H OH metabolites OH Review Bioactive Ether Lipids: Primordial Modulators of Cellular Signaling Nikhil Rangholia 1,† , Tina M. Leisner 2 and Stephen P. Holly 1,* 1 Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, Campbell University, Buies Creek, NC 27506, USA;
[email protected] 2 Eshelman School of Pharmacy, Division of Chemical Biology and Medicinal Chemistry, Center for Integrative Chemical Biology and Drug Discovery, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA;
[email protected] * Correspondence:
[email protected] † Current address: Frontage Laboratories Inc., 75 E. Uwchian Ave, STE 100, Exton, PA 19341, USA. Abstract: The primacy of lipids as essential components of cellular membranes is conserved across taxonomic domains. In addition to this crucial role as a semi-permeable barrier, lipids are also increasingly recognized as important signaling molecules with diverse functional mechanisms ranging from cell surface receptor binding to the intracellular regulation of enzymatic cascades. In this review, we focus on ether lipids, an ancient family of lipids having ether-linked structures that chemically differ from their more prevalent acyl relatives. In particular, we examine ether lipid biosynthesis in the peroxisome of mammalian cells, the roles of selected glycerolipids and glycerophospholipids in signal transduction in both prokaryotes and eukaryotes, and finally, the potential therapeutic contributions of synthetic ether lipids to the treatment of cancer. Keywords: ether lipid; alkylglycerol; signaling; signal transduction; glycerolipid; glycerophospho- lipid; apoptosis; platelet; cancer 1. Introduction Citation: Rangholia, N.; Leisner, Much like many other types of organic molecules, lipids are essential for life—even T.M.; Holly, S.P.