title: Can proton pumping by SERCA enhance the regulatory role of phospholamban and sarcolipin?
abstract: The effect of the incorporation of phosphorylated phospholamban (pPLN) and sarcolipin (SLN) in mercury-supported self-assembled lipid monolayers and in lipid bilayers tethered to mercury via a hydrophilic spacer was investigated by voltammetric techniques and electrochemical impedance spectroscopy. It was shown that pPLN and SLN do not permeabilize lipid bilayers toward ions at physiological pH. However, they exert a permeabilizing action toward inorganic monovalent cations such as K(+) and Tl(+), but not toward divalent cations such as Ca(2+) and Cd(2+), following a small decrease in pH. This behavior can be associated with their regulatory action on the Ca-ATPase of the sarcoplasmic reticulum (SERCA). SERCA pumps two Ca(2+) ions from the cytosol to the lumen of the sarcoplasmic reticulum (SR) and two protons in the opposite direction, causing a transient decrease of pH in the immediate vicinity of its cytoplasmic domain. This decrease is expected to activate the liberated pPLN molecules and SLN to make the SR membrane leakier toward K(+) and Na(+) and the SLN ion channel to translocate small inorganic anions, such as Cl(-). The effect of pPLN and SLN, which becomes synergic when they are both present in the SR membrane, is expected to favor a rapid equilibration of ions on both sides of the membrane.
authors.affiliation: Department of Chemistry, University of Padova, Via Marzolo 1, 35131, Padova, Italy. Electronic address: lucia.becucci@unifi.it.
authors.forename: Lucia
authors.initials: L
authors.lastname: Becucci
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Foresti
authors.forename: Adrian
authors.initials: A
authors.lastname: Schwan
authors.forename: Rolando
authors.initials: R
authors.lastname: Guidelli
mesh_terms: D002135:Calcium-Binding Proteins / Q000378:metabolism*; D058266:Dielectric Spectroscopy; D008051:Lipid Bilayers; D008628:Mercury / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism; D011510:Proteolipids / Q000378:metabolism*; D017494:Proton Pumps / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000378:metabolism*; D000099211:Phospholamban
chemical_list: D002135:Calcium-Binding Proteins; D008051:Lipid Bilayers; D008628:Mercury; D009124:Muscle Proteins; D010713:Phosphatidylcholines; D011510:Proteolipids; D017494:Proton Pumps; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000099211:Phospholamban; C077258:sarcolipin; C017251:1,2-oleoylphosphatidylcholine
keywords: Bioelectrochemistry; Cyclic voltammetry; Dioleoylphosphatidylcholine; Self-assembled lipid monolayers; Tethered bilayer lipid membranes