Phosphatidylethanol stimulates the plasma-membrane calcium pump from human erythrocytes

Abstract

Phosphatidylethanol is formed by "transphosphatidylation' of phospholipids with ethanol catalysed by phospholipase D and can be accumulated in the plasma membrane of mammalian cells after treatment of animals with ethanol. In the present work we show that phosphatidylalcohols, such as phosphatidylethanol and phosphatidylbutanol, produced a twofold stimulation of the Ca(2+)-ATPase activity of human erythrocytes. This stimulation occurs with the purified, solubilized enzyme as well as with ghost preparations, where the enzyme is in its natural lipidic environment and is different to that obtained with other acidic phospholipids such as phosphatidylserine. Addition of either phosphatidylserine, phosphatidylethanol or phosphatidylbutanol to the purified Ca(2+)-ATPase, or to ghosts preparations, increased the affinity of the enzyme for Ca2+ and the maximal velocity of the reaction as compared with controls in the absence of acidic phospholipids. However, in contrast with what occurs with phosphatidylserine, simultaneous addition of phosphatidyl-alcohols and calmodulin increased the affinity of the enzyme for Ca2+ to a greater extent than each added separately. When ethanol was added to either the purified erythrocyte Ca(2+)-ATPase or to erythrocyte-ghost preparations in the presence of acidic phospholipids, an additive effect was observed. There was an increase in the affinity for Ca2+ and in the maximal velocity of the reaction, well above the values obtained with ethanol or with the acidic phospholipids tested separately. These findings could have pharmacological importance. It is conceivable that the decrease in the intracellular Ca(2+) concentration that has been reported in erythrocytes as a result of ethanol intoxication could be due to the stimulation of the Ca(2+)-ATPase by the accumulated phosphatidylethanol, to a direct effect of ethanol on the enzyme or to an additive combination of both.

Ceramide and sphingosine have an antagonistic effect on the plasma-membrane Ca2+-ATPase from human erythrocytes

“…An interesting property of this Ca# + -ATPase that distinguishes it from other P-type ionic pumps is the multiplicity of regulatory mechanisms [3]. Thus this ionic pump is regulated by calmodulin (CaM) [4,5], protein kinases A [6] and C [7], acidic phospholipids [8], controlled proteolysis [9,10], auto-aggregation [11], organic solvents [12] and phosphatidylethanol [13]. We have shown previously that ethanol is able to stimulate this pump to a greater extent than all the effectors mentioned above [14,15].…”

The Effect of Ethanol on the Plasma Membrane Calcium Pump Is Isoform-specific

“…It was effective at pharmacological concentrations (7), a finding suggesting the possible in vivo involvement of the activation of the pump. Phosphatidylethanol, which is formed by a phospholipase D-catalyzed transphosphatidylation of phospholipids with ethanol, was found to accumulate in the plasma membrane after treatment of the animals with ethanol (7) and to stimulate the Ca 2ϩ -ATPase of human erythrocytes (8) in a manner additive with calmodulin. These observations are all consistent with the suggestion that the decrease in the intracellular Ca 2ϩ concentration reported in some cells after ethanol intoxication could be due to the stimulation of the Ca 2ϩ -ATPase.…”

Abscisic acid signal transduction in the barley aleurone is mediated by phospholipase D activity

“…Though the product of PLD transphosphatidylation, phosphatidylalcohol is not readily metabolized further in vivo, it has been reported to affect an enzyme activity in mammalian cells (37). Phosphatidylbutanol applied at 0.1% had no effect on either the GA or ABA response (data not shown), suggesting the biological action of 1-butanol was most likely attributable to PLD inhibition rather than the effect of the phosphatidylalcohol.…”