Differential effects of ethyl 5-amino-2-methyl-1,2-dihydro-3-phenylpyrido[3,4-b]pyrazin-7-yl carbamate analogs modified at position C2 on tubulin polymerization, binding, and conformational changes.
NSC 613863 (R)-(+) and NSC 613862 (S)-(-) (CI980) are two chiral isomers of ethyl 5-amino 2-methyl-1,2-dihydro-3-phenylpyrido[3,4-b]pyrazin-7-yl carbamate which have potent antitubulin activity. The S-isomer is a more potent antimitotic compound than the R-isomer, and the two isomers differ markedly in binding to tubulin [Leynadier, D., Peyrot, V., Sarrazin, M., Briand, C., Andreu, J. M., Rener, G. A., & Temple, C., Jr. (1993) Biochemistry 32, 10675-10682]. To understand the origin of such differences, we studied the interactions of three R- and S-isomer structural analogs which differ in C2 (the chiral carbon), i.e., C179, NSC 337238, and NSC 330770. C179 is a methylated dehydrogenated achiral compound. It bound to tubulin with an apparent affinity Ka of (2.29 +/- 0.17) x 10(4) M-1, inhibited tubulin polymerization in vitro at a half-inhibitory concentration (IC50) of 100 microM, and presented no GTPase activity. The substitution of -CH3 by -H leads to the NSC 337238 compound. It bound to tubulin with a higher affinity [Ka = (2.62 +/- 0.35) x 10(5) M-1] and inhibited tubulin polymerization at a lower concentration (IC50 = 14 microM). It presented no GTPase activity and induced the formation of abnormal polymers at a protein critical concentration (Cr) of 2 mg mL-1. NSC 330770, a demethylated hydrogenated molecule, interacted strongly with tubulin [Ka = (3.30 +/- 0.56) x 10(6) M-1].(ABSTRACT TRUNCATED AT 250 WORDS)
Barbier
P
P
URA-CNRS 1924, Faculté Pharmacie, Marseille, France.
Peyrot
V
V
Sarrazin
M
M
Rener
G A
GA
Briand
C
C
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001665:Binding Sites; D002417:Cattle; D003078:Colchicine / Q000494:pharmacology; D004563:Electrochemistry; D020558:GTP Phosphohydrolases / Q000378:metabolism; D066298:In Vitro Techniques; D007700:Kinetics; D008024:Ligands; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D011108:Polymers / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects; D011487:Protein Conformation / Q000187:drug effects; D011719:Pyrazines / Q000494:pharmacology*; D013050:Spectrometry, Fluorescence; D013237:Stereoisomerism; D013816:Thermodynamics; D014404:Tubulin / Q000737:chemistry / Q000378:metabolism; D050257:Tubulin Modulators
D000970:Antineoplastic Agents; D008024:Ligands; D011108:Polymers; D011719:Pyrazines; D014404:Tubulin; D050257:Tubulin Modulators; C051598:NSC 330770; C047150:NSC 350386; D020558:GTP Phosphohydrolases; D003078:Colchicine