Phosphoarginine stimulation of Na(+)‐Ca2+ exchange in squid axons‐‐a new pathway for metabolic regulation?

DiPolo, Reinaldo; Beaugé, Luis

doi:10.1113/jphysiol.1995.sp020861

Cited by 14 publications

(11 citation statements)

References 27 publications

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“…The experimental evidence to be reviewed below shows that PA does not simply replace ATP, but it has a role of its own; it acts independently and through a metabolic pathway different from, and in parallel with, that of the nucleotide. In addition, the kinetics consequences are also different (85,87,90). Figure 31A Figure 31B is that neither 5 mM arginine nor 5 mM PCr reproduces the stimulation seen with 5 mM PA.…”

mentioning

confidence: 95%

Sodium/Calcium Exchanger: Influence of Metabolic Regulation on Ion Carrier Interactions

DiPolo¹,

Beaugé²

2006

Physiological Reviews

191

157

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The Na+/Ca2+ exchanger's family of membrane transporters is widely distributed in cells and tissues of the animal kingdom and constitutes one of the most important mechanisms for extruding Ca2+ from the cell. Two basic properties characterize them. 1) Their activity is not predicted by thermodynamic parameters of classical electrogenic countertransporters (dependence on ionic gradients and membrane potential), but is markedly regulated by transported (Na+ and Ca2+) and nontransported ionic species (protons and other monovalent cations). These modulations take place at specific sites in the exchanger protein located at extra-, intra-, and transmembrane protein domains. 2) Exchange activity is also regulated by the metabolic state of the cell. The mammalian and invertebrate preparations share MgATP in that role; the squid has an additional compound, phosphoarginine. This review emphasizes the interrelationships between ionic and metabolic modulations of Na+/Ca2+ exchange, focusing mainly in two preparations where most of the studies have been carried out: the mammalian heart and the squid giant axon. A surprising fact that emerges when comparing the MgATP-related pathways in these two systems is that although they are different (phosphatidylinositol bisphosphate in the cardiac and a soluble cytosolic regulatory protein in the squid), their final target effects are essentially similar: Na+-Ca2+-H+ interactions with the exchanger. A model integrating both ionic and metabolic interactions in the regulation of the exchanger is discussed in detail as well as its relevance in cellular Cai2+ homeostasis.

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confidence: 95%

Sodium/Calcium Exchanger: Influence of Metabolic Regulation on Ion Carrier Interactions

DiPolo¹,

Beaugé²

2006

Physiological Reviews

191

157

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“…We have found recently in squid nerve fibres a novel form of up‐regulation of the Na + ‐Ca 2+ exchanger induced by a high‐energy non‐nucleotide phosphagen: phosphoarginine (Pa) (DiPolo & Beaugé, 1995), a compound that is normally present at millimolar concentrations in the cytosol of all invertebrates. The Pa stimulation: (i) occurs in the complete absence of ATP or ADP, (ii) is independent of and additive to the MgATP‐stimulated exchange, (iii) is largely, but not absolutely dependent on Mg 2+ ions and (iv) is fully and rapidly reversible with a K m of around 7.7 mM.…”

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confidence: 99%

“…The Pa stimulation: (i) occurs in the complete absence of ATP or ADP, (ii) is independent of and additive to the MgATP‐stimulated exchange, (iii) is largely, but not absolutely dependent on Mg 2+ ions and (iv) is fully and rapidly reversible with a K m of around 7.7 mM. The large magnitude of the stimulating effect of Pa, combined with its strong dependence on Ca i 2+ (DiPolo & Beaugé, 1995), makes this process suitable for extruding [Ca 2+ ] i from regions in neurons where [Ca 2+ ] i can reach very high levels (Llinas, Sugimory & Siver, 1994). The MgATP modulation of Na + ‐Ca 2+ exchange has been characterized with respect to transport (Na + o , Na + i , Ca 2+ o , Ca i 2+ ), regulatory (Ca i 2+ ) and other ligand (Mg i 2+ , inorganic phosphate, vanadate) interactions (DiPolo & Beaugé, 1991).…”

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confidence: 99%

Differential up‐regulation of Na⁺‐Ca²⁺ exchange by phosphoarginine and ATP in dialysed squid axons

DiPolo

Beaugé

1998

The Journal of Physiology

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The aim of this study was to characterize further the two main metabolic pathways of regulation of the Na+‐Ca2+ exchanger in squid axons induced by its two naturally ocurring high‐energy compounds: ATP and phosphoarginine (Pa). [Na+]o‐dependent Ca2+ efflux (forward Na+o‐Ca2+i exchange) and [Ca2+]o‐dependent Ca2+ efflux (Ca2+o‐Ca2+i exchange) were measured in internally dialysed squid axons at 16–17 °C. Measurements of changes in the apparent affinity of the Na+‐Ca2+ exchanger for transporting (Na+o, Na+i, Ca2+o, Ca2+i) and regulatory (Ca2+i) ions induced by ATP and Pa show marked differences for the two substrates: (i) ATP strongly alters the affinity for Na+o and Na+i, while Pa does not, and (ii) in the absence of Na+i, ATP has no stimulatiory effect; on the other hand, Pa causes a dramatic increase in Na+o‐Ca2+i exchange with little activation of Ca2+o‐Ca2+i exchange. The MgATP analogue chromium‐ATP (CrATP) completely inhibits MgATP stimulation of the Na+‐Ca2+ exchanger. Nevertheless, even with the effects of the nucleotide blocked, Pa exhibits its usual activation of the [Na+]o‐dependent Ca2+ efflux. None of the classical serine‐threonine‐tyrosine kinase inhibitors, nor the PP1 and PP2 phosphatase inhibitors, affects either the ATP or the Pa effect. However, intracellular microinjections of an exogenous phosphatase (alkaline phosphatase) completely reverses the stimulation of the Na+‐Ca2+ exchange induced by ATP and Pa. Prolonged intracellular dialysis with highly permeable porous capillaries (18 kDa molecular weight cut‐off), which normally induces a complete run‐down of the MgATP effect, does not alter the Pa stimulation of the exchanger, even after 6 h of continuous dialysis. We conclude that the ATP and Pa modulation of Na+‐Ca2+ exchange in an invertebrate nerve fibre are two genuinely different mechanisms, which affect the carrier properties in very different ways. An interesting similarity between ATP and Pa is that a phosphorylation‐dephosphorylation process seems to be a common feature of these two regulation modes.

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“…The different transport kinetic effects and phosphorylation patterns due to MgATP and PA, and the fact that upregulation of the exchanger by PA does not require the SCRP 11,12 agree with the existence of two metabolic pathways for stimulation of the squid nerve Na + /Ca 2+ exchanger by these ligands. [10][11][12] Based on the labile PA phosphorylation of the small NF, it could be argued that MgATP phosphorylation of the exchanger may be lost after the hard conditions of immunoprecipitation. Nonetheless, MgATP phosphorylation patterns of total membrane proteins not subjected to immunoprecipitation are exactly the same with or without the SCRP (not shown here).…”

Section: Atp and Pa Phosphorylation Of Membrane Proteins In Squid Nermentioning

confidence: 99%

“…9 A second metabolic upregulator of the squid Na + /Ca 2+ exchanger is phosphoarginine (PA). 10,11 Its metabolic pathway looks different from that of ATP 11,12 since: (a) Activation of the exchanger by PA is effective even when the MgATP effect is blocked by CrATP; (b) full PA stimulation is still observed at saturating ATP concentrations; and (c) PA does not require cytosolic factor since it activates in axons after prolonged dialysis and also in isolated squid nerve membrane vesicles in the absence of the SCRP. On the other hand, PA modulation seems also related to a phosphorylation process because, as it happens with MgATP, it is blocked by exogenous alkaline phosphatases.…”

Section: Introductionmentioning

confidence: 99%

Some Biochemical Properties of the Upregulation of the Squid Nerve Na⁺/Ca²⁺ Exchanger by MgATP and Phosphoarginine

Berberián¹,

DiPolo²,

Beaugé³

2007

Annals of the New York Academy of Sciences

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In squid nerve MgATP upregulation of Na+/Ca2+ exchange requires a soluble cytosolic regulatory protein (SCRP) of about 13 kDa; phosphoarginine (PA) stimulation does not. MgATP-gamma-S mimics MgATP. When a 30-10-kDa cytosolic fraction is exposed to 0.5 mM [32P]ATP in the same solution used for transport assays, and in the presence of native membrane vesicles, a 13-kDa and a 25-kDa band become phosphorylated. Membrane vesicles alone do not show these phosphorylated bands and heat denaturation of the cytosolic fraction prevents phosphorylation. Moreover, staurosporine, a general inhibitor of kinases, does not affect MgATP + SCRP stimulation of the exchanger or the phosphorylation of the 13 kDa but prevents phosphorylation of the 25-kDa cytosolic band. The 30-10-kDa fraction phosphorylated in the presence of staurosporine stimulates Na+/Ca2+ exchange in vesicles in the absence of ATP but with Mg2+ in the medium. The 30-10-kDa fraction is not phosphorylated by PA. In membrane vesicles two protein bands, at about 60 kDa and 70 kDa identified as the low molecular weight neurofilament (NF), are phosphorylated by PA, but not by MgATP. This phosphorylation is specific for PA, insensitive to staurosporine (similar to the PA-stimulated fluxes), and labile. In addition, co-immunoprecipitation was observed between the NF and the exchanger protein. Under the conditions of these experiments no phosphorylation of the exchanger is detected, either with MgATP or PA.

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Phosphoarginine stimulation of Na(+)‐Ca2+ exchange in squid axons‐‐a new pathway for metabolic regulation?

Cited by 14 publications

References 27 publications

Sodium/Calcium Exchanger: Influence of Metabolic Regulation on Ion Carrier Interactions

Sodium/Calcium Exchanger: Influence of Metabolic Regulation on Ion Carrier Interactions

Differential up‐regulation of Na⁺‐Ca²⁺ exchange by phosphoarginine and ATP in dialysed squid axons

Some Biochemical Properties of the Upregulation of the Squid Nerve Na⁺/Ca²⁺ Exchanger by MgATP and Phosphoarginine

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Phosphoarginine stimulation of Na(+)‐Ca2+ exchange in squid axons‐‐a new pathway for metabolic regulation?

Cited by 14 publications

References 27 publications

Sodium/Calcium Exchanger: Influence of Metabolic Regulation on Ion Carrier Interactions

Sodium/Calcium Exchanger: Influence of Metabolic Regulation on Ion Carrier Interactions

Differential up‐regulation of Na+‐Ca2+ exchange by phosphoarginine and ATP in dialysed squid axons

Some Biochemical Properties of the Upregulation of the Squid Nerve Na+/Ca2+ Exchanger by MgATP and Phosphoarginine

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Differential up‐regulation of Na⁺‐Ca²⁺ exchange by phosphoarginine and ATP in dialysed squid axons

Some Biochemical Properties of the Upregulation of the Squid Nerve Na⁺/Ca²⁺ Exchanger by MgATP and Phosphoarginine