Cycloheximide

IC50: N/A

Cycloheximide is an inhibitor of protein biosynthesis in eukaryotic organisms widely used in biomedical research to inhibit protein synthesis in eukaryotic cells studied in vitro. Due to significant toxic side effects, including teratogenesis, DNA damage, and other reproductive effects, cycloheximide is generally used only in in vitro research applications, but not suitable for human use as a therapeutic compound.

In vitro: Cycloheximide blocks the movement of peptidyl-tRNA from acceptor site to the donor site on reticulocyte ribosomes. This translocation reaction is dependent on the transfer enzyme, TF-II, and GTP hydrolysis. Cycloheximide has no effect on the ribosome dependent GTPase activity of TF-II or peptidyl transferase reaction by which peptides on tRNA in the donor ribosomal site are transferred to an amino acid on tRNA in the acceptor site [1].

In vivo: Cycloheximide treatment was effective in attenuating rat brain injury within a 6 hr therapeutic window after hypoxia-ischemia in a newborn rat pup model. These data support the possibility that protein synthesis inhibitors, as well as other anti-apoptotic strategies, may have therapeutic utility in hypoxic-ischemic (HI) events of the developing newborn brain even when treatment is delayed for up to 6 hr after the primary asphyxial insult [2].

Clinical trial: Up to now, cycloheximide is still in the preclinical development stage.

References:
[1] McKeehan W, Hardesty B.  The mechanism of cycloheximide inhibition of protein synthesis in rabbit reticulocytes. Biochem Biophys Res Commun. 1969 Aug 15;36(4):625-30.
[2] Park WS, Sung DK, Kang S, Koo SH, Kim YJ, Lee JH, Chang YS, Lee M.  Therapeutic window for cycloheximide treatment after hypoxic-ischemic brain injury in neonatal rats. J Korean Med Sci. 2006 Jun;21(3):490-4.

Cycloheximide Inhibits Actin Cytoskeletal Dynamics by Suppressing Signaling via RhoA.[Pubmed:27192630]

J Cell Biochem. 2016 Dec;117(12):2886-2898.

Genome-wide screening of the yeast Saccharomyces cerevisiae knockout collection was used to characterize chemical-genetic interactions of Cycloheximide (CHX). The results showed that while the act1Delta mutant was the only deletion mutant in the heterozygous essential gene deletion collection that showed hypersensitivity to sub-inhibitory concentrations of CHX, deletion of nonessential genes that work in concert with either cytoplasmic or nuclear actin in the homozygous deletion collection also highly sensitized yeast to CHX. Fluorescence microscopy analysis revealed that CHX disrupts filamentous actin structures and fluid phase endocytosis in the yeast cell. It also showed that CHX disrupts transforming growth factor-beta1 (TGF-beta1)-induced actin reorganization and polygonal architecture of microfilaments in mammalian cells. This inhibitory effect is mediated, at least in part, through the actin dynamics signaling pathway via suppression of activation of the small GTPase RhoA. J. Cell. Biochem. 117: 2886-2898, 2016. (c) 2016 Wiley Periodicals, Inc.

Genomic and Secondary Metabolite Analyses of Streptomyces sp. 2AW Provide Insight into the Evolution of the Cycloheximide Pathway.[Pubmed:27199910]

Front Microbiol. 2016 May 3;7:573.

The dearth of new antibiotics in the face of widespread antimicrobial resistance makes developing innovative strategies for discovering new antibiotics critical for the future management of infectious disease. Understanding the genetics and evolution of antibiotic producers will help guide the discovery and bioengineering of novel antibiotics. We discovered an isolate in Alaskan boreal forest soil that had broad antimicrobial activity. We elucidated the corresponding antimicrobial natural products and sequenced the genome of this isolate, designated Streptomyces sp. 2AW. This strain illustrates the chemical virtuosity typical of the Streptomyces genus, producing Cycloheximide as well as two other biosynthetically unrelated antibiotics, neutramycin, and hygromycin A. Combining bioinformatic and chemical analyses, we identified the gene clusters responsible for antibiotic production. Interestingly, 2AW appears dissimilar from other Cycloheximide producers in that the gene encoding the polyketide synthase resides on a separate part of the chromosome from the genes responsible for tailoring Cycloheximide-specific modifications. This gene arrangement and our phylogenetic analyses of the gene products suggest that 2AW holds an evolutionarily ancestral lineage of the Cycloheximide pathway. Our analyses support the hypothesis that the 2AW glutaramide gene cluster is basal to the lineage wherein Cycloheximide production diverged from other glutarimide antibiotics. This study illustrates the power of combining modern biochemical and genomic analyses to gain insight into the evolution of antibiotic-producing microorganisms.

Cycloheximide Can Induce Bax/Bak Dependent Myeloid Cell Death Independently of Multiple BH3-Only Proteins.[Pubmed:27806040]

PLoS One. 2016 Nov 2;11(11):e0164003.

Apoptosis mediated by Bax or Bak is usually thought to be triggered by BH3-only members of the Bcl-2 protein family. BH3-only proteins can directly bind to and activate Bax or Bak, or indirectly activate them by binding to anti-apoptotic Bcl-2 family members, thereby relieving their inhibition of Bax and Bak. Here we describe a third way of activation of Bax/Bak dependent apoptosis that does not require triggering by multiple BH3-only proteins. In factor dependent myeloid (FDM) cell lines, Cycloheximide induced apoptosis by a Bax/Bak dependent mechanism, because Bax-/-Bak-/- lines were profoundly resistant, whereas FDM lines lacking one or more genes for BH3-only proteins remained highly sensitive. Addition of Cycloheximide led to the rapid loss of Mcl-1 but did not affect the expression of other Bcl-2 family proteins. In support of these findings, similar results were observed by treating FDM cells with the CDK inhibitor, roscovitine. Roscovitine reduced Mcl-1 abundance and caused Bax/Bak dependent cell death, yet FDM lines lacking one or more genes for BH3-only proteins remained highly sensitive. Therefore Bax/Bak dependent apoptosis can be regulated by the abundance of anti-apoptotic Bcl-2 family members such as Mcl-1, independently of several known BH3-only proteins.

Data on the concentrations of etoposide, PSC833, BAPTA-AM, and cycloheximide that do not compromise the vitality of mature mouse oocytes, parthenogencially activated and fertilized embryos.[Pubmed:27547800]

Data Brief. 2016 Jul 30;8:1215-20.

These data document the vitality of mature mouse oocytes (Metaphase II (MII)) and early stage embryos (zygotes) following exposure to the genotoxic chemotherapeutic agent, etoposide, in combination with PSC833, a selective inhibitor of permeability glycoprotein. They also illustrate the vitality of parthenogencially activated and fertilized embryos following incubation with the calcium chelator BAPTA-AM (1,2-Bis(2-aminophenoxy)ethane- N,N,N',N'-tetraacetic acid tetrakis (acetoxymethyl ester)), Cycloheximide (an antibiotic that is capable of inhibiting protein synthesis), and hydrogen peroxide (a potent reactive oxygen species). Finally, they present evidence that permeability glycoprotein is not represented in the proteome of mouse spermatozoa. Our interpretation and discussion of these data feature in the article "Identification of a key role for permeability glycoprotein in enhancing the cellular defense mechanisms of fertilized oocytes" (Martin et al., in press) [1].

Synthesis and cytotoxic evaluation of cycloheximide derivatives as potential inhibitors of FKBP12 with neuroregenerative properties.[Pubmed:10479292]

J Med Chem. 1999 Sep 9;42(18):3615-22.

On the basis of the new finding that the protein synthesis inhibitor Cycloheximide (1, 4-[2-(3, 5-dimethyl-2-oxocyclohexyl)-2-hydroxyethyl]-2,6-piperidinedione) is able to competitively inhibit hFKBP12 (K(i) = 3.4 microM) and homologous enzymes, a series of derivatives has been synthesized. The effect of the compounds on the activity of hFKBP12 and their cytotoxicity against eukaryotic cell lines (mouse L-929 fibroblasts, K-562 leukemic cells) were determined. As a result, several less toxic or nontoxic Cycloheximide derivatives were identified by N-substitution of the glutarimide moiety and exhibit IC(50) values in the range of 22.0-4.4 microM for inhibition of hFKBP12. Among these compounds Cycloheximide-N-(ethyl ethanoate) (10, K(i) = 4.1 microM), which exerted FKBP12 inhibition to an extent comparable to that of Cycloheximide (1), was found to cause an approximately 1000-fold weaker inhibitory effect on eukaryotic protein synthesis (IC(50) = 115 microM). Cycloheximide-N-(ethyl ethanoate) (10) was able to significantly speed nerve regeneration in a rat sciatic nerve neurotomy model at dosages of 30 mg/kg.

Cycloheximide-induced T-cell death is mediated by a Fas-associated death domain-dependent mechanism.[Pubmed:10066786]

J Biol Chem. 1999 Mar 12;274(11):7245-52.

Cycloheximide (CHX) can contribute to apoptotic processes, either in conjunction with another agent (e.g. tumor necrosis factor-alpha) or on its own. However, the basis of this CHX-induced apoptosis has not been clearly established. In this study, the molecular mechanisms of CHX-induced cell death were examined in two different human T-cell lines. In T-cells undergoing CHX-induced apoptosis (Jurkat), but not in T-cells resistant to the effects of CHX (CEM C7), caspase-8 and caspase-3 were activated. However, the Fas ligand was not expressed in Jurkat cells either before or after treatment with CHX, suggesting that the activation of these caspases does not involve the Fas receptor. To determine whether CHX-induced apoptosis was mediated by a Fas-associated death domain (FADD)-dependent mechanism, a FADD-DN protein was expressed in cells prior to CHX treatment. Its expression effectively inhibited CHX-induced cell death, suggesting that CHX-mediated apoptosis primarily involves a FADD-dependent mechanism. Since CHX treatment did not result in the induction of Fas or FasL, and neutralizing anti-Fas and anti-tumor necrosis factor receptor-1 antibodies did not block CHX-mediated apoptosis, these results may also indicate that FADD functions in a receptor-independent manner. Surprisingly, death effector filaments containing FADD and caspase-8 were observed during CHX treatment of Jurkat, Jurkat-FADD-DN, and CEM C7 cells, suggesting that their formation may be necessary, but not sufficient, for cell death.

Cycloheximide (Naramycin A), an antifungal antibiotic, is an eukaryote protein synthesis inhibitor, with IC50s of 532.5 nM and 2880 nM for protein synthesis and RNA synthesis in vivo, respectively. Cycloheximide suppresses ferroptosis and inhibits autophagy.

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