Human immunodeficiency virus type 2 (HIV-2) carries an accessory protein Vpx that is important for viral replication in natural target cells. In its C-terminal region, there is a highly conserved poly-proline motif (PPM) consisting of seven consecutive prolines, encoded in a poly-pyrimidine tract. We have previously shown that PPM is critical for Vpx expression and viral infectivity. To elucidate the molecular basis underlying this observation, we analysed the expression of Vpx proteins with various PPM mutations by in vivo and in vitro systems. We found that the number and position of consecutive prolines in PPM are important for Vpx expression, and demonstrated that PPM is essential for efficient Vpx translation. Furthermore, mutational analysis to synonymously disrupt the poly-pyrimidine tract suggested that the context of PPM amino acid sequences is required for efficient translation of Vpx. We similarly analysed HIV-1 and HIV-2 Vpr proteins structurally related to HIV-2 Vpx. Expression level of the two Vpr proteins lacking PPM was shown to be much lower relative to that of Vpx, and not meaningfully enhanced by introduction of PPM at the C terminus. Finally, we examined the Vpx of simian immunodeficiency virus from rhesus monkeys (SIVmac), which also has seven consecutive prolines, for PPM-dependent expression. A multi-substitution mutation in the PPM markedly reduced the expression level of SIVmac Vpx. Taken together, it can be concluded that the notable PPM sequence enhances the expression of Vpx proteins from viruses of the HIV-2/SIVmac group at the translational level.
Despite the development of antiretroviral therapy against HIV, eradication of the virus from the body, as a means to a cure, remains in progress. A “kick and kill” strategy proposes “kick” of the latent HIV to an active HIV to eventually be “killed”. Latency-reverting agents that can perform the “kick” function are under development and have shown promise. Management of the infected cells not to produce virions after the “kick” step is important to this strategy. Here we show that a newly synthesized compound, L-HIPPO, captures the HIV-1 protein Pr55Gag and intercepts its function to translocate the virus from the cytoplasm to the plasma membrane leading to virion budding. The infecting virus thus “locked-in” subsequently induces apoptosis of the host cells. This “lock-in and apoptosis” approach performed by our novel compound in HIV-infected cells provides a means to bridge the gap between the “kick” and “kill” steps of this eradication strategy. By building upon previous progress in latency reverting agents, our compound appears to provide a promising step toward the goal of HIV eradication from the body.
New pyrazoline derivatives were synthesized and evaluated for their cytotoxic effects on AsPC-1 human pancreatic adenocarcinoma, U87 and U251 human glioblastoma cell lines. 1-[((5-(4-Methylphenyl)-1,3,4-oxadiazol-2-yl)thio)acetyl]-3-(2-thienyl)-5-(4-chlorophenyl)-2-pyrazoline (11) was found to be the most effective anticancer agent against AsPC-1 and U251 cell lines, with IC50 values of 16.8 µM and 11.9 µM, respectively. Tumor selectivity of compound 11 was clearly seen between Jurkat human leukemic T-cell line and human peripheral blood mononuclear cells (PBMC). Due to its promising anticancer activity, compound 11 was chosen for apoptosis/necrosis evaluation and DNA-cleavage analysis in U251 cells. Compound 11-treated U251 cells exhibited apoptotic phenotype at low concentration (1.5 µM). DNA-cleaving efficiency of this ligand was more significant than cisplatin and was clearly enhanced by Fe(II)-H2O2-ascorbic acid systems. This result pointed out the relationship between the DNA cleavage and the cell death.
SummaryThe discovery of the chimeric tyrosine kinase breakpoint cluster region kinase-Abelson kinase (BCR-ABL)-targeted drug imatinib conceptually changed the treatment of chronic myelogenous leukemia (CML). However, some CML patients show drug resistance to imatinib. To address this issue, some artificial heterocyclic compounds have been identified as BCR-ABL inhibitors. Here we examined whether plant-derived pentacyclic triterpenoid gypsogenin and/or their derivatives show inhibitory activity against BCR-ABL. Among the three derivatives, benzyl 3-hydroxy-23-oxoolean-12-en-28-oate (1c) was found to be the most effective anticancer agent on the CML cell line K562, with an IC 50 value of 9.3 µM. In contrast, the IC 50 against normal peripheral blood mononuclear cells was 276.0 µM, showing better selectivity than imatinib. Compound 1c had in vitro inhibitory activity against Abelson kinase 1 (ABL1) (IC 50 =8.7 μM), the kinase component of BCR-ABL. In addition, compound 1c showed a different inhibitory profile against eight kinases compared with imatinib. The interaction between ATP binding site of ABL and 1c was examined by molecular docking study, and the binding mode was different from imatinib and newer generation inhibitors. Furthermore, 1c suppresses signaling downstream of BCR-ABL. This study suggests the possibility that plant extracts may be a source for CML treatment and offer a strategy to overcome drug resistance to known BCR-ABL inhibitors. KeywordsGypsogenin, Abelson tyrosine-protein kinase 1, chronic myelogenous leukemia Biological and Pharmaceutical Bulletin Advance PublicationCancer is a worldwide health problem, and despite intensive research efforts over the last several decades, an effective cure has not been identified. 1)However, the recent discovery of molecular targeted drugs against cancer at the end of the 20 th century has led to promising results. 1,2) Imatinib (Fig. 1), which targets the chimeric tyrosine kinase breakpoint cluster region kinase-Abelson kinase (BCR-ABL), [3][4][5][6] was discovered based on the findings that chronic myelogenous leukemia (CML) is caused by a chromosomal translocation that results in the constitutively expressed and active BCR-ABL. 7,8) While imatinib can be initially effective in treating CML, some patients have shown drug resistance to imatinib. [9][10][11] Several new generation drugs with a different binding mode to Abelson kinase (ABL) have thus been developed. 6,[12][13][14][15][16] These drugs are artificial heterocyclic compounds, however, if widely distributed natural products and/or their derivatives show the inhibitory activity against BCR-ABL, it would be more convenient to get.Pentacyclic triterpenoids, a category of natural compounds, can be extracted from a variety of plants and show various activities. 17,18) Some of these triterpenoids were reported to exhibit anti-tyrosine kinase activity. 19,20) Here we focused on a pentacyclic triterpenoid gypsogenin, 21,22) extracted from Gypsophila species, 23,24) which is widely distributed in the Eu...
Human immunodeficiency virus 2 Vpx coordinates zinc through residues H39, H82, C87 and C89. We reported previously that H39, H82 and C87 mutants maintain Vpx activity to facilitate the degradation of SAMHD1. Herein, the expression of Vpx mutants in cells was examined in detail. We demonstrated that the zinc-binding site stabilizes the protein to keep its function in virus growth when low levels of Vpx are expressed. At higher levels of expression, Vpx aggregation could occur, and zinc binding would suppress such aggregation. Among the amino acids involved in zinc coordination, H39 plays the most critical role. In summary, zinc binding appears to mitigate flexibility of the three-helix fold of Vpx, thereby preventing dysfunction.
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