The effects of conformational constraints and steric bulk in the amino acid moiety of philanthotoxins on AMPAR antagonism

TY - JOUR

T1 - The effects of conformational constraints and steric bulk in the amino acid moiety of philanthotoxins on AMPAR antagonism

AU - Jørgensen, Malene

AU - Olsen, Christian A

AU - Mellor, Ian R

AU - Usherwood, Peter N R

AU - Witt, Matthias

AU - Franzyk, Henrik

AU - Jaroszewski, Jerzy W

PY - 2005

Y1 - 2005

N2 - Philanthotoxin-343 (PhTX-343), a synthetic analogue of wasp toxin PhTX-433, is a noncompetitive antagonist at ionotropic receptors (e.g., AChR or iGluR). To determine possible effects of variations of the amino acid side chain, a library consisting of seventeen PhTX-343 analogues was prepared. Thus, tyrosine was replaced by either apolar, conformationally constrained, or bulky amino acids, whereas the acyl unit and the polyamine moiety were kept unchanged. Analogues with tertiary amide groups were prepared for the first time. Pentafluorophenyl esters were employed for amide bond formation, establishing general protocols for philanthotoxin solution- and solid-phase synthesis (39-90% and 42-54% overall yields, respectively). The analogues were tested for their ability to antagonize kainate-induced currents of 2-amino-3-(3-hydroxy-5-methyl-4-isoxazoyl)propanoic acid receptors (AMPAR) expressed in Xenopus oocytes from rat brain mRNA. This showed that steric bulk in the amino acid moiety is well tolerated and suggests that binding to AMPAR does not involve the alpha-NHCO group as a donor in hydrogen bonding.

AB - Philanthotoxin-343 (PhTX-343), a synthetic analogue of wasp toxin PhTX-433, is a noncompetitive antagonist at ionotropic receptors (e.g., AChR or iGluR). To determine possible effects of variations of the amino acid side chain, a library consisting of seventeen PhTX-343 analogues was prepared. Thus, tyrosine was replaced by either apolar, conformationally constrained, or bulky amino acids, whereas the acyl unit and the polyamine moiety were kept unchanged. Analogues with tertiary amide groups were prepared for the first time. Pentafluorophenyl esters were employed for amide bond formation, establishing general protocols for philanthotoxin solution- and solid-phase synthesis (39-90% and 42-54% overall yields, respectively). The analogues were tested for their ability to antagonize kainate-induced currents of 2-amino-3-(3-hydroxy-5-methyl-4-isoxazoyl)propanoic acid receptors (AMPAR) expressed in Xenopus oocytes from rat brain mRNA. This showed that steric bulk in the amino acid moiety is well tolerated and suggests that binding to AMPAR does not involve the alpha-NHCO group as a donor in hydrogen bonding.

KW - Animals

KW - Biochemistry

KW - Brain

KW - Cells, Cultured

KW - Drug Evaluation, Preclinical

KW - Excitatory Amino Acid Antagonists

KW - Female

KW - Inhibitory Concentration 50

KW - Oocytes

KW - Phenols

KW - Polyamines

KW - Rats

KW - Receptors, Glutamate

KW - Structure-Activity Relationship

U2 - 10.1021/jm049906w

DO - 10.1021/jm049906w

M3 - Journal article

C2 - 15634001

SN - 0022-2623

VL - 48

SP - 56

EP - 70

JO - Journal of Medicinal Chemistry

JF - Journal of Medicinal Chemistry

IS - 1

ER -