Role of the phospholipid environment in modulating the activity of the rat brain synaptic plasma membrane calcium ATPase

Abstract

The role of the phospholipid environment in modulating the activity of the rat brain synaptic plasma membrane (SPM) Ca2(+)-ATPase was investigated by its reconstitution into different phospholipids. Retention of activity of the solubilized Ca2(+)-ATPase depended on addition of exogenous phospholipids. As the cholate concentration used for solubilization of native SPM increased, a larger excess of exogeneous phospholipids, relative to membrane protein, had to be added to maintain optimal activity. Highest ATP-dependent Ca2+ transport activity was obtained when reconstitution was carried out in calf brain phospholipids (BPLs) followed by soybean phospholipids (SPLs) and the lowest in egg PC; reconstitution at a 40:1 weight ratio of exogenous phospholipids to native SPM protein resulted in ATP-dependent Ca2+ transport of 40.0 +/- 4.16, 23.4 +/- 8.48, and 11.54 +/- 2.31 nmol of Ca2+ (mg of protein)-1 (5 min)-1, respectively. Partial substitution of egg PC with BPLs led to an increase in the activity of the reconstituted Ca2+ pump. The highest ATP-dependent Ca2+ uptake was obtained when ratios of 15:25 or 10:30 egg PC to BPLs were used. Testing the individual phospholipids participating in the BPL mixture showed that addition of PS to egg PC led to a consistent increase in Ca2+ pump activity. Substitution of 50% of the PC with PS resulted in a 3.8-fold higher ATP-dependent Ca2+ uptake than that obtained in egg PC alone. No other phospholipid tested--PE, SM, or PI--had a similar effect. Increasing the proportion of PS within the BPL mixture above its original content led to a gradual decrease in the reconstituted SPM Ca2+ pump activity. Enrichment of asolectin with PS led first to increased Ca2+ pump activity; then, as the proportion of PS increased, Ca2+ transport of the reconstituted pump decreased. An increased proportion of PE, SM, or PI within the BPLs or asolectin, above their original contents, resulted in decreased Ca2+ transport. These results indicate that optimal SPM Ca2+ pump activity requires the combined presence of a critical amount of PC and PS within the reconstituted membrane.

The plasma membrane calcium pump: Functional domains, regulation of the activity, and tissue specificity of isoform expression

“…The presence of several Ca2+-ATPases in neuronal tissues (mainly synaptosomes) is now documented ( Hermoni-Levine and Rahamimoff, 1990;Hakim et al, 1982;Kaprielian et al, 1989;Lin and Way, 1984;Michaelis et al, 1987;Palayoor et al, 1986). A pump described in cerebellar Purkinje cells (Kaprielian et a]., 1989) corresponds to the Ca*+-ATPase of the sarcoplasmatic reticulum (SERCA), but the presence of the plasma membrane Ca2+-ATPase in neuronal tissues can be also considered as conclusively documented (Hakim et al,198 1 ). cDNA cloning and mRNA analysis by PCR has detected the transcripts of the four gene products and their different splice forms in neuronal tissues of different species ( Brandt et a]., 1992;Brandt and Neve, 1992c;Burk and Shull, 1992;Greeb, and Shull, 1989;Keeton et al, 1993;Shull and Greeb, 1989;Stauffer et al, 1993).…”

Regulation of plant plasma membrane H+‐ATPase activity

“…Acidic phospholipids mimic the stimulatory effect of calmodulin on this particular pump (Niggli et al 1981, Choquette et al 1984. It has been suggested that the stimulatory effect of phosphatidylserine on the plasma membrane Ca-*-ATPase is linked to the ability of this acidic phospholipid to promote Ca^* binding (Hermoni-Levine and Rahamimoff 1990). The presence of phosphatidylserine could be involved, for example, in Ca-+ binding to the ATPase.…”

Changes in Cellular and Plasma Membrane Phospholipid Composition after Lipopolysaccharide Stimulation of Human Neutrophils, Studied by 31P NMR

“…The overall increased PtdSer content could be of great importance to cell function. The induction of a different ionic environment by increased levels of acidic PtdSer may occur on stimulation of the cells and this could be linked to the activities of PtdSer-dependent enzymes, such as protein kinase C and Ca2 ' -ATPase (Nishizuka, 199.5 ;Hermoni-Levine and Rahamimoff, 1990). While the bilayer distribution of the PtdSer under the conditions of stimulation used here is unknown, surface exposure of PtdSer and certain proteins on the neutrophils may be linked to their apoptosis and subsequent phagocytosis by macrophages, thus avoiding the release of inflammatory components which would occur if the cells lysed (Fadok et al, 1993).…”