Synthesis and hydrolytic stability of cyclic phosphatidic acids: implications for synthetic- and proto-cell studies

Mg2+-driven selection of natural phosphatidic acids in primitive membranes

Biological membranes are composed exclusively of phospholipids comprising glycerol-1-phosphate or glycerol-3-phosphate. By contrast, primitive membranes would have likely been composed of heterogeneous mixtures of phospholipids, including non-natural analogues comprising glycerol-2-phosphate, as delivered by prebiotic synthesis. Thus, it is not clear how the selection of natural phospholipids could have come about. Here we show how differences in supramolecular properties, but not molecular properties, could have driven the selection of natural phosphatidic acids in primitive membranes. First, we demonstrate that at the molecular level it is unlikely that any prebiotic synthesis or hydrolysis pathway would have enabled the selection of natural phosphatidic acids. Second, we report that at the supramolecular level, natural phospholipids display a greater tendency to self-assemble in more packed and rigid membranes than non-natural analogues of the same chain length. Finally, taking advantage of these differences, we highlight that Mg2+, but not Na+, K+, Ca2+ or Zn2+, drives the selective precipitation of non-natural phosphatidic acids from heterogeneous mixtures obtained by prebiotic synthesis, leaving membranes proportionally enriched in natural phosphatidic acids. Our findings delineate a plausible pathway by which the transition towards biological membranes could have occurred under conditions compatible with prebiotic metal-driven processes, such as non-enzymatic RNA polymerization.

Chemical Synthesis of 6-Azido-6-Deoxy Derivatives of Phosphatidylinositol Containing Different Fatty Acid Chains

This paper describes the synthesis of two 6-azido-6-deoxy derivatives of phosphatidylinositol (PI), which contained different fatty acid chains. These syntheses, starting from methyl α-d-glucopyranoside, employed multiple regioselective transformations with Ferrier rearrangement as one of the key steps. The PI derivatives contained different fatty acid chains in the lipids and an azido group in the inositol residue to facilitate their further functionalization under bioorthogonal conditions. Therefore, they should be useful probes for the investigation of PI and related biology, such as PI phosphorylation, PI interaction with other molecules in cells, and the functions of lipid structures in these processes.

Protocol for preparing cyclic-phospholipid decanoate and glyceryl-didecanoate-phosphate-containing vesicles

Cyclic-phospholipids-based vesicles can play a role in facilitating the chemical evolution of protocells from the structurally simple to the functionally more complex form. Here, we present a protocol for preparing decanoic acid-derived cyclic phospholipid and glyceryl-diester phosphate-containing vesicles. We describe steps for sample preparation, equilibration, and image acquisition using confocal microscopy. This protocol has the potential for preparing a wide variety of these phospholipid-based artificial cell constructs. For complete details on the use and execution of this protocol, please refer to Pulletikurti et al.1.

Cyclophospholipids Enable a Protocellular Life Cycle

There is currently no plausible path for the emergence of a self-replicating protocell, because prevalent formulations of model protocells are built with fatty acid vesicles that cannot withstand the concentrations of Mg2+ needed for the function and replication of nucleic acids. Although prebiotic chelates increase the survivability of fatty acid vesicles, the resulting model protocells are incapable of growth and division. Here, we show that protocells made of mixtures of cyclophospholipids and fatty acids can grow and divide in the presence of Mg2+-citrate. Importantly, these protocells retain encapsulated nucleic acids during growth and division, can acquire nucleotides from their surroundings, and are compatible with the nonenzymatic extension of an RNA oligonucleotide, chemistry needed for the replication of a primitive genome. Our work shows that prebiotically plausible mixtures of lipids form protocells that are active under the conditions necessary for the emergence of Darwinian evolution.

A Review of Cyclic Phosphatidic Acid and Other Potential Therapeutic Targets for Treating Osteoarthritis

Osteoarthritis (OA), a chronic degenerative joint disease, is the most common form of arthritis. OA occurs when the protective cartilage that cushions the ends of bones gradually breaks down. This leads to the rubbing of bones against each other, resulting in pain and stiffness. Cyclic phosphatidic acid (cPA) shows promise as a treatment for OA. In this article, we review the most recent findings regarding the biological functions of cPA signaling in mammalian systems, specifically in relation to OA. cPA is a naturally occurring phospholipid mediator with unique cyclic phosphate rings at the sn-2 and sn-3 positions in the glycerol backbone. cPA promotes various responses, including cell proliferation, migration, and survival. cPA possesses physiological activities that are distinct from those elicited by lysophosphatidic acid; however, its biochemical origin has rarely been studied. Although there is currently no cure for OA, advances in medical research may lead to new therapies or strategies in the future, and cPA has potential therapeutic applications.

GDE7 produces cyclic phosphatidic acid in the ER lumen functioning as a lysophospholipid mediator

Cyclic phosphatidic acid (cPA) is a lipid mediator, which regulates adipogenic differentiation and glucose homeostasis by suppressing nuclear peroxisome proliferator-activated receptor γ (PPARγ). Glycerophosphodiesterase 7 (GDE7) is a Ca2+-dependent lysophospholipase D that localizes in the endoplasmic reticulum. Although mouse GDE7 catalyzes cPA production in a cell-free system, it is unknown whether GDE7 generates cPA in living cells. Here, we demonstrate that human GDE7 possesses cPA-producing activity in living cells as well as in a cell-free system. Furthermore, the active site of human GDE7 is directed towards the luminal side of the endoplasmic reticulum. Mutagenesis revealed that amino acid residues F227 and Y238 are important for catalytic activity. GDE7 suppresses the PPARγ pathway in human mammary MCF-7 and mouse preadipocyte 3T3-L1 cells, suggesting that cPA functions as an intracellular lipid mediator. These findings lead to a better understanding of the biological role of GDE7 and its product, cPA.