Molecular requisites for drug binding to muscle CLC-1 and renal CLC-K channel revealed by the use of phenoxy-alkyl derivatives of 2-(p-chlorophenoxy)propionic acid.
CLC channels are a gene family of Cl(-) channels that serve a variety of functions, several of which are involved in genetic diseases. Few specific ligands of CLC channels are known that could be useful as pharmacological tools or potential drugs. We synthesized various derivatives of 2-(p-chlorophenoxy)propionic acid, the S(-)-enantiomer of which is a specific blocker of the muscle channel CLC-1. In particular, compounds with different alkyl or phenoxy-alkyl groups on the chiral center, isosteres of the oxygen in the aryloxy moiety, or bioisosteres of the carboxy function were prepared. We found that compounds containing a phenoxy and a phenoxy-alkyl group on the chiral center (bis-phenoxy derivatives) specifically inhibited renal CLC-K channels from the extracellular side with an affinity in the 150-microM range and with almost no effect on other CLC channels when applied from the outside. Surprisingly, the same substances inhibited CLC-1 from the intracellular side in a voltage-dependent manner with an apparent K(D) of <5 microM at -140 mV, thus being the most potent blockers of a CLC channel known so far. Although the chlorine atom in para- position of the second phenoxy group was essential for inhibition of CLC-K channels from the outside, it could be substituted by a methoxy group without changing the potency of block for CLC-1 from the inside. These newly identified substances provide powerful tools for studying the structure-function relationship and the physiological role of CLC channels and may represent a starting point for the development of useful drugs targeting CLC-K channels.
Istituto di Cibernetica e Biofisica, Consiglio Nazionale delle Ricerche, Genova, Italy.
Antonella
A
Liantonio
Alessio
A
Accardi
Giuseppe
G
Carbonara
Giuseppe
G
Fracchiolla
Fulvio
F
Loiodice
Paolo
P
Tortorella
Sonia
S
Traverso
Patrizia
P
Guida
Sabata
S
Pierno
Annamaria
A
De Luca
Diana Conte
DC
Camerino
Michael
M
Pusch
D008456:2-Methyl-4-chlorophenoxyacetic Acid / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D027321:Anion Transport Proteins; D000090007:CLC-2 Chloride Channels; D018118:Chloride Channels / Q000378:metabolism*; D006801:Humans; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000037:antagonists & inhibitors; D013329:Structure-Activity Relationship; D014162:Transfection; D029867:Xenopus Proteins; D014982:Xenopus laevis
D027321:Anion Transport Proteins; C086321:CLC-1 channel; D000090007:CLC-2 Chloride Channels; C097503:CLC-5 chloride channel; C489932:CLCNKA protein, human; C412733:CLCNKB protein, human; D018118:Chloride Channels; C082118:Clcnka protein, rat; C486572:Clcnkb protein, rat; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D029867:Xenopus Proteins; C489934:clcnka protein, Xenopus; C048213:2-(4-chlorophenoxy)propionic acid; D008456:2-Methyl-4-chlorophenoxyacetic Acid