Identification of the molecular attributes required for aminoglycoside activity against Leishmania

Abstract

Leishmaniasis, a parasitic disease caused by protozoa of the genus Leishmania , affects millions of people worldwide. Aminoglycosides are mostly known as highly potent, broad-spectrum antibiotics that exert their antibacterial activity by selectively targeting the decoding A site of the bacterial ribosome, leading to aberrant protein synthesis. Recently, some aminoglycosides have been clinically approved and are currently used worldwide for the treatment of leishmaniasis; however the molecular details by which aminoglycosides induce their deleterious effect on Leishmaina is still rather obscure. Based on high conservation of the decoding site among all kingdoms, it is assumed that the putative binding site of these agents in Leishmania is the ribosomal A site. However, although recent X-ray crystal structures of the bacterial ribosome in complex with aminoglycosides shed light on the mechanism of aminoglycosides action as antibiotics, no such data are presently available regarding their binding site in Leishmania . We present crystal structures of two different aminoglycoside molecules bound to a model of the Leishmania ribosomal A site: Geneticin (G418), a potent aminoglycoside for the treatment of leishmaniasis at a 2.65-Å resolution, and Apramycin, shown to be a strong binder to the leishmanial ribosome lacking an antileishmanial activity at 1.4-Å resolution. The structural data, coupled with in vitro inhibition measurements on two strains of Leishmania , provide insight as to the source of the difference in inhibitory activity of different Aminoglycosides. The combined structural and physiological data sets the ground for rational design of new, and more specific, aminoglycoside derivatives as potential therapeutic agents against leishmaniasis.

A Bright Future for Antibiotics?

“…Furthermore, owing to their key role in life, ribosomes are targeted by many antimicrobial drugs. The high-resolution crystal structures of ribosomes, from bacteria suitable to serve as pathogen models in complex with antibiotics and their semisynthetic derivatives, provide matchless insights into common properties of antibiotic action (6,. Thus, almost all of the structural elements involved in antibiotic binding and of the mechanisms underlying the inhibition action of antimicrobial therapeutics have been identified.…”

“…Among these are the oxazolidinone linezolid and several selective aminoglycoside variants capable of "fixing" damaged genes during the translation process and thus may provide a general tool for the treatment of genetic diseases caused by nonsense mutations (52,53) as well as inhibit protein biosynthesis in parasites such as Leishmania spp. (6,54).…”

Antileishmanial Chemotherapy: A Literature Review

“…[122][123] Nestes trabalhos, destacam-se os derivados de paromomicina dissubstituídos, incluindo geneticina (G418), como candidatos promissores que atuam no RNA ribossomal (RNAr) do protozoário. Os rearranjos estruturais, promovidos pela interação destes derivados, no sítio de ligação do RNAr se assemalham aos encontrados em RNAr bacterianos.…”

“…Dessa forma, sugere-se que o mecanismo de ação desses agentes antileishmaniais se assemelha ao descrito para bactérias. [122][123] De acordo com Shalev e colaboradores (2015), a paromomicina se liga ao sítio A do RNAr através dos anéis I e II, denominados de grupo paromamina. Assim, o anel I interage via ligação de hidrogênio com adenina-1491 (A1491) e guanina-1408 (G1408), e o anel II interage com A1492 e A1493 via interação eletrostática iônica, estabilizando uma conformação em que os nucleotídeos se localizam para fora da porção central da hélice de RNAr.…”

“…Assim, o anel I interage via ligação de hidrogênio com adenina-1491 (A1491) e guanina-1408 (G1408), e o anel II interage com A1492 e A1493 via interação eletrostática iônica, estabilizando uma conformação em que os nucleotídeos se localizam para fora da porção central da hélice de RNAr. [121][122][123][124] Interações semelhantes foram relatadas entre aminoglicosídeos, que apresentam o grupo paromamina, e RNAr bacterianos, indicando que esses dois anéis são essenciais para a interação com ribossomos de procariotos e eucariotos. [121][122][123][124] Em adição, a presença do grupo -OH na posição ' do a el I au e ta a ati idade antileishmania desses compostos, quando comparados com derivados que apresentam o grupo -NH 2 na mesma posição.…”