Chaperone-like Properties of Lysophospholipids Rene ´e Kern, Danie `le Joseleau-Petit, Madhab K. Chattopadhyay, and Gilbert Richarme 1 Stress Molecules, Institut Jacques Monod, Universite ´ Paris 7, 2 place Jussieu, 75005 Paris, France Received November 6, 2001 Lysophospholipids are metabolic intermediates in phospholipid turnover, detergent molecules with membrane-modulating effects, and multifunctional cellular growth factors in eukaryotic cells. In bacterial cells, lysophospholipids are mostly found in the form of lysophosphatidylethanolamine. We show that a heat shock from 30 to 42°C increases four-fold the Esche- richia coli pool of lysophosphoethanolamine and that lysophospholipids display chaperone-like properties. Lysophosphatidylethanolamine, like molecular chap- erones such as DnaK, promotes the functional folding of citrate synthase and -glucosidase after urea de- naturation. Like chaperones, lysophophatidyletha- nolamine, lysophosphatidylcholine, lysophosphatidyl- inositol and lysophosphatidic acid prevent the aggre- gation of citrate synthase at 42°C. The renaturation and solubilisation of proteins by lysophospholipids oc- cur at micromolar concentrations of these compounds, close to their critical micellar concentration. Further- more, lysophosphatidylethanolamine is much more efficient than other detergents tested for the renatur- ation and solubilisation of citrate synthase. In con- trast with lysophospholipids, phosphatidylethanol- amine and phosphatidylcholine are not able to pro- mote citrate synthase folding nor to prevent its aggre- gation at 42°C. The chaperone-like properties of lyso- phospholipids suggest that, in addition to their known functions, they might affect the structure and function of hydrophilic proteins. © 2001 Elsevier Science Key Words: lysophospholipids; lysophosphatidyleth- anolamine; detergents; chaperone; protein folding; protein aggregation. Lysophospholipids can be biosynthetized by cells ei- ther de novo from the reaction of glycerol 3-phosphate with a fatty acyl-CoA or through conversion of glycero- phospholipids to lysophospholipids by A1 or A2 phos- pholipases. Cell membranes contain only low levels of free lysophospholipids, presumably because these lat- ter are converted back to phospholipids by lysophos- pholipid acyltransferases (1). Lysophospholipids be- long to the family of detergent molecules (2). Like other detergents, they interact with the lipid and the protein moiety of membranes, and modulate the function of membrane proteins, including several ion channels and the Na + ,K + -ATPase (3, 4). In eukaryotic cells, lysophosphatidic acid and sphingosine 1-phosphate are highly active cellular growth factors which act via G-protein-coupled membrane receptors (5). In bacteria, lysophospholipids exist mainly in the form of lysophos- phatidylethanolamine. LPE is found in small amounts (around 2% of phosphatidylethanolamine) (6). Phos- phatidylethanolamine hydrolysis is catalyzed by phos- pholipase A1 (the pldA gene product) located in the outer membrane (7). Another phospholipase A activity has been detected in the bacterial cytoplasm (8). Sev- eral other enzymatic systems participate in LPE me- tabolism: 2-acylLPE is reacylated to phosphatidyleth- anolamine by the aas gene product, located in the inner membrane (9). 2-Acyl LPE can also be converted to glycerol-3-phosphoethanolamine by lysophospholipase L2 (the pldB gene product), located in the inner mem- brane (10) or by lysophospholipase L1 which is cyto- plasmic (11). The phospholipase activity in Escherichia coli cells increases considerably in certain conditions: during phage lysis, colicin release, EDTA treatment, or after a shift to high temperatures (50 –55°C) that are not compatible with bacterial growth (7). For colicin excretion, the bacteriocin-release protein activates phospholipase A1 by dimerisation (12), resulting in a large increase in LPE pools and a perturbation of en- velope integrity (13). In the present study we show that a mild heat shock from 30 to 42°C leads to a 4-fold increase in LPE pools of growing E. coli. We also show that lysophosphati- dylethanolamine, like molecular chaperones (14, 15) and chemical chaperones (16, 17), increases the refold- ing of unfolded proteins after urea denaturation and that several lysophospolipids protect citrate synthase against thermal denaturation. Molecular chaperones form a class of polypeptide binding proteins that are Abbreviations used: LPE, lysophosphatidylethanolamine; LPA, ly- sophosphatidic acid; LPI, lysophosphatidylinositol; LPC, lysophos- phatidylcholine; CHAPS, (3-(3-cholamidopropyl)-dimethylammo- nio)-1-propanesulfonate); cmc, critical micellar concentration. 1 To whom correspondence should be addressed. Fax: 33 01 44 27 35 80. E-mail: richarme@ccr.jussieu.fr. Biochemical and Biophysical Research Communications 289, 1268 –1274 (2001) doi:10.1006/bbrc.2001.6093, available online at http://www.idealibrary.com on 1268 0006-291X/01 $35.00 © 2001 Elsevier Science All rights reserved.