Diazonamide A and a synthetic structural analog: disruptive effects on mitosis and cellular microtubules and analysis of their interactions with tubulin.
The marine ascidian Diazona angulata was the source organism for the complex cytotoxic peptide diazonamide A. The molecular structure of this peptide was recently revised after synthesis of a biologically active analog of diazonamide A in which a single nitrogen atom was replaced by an oxygen atom. Diazonamide A causes cells to arrest in mitosis, and, after exposure to the drug, treated cells lose both interphase and spindle microtubules. Both diazonamide A and the oxygen analog are potent inhibitors of microtubule assembly, equivalent in activity to dolastatin 10 and therefore far more potent than dolastatin 15. This inhibition of microtubule assembly is accompanied by potent inhibition of tubulin-dependent GTP hydrolysis, also comparable with the effects observed with dolastatin 10. However, the remaining biochemical properties of diazonamide A and its analog differ markedly from those of dolastatin 10 and closely resemble the properties of dolastatin 15. Neither diazonamide A nor the analog inhibited the binding of [3H]vinblastine, [3H]dolastatin 10, or [8-14C]GTP to tubulin. Nor were they able to stabilize the colchicine binding activity of tubulin. These observations indicate either that diazonamide A and the analog have a unique binding site on tubulin differing from the vinca alkaloid and dolastatin 10 binding sites, or that diazonamide A and the analog bind weakly to unpolymerized tubulin but strongly to microtubule ends. If the latter is correct, diazonamide A and its oxygen analog should have uniquely potent inhibitory effects on the dynamic properties of microtubules.
Cruz-Monserrate
Zobeida
Z
Building 469, Room 104, National Cancer Institute at Frederick, Frederick, MD 21702, USA.
Vervoort
Hélène C
HC
Bai
Ruoli
R
Newman
David J
DJ
Howell
Stephen B
SB
Los
Gerrit
G
Mullaney
Jeffrey T
JT
Williams
Michael D
MD
Pettit
George R
GR
Fenical
William
W
Hamel
Ernest
E
D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D047630:Depsipeptides; D004354:Drug Screening Assays, Antitumor; D006160:Guanosine Triphosphate / Q000378:metabolism; D006576:Heterocyclic Compounds, 4 or More Rings / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D006868:Hydrolysis; D008870:Microtubules / Q000187:drug effects*; D008938:Mitosis / Q000187:drug effects*; D009842:Oligopeptides / Q000494:pharmacology; D010080:Oxazoles / Q000737:chemistry / Q000494:pharmacology*; D014404:Tubulin / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D047630:Depsipeptides; D006576:Heterocyclic Compounds, 4 or More Rings; D009842:Oligopeptides; D010080:Oxazoles; D014404:Tubulin; C075610:dolastatin 15; C408862:diazonamide A; D006160:Guanosine Triphosphate; C064570:dolastatin 10