Tao Ye Group
School of Chemical Biology & Biotechnology

Part I: Total Synthesis of Bioactive Natural Products and Related Studies

37:Total synthesis of amphidinins E, F and epi-amphidinin F,2017,ASAP

Abstract:A unified approach leading to the total synthesis of amphidinins E, F and epi-amphidinin F of a new structural class of linear marine polyketides is described

36:Total syntheses of smenothiazoles A and B,Org. Biomol. Chem., 2017, 15, 7196–7203

Abstract:Concise total syntheses of smenothiazoles A (1) and B (2), two distinguished vinyl chloride containing natural products isolated from the marine sponge S. aurea, have been developed. Silastannation, Stille reaction and a carefully controlled desilylchlorination were employed as key steps to construct unique polyketide acid fragments, and the optimized reaction conditions avoided migration of 2,5-diene to a 2,4-conjugated system. This report unambiguously confirmed the structures of both natural products

35:Regio- and Stereospecific Construction of 3a-(1H-Indol-3-yl)pyrrolidinoindolines and Application to the Formal Syntheses of Gliocladins B and C,Org. Lett. 2017, 19, 5134−5137

Abstract: A one-pot regio- and stereospecific strategy for the construction of 3a-(3-indolyl)-hexahydropyrrolo[2,3-b]indoles based on the condensation of an indole and an in situ generated cyclopropylazetoindoline has been developed. This unified strategy works with a variety of substituted indoles to produce 3a-(3-indolyl)-hexahydropyrrolo[2,3-b]indole products in high yields. The utility of this transformation was highlighted in the formal total syntheses of gliocladins B and C.

34:Total Synthesis and StereochemicalAssignment of Actinoranone,Chem. Eur.J .2017, 23,3572–3576

P~L{97)PP)PZR}D_R3]XDDD

Abstract: The total synthesis of four actinoranone stereoisomersled to unambiguous assignment of relative and absolute stereochemistry of the natural product. Key features of the convergent, fully stereocontrolled route include the use of aN egishi carbozirconation/iodination, a Friedel–Craftscyclization,aFelkin-controlled additionreaction,aMitsunobu reaction, and alate-stage C-H oxidation.

33:Concise Total Synthesis of Nannocystin A,Angew. Chem. Int. Ed. 2016, 55, ASAP

20160919103935926

Abstract:Nannocystin A, a structurally unique 21-membered macrocyclic depsipeptide with low nanomolar inhibitory activity against elongation factor 1A, was synthesized according to a strategy involving the vinylogous Mukaiyama aldol reaction, Sharpless epoxidation, olefin metathesis, the Mitsunobu reaction, and a palladium-catalyzed intramolecular Suzuki coupling of a highly complex cyclization substrate. The overall synthesis is efficient and paves the way for preparation of analogues for drug development efforts.

32: Total Synthesis and Stereochemical Assignment of Callyspongiolide, J. Am. Chem. Soc., 2016, 138, 6948

MMBX6C4SBZ_Y)_Q4BEARGTB

Abstract: Total synthesis of four callyspongiolide stereoisomers led to unambiguous assignment of relative and absolute stereochemistry of the natural product. Key features of the convergent, fully stereocontrolled route include the use of Krische allylation, Kiyooka Aldol reaction, Kociénski−Julia olefination, Still−Gennari olefination, Yamaguchi macrocyclization, and Sonogashira coupling reaction. Biological evaluation of the synthesized compounds against an array of cancer cells revealed that the stereochemistry of the macrolactone core played an important role.

31: Discovery, Total Synthesis and Key Structural Elements for the Immunosuppressive Activity of Cocosolide, a Symmetrical Glycosylated Macrolide Dimer from Marine Cyanobacteria, Chem. Eur. J., 2016, 22, 8158

11

Abstract: A new dimeric macrolide xylopyranoside, cocosolide (1), was isolated from the marine cyanobacterium preliminarily identified as Symploca sp. from Guam. The structure was determined by a combination of NMR spectroscopy, HRMS, X-ray diffraction studies and Mosher’s analysis of the base hydrolysis product. Its carbon skeleton closely resembles that of clavosolides A–D isolated from the sponge Myriastra clavosa, for which no bioactivity is known. We performed the first total synthesis of cocosolide (1) along with its [α,α]-anomer (26) and macrocyclic core (28), thus leading to the confirmation of the structure of natural 1. The convergent synthesis featured Wadsworth–Emmons cyclopropanation, Sakurai annulation, Yamaguchi macrocyclization/dimerization reaction, α-selective glycosidation and β-selective glycosidation. Compounds 1 and 26 potently inhibited IL-2 production in both T-cell receptor dependent and independent manners. Full activity requires the presence of the sugar moiety as well as the intact dimeric structure. Cocosolide also suppressed the proliferation of anti-CD3-stimulated T-cells in a dose-dependent manner.

30: The total synthesis and stereochemical assignment of scytonemin A, Chem. Commun.,2016, 52, 1002

新建位图图像3

Abstract: The total synthesis of scytonemin A and its C-9 epimer, as well as elucidation of the absolute stereochemistry of natural scytonemin A is described.

29:Total synthesis of largamide B,Chem. Commun.,201551,2510
111Abstract:Total synthesis of the cyanobacterial metabolite largamide B and the disproval of its originally assigned stereochemistry as well as confirmation of the revised stereochemistry are reported.

28:Total Synthesis and Stereochemical Reassignment of Mandelalide A, Angew. Chem. Int. Ed. 2014, 53, online paper.

Abstract: The total synthesis of the tunicate metabolite mandelalide A and the correction of its originally assigned stereochemistry are reported. Key features of the convergent, fully stereocontrolled route include the use of a Prins cyclization for the diastereoselective construction of the tetrahydropyran subunit, Rychnovsky–Bartlett cyclization for the preparation of the tetrahydrofuran moiety, Suzuki coupling, Horner–Wadsworth–Emmons macrocyclization, and glycosylation to append the l-rhamnose-derived pyranoside.

27:Total Synthesis of the Proposed Structure for Itralamide B, Synlett 2014, 25, 1014-1018

Abstract: A stereocontrolled total synthesis of the cyclodepsipeptide, itralamide B has been achieved. Both R- and S-stereomers of the side chain were attached to the macrocyclic ring. The structure synthesized appears to be different from that of the marine natural product.

26:Cross Metathesis Approach for Stereocontrolled Synthesis of C1-C15 Fragment of Rhizopodin, Synlett 2014, 25, 138-142

Abstract: The C1-C15 fragment of rhizopodin was synthesized via either Suzuki coupling reaction of vinyl iodide and vinyl boronate or a cross metathesis of a terminal olefin and a diene adduct in the presence of Hoveyda-Grubbs II catalyst.

25:Synthesis of the Macrocyclic Core of Rhizopodin– Chem. Asian J. 2013, 8, 2955-2959.

 

Chem.-Asian-J.-2013-8-2955-2959

Abstract: A stereoselective synthesis of the fully functionalized macrocyclic core of rhizopodin, a cytotoxic 38-membered macrolide, is disclosed. The key steps involve Sharpless epoxidation, Robinson−Gabriel oxazole synthesis, olefin cross-metathesis, Suzuki coupling, Yamaguchi esterification and Shiina macrolactonization.

24: Total Synthesis and Biological Evaluation of Grassypeptolide A, Chem. Eur. J. 2013, 19, 6774-6884.

 

Grassypeptolide-EJOC

Abstract: Herein, we describe in full our investigations into the synthesis of grassypeptolide A (1) in 17 linear steps with an overall yield of 11.3%. In particular, this work features the late-stage introduction of sensitive bis(thiazoline) heterocycles and 31-membered macrocyclization conducted at the sterically congested secondary amide site in superb conversion (72% yield). Biological evaluation indicated that grassypeptolide A significantly inhibited cancer cell proliferation in a dose-dependent manner. It induced cancer cell apoptosis, which was associated with increased cleavage of poly(ADPribose) polymerase (PARP) and decreased expression of bcl-2 and bcl-xL. Furthermore, grassypeptolide A also caused cell cycle redistribution by increasing cells in the G1 phase and decreasing cells in the S and G2 phases. In addition, cell cycle arrest was correlated with downregulation of cyclin D and upregulation of p27 and p21.

23: Total synthesis of padanamides A and B, Chem. Commun. 2013, 49, 2977-2979.

 

Pandanamides

Abstract: The first total syntheses of padanamides A and B have been achieved, unambiguously confirming their structures.

This paper was selected as inner cover picture of the issue:

Pandamide

 

22: Total synthesis and stereochemical revision of lagunamide A, Chem. Commun. 2012, 48, 8697-8699.

 

 Lagunamide-A

Abstract: A revised configurational assignment for the marine metabolite lagunamide A is proposed and validated by total synthesis.

21: Total Synthesis and Stereochemical Revision of Burkholdac A, Synlett. 2012, 23, 783-787.

Iriomoteolide-1a macrocyclic core

 Abstract: A stereocontrolled total synthesis of burkholdac A was completed, leading to a revision of the reported stereochemistry.

20: Total Synthesis and Absolute Configuration of Nocardioazine B, Chem. Commun.2012, 4344-4346.

picture

 Abstract: The first total synthesis of the indole alkaloid nocardioazine B was accomplished in 10 steps with an overall yield of 11.8%, establishing the absolute stereochemistry of the natural product.

19: Total Synthesis of Hoiamide C, Org. Lett., 201113, 2506-2509.

Iriomoteolide-1a macrocyclic core

 Abstract: Hoiamide C was synthesized in 16 steps with an overall yield of 1.8% starting from homoallylic alcohol 18, unambiguously confirming its structure.

18:Bioactive macrocyclic natural products.

Heterocycles in Natural Product Synthesis2011, 569-619. Editor(s): Krishna C. Majumdar, Shital K. Chattopadhyay. Print ISBN: 9783527327065; Online ISBN: 9783527634880. DOI: 10.1002/9783527634880.

 

17: Thiazoline and Thiazole and their Derivatives, 

Heterocycles in Natural Product Synthesis2011, 459-505. Editor(s): Krishna C. Majumdar, Shital K. Chattopadhyay. Print ISBN: 9783527327065; Online ISBN: 9783527634880. DOI: 10.1002/9783527634880.

 

16: Total Synthesis of Grassypeptolide, Chem. Commun., 201046, 7496-7488.

Iriomoteolide-1a macrocyclic core

 Abstract: The first total synthesis of grassypeptolide, an anticancer cyclodepsipeptide isolated from marine cyanobacteria, has been achieved in 17 steps and an overall 11.3% yield.

This paper was selected as inner cover picture of the issue, and being highlighted by “Nature China

GrassypeptolideNATURE-CHINA-Highlight-Grassy

15: Synthesis of the Macrocyclic Core of Iriomoteolide-1a, Chem. Commun., 201046, 4773-4775.

Iriomoteolide-1a macrocyclic core

 Abstract: The fully functionalized macrocyclic core of the marine natural product iriomoteolide-1a has been successfully constructed in a convergent and enantioselective manner.

14: The Total Synthesis and Stereochemical Revision of Bisebromoamide, Org. Lett., 201012, 3018-3021.

Iriomoteolide-1a macrocyclic core

 Abstract: A revised configurational assignment for the thiazoline moiety of the marine peptide bisebromoamide is proposed and validated by total synthesis.

13: Synthesis of the C9-C23 (C9′-C23′) Fragment of the Dimeric Natural Product Rhizopodin, Org. Lett., 201012, 2036-2039.

Iriomoteolide-1a macrocyclic core

 Abstract: A stereoselective assembly of the C9-C23 (C9’-C23’) fragment of rhizopodin, a 38-membered bis-lactone natural product, has been developed. A highly efficient approach to this fragment assembles > 50% of the carbon skeleton and the stereochemical elements present in the natural product.

12: Total Synthesis of Sintokamide C, Org. Lett., 201012, 1100-1103.

Iriomoteolide-1a macrocyclic core

 Abstract: A convergent stereoselective synthesis of sintokamide C was accomplished in 14 steps with an overall yield of 3.8% starting from Garner’s aldehyde, unambiguously confirming its structure.

11: Towards the Stereochemical Assignment of Natural Lydiamycin A, Chem. Commun., 201046, 574-576.

Iriomoteolide-1a macrocyclic core

 Abstract: A convergent approach leading to the stereoselective synthesis of four diastereomers of lydiamycin A has been established and verified.

10: Total Synthesis of Largamide H, Chem. Commun.201046, 153-155.

Iriomoteolide-1a macrocyclic core

 Abstract: The first total synthesis of largamide H has been completed, utilising the oxidative elimination reaction of enantiomeric pure 2-amino-3-(phenylselenyl)butanoic acid residues to stereospecifically install both (Z)- and (E)-2,3-dehydro-2-aminobutanoic moieties.

9: Progress toward the Total Synthesis of Scytonemin A: Asymmetric Synthesis of (2S,3R, 4R)-4-Hydroxy-3-Methylproline, Synlett2010, 563-566.

Iriomoteolide-1a macrocyclic core

 Abstract: During the total synthesis of the novel cyclopeptide scytonemin A, the fragment containing two (2S,3R,4R)-4-hydroxyl-3- methylproline units was successfully prepared. Two approaches leading to (2S,3R,4R)-4-hydroxyl-3-methylproline have been explored. They involve the following key transformations: asymmetric crotylation, Sharpless epoxidation/subsequent epoxidation-opening, intramolecular amidomercuration-oxidation.

8: Stereoselective Synthesis of the C1–C12 Fragment of the Thuggacins, Tetrahedron: Asymmetry, 2009, 20, 2027-2032.

Iriomoteolide-1a macrocyclic core

Abstract: A concise asymmetric synthesis of the C1-C12 fragment of the antibacterial natural product thuggacins has been achieved. The stereochemistry of this fragment was efficiently established via stereoselective reduction and Evans-aldol condensation. Hanztsch method and Horner-Wardsworth-Emmnons reaction were employed for thiazole formation and the construction of the Ea, b-unsaturated double bond.

7: Total Synthesis of Emericellamides A & B, Tetrahedron2009, 65, 2695-2702.

Iriomoteolide-1a macrocyclic core

 Abstract: Total synthesis of emericellamides A and B is reported. A convergent, flexible strategy employing peptide chemistry, asymmetric alkylations and culminating in macrolactamisation is described.

6: Total Synthesis of Largazole, Synlett2008, 2379-2383.

Iriomoteolide-1a macrocyclic core

 Abstract: The stereocontrolled total synthesis of largazole was accomplished, unambiguously confirming its structure. Key steps included the use of the Nagao thiazolidinethione auxiliary for a diastereoselective acetate aldol reaction, thiazoline-thiazole formation and macrolactamization by the use of Mukaiyama’s reagent.

5: Total Synthesis of the Proposed Structure of LL15G256g, Synlett2008, 569-74.

Iriomoteolide-1a macrocyclic core

 Abstract: The first total synthesis of a molecule possessing the stereochemistry proposed for LL15G256g is described. The structure synthesized appears to be different from that of the marine natural product.

4: Total Synthesis of Lyngbyabellin A, Lett. Org. Chem.2005, 2, 699-702.

Iriomoteolide-1a macrocyclic core

 Abstract: The total synthesis of lyngbyabellin A, a biologically active metabolite from the marine cyanobacterium Lyngbya majuscula, is reported. There is flexibility in the approach which can readily allow structural modifications to be introduced

3: The Total Synthesis and Stereochemical Revision of Dragonamide, Tetrahedron200561, 11132-11140.

Iriomoteolide-1a macrocyclic core

 Abstract: The first total synthesis of dragonamide is reported. The synthesis has led to a reassignment of the configuration at the stereogenic centre on the alkyne-bearing fragment of the molecule.

2: Total Synthesis of Pitipeptolide A, Lett. Org. Chem.20052, 703-706.

Iriomoteolide-1a macrocyclic core

 Abstract: An efficient synthesis of the marine cyanobacterium metabolite pitipeptolide A is presented. The approach incorporates a variety of peptide coupling methods, asymmetric synthesis and macrocyclization. The route is versatile and allows scope for structural modification.

1: Synthesis of 2,4,5-trisubstituted thiazoline via a novel stereoselective intramolecular conjugate addition, Tetrahedron: Asymmetry200516, 1905-12.

Iriomoteolide-1a macrocyclic core

 Abstract: A convenient stereoselective preparation of 2,4,5-trisubstituted thiazolines is reported. The procedure involves the cyclisation of an unsaturated thioamide under mildly acidic conditions, and proceeds with excellent stereocontrol. A range of substrates are presented, and an explanation of the stereochemical outcome discussed.

Part II: Chemical Biology and Related Studies

 

14:LSD1 Regulates Pluripotency of Embryonic Stem/Carcinoma Cells through Histone Deacetylase 1-Mediated Deacetylation of Histone H4 at Lysine 16 Mol. Cell. Biol. 2014, 34, 158-179.

Abstract: LSD1 is essential for the maintenance of pluripotency of embryonic stem (ES) or embryonic carcinoma/teratocarcinoma (EC) cells. We have previously developed novel LSD1 inhibitors that selectively inhibit ES/EC cells. However, the critical targets of LSD1 remain unclear. Here, we found that LSD1 interacts with histone deacetylase 1 (HDAC1) to regulate the proliferation of ES/EC cells through acetylation of histone H4 at lysine 16 (H4K16), which we show is a critical substrate of HDAC1. The LSD1 demethylase and HDAC1 deacetylase activities were both inactivated if one of them in the complex was chemically inhibited in ES/EC cells or in reconstituted protein complexes. Loss of HDAC1 phenocopied the selective growth-inhibitory effects and increased the levels of H3K4 methylation and H4K16 acetylation of LSD1 inactivation on ES/EC cells. Reduction of acetylated H4K16 by ablation of the acetyltransferase males absent on the first (MOF) is sufficient to rescue the growth inhibition induced by LSD1 inactivation. While LSD1 or HDAC1 inactivation caused the downregulation of Sox2 and Oct4 and induction of differentiation genes, such as FOXA2 or BMP2, depletion of MOF restored the levels of Sox2, Oct4, and FoxA2 in LSD1-deficient cells. Our studies reveal a novel mechanism by which LSD1 acts through the HDAC1- and MOF-mediated regulation of H4K16 acetylation to maintain the pluripotency of ES/EC cells.

 

 

13:A novel CyclinE/CyclinA-CDK Inhibitor targets p27Kip1 degradation, cell cycle progression and cell survival: Implications in cancer therapy. Cancer Lett. 2013, 333, 103-112.

Abstract: p27Kip1 (p27) binds and inhibits the cyclin E- or cyclin A-associated cyclin-dependent kinases (CDKs)2 and other CDKs, and negatively regulates G1–G2 cell cycle progression. To develop specific CDK inhibitors, we have modeled the interaction between p27 and cyclin A-CDK2, and designed a novel compound that mimics p27 binding to cyclin A-CDK2. The chemically synthesized inhibitor exhibited high potency and selective inhibition towards cyclin E/cyclin A-CDK2 kinase in vitro but not other kinases. To facilitate permeability of the inhibitor, a cell penetrating peptide (CPP) was conjugated to the inhibitor to examine its effect in several cancer cell lines. The CPP-conjugated inhibitor significantly inhibited the proliferation of cancer cells. The treatment of the inhibitor resulted in the increased accumulation of p27 and p21Cip1/Waf1 (p21) and hypo-phosphorylation of retinoblastoma protein (Rb). The degradation of p27, mediated through the phosphorylation of threonine-187 in p27, was also inhibited. Consequently, exposure of cells to the inhibitor caused cell cycle arrest and apoptosis. We conclude that specific cyclinE/cyclin A-CDK2 inhibitors can be developed based on the interaction between p27 and cyclin/CDK to block cell cycle progression to prevent tumor growth and survival.

 

12:Pluripotent Stem Cell Protein Sox2 Confers Sensitivity to LSD1 Inhibition in Cancer Cells Cell Rep. 2013, 5, 445-457.

 

Gene amplification of Sox2 at 3q26.33 is a common event in squamous cell carcinomas (SCCs) of the lung and esophagus, as well as several other cancers. Here, we show that the expression of LSD1/KDM1 histone demethylase is significantly elevated in Sox2-expressing lung SCCs. LSD1-specific inhibitors selectively impair the growth of Sox2-expressing lung SCCs, but not that of Sox2-negative cells. Sox2 expression is associated with sensitivity to LSD1 inhibition in lung, breast, ovarian, and other carcinoma cells. Inactivation of LSD1 reduces Sox2 expression, promotes G1 cell-cycle arrest, and induces genes for differentiation by selectively modulating the methylation states of histone H3 at lysines 4 (H3K4) and 9 (H3K9). Reduction of Sox2 further suppresses Sox2-dependent lineage-survival oncogenic potential, elevates trimethylation of histone H3 at lysine 27 (H3K27) and enhances growth arrest and cellular differentiation. Our studies suggest that LSD1 serves as a selective epigenetic target for therapy in Sox2-expressing cancers.

11: NuRD Blocks Reprogramming of Mouse Somatic Cells into Pluripotent Stem Cells. Stem Cells,  2013, in press,

Abstract: Reprogramming of somatic cells into induced pluripotent stem cells (iPSCs) by overexpression of a defined set of transcription factors requires epigenetic changes of pluripotency genes. Nuclear reprogramming is an inefficient process and the molecular mechanisms that reset the epigenetic state during iPSC generation are largely unknown. Here we show that down-regulation of the NuRD (Nucleosome Remodeling and Deacetylation) complex is required for efficient reprogramming. Overexpression of Mbd3, a subunit of NuRD, inhibits induction of iPSCs by establishing heterochromatic features and silencing ES cell-specific marker genes, including Oct4 and Nanog. Depletion of Mbd3, on the other hand, improves reprogramming efficiency and facilitates the formation of pluripotent stem cells that are capable of generating viable chimeric mice, even in the absence of c-Myc or Sox2. The results establish Mbd3/NuRD as an important epigenetic regulator that restricts the expression of key pluripotency genes, suggesting that drug-induced downregulation of Mbd3/NuRD may be a powerful means to improve the efficiency and fidelity of reprogramming.

 

10: A histone deacetylase inhibitor, largazole, decreases liver fibrosis and angiogenesis by inhibiting transforming growth factor-b and vascular endothelial growth factor signaling. Liver Int. 2013, 33, 504-515.

Abstract: Largazole augmented acetylation of histone H3 (H3) and histone H4 (H4) in HSCs. It directly inhibited the activation of HSCs owing to HDAC inhibitory activity as the antifibrotic effect of largazole was significantly decreased in cells with HDAC1, HDAC2 and HDAC3 knockdown. Largazole also induced apoptosis of HSCs. Largazole not only inhibited the expression of TGFβR2, but also reduced phosphorylation of Smad2 and Akt induced by TGF-β1. Largazole also inhibited the expression of vascular endothelial growth factor (VEGF) and its receptor. VEGF-induced proliferation of HSCs and activation of Akt and p38MAPK were also suppressed by largazole.In vivo, largazole reduced the expression of collagen I, α-smooth muscle actin and tissue inhibitor of metalloproteinase-1 in CCl4–induced fibrosis, and these antifibrotic effects were associated with increased acetylation of H3 and H4. Largazole also induced HSCs to undergo apoptosis in vivo, which was correlated with downregulation of bcl-2 and bcl-xL. Furthermore, largazole inhibited angiogenesis in vivo as evidenced by reduced expression of CD34, VEGF and VEGFR. In addition to its antifibrotic activity, the drug reduced inflammatory activity in CCl4-induced liver fibrosis.

 

9: A Novel CyclinE/CyclinA-CDK2 Inhibitor Targets p27Kip1 Degradation, Cell Cycle Progression and Cell Survival: Implications in Cancer Therapy.   Cancer Lett., 2013, 333, 103-112.

Abstract: p27Kip1 (p27) binds and inhibits the cyclin E- or cyclin A-associated cyclin-dependent kinases (CDKs)2 and other CDKs, and negatively regulates G1–G2 cell cycle progression. To develop specific CDK inhibitors, we have modeled the interaction between p27 and cyclin A-CDK2, and designed a novel compound that mimics p27 binding to cyclin A-CDK2. The chemically synthesized inhibitor exhibited high potency and selective inhibition towards cyclin E/cyclin A-CDK2 kinase in vitro but not other kinases. To facilitate permeability of the inhibitor, a cell penetrating peptide (CPP) was conjugated to the inhibitor to examine its effect in several cancer cell lines. The CPP-conjugated inhibitor significantly inhibited the proliferation of cancer cells. The treatment of the inhibitor resulted in the increased accumulation of p27 and p21Cip1/Waf1 (p21) and hypo-phosphorylation of retinoblastoma protein (Rb). The degradation of p27, mediated through the phosphorylation of threonine-187 in p27, was also inhibited. Consequently, exposure of cells to the inhibitor caused cell cycle arrest and apoptosis. We conclude that specific cyclinE/cyclin A-CDK2 inhibitors can be developed based on the interaction between p27 and cyclin/CDK to block cell cycle progression to prevent tumor growth and survival.

 

8: Synergistic Triggering of Superoxide Flashes by Mitochondrial Ca2+ Uniport and Basal ROS Elevation. J. Biol. Chem. 2013, 288, 4602–4612.

Abstract: Mitochondrial superoxide flashes reflect a quantal, bursting mode of reactive oxygen species (ROS) production that arises from stochastic, transient opening of the mitochondrial permeability transition pore (mPTP) in many types of cells and in living animals. However, the regulatory mechanisms and the exact nature of the flash-coupled mPTP remain poorly understood. Here we demonstrate a profound synergistic effect between mitochondrial Ca2+ uniport and elevated basal ROS production in triggering superoxide flashes in intact cells. Hyperosmotic stress potently augmented the flash activity while simultaneously elevating mitochondrial Ca2+ and ROS. Blocking mitochondrial Ca2+ transport by knockdown of MICU1 or MCU, newly identified components of the mitochondrial Ca2+ uniporter, or scavenging mitochondrial basal ROS markedly diminished the flash response. More importantly, whereas elevating Ca2+ or ROS production alone was inefficacious in triggering the flashes, concurrent physiological Ca2+and ROS elevation served as the most powerful flash activator, increasing the flash incidence by an order of magnitude. Functionally, superoxide flashes in response to hyperosmotic stress participated in the activation of JNK and p38. Thus, physiological levels of mitochondrial Ca2+ and ROS synergistically regulate stochastic mPTP opening and quantal ROS production in intact cells, marking the flash as a coincidence detector of mitochondrial Ca2+ and ROS signals.

 

7: Novel Histone Demethylase LSD1 Inhibitors Selectively Target Cancer Cells with Pluripotent Stem Cell Properties, Cancer Res.,201171(23), 7238-7249.

Abstract: Histone modification determines epigenetic patterns of gene expression with methylation of histone H3 at lysine 4 (H3K4) often associated with active promoters. LSD1/KDM1 is a histone demethylase that suppresses gene expression by converting dimethylated H3K4 to mono- and unmethylated H3K4. LSD1 is essential for metazoan development, but its pathophysiologic functions in cancer remain mainly uncharacterized. In this study, we developed specific bioactive small inhibitors of LSD1 that enhance H3K4 methylation and derepress epigenetically suppressed genes in vivo. Strikingly, these compounds inhibited the proliferation of pluripotent cancer cells including teratocarcinoma, embryonic carcinoma, and seminoma or embryonic stem cells that express the stem cell markers Oct4 and Sox2 while displaying minimum growth-inhibitory effects on nonpluripotent cancer or normal somatic cells. RNA interference–mediated knockdown of LSD1 expression phenocopied these effects, confirming the specificity of small molecules and further establishing the high degree of sensitivity and selectivity of pluripotent cancer cells to LSD1 ablation. In support of these results, we found that LSD1 protein level is highly elevated in pluripotent cancer cells and in human testicular seminoma tissues that express Oct4. Using these novel chemical inhibitors as probes, our findings establish LSD1 and histone H3K4 methylation as essential cancer-selective epigenetic targets in cancer cells that have pluripotent stem cell properties.

This paper was highlighted by “Nature China”

NATURE-CHINA-Highlight-Cancer-Biology

 

6: Superoxide Flashes: Early mitochondrial signals for oxidative stress-induced apoptosis, J. Bio. Chem.2011286, 27573-27581, S27573/1-S27573/8.

Abstract: As a critical apoptosis executioner, caspase-3 becomes activated and then enters into the nucleus to exert its function. However, the molecular mechanism of this nuclear entry of active caspase-3 is still unknown. In this study, we revealed that caspase-3 harbors a crm-1-independent nuclear export signal (NES) in its small subunit. Using reversecaspase- 3 as the study model, we found that the function of the NES in caspase-3 was not disturbed by the conformational changes during induced caspase-3 activation. Mutations disrupting the cleavage activity or p3-recognition site resulted in a defect in the nuclear entry of active caspase-3. We provide evidence that the p3-mediated specific cleavage activity of active caspase-3 abrogated the function of the NES. In conclusion, our results demonstrate that during caspase-3 activation, NES is constitutively present. p3-mediated specific cleavage activity abrogates the NES function in caspase-3, thus facilitating the nuclear entry of active caspase-3.

 

5: Nuclear Entry of Active Caspase 3 Is Facilitated by Its P3 Recognition Based Specific Cleavage Activity to Abrogate the NES Function of Caspase3, Cell Res.201020, 211-222.

Abstract: As a critical apoptosis executioner, caspase-3 becomes activated and then enters into the nucleus to exert its function. However, the molecular mechanism of this nuclear entry of active caspase-3 is still unknown. In this study, we revealed that caspase-3 harbors a crm-1-independent nuclear export signal (NES) in its small subunit. Using reversecaspase- 3 as the study model, we found that the function of the NES in caspase-3 was not disturbed by the conformational changes during induced caspase-3 activation. Mutations disrupting the cleavage activity or p3-recognition site resulted in a defect in the nuclear entry of active caspase-3. We provide evidence that the p3-mediated specific cleavage activity of active caspase-3 abrogated the function of the NES. In conclusion, our results demonstrate that during caspase-3 activation, NES is constitutively present. p3-mediated specific cleavage activity abrogates the NES function in caspase-3, thus facilitating the nuclear entry of active caspase-3.

 

4: Therapeutic targeting of the PDGF and TGF-beta-signaling pathways in hepatic stellate cells by PTK787/ZK22258, Lab. Invest.200989, 1152–1160.

Abstract: Stimulation of hepatic stellate cells (HSCs) by platelet-derived growth factor (PDGF) and transforming growth factor-b1 (TGF-b1) is an essential pathway of proliferation and fibrogenesis, respectively, in liver fibrosis. We provide evidence that PTK787/ZK222584 (PTK/ZK), a potent tyrosine kinase inhibitor that blocks vascular endothelial growth factor receptor (VEGFR), significantly inhibits PDGF receptor expression, as well as PDGF-simulated HSC proliferation, migration and phosphorylation of ERK1/2, Akt and p70S6 kinase. Interestingly, PTK/ZK also antagonizes the TGF-b1-induced expression of VEGF and VEGFR1. Furthermore, PTK/ZK downregulates TGF-b receptor expression, which is associated with reduced Akt, ERK and p38MAPK phosphorylation. Furthermore, PDGF-induced TGF-b1 expression is inhibited by PTK/ZK. These findings provide evidence that PTK/ZK targets multiple essential pathways of stellate cell activation that provoke proliferation and fibrogenesis. Our study underscores the potential use of PTK/ZK as an antifibrotic drug in chronic liver disease.

 

3: PTK787/ZK22258 attenuates stellate cell activation and hepatic fibrosis in vivo by inhibiting VEGF signaling, Lab. Invest., 200989, 209–221.

Abstract: Liver fibrosis due to hepatic stellate cell (HSC) activation represents a common response to chronic liver injury. PTK787/ZK222584 (PTK/ZK) is a pan-VEGFR tyrosine kinase inhibitor. The aim of this study was to examine the effect of PTK/ZK in liver fibrosis. In primary HSCs, PTK/ZK inhibited the expression of a-smooth muscle actin (a-SMA), collagen, tissue inhibitor of metalloproteinase-1 (TIMP-1), as well as cell proliferation, migration and actin filament formation. PTK/ ZK-induced apoptosis of HSCs, which was correlated with increased caspase-3 activation and suppressed Bcl-2 expression. PTK/ZK also induced cell cycle arrest, accompanied by increasing the expression of p27Kip1 and downregulation of cyclin D1 and cyclin E. PTK/ZK significantly inhibited vascular endothelial growth factor (VEGF) expression, as well as VEGF-simulated cell proliferation and phosphorylation of Akt in activated HSCs. In a murine fibrotic liver, PTK/ZK attenuated collagen deposition and a-SMA expression in carbon tetrachloride-induced fibrosis in both a ‘prevention’ and ‘treatment’ dosing scheme. These beneficial effects were associated with reduced phosphorylation of Akt and suppressed mRNA expression of procollagen-(I), TIMP-1, matrix metalloproteinase-9 and CD31. These findings provide novel insights into the potential value of blocking VEGF signaling by a small molecule tyrosine kinase inhibitor in treating hepatic fibrosis.

 

2: CUL4/DDB1 Ubiquitin E3 Ligase Interacts with Multiple WD40-repeat Proteins and Regulates Histone H3 Methylation at K4 through WDR5, Nat. Cell Biol., 2006, 8, 1277-1283.

Abstract: The CUL4–DDB1–ROC1 ubiquitin E3 ligase regulates cellcycle progression, replication and DNA damage response1–4. However, the substrate-specific adaptors of this ligase remain uncharacterized. Here, we show that CUL4–DDB1 complexes interact with multiple WD40-repeat proteins (WDRs) including TLE1-3, WDR5, L2DTL (also known as CDT2) and the Polycomb-group protein EED (also known as ESC). WDR5 and EED are core components of histone methylation complexes that are essential for histone H3 methylation and epigenetic control at K4 or K9 and K27, respectively5–7, whereas L2DTL regulates CDT1 proteolysis after DNA damage through CUL4–DDB1 (ref. 8). We found that CUL4A–DDB1 interacts with H3 methylated mononucleosomes and peptides. Inactivation of either CUL4 or DDB1 impairs these histone modifications. However, loss of WDR5 specifically affects histone H3 methylation at K4 but not CDT1 degradation, whereas inactivation of L2DTL prevents CDT1 degradation but not histone methylation. Our studies suggest that CUL4–DDB1 ligases use WDR proteins as molecular adaptors for substrate recognition, and modulate multiple biological processes through ubiquitin-dependent proteolysis.

 

1: L2DTL/CDT2 and PCNA Interact with p53 and Regulate p53 Polyubiquitination and Protein Stability through MDM2 and CUL4A/DDB1 Complexes,Cell Cycle, 200615, 1719-1729.

Abstract: The CUL4-ROC1 E3 ligase complex regulates genome stability, replication and cell cycle progression. A novel WD40 domain-containing protein, L2DTL/CDT2 and PCNA were identified as proteins associated with CUL4/DDB1 complexes. Inactivation of CUL4A, L2DTL, PCNA, DDB1 or ROC1 induced p53 stabilization and growth arrest. L2DTL, PCNA and DDB1/CUL4A complexes were found to physically interact with p53 tumor suppressor and its regulator MDM2/HDM2. The isolated CUL4A complexes display potent and robust polyubiquitination activity towards p53 and this activity is dependent on L2DTL, PCNA, DDB1, ROC1 and MDM2/HDM2. We also found that the interaction between p53 and CUL4 complex is regulated by DNA damage. Our data further showed that MDM2/HDM2 is rapidly proteolyzed in response to UV irradiation and this process is regulated by CUL4/DDB1 and PCNA. Our studies demonstrate that PCNA, L2DTL and the DDB1-CUL4A complex play critical and differential roles in regulating the protein stability of p53 and MDM2/HDM2 in unstressed and stressed cells.