Interaction of the tumor inhibitor IKP-104, a 4(1H)-pyridinone derivative, with microtubule proteins.
The effects of a mitotic arrestant, IKP-104, which has an antitumor activity, on the in vitro polymerization and depolymerization of rat brain microtubules were investigated. IKP-104 inhibited microtubule polymerization at concentrations greater than 0.71 x 10(-6) M, and its IC50 value was determined to be 1.31 x 10(-6) M by probit analysis. Fifty-two percent of pre-polymerized microtubules depolymerized at 1.31 x 10(-6) M IKP-104. Electron micrographs of microtubules taken immediately after treatment with 1 x 10(-3) M IKP-104 revealed a fraying of microtubule ends into elongated coil-like filaments, which were composed of 2 or 3 protofilaments. When microtubule protein treated with 1 x 10(-3) M IKP-104 was cleaved by trypsin, fragments of 41, 36, 34, 23, 21, 19 and 16 kilodaltons (kDa) derived from alpha-tubulin were produced. In particular, the 19, 23, and 34 kDa fragments were characteristically observed in the trypsin cleavage of microtubules tested with IKP-104, and these fragments were not observed with untreated microtubules. The effects of IKP-104 on microtubule protein mentioned above were mostly similar to those of vinblastine (VLB) and we suggest that IKP-104 bound to the site or sites near "VLB-binding site or sites" of alpha-tubulin subunit, resulting in induction of conformational changes.
Mizuhashi
F
F
Life Science Research Institute, Kumiai Chemical Industry Co., Ltd., Shizuoka.
Murata
K
K
Kitagaki
T
T
Tomita
I
I
D000818:Animals; D003078:Colchicine / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D005455:Fluorescent Antibody Technique; D015151:Immunoblotting; D008854:Microscopy, Electron; D008868:Microtubule Proteins / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D011728:Pyridones / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D014747:Vinblastine / Q000494:pharmacology
D008868:Microtubule Proteins; D011728:Pyridones; C067096:IKP 104; D014747:Vinblastine; D003078:Colchicine