Membrane Organization and Ionization Behavior of the Minor but Crucial Lipid Ceramide-1-Phosphate

@article{citeulike:2800265, abstract = {Ceramide-1-phosphate (Cer-1-P), one of the simplest of all sphingophospholipids, occurs in minor amounts in biological membranes. Yet recent evidence suggests important roles of this lipid as a novel second messenger with crucial tasks in cell survival and inflammatory responses. We present a detailed description of the physical chemistry of this hitherto little explored membrane lipid. At full hydration Cer-1-P forms a highly organized subgel (crystalline) bilayer phase (Lc) at low temperature, which transforms into a regular gel phase (L) at [\~{}]45{degrees}C, with the gel to fluid phase transition (L-L{alpha}) occurring at [\~{}]65{degrees}C. When incorporated at 5 mol \% in a phosphatidylcholine bilayer, the pKa2 of Cer-1-P, 7.39 {+/-} 0.03, lies within the physiological pH range. Inclusion of phosphatidylethanolamine in the phosphatidylcholine bilayer, at equimolar ratio, dramatically reduces the pKa2 to 6.64 {+/-} 0.03. We explain these results in light of the novel electrostatic/hydrogen bond switch model described recently for phosphatidic acid. In mixtures with dielaidoylphosphatidylethanolamine, small concentrations of Cer-1-P cause a large reduction of the lamellar-to-inverted hexagonal phase transition temperature, suggesting that Cer-1-P induces, like phosphatidic acid, negative membrane curvature in these types of lipid mixtures. These properties place Cer-1-P in a class more akin to certain glycerophospholipids (phosphatidylethanolamine, phosphatidic acid) than to any other sphingolipid. In particular, the similarities and differences between ceramide and Cer-1-P may be relevant in explaining some of their physiological roles. 10.1529/biophysj.107.121046}, author = {Kooijman, Edgar E. and Sot, Jesus and Montes and Alonso, Alicia and Gericke, Arne and de Kruijff, Ben and Kumar, Satyendra and Goni, Felix M. }, citeulike-article-id = {2800265}, doi = {http://dx.doi.org/10.1529/biophysj.107.121046}, journal = {Biophys. J.}, keywords = {biomembranes, pka}, month = {June}, number = {11}, pages = {4320--4330}, posted-at = {2008-07-08 12:07:18}, priority = {0}, title = {Membrane Organization and Ionization Behavior of the Minor but Crucial Lipid Ceramide-1-Phosphate}, url = {http://dx.doi.org/10.1529/biophysj.107.121046}, volume = {94}, year = {2008} }

TY - JOUR ID - citeulike:2800265 L3 - citeulike-article-id:2800265 TI - Membrane Organization and Ionization Behavior of the Minor but Crucial Lipid Ceramide-1-Phosphate JF - Biophys. J. VL - 94 IS - 11 SP - 4320 EP - 4330 N2 - Ceramide-1-phosphate (Cer-1-P), one of the simplest of all sphingophospholipids, occurs in minor amounts in biological membranes. Yet recent evidence suggests important roles of this lipid as a novel second messenger with crucial tasks in cell survival and inflammatory responses. We present a detailed description of the physical chemistry of this hitherto little explored membrane lipid. At full hydration Cer-1-P forms a highly organized subgel (crystalline) bilayer phase (Lc) at low temperature, which transforms into a regular gel phase (L) at [~]45{degrees}C, with the gel to fluid phase transition (L-L{alpha}) occurring at [~]65{degrees}C. When incorporated at 5 mol % in a phosphatidylcholine bilayer, the pKa2 of Cer-1-P, 7.39 {+/-} 0.03, lies within the physiological pH range. Inclusion of phosphatidylethanolamine in the phosphatidylcholine bilayer, at equimolar ratio, dramatically reduces the pKa2 to 6.64 {+/-} 0.03. We explain these results in light of the novel electrostatic/hydrogen bond switch model described recently for phosphatidic acid. In mixtures with dielaidoylphosphatidylethanolamine, small concentrations of Cer-1-P cause a large reduction of the lamellar-to-inverted hexagonal phase transition temperature, suggesting that Cer-1-P induces, like phosphatidic acid, negative membrane curvature in these types of lipid mixtures. These properties place Cer-1-P in a class more akin to certain glycerophospholipids (phosphatidylethanolamine, phosphatidic acid) than to any other sphingolipid. In particular, the similarities and differences between ceramide and Cer-1-P may be relevant in explaining some of their physiological roles. 10.1529/biophysj.107.121046 KW - biomembranes KW - pka AU - Kooijman, Edgar AU - Sot, Jesus AU - Montes AU - Alonso, Alicia AU - Gericke, Arne AU - de Kruijff, Ben AU - Kumar, Satyendra AU - Goni, Felix PY - 2008/06/01/ UR - http://dx.doi.org/10.1529/biophysj.107.121046 ER -