A glycosylated antitumor ether lipid kills cells via paraptosis-like cell death.
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.
Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, MB R3E0W3, Canada.
Pranati
P
Samadder
Robert
R
Bittman
Hoe-Sup
HS
Byun
Gilbert
G
Arthur
D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D001343:Autophagy / Q000187:drug effects; D000071187:Autophagy-Related Protein 5; D016466:CHO Cells; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D004354:Drug Screening Assays, Antitumor; D006017:Glycolipids / Q000737:chemistry / Q000494:pharmacology*; D006031:Glycosylation / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D048848:MAP Kinase Kinase Kinase 5 / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000172:deficiency / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011494:Protein Kinases / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D058570:TOR Serine-Threonine Kinases; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism
C542419:1-O-hexadecyl-2-O-methyl-3-O-(2'-amino-2'-deoxy-beta-D-glucopyranosyl)-sn-glycerol; D000970:Antineoplastic Agents; C495773:Atg5 protein, mouse; D000071187:Autophagy-Related Protein 5; D006017:Glycolipids; D008869:Microtubule-Associated Proteins; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D011494:Protein Kinases; C546842:MTOR protein, human; C546843:mTOR protein, mouse; D058570:TOR Serine-Threonine Kinases; D048848:MAP Kinase Kinase Kinase 5; C482859:Map3k5 protein, mouse; D020169:Caspases