Effects of pH on phosphorylation of the Ca2+-ATPase of sarcoplasmic reticulum by inorganic phosphate

Khan, Y M; East, J. Malcolm; Lee, A G

doi:10.1042/bj3210671

Cited by 10 publications

(12 citation statements)

References 32 publications

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“…However, considering the fact that Ca 2þ ER stores are increased in IduaÀ/À mice (Fig. 1C) and that the effect of Nigericin on Ca 2þ mobilization is not specific to the lysosomes, it is possible that Ca 2þ release from the ER and even from mitochondria could contribute to these results, because other regulation mechanisms of channels and transporters (like phosphorilation by kinases) in each organelle could be triggered (Sumbilla et al, 1993;Khan et al, 1997).Thus, to confirm this alteration, a more specific drug for lysosome was used-Bafilomycin A 1 mM-which is an inhibitor of lysosomal H þ /ATPase. The fluorescence ratio F/F 0 was also higher in IduaÀ/À cells, with a similar diference between groups (1.37 AE 0.19 and 1.16 AE 0.07 for IduaÀ/À and þ/þ respectively; Fig.…”

Section: Calcium Mobilization From the Endoplasmic Reticulummentioning

confidence: 94%

Evidence of lysosomal membrane permeabilization in mucopolysaccharidosis type I: Rupture of calcium and proton homeostasis

Pereira

Gazarini

RODRIGUES

et al. 2010

Journal Cellular Physiology

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Mucopolysaccharidosis type I (MPS I) is caused by a deficiency of alpha-iduronidase (IDUA), which leads to intralysosomal accumulation of glysosaminoglycans. Patients with MPS I present a wide range of clinical manifestations, but the mechanisms by which these alterations occur are still not fully understood. Genotype-phenotype correlations have not been well established for MPS I; hence, it is likely that secondary and tertiary alterations in cellular metabolism and signaling may contribute to the physiopathology of the disease. The aim of this study was to analyze Ca(2+) and H(+) homeostasis, lysosomal leakage of cysteine proteases, and apoptosis in a murine model of MPS I. After exposition to specific drugs, cells from Idua-/- mice were shown to release more Ca(2+) from the lysosomes and endoplasmic reticulum than Idua+/+ control mice, suggesting a higher intraorganelle store of this ion. A lower content of H(+) in the lysosomes and in the cytosol was found in cells from Idua-/- mice, suggesting an alteration of pH homeostasis. In addition, Idua-/- cells presented a higher activity of cysteine proteases in the cytosol and an increased rate of apoptotic cells when compared to the control group, indicating that lysosomal membrane permeabilization might occur in this model. Altogether, our results suggest that secondary alterations-as changes in Ca(2+) and H(+) homeostasis and lysosomal membrane permeabilization-may contribute for cellular damage and death in the physiopathology of MPS I.

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Section: Calcium Mobilization From the Endoplasmic Reticulummentioning

confidence: 94%

Evidence of lysosomal membrane permeabilization in mucopolysaccharidosis type I: Rupture of calcium and proton homeostasis

Pereira

Gazarini

RODRIGUES

et al. 2010

Journal Cellular Physiology

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“…We attributed this change to binding of Mg# + at a ' gating site ' on the ATPase, controlling the rate of dissociation of Ca# + from the high-affinity sites on the cytoplasmic side of the ATPase [11]. Phosphorylation of the ATPase by ATP in the presence of Ca# + , addition of a high concentration of vanadate, or addition of the specific inhibitors thapsigargin or thapsivillosin, all result in about a 16 % decrease in fluorescence intensity at pH 6.0 [41]. The fluorescence response of DMClabelled ATPase in di(C ") : " )PS or di(C ") : " )PA to the addition of Mg# + is very different to that seen for the unreconstituted DMClabelled ATPase (Figure 7) ; the maximal fluorescence changes on addition of Mg# + are 13.9 % and 19 % in di(C ") : " )PS and di(C ") : " )PA respectively (fitted values, see below).…”

Section: Fluorescence Of Dmc-labelled Atpasementioning

confidence: 99%

Interaction of phosphatidic acid and phosphatidylserine with the Ca2+-ATPase of sarcoplasmic reticulum and the mechanism of inhibition

Dalton

East

Mall

et al. 1998

Biochemical Journal

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The sarcoplasmic reticulum of skeletal muscle contains anionic phospholipids as well as the zwitterionic phosphatidylcholine and phosphatidylethanolamine. Here we study the effects of anionic phospholipids on the activity of the Ca2+-ATPase purified from the membrane. Reconstitution of the Ca2+-ATPase into dioleoylphosphatidylserine [di(C18:1)PS] or dioleoylphosphatidic acid [di(C18:1)PA] leads to a decrease in ATPase activity. Measurements of the quenching of the tryptophan fluorescence of the ATPase by brominated phospholipids give a relative binding constant for the anionic lipids compared with dioleoylphosphatidylcholine close to 1 and suggest that phosphatidic acid only binds to the ATPase at the bulk lipid sites around the ATPase. Addition of di(C18:1)PS or di(C18:1)PA to the ATPase in the short-chain dimyristoleoylphosphatidylcholine [di(C14:1)PC] reverse the effects of the short-chain lipid on ATPase activity and on Ca2+ binding, as revealed by the response of tryptophan fluorescence intensity to Ca2+ binding. It is concluded that the lipid headgroup and lipid fatty acyl chains have separate effects on the function of the ATPase. The anionic phospholipids have no significant effect on Ca2+ binding to the ATPase; the level of Ca2+ binding to the ATPase, the affinity of binding and the rate of dissociation of Ca2+ are unchanged by reconstitution into di(C18:1)PA. The major effect of the anionic lipids is a reduction in the maximal level of binding of MgATP. This is attributed to the formation of oligomers of the Ca2+-ATPase, in which only one molecule of the ATPase can bind MgATP dimers in di(C18:1)PS and trimers or tetramers in di(C18:1)PA. The rates of phosphorylation and dephosphorylation for the proportion of the ATPase still able to bind ATP are unaffected by reconstitution. Larger changes were observed in the level of phosphorylation of the ATPase by Pi, which became very low in the anionic phospholipids. The fluorescence response to Mg2+ for the ATPase labelled with 4-(bromomethyl)-6,7-dimethoxycoumarin was also changed in di(C18:1)PS and di(C18:1)PA, so that effects of Mg2+ became comparable with those seen on phosphorylation for the unreconstituted ATPase. The anionic phospholipids could induce a conformational change in the ATPase on binding Mg2+ equivalent to that normally induced by phosphorylation or by binding inhibitors such as thapsigargin.

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“…Following loss of Ca 2ϩ from these sites, the ATPase can be dephosphorylated to give E2, which can then undergo a conformational change back to E1. However, this model predicts that binding of Ca 2ϩ to the ATPase from the lumenal side of the membrane (to E2) will be competitive with binding of Ca 2ϩ to the ATPase from the cytoplasmic side of the membrane (to E1), whereas experimentally binding from the two sides of the membrane has been found to be noncompetitive (2)(3)(4). A four-site model for the ATPase has therefore been proposed in which the Ca 2ϩ -ATPase contains two pairs of sites for Ca 2ϩ , a high affinity pair of sites facing the cytoplasm and a low affinity pair of sites facing the lumen (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…In contrast, binding of Ca 2ϩ to the low affinity, lumenal pair of Ca 2ϩ -binding sites on the ATPase leads to increased levels of phosphorylation by P i , an effect particularly marked at neutral pH values where the levels of phosphorylation are otherwise low (2,4,29). Levels of phosphorylation can either be measured directly using 32 P i or through the decrease in the fluorescence intensity of DMClabeled ATPase, which occurs upon phosphorylation (4).…”

Section: Effect Of Edc On Ca 2ϩ Dependence Of Phosphorylation Of the mentioning

confidence: 99%

“…However, recent experiments have identified problems with this model. In particular, the alternating site model predicts that binding of Ca 2ϩ from the cytoplasmic side of the membrane should be competitive with binding of Ca 2ϩ from the lumenal side, but a variety of equilibrium and kinetic experiments have shown that binding from the two sides of the membrane is, in fact, noncompetitive (2)(3)(4). These data are consistent with a foursite model for the ATPase, with separate pairs of binding sites for Ca 2ϩ on the two sides of the membrane; transport of Ca 2ϩ by the Ca 2ϩ -ATPase then corresponds to transfer of Ca 2ϩ from the cytoplasmic pair of sites to the lumenal pair of sites, driven by phosphorylation of the ATPase by ATP (Fig.…”

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confidence: 99%

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The Importance of Carboxyl Groups on the Lumenal Side of the Membrane for the Function of the Ca2+-ATPase of Sarcoplasmic Reticulum

Webb

Khan

East

et al. 2000

Journal of Biological Chemistry

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The conventional model for transport of Ca 2؉ by the Ca 2؉ -ATPase of skeletal muscle sarcoplasmic reticulum (SR) involves a pair of binding sites for Ca 2؉ that change upon phosphorylation of the ATPase from being high affinity and exposed to the cytoplasm to being low affinity and exposed to the lumen. However, a number of recent experiments suggest that in fact transport involves two separate pairs of binding sites for Ca

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Effects of pH on phosphorylation of the Ca2+-ATPase of sarcoplasmic reticulum by inorganic phosphate

Cited by 10 publications

References 32 publications

Evidence of lysosomal membrane permeabilization in mucopolysaccharidosis type I: Rupture of calcium and proton homeostasis

Evidence of lysosomal membrane permeabilization in mucopolysaccharidosis type I: Rupture of calcium and proton homeostasis

Interaction of phosphatidic acid and phosphatidylserine with the Ca2+-ATPase of sarcoplasmic reticulum and the mechanism of inhibition

The Importance of Carboxyl Groups on the Lumenal Side of the Membrane for the Function of the Ca2+-ATPase of Sarcoplasmic Reticulum

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