The Amaryllidaceae Alkaloid Haemanthamine Binds the Eukaryotic Ribosome to Repress Cancer Cell Growth

Abstract

Alkaloids isolated from the Amaryllidaceae plants have potential as therapeutics for treating human diseases. Haemanthamine has been studied as a novel anticancer agent due to its ability to overcome cancer cell resistance to apoptosis. Biochemical experiments have suggested that hemanthamine targets the ribosome. However, a structural characterization of its mechanism has been missing. Here we present the 3.1 Å resolution X-ray structure of haemanthamine bound to the Saccharomyces cerevisiae 80S ribosome. This structure reveals that haemanthamine targets the A-site cleft on the large ribosomal subunit rearranging rRNA to halt the elongation phase of translation. Furthermore, we provide evidence that haemanthamine and other Amaryllidaceae alkaloids also inhibit specifically ribosome biogenesis, triggering nucleolar stress response and leading to p53 stabilization in cancer cells. Together with a computer-aided interpretation of existing structure-activity relationships of Amaryllidaceae alkaloids congeners, we provide a rationale for designing molecules with enhanced potencies and reduced toxicities.

Ribosome biogenesis: An emerging druggable pathway for cancer therapeutics

“…1 -Boxes 2 and 3) could be developed. One such case is haemanthamine, a natural alkaloid extracted from Daffodil bulbs, the anticancer properties of which have been used in folk medicine for centuries and have only recently been deciphered [60]. Indeed, it was demonstrated that this molecule targets both ribosome function, by sterically blocking translation, and ribosome production, by inhibiting RNA processing specifically; this latter property providing the added advantage of a potent activation of the nucleolar stress response leading to strong p53 stabilization [60].…”

“…In particular, recent structural analysis of prokaryotic and eukaryotic ribosomes demonstrated that selectivity of ligand [Note: By "ligand", we refer to any molecule that can bind to the ribosome, i.e. tRNA, r-protein, translational factor, or small molecule inhibitors, including antibiotics and compounds active towards eukaryotic ribosomes] binding is often provided by subtle differences in the structure of the ribosome [60,[90][91][92][93][94][95]. For instance, the anticancer compound haemanthamine, presented above, binds exclusively to eukaryotic ribosomes, since its binding site is slightly different in bacterial compared to human ribosomes, and is consequently only active in human cells [60].…”

“…tRNA, r-protein, translational factor, or small molecule inhibitors, including antibiotics and compounds active towards eukaryotic ribosomes] binding is often provided by subtle differences in the structure of the ribosome [60,[90][91][92][93][94][95]. For instance, the anticancer compound haemanthamine, presented above, binds exclusively to eukaryotic ribosomes, since its binding site is slightly different in bacterial compared to human ribosomes, and is consequently only active in human cells [60]. Interestingly, resistance to antibiotics often relies on chemical modifications of the ribosomes [90,96], illustrating that changes as faint as a single chemical modification are sufficient to prevent the binding of small molecule inhibitors.…”

A Brief Up-to-Date Overview of Amaryllidaceae Alkaloids: Phytochemical Studies of Narcissus tazetta subsp. tazetta L., Collected in Turkey

“…13 Furthermore, studies on haemanthamine's mode of action involving the ribosome receptor were also recently reported. 14 A new alkaloid, jonquailine (4, Figure 1), belonging to the pretazettine group of Amaryllidaceae alkaloids, was isolated from dried bulbs of Narcissus jonquilla (quail) collected in Middlesex county of southeast England. 15 The main alkaloids of N. jonquilla quail were galanthamine and haemanthamine.…”

Anti-Tumor Activity of Some Natural Compounds

“…Изохинолиновые алкалоиды хемантамин и хемантидин из растений семейства Amaryllidaceae блокируют синтез белков рибосомами, что замедляет рост опухолевых клеток, вызывает апоптоз p53-негативныхJurkat-клеток человеческой лейкемии. Апоптотический эффект гемантамина и гемантидина на лейкемические клетки более выражен, чем у гамма-излучения[23,24].Достаточно много исследований посвящено противоопухолевой активности растительных терпеноидов[4,5,25]. Структурная схожесть с терпеноидами клеток млекопитающих объясняет их способность снижать активность фарнезилтрансферазы и участвовать в регуляции сигналов белков семейства Ras[26].…”