Mitochondrial genome-knockout cells demonstrate a dual mechanism of action for the electron transport complex I inhibitor mycothiazole.
Mycothiazole, a polyketide metabolite isolated from the marine sponge Cacospongia mycofijiensis, is a potent inhibitor of metabolic activity and mitochondrial electron transport chain complex I in sensitive cells, but other cells are relatively insensitive to the drug. Sensitive cell lines (IC(50) 0.36-13.8 nM) include HeLa, P815, RAW 264.7, MDCK, HeLa S3, 143B, 4T1, B16, and CD4/CD8 T cells. Insensitive cell lines (IC(50) 12.2-26.5 μM) include HL-60, LN18, and Jurkat. Thus, there is a 34,000-fold difference in sensitivity between HeLa and HL-60 cells. Some sensitive cell lines show a biphasic response, suggesting more than one mechanism of action. Mitochondrial genome-knockout ρ(0) cell lines are insensitive to mycothiazole, supporting a conditional mitochondrial site of action. Mycothiazole is cytostatic rather than cytotoxic in sensitive cells, has a long lag period of about 12 h, and unlike the complex I inhibitor, rotenone, does not cause G(2)/M cell cycle arrest. Mycothiazole decreases, rather than increases the levels of reactive oxygen species after 24 h. It is concluded that the cytostatic inhibitory effects of mycothiazole on mitochondrial electron transport function in sensitive cell lines may depend on a pre-activation step that is absent in insensitive cell lines with intact mitochondria, and that a second lower-affinity cytotoxic target may also be involved in the metabolic and growth inhibition of cells.
Centre for Biodiscovery and Schools of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
Kirsten J
KJ
Meyer
Centre for Biodiscovery and School of Chemical and Physical Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
A Jonathan
AJ
Singh
Malaghan Institute of Medical Research, Wellington, New Zealand.
Alanna
A
Cameron
Malaghan Institute of Medical Research, Wellington, New Zealand.
An S
AS
Tan
Centre for Biodiscovery and Schools of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
Dora C
DC
Leahy
Centre for Biodiscovery and Schools of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
David
D
O'Sullivan
Centre for Biodiscovery and Schools of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
Praneta
P
Joshi
Centre for Biodiscovery and Schools of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
Anne C
AC
La Flamme
Centre for Biodiscovery and School of Chemical and Physical Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
Peter T
0000-0001-8168-2215
PT
Northcote
Malaghan Institute of Medical Research, Wellington, New Zealand.
Michael V
MV
Berridge
Centre for Biodiscovery and Schools of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington, New Zealand.
John H
JH
Miller
D000818:Animals; D059001:Aquatic Organisms / Q000737:chemistry / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004285:Dogs; D042967:Electron Transport Complex I / Q000037:antagonists & inhibitors*; D054629:Genome, Mitochondrial; D018922:HL-60 Cells; D006367:HeLa Cells; D006801:Humans; D019169:Jurkat Cells; D051379:Mice; D008928:Mitochondria / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D011161:Porifera / Q000737:chemistry / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013844:Thiazoles / Q000494:pharmacology*
D017382:Reactive Oxygen Species; D013844:Thiazoles; C508681:mycothiazole; D042967:Electron Transport Complex I