A glycosylated antitumor ether lipid kills cells via paraptosis-like cell death

Biochem Cell Biol. 2009 Apr;87(2):401-14. doi: 10.1139/o08-147.

Abstract

Glycosylated antitumor ether lipids (GAELs) have superior anticancer properties relative to the alkyllysophospholipid class, but there have been no studies of the mechanisms of these compounds. The prototype GAEL, 1-O-hexadecyl-2-O-methyl-3-O-(2'-amino-2'-deoxy-beta-D-glucopyranosyl)-sn-glycerol (Gln), effectively killed mouse embryonic fibroblasts (MEFs) lacking key molecules involved in caspase-dependent apoptosis, and cell death was not prevented by caspase inhibitors. Gln did not cause a loss of mitochondrial membrane potential, even in rounded-up dying cells. Gln stimulated the appearance and accumulation of LC3-II, a protein marker for autophagy, in a variety of cells, including wild-type MEFs, but not in MEFs lacking ATG5, a key protein required for autophagy. Gln induced LC3 puncta formation in Chinese hamster ovary cells stably expressing a LC3-green fluorescent protein fusion protein. Thus, Gln appears to induce autophagy. Autophagy was mTOR-independent and was not inhibited by 3-methyladenine or wortmannin. Although Gln is toxic, cellular ability to undergo autophagy was not essential for its toxicity. Furthermore, the GAEL analog 2-deoxy-C-Glc induced LC3 puncta formation but did not kill the cells. Gln, but not 2-deoxy-C-Glc, caused the accumulation of cytoplasmic acidic vacuoles in the cells. Our data suggest that GAELs may activate autophagy; however, GAELs do not kill cells by apoptosis or autophagy but rather by a paraptosis-like cell death mechanism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antineoplastic Agents / chemistry
  • Antineoplastic Agents / pharmacology*
  • Autophagy / drug effects
  • Autophagy-Related Protein 5
  • CHO Cells
  • Caspases / metabolism
  • Cell Death / drug effects
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Cricetinae
  • Cricetulus
  • Drug Screening Assays, Antitumor
  • Glycolipids / chemistry
  • Glycolipids / pharmacology*
  • Glycosylation / drug effects
  • Green Fluorescent Proteins / metabolism
  • Humans
  • MAP Kinase Kinase Kinase 5 / metabolism
  • Membrane Potential, Mitochondrial / drug effects
  • Mice
  • Microtubule-Associated Proteins / deficiency
  • Microtubule-Associated Proteins / metabolism
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein Kinase Inhibitors / pharmacology
  • Protein Kinases / metabolism
  • Recombinant Fusion Proteins / metabolism
  • TOR Serine-Threonine Kinases
  • Vacuoles / drug effects
  • Vacuoles / metabolism

Substances

  • 1-O-hexadecyl-2-O-methyl-3-O-(2'-amino-2'-deoxy-beta-D-glucopyranosyl)-sn-glycerol
  • Antineoplastic Agents
  • Atg5 protein, mouse
  • Autophagy-Related Protein 5
  • Glycolipids
  • Microtubule-Associated Proteins
  • Phosphoinositide-3 Kinase Inhibitors
  • Protein Kinase Inhibitors
  • Recombinant Fusion Proteins
  • Green Fluorescent Proteins
  • Protein Kinases
  • MTOR protein, human
  • mTOR protein, mouse
  • TOR Serine-Threonine Kinases
  • MAP Kinase Kinase Kinase 5
  • Map3k5 protein, mouse
  • Caspases