcium Channels and Is Correlated with Temporal Modifications in Protein Dephosphorylation

Martínez‐Serrano

Bogónez

Vitórica

et al. 1989

Journal of Neurochemistry

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“…An increase in cellular Ca2+ and diminution in thiols may occur in certain tissues as a result of age-associated processes (11,(26)(27)(28)(29), such as those attributed to free radical reactions and oxidative damage (30,31). Thus, our results suggest that certain age-related changes may lead to an enhanced binding of calpain to the cell membrane, followed by calpain activation, degradation of certain proteins, and loss of the enzyme.…”

Section: Discussionmentioning

confidence: 99%

Calpain (Ca(2+)-dependent thiol protease) in erythrocytes of young and old individuals.

Glaser

Schwarz-Benmeir

Barnoy

et al. 1994

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

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Limited proteolysis by calpain (Ca2+-activated protease; EC 3.4.22.17) is believed to regulate the function of membrane enzymes and modify the behavior of membrane structural proteins. Calpain is activated by autolysis. The degradation of band 3 protein by #-calpain is known to be enhanced in erythrocyte membranes from human individuals >70 years old (old) as compared with that from individuals 20-30 years old (young). In the present study, monoclonal antibody to IA-calpain was used to study the behavior of calpain in erythrocytes of young and old individuals. Less calpain was found in erythrocyte cytosol and membranes from old than in those from young. Increasing the erythrocyte Ca2+ induced translocation of calpain to the cell membrane and autolysis of the enzyme. Alkylation of erythrocyte thiols also promoted translocation of calpain to the membrane, especially in the presence of Ca2+. When calpain was added to erythrocyte membranes, initial binding was greater and subsequent autolysis faster in old than in young individuals, possibly arising from alterations in cell membranes of old individuals. The enhanced calpain autolysis was accompanied by enhanced degradation of band 3 protein in the old. The results suggest that calpain in old individuals is translocated to the cell membrane and is activated by autolysis, resulting in degradation of certain membrane proteins and loss of calpain. Enhanced calpain-induced membrane proteolysis may play a role in abnormal cell destruction (e.g., shortening the iffe span oferythrocytes in the aged, neuronal degeneration, etc). The erythrocyte membrane provides a convenient model for the study of age-associated alterations in cell membranes and in calpain behavior.Calpain is a neutral Ca2+-dependent thiol protease (EC 3.4.22.17), present in a wide variety of vertebrate cells. Two major isozymes are known, g-calpain and m-calpain, requiring juM and mM Ca2+ for activation, respectively (1-5). The isozyme types and amounts of the protease vary among cells and among species. Calpain is found mainly in the cell cytosol and is usually present in an inactive form. It has been suggested that, in the presence of Ca2+, calpain is activated by limited autolysis, a process that is enhanced by the translocation of calpain to the cell membrane (4-10). Activated calpain causes a limited degradation of certain membrane and cytoskeletal proteins and enzymes. The calpaininduced limited proteolysis may regulate enzyme activities and modulate the behavior of membrane structural proteins (3)(4)(5)(11)(12)(13).The mammalian erythrocyte contains the 1L-calpain isozyme (2). We have shown previously that calpain plays a role in membrane fusion: specifically, that degradation of certain membrane proteins by calpain is a prerequisite for membrane fusion induced by the membrane mobility agent A2C (14-16). In addition to calpain-induced changes associated with membrane fusion, we have also discovered that the degradation of band 3 protein by p.-calpain is enhanced in erythrocyte membranes of o...

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“…To investigate the response of synaptosomal phosphorylation and dephosphorylation systems to high-K+ depolarization under conditions restricting calcium entry, we have studied the pattern of changes in protein phosphorylation when synaptosomes are incubated in media of low Na+ concentration (32 mM) that was held constant through the depolarization pulse (Cho+based media). Under this condition of depolarization, the contribution of the [Ca2'],/[Na']i exchange to the entry of calcium into synaptosomes is minimal and calcium influx proceeds mainly through VSCC (Coutinho et al, 1984;Martinez et al, 1987). Moreover, to limit calcium entry through VSCC, we used 0.25 mM CaC12 and an external pH of 6.5.…”

Section: Protein Phosphorylation Under Depolarization Conditions Thatmentioning

confidence: 99%

Conditions Restricting Depolarization‐Dependent Calcium Influx in Synaptosomes Reveal a Graded Response of P96 Dephosphorylation and a Transient Dephosphorylation of P65

Gómez‐Puertas

Martínez‐Serrano

Blanco

et al. 1991

Journal of Neurochemistry

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Temporal changes in the phosphorylation level of synaptosomal phosphoproteins following depolarization of synaptosomes were investigated under conditions restricting calcium influx. High-K+ depolarization in media of low [Na+]o (32 mM during preincubation and depolarization) at pH 6.5 resulted in a pronounced fall in the cytosolic free calcium concentration transient, and in a reduction in the initial K(+)-stimulated 45Ca2+ uptake and endogenous acetylcholine release relative to the values obtained with control synaptosomes (preincubated and depolarized in Na(+)-based media). This reduction was paralleled by a decrease in the rate of dephosphorylation of the synaptosomal protein P96. A slower dephosphorylation of P96 also was observed on exposure to 20 microM veratridine at 0.5 mM external calcium. Our results indicate that, similar to synapsin I phosphorylation, P96 dephosphorylation shows a graded response to the amount of calcium entering the presynaptic terminal. Depolarization of synaptosomes under conditions restricting the influx of calcium revealed a transient dephosphorylation (reversed within 10 s) of the phosphoprotein P65. The possible significance of this finding to the process of neurotransmitter release is discussed.

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Differential effects of age on the pathways of calcium influx into nerve terminals

Cited by 39 publications

References 36 publications

Reduction of K⁺‐Stimulated ⁴⁵Ca²⁺ Influx in Synaptosomes with Age Involves Inactivating and Noninactivating Calcium Channels and Is Correlated with Temporal Modifications in Protein Dephosphorylation

Reduction of K⁺‐Stimulated ⁴⁵Ca²⁺ Influx in Synaptosomes with Age Involves Inactivating and Noninactivating Calcium Channels and Is Correlated with Temporal Modifications in Protein Dephosphorylation

Calpain (Ca(2+)-dependent thiol protease) in erythrocytes of young and old individuals.

Conditions Restricting Depolarization‐Dependent Calcium Influx in Synaptosomes Reveal a Graded Response of P96 Dephosphorylation and a Transient Dephosphorylation of P65

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Differential effects of age on the pathways of calcium influx into nerve terminals

Cited by 39 publications

References 36 publications

Reduction of K+‐Stimulated 45Ca2+ Influx in Synaptosomes with Age Involves Inactivating and Noninactivating Calcium Channels and Is Correlated with Temporal Modifications in Protein Dephosphorylation

Reduction of K+‐Stimulated 45Ca2+ Influx in Synaptosomes with Age Involves Inactivating and Noninactivating Calcium Channels and Is Correlated with Temporal Modifications in Protein Dephosphorylation

Calpain (Ca(2+)-dependent thiol protease) in erythrocytes of young and old individuals.

Conditions Restricting Depolarization‐Dependent Calcium Influx in Synaptosomes Reveal a Graded Response of P96 Dephosphorylation and a Transient Dephosphorylation of P65

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Reduction of K⁺‐Stimulated ⁴⁵Ca²⁺ Influx in Synaptosomes with Age Involves Inactivating and Noninactivating Calcium Channels and Is Correlated with Temporal Modifications in Protein Dephosphorylation

Reduction of K⁺‐Stimulated ⁴⁵Ca²⁺ Influx in Synaptosomes with Age Involves Inactivating and Noninactivating Calcium Channels and Is Correlated with Temporal Modifications in Protein Dephosphorylation