A kainate receptor–selective RNA aptamer

Abstract

Kainate and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors are two major, closely related receptor subtypes in the glutamate ion channel family. Excessive activities of these receptors have been implicated in a number of central nervous system diseases. Designing potent and selective antagonists of these receptors, especially of kainate receptors, is useful for developing potential treatment strategies for these neurological diseases. Here, we report on two RNA aptamers designed to individually inhibit kainate and AMPA receptors. To improve the biostability of these aptamers, we also chemically modified these aptamers by substituting their 2′-OH group with 2′-fluorine. These 2′-fluoro aptamers, FB9s-b and FB9s-r, were markedly resistant to RNase-catalyzed degradation, with a half-life of ∼5 days in rat cerebrospinal fluid or serum-containing medium. Furthermore, FB9s-r blocked AMPA receptor activity. Aptamer FB9s-b selectively inhibited GluK1 and GluK2 kainate receptor subunits, and also GluK1/GluK5 and GluK2/GluK5 heteromeric kainate receptors with equal potency. This inhibitory profile makes FB9s-b a powerful template for developing tool molecules and drug candidates for treatment of neurological diseases involving excessive activities of the GluK1 and GluK2 subunits.

Kainate Receptor Antagonists: Recent Advances and Therapeutic Perspective

“…Natural RNA undergoes degradation at the 2′-OH position of the nucleoside, with the half-life (t1/2) of unmodified aptamers typically lasting a few minutes. Chemical modifications aimed at improving RNA stability and that can extend t1/2 up to several days have included the replacement of the 2'-OH group with 2′-fluoro (2′-F), 2′-OCH3 or 2′-NH2 group, capping of the 3′-end, or conjugation with polyethylene glycol (PEG) (Figure 9) [212][213][214][215][216]. [217]).…”

“…Jaremko et al applied a similar strategy in the search for selective aptamers [216,219]. The full-length leading structure-AB9 (67, 101-nt) had the ability to selectively inhibit the GluA1 and GluA2 subunits.…”

“…AB9s-r favored the AMPA receptor subunits, while AB9s-b inhibited the homomeric GluK1-3 receptors, as well as the heteromers containing the GluK5 subunit. The next step, chemical modification involving the introduction of 2 -F groups, led to the corresponding derivatives: FBs-r (71) and FBs-b (72), and both exhibited much higher stability than their precursors, but maintained the same desired selectivity [216].…”

Glutamate Receptors in Schizophrenia: A Review

“…the ion channel must be opened, so there must be cooperatively between multiple sites for uncompetitive antagonism to occur. 10 Binding sites are associated with different subunits and their affinities can vary depending on subunit composition. NMDAR1 homomers forms glycine binding sites, while NMDAR2 subunit apparently needs to form both glutamate and MK-801binding sites.…”