Betulinic acid derivatives modified at the C28 position are HIV-1entry inhibitors such as compound A43D; however, modified at the C3 position instead of C28 give HIV-1 maturation inhibitor such as bevirimat. Bevirimat exhibited promising pharmacokinetic profiles in clinical trials, but its effectiveness was compromised by the high baseline drug resistance of HIV-1 variants with polymorphism in the putative drug binding site. In an effort to determine whether the viruses with bevirimat resistant polymorphism also altered their sensitivities to the betulinic acid derivatives that inhibit HIV-1 entry, a series of new betulinic acid entry inhibitors were synthesized and tested for their activities against HIV-1 NL4-3 and NL4-3 variants resistant to bevirimat. The results show that the bevirimat resistant viruses were approximately 5- to10-fold more sensitive to three new glutamine ester derivatives (13, 15 and 38) and A43D in an HIV-1 multi-cycle replication assay. In contrast, the wild type NL4-3 and the bevirimat resistant variants were equally sensitive to the HIV-1 RT inhibitor AZT. In addition, these three new compounds markedly improved microsomal stability compared to A43D.
HIV-1; Entry inhibitor; Maturation inhibitor; Betulinic acid; Berivimat; Berivimat-resistance
The question of how HIV-1 interfaces with cellular microRNA (miRNA) biogenesis and effector mechanisms has been highly controversial. Here, we first used deep sequencing of small RNAs present in two different infected cell lines (TZM-bl and C8166) and two types of primary human cells (CD4+ peripheral blood mononuclear cells [PBMCs] and macrophages) to unequivocally demonstrate that HIV-1 does not encode any viral miRNAs. Perhaps surprisingly, we also observed that infection of T cells by HIV-1 has only a modest effect on the expression of cellular miRNAs at early times after infection. Comprehensive analysis of miRNA binding to the HIV-1 genome using the photoactivatable ribonucleoside-induced cross-linking and immunoprecipitation (PAR-CLIP) technique revealed several binding sites for cellular miRNAs, a subset of which were shown to be capable of mediating miRNA-mediated repression of gene expression. However, the main finding from this analysis is that HIV-1 transcripts are largely refractory to miRNA binding, most probably due to extensive viral RNA secondary structure. Together, these data demonstrate that HIV-1 neither encodes viral miRNAs nor strongly influences cellular miRNA expression, at least early after infection, and imply that HIV-1 transcripts have evolved to avoid inhibition by preexisting cellular miRNAs by adopting extensive RNA secondary structures that occlude most potential miRNA binding sites.
MicroRNAs (miRNAs) are a ubiquitous class of small regulatory RNAs that serve as posttranscriptional regulators of gene expression. Previous work has suggested that HIV-1 might subvert the function of the cellular miRNA machinery by expressing viral miRNAs or by dramatically altering the level of cellular miRNA expression. Using very sensitive approaches, we now demonstrate that neither of these ideas is in fact correct. Moreover, HIV-1 transcripts appear to largely avoid regulation by cellular miRNAs by adopting an extensive RNA secondary structure that occludes the ability of cellular miRNAs to interact with viral mRNAs. Together, these data suggest that HIV-1, rather than seeking to control miRNA function in infected cells, has instead evolved a mechanism to become largely invisible to cellular miRNA effector mechanisms.
In this study, 1R,2R-dicamphanoyl-3,3-dimethydihydropyrano[2,3-c]xanthen-7(1H)-one (DCX) derivatives were designed and synthesized as novel anti-HIV agents against both wild-type and nonnucleoside reverse transcriptase (RT) inhibitor-resistant HIV-1 (RTMDR-1) strains. Twenty-four DCX analogs (6-29) were synthesized and evaluated against the non-drug-resistant HIV-1 NL4-3 strain, and selected analogs were also screened for their ability to inhibit the RTMDR-1 strain. Compared with the control 2-ethyl-3′,4′-di-O-(-)-camphanoyl-2′,2′-dimethyldihydropyrano[2,3-f]chromone (2-EDCP, 2), one of the best anti-HIV coumarin derivatives in our prior study, three DCX compounds (7, 12, and 22) showed better activity against both HIV strains with an EC50 range of 0.062 – 0.081 μM, and five additional compounds (8, 11, 16, 18, and 21) exhibited comparable anti-HIV potency. Six DCX analogs (7, 11-12, 18, and 21-22) also showed enhanced selectivity index (SI) values in comparison to the control. Structure-activity relationship (SAR) information suggested that the extended conjugated system of the pyranoxanthone skeleton facilitates the interaction of the small DCX molecule within the viral binding pocket, consequently leading to enhanced anti-HIV activity and selectivity. Compared to DCP compounds, DCX analogs are a more promising new class of anti-HIV agents.
1R,2R-dicamphanoyl-3,3-dimethydihydropyrano[2,3-c]xanthen-7(1H)-one (DCX); Anti-HIV activity; Structure-activity relationship (SAR)
HIV-1 envelope glycoproteins are the key viral proteins that mediate HIV-1 entry and cell–cell fusion. In contrast to HIV-1 entry, the mechanism of HIV-1 Env-mediated cell–cell fusion is relatively unclear. This study demonstrated that dynasore, a dynamin inhibitor, suppressed HIV-1 Env-mediated cell–cell fusion. Dynasore sensitivity of HIV-1 Env-mediated cell–cell fusion varied depending on the viral strains. Results from testing a panel of gp41 cytoplasmic tail truncation mutants suggested that the gp41 cytoplasmic tail might play a role in dynasore sensitivity. HIV-1 Env-mediated cell–cell fusion could also be suppressed by a dynamin dominant-negative mutant DNM2(K44A). In summary, these results suggested that dynamin 2 might play a role in HIV-1 Env-mediated cell–cell fusion.
A new class of proteasome inhibitors was synthesized using lithocholic acid as a scaffold. Modification at the C-3 position of lithocholic acid with a series of acid acyl groups yielded compounds with a range of potency on proteasome inhibition. Among them, the phenylene diacetic acid hemiester derivative (13) displayed the most potent proteasome inhibition with IC50 = 1.9 μM. Enzyme kinetic analysis indicates that these lithocholic acid derivatives are non-competitive inhibitors of the proteasome.
Lithocholic acid; proteasome; proteasome inhibitor
Highly active antiretroviral therapy (HAART) has offered a promising approach for controlling HIV-1 replication in infected individuals. However, with HARRT, HIV-1 is suppressed rather than eradicated due to persistence of HIV-1 in latent viral reservoirs. Thus, purging the virus from latent reservoirs is an important strategy toward eradicating HIV-1 infection. In this study, we discovered that the daphnane diterpene gnidimacrin, which was previously reported to have potent anti-cancer cell activity, activated HIV-1 replication and killed persistently-infected cells at picomolar concentrations. In addition to its potential to purge HIV-1 from latently infected cells, gnidimacrin potently inhibited a panel of HIV-1 R5 virus infection of peripheral blood mononuclear cells (PBMCs) at an average concentration lower than 10 pM. In contrast, gnidimacrin only partially inhibited HIV-1 ×4 virus infection of PBMCs. The strong anti-HIV-1 R5 virus activity of gnidimacrin was correlated with its effect on down-regulation of the HIV-1 coreceptor CCR5. The anti-R5 virus activity of gnidimacrin was completely abrogated by a selective protein kinase C beta inhibitor enzastaurin, which suggests that protein kinase C beta plays a key role in the potent anti-HIV-1 activity of gnidimacrin in PBMCs. In summary, these results suggest that gnidimacrin could activate latent HIV-1, specifically kill HIV-1 persistently infected cells, and inhibit R5 viruses at picomolar concentrations.
In a continued study, 23 3′R,4′R-di-O-(−)-camphanoyl-2′,2′-dimethyldihydropyrano[2,3-f]chromone (DCP) derivatives (5–27) were synthesized, and screened for anti-HIV activity against both a non-drug-resistant NL4-3 strain and multiple reverse transcriptase (RT) inhibitor-resistant (RTMDR-1) strain, using 2-EDCP (4) and 2-MDCP (35) as controls. New DCP analogs 5, 9, 14, and 22 exhibited potent anti-HIV activity against HIVNL4-3 with EC50 and therapeutic index (TI) values ranging from 0.036 μM to 0.14 μM and from 110 to 420, respectively. Compounds 5 and 9 also exhibited good activity against RTMDR-1 (EC50 0.049 and 0.054 μM; TI 310 and 200, respectively), and were two-fold more potent than the leads 4 and 35 (EC50 0.11 and 0.19 μM; TI 60 and 58, respectively). Evaluation of water solubility showed that 5 and 22 were 5–10 times more water soluble than 4. Quantitative structure-activity relationship (QSAR) modeling results were first performed on this compound type, and the models should aid in design of future anti-HIV DCP analogs and potential clinical drug candidates.
3′R,4′R-Di-O-(−)-camphanoyl-2′,2′-dimethyldihydropyrano[2,3-f]chromone (DCP) derivatives; HIV-1; Reverse transcriptase (RT); Structure-activity relationship (SAR)
We previously reported that [[N-[3β-hydroxyl-lup-20(29)-en-28-oyl]-7-aminoheptyl]-carbamoyl]methane (A43D, 4) was a potent HIV-1 entry inhibitor. However, 4 was inactive against HIV-2 virus, suggesting the structural requirements for targeting these two retroviruses are different. In this study, a series of new betulinic acid derivatives were synthesized, and some of them displayed selective anti-HIV-2 activity at nanomolar concentrations. In comparison to compounds with anti-HIV-1 activity, a shorter C-28 side chain is required for optimal anti-HIV-2 activity.
Betulinic acid; HIV-2; HIV-1
This study discovered that glycyrrhetinic acid inhibited the human 20S proteasome at 22.3 µM. Esterification of the C-3 hydroxyl group on glycyrrhetinic acid with various carboxylic acid reagents yielded a series of analogs with marked improved potency. Among the derivatives, glycyrrhetinic acid 3-O-isophthalate (17) was the most potent compound with IC50 of 0.22 µM, which was approximately 100-fold more potent than glycyrrhetinic acid.
Glycyrrhetinic acid; proteasome inhibitor; triterpene
This study discovered that betulinic acid (BA) is a potent proteasome activator that preferentially activates the chymotrypsin-like activity of proteasomes. Chemical modifications can transform BA into proteasome inhibitors. Chemical modifications at the C-3 position of BA resulted in compounds, such as dimethylsuccinyl BA (DSB), with various inhibitory activities against human 20S proteasomes. Interestingly, the proteasomal activation by BA and the inhibitory activity of DSB could be abrogated by introducing a side chain at the C-28 position. In summary, this study discovered a class of small molecules that can either activate or inhibit human proteasome activity depending on side chain modifications.
Betulinic acid; proteasome inhibitor; proteasome activator
Betulinic acid (BA) derivatives can inhibit human immunodeficiency virus type 1 (HIV-1) entry or maturation depending on side chain modifications. While BA derivatives with antimaturation activity have attracted considerable interest, the anti-HIV-1 profile and molecular mechanism of BA derivatives with anti-HIV-1 entry activity (termed BA entry inhibitors) have not been well defined. In this study, we have found that two BA entry inhibitors, IC9564 and A43D, exhibited a broad spectrum of anti-HIV-1 activity. Both compounds inhibited multiple strains of HIV-1 from clades A, B, and C at submicromolar concentrations. Clade C viruses were more sensitive to the compounds than clade A and B viruses. Interestingly, IC9564 at subinhibitory concentrations could alter the antifusion activities of other entry inhibitors. IC9564 was especially potent in increasing the sensitivity of HIV-1YU2 Env-mediated membrane fusion to the CCR5 inhibitor TAK-779. Results from this study suggest that the V3 loop of gp120 is a critical determinant for the anti-HIV-1 activity of IC9564. IC9564 escape viruses contained mutations near the tip of the V3 loop. Moreover, IC9564 could compete with the binding of V3 monoclonal antibodies 447-52D and 39F. IC9564 also competed with the binding of gp120/CD4 complexes to chemokine receptors. In summary, these results suggest that BA entry inhibitors can potently inhibit a broad spectrum of primary HIV-1 isolates by targeting the V3 loop of gp120.