Development of dual casein kinase 1δ/1ε (CK1δ/ε) inhibitors for treatment of breast cancer

Casein kinase 1δ/ε have been identified as promising therapeutic target for oncology application, including breast and brain cancer. Here, we described our continued efforts in optimization of a lead series of purine scaffold inhibitors that led to identification of two new CK1δ/ε inhibitors 17 and 28 displaying low nanomolar values in antiproliferative assays against the human MDA-MB-231 triple negative breast cancer cell line and have physical, in vitro and in vivo pharmacokinetic properties suitable for use in proof of principle animal xenograft studies against human cancers.     

Interactions of Npc1 and amyloid accumulation/deposition in the APP/PS1 mouse model of Alzheimer’s

Although Niemann-Pick C1 disease has frequently been called “juvenile Alzheimer’s”, the effects of introducing Npc1 mutations into a mouse model of Alzheimer’s have not previously been performed. We have crossed Npc1 ^+/− mice with APP/PS1 “Alzheimer’s” mice and studied Aβ42 accumulation and amyloid plaque formation. Mice heterozygous for Npc1 and positive for the APP and PS1 transgenes accumulated Aβ42 more rapidly than the APP/PS1 controls and this correlated, as expected, with the area of amyloid plaques. We conclude that the alterations of intracellular cholesterol present in Npc1 ^+/− mice can influence the progress of Alzheimer’s disease in the APP/PS1 mouse model.     

Effect of ε subunit on the rotation of thermophilic Bacillus F1-ATPase

F₁-ATPase is an ATP-driven motor in which γε rotates in the α₃β₃-cylinder. It is attenuated by MgADP inhibition and by the ε subunit in an inhibitory form. The non-inhibitory form of ε subunit of thermophilic Bacillus PS3 F₁-ATPase is stabilized by ATP-binding with micromolar K_d at 25 °C. Here, we show that at [ATP] > 2 μM, ε does not affect rotation of PS3 F₁-ATPase but, at 200 nM ATP, ε prolongs the pause of rotation caused by MgADP inhibition while the frequency of the pause is unchanged. It appears that ε undergoes reversible transition to the inhibitory form at [ATP] below K_d.     

Design and synthesis of selective CYP1B1 inhibitor via dearomatization of α-naphthoflavone

Selective cytochrome P450 (CYP) 1B1 inhibition has potential as an anticancer strategy that is unrepresented in the current clinical arena. For development of a selective inhibitor, we focused on the complexity caused by sp³-hybridized carbons and synthesized a series of benzo[h]chromone derivatives linked to a non-aromatic B-ring using α-naphthoflavone (ANF) as the lead compound. Ring structure comparison suggested compound 37 as a suitable cyclohexyl-core with improved solubility. Structural evolution of 37 produced the azide-containing cis-49a, which had good properties in three important respects: (1) selectivity for CYP1B1 over CYP1A1 and CYP1A2 (120-times and 150-times, respectively), (2) greater inhibitory potency of >2 times that of ANF, and (3) improved solubility. The corresponding aromatic B-ring compound 59a showed low selectivity and poor solubility. To elucidate the binding mode, we performed X-ray crystal structure analysis, which revealed the interaction mode and explained the subtype selectivity of cis-49a.     

Structure–activity relationship of isoform selective inhibitors of Rac1/1b GTPase nucleotide binding

The synthesis of a series of berberine, phenantridine and isoquinoline derivatives was realized to explore their Rho GTPase nucleotide inhibitory activity. The compounds were evaluated in a nucleotide binding competition assay against Rac1, Rac1b, Cdc42 and in a cellular Rac GTPase activation assay. The insertion of 19 AA in the splice variant Rac1b is shown to be sufficient to introduce a conformational difference that allows compounds 4, 21, 22, and 26 to exhibit selective inhibition of Rac 1b over Rac1.     

Up-regulation of BMP-2 antagonizes TGF-β1/ROCK-enhanced cardiac fibrotic signalling through activation of Smurf1/Smad6 complex

Rho‐associated kinase (ROCK) plays a critical role in pressure overload‐induced left ventricular remodelling. However, the underlying mechanism remains unclear. Here, we reported that TGF‐β1‐induced ROCK elevation suppressed BMP‐2 level and strengthened fibrotic response. Exogenous BMP‐2 supply effectively attenuated TGF‐β1 signalling pathway through Smad6‐Smurf‐1 complex activation. In vitro cultured cardiomyocytes, mechanical stretch up‐regulated cardiac TGF‐β1, TGF‐β1‐dependent ROCK and down‐regulated BMP‐2, but BMP‐2 level could be reversed through blocking TGF‐β1 receptor by SB‐431542 or inhibition of ROCK by Y‐27632. TGF‐β1 could also activate ROCK and suppress endogenous BMP‐2 level in a dose‐dependent manner. Knock‐down BMP‐2 enhanced TGF‐β1‐mediated PKC‐δ and Smad3 signalling cascades. In contrast, treatment with Y‐27632 or SB‐431542, respectively suppressed ROCK‐dependent PKC‐δ and Smad3 activation, but BMP‐2 was only up‐regulated by Y‐27632. In addition, BMP‐2 silencing abolished the effect of Y‐27632, but not SB‐431542 on suppression of TGF‐β1 pathway. Further experiments showed that Smad6 Smurf1 interaction were required for BMP‐2‐evoked antagonizing effects. Smad6 overexpression attenuated TGF‐β1‐induced activation of PKC‐δ and Smad3, promoted TGF‐β RI degradation in BMP‐2 knock‐down cardiomyocytes, and could be abolished after knocking‐down Smurf‐1, in which Smad6/Smurf1 complex formation was critically involved. In vivo data showed that pressure overload‐induced collagen deposition was attenuated, cardiac function was improved and TGF‐β1‐dependent activation of PKC‐δ and Smad3 was reduced after 2 weeks treatment with rhBMP‐2(0.5 mg/kg) or Y‐27632 (10 mg/kg) in mice that underwent surgical transverse aortic constriction. In conclusion, we propose that BMP‐2, as a novel fibrosis antagonizing cytokine, may have potential beneficial effect in attenuating pressure overload‐induced cardiac fibrosis.     

Kinetics of β-phase formation in 1-O-alkylglycerols

The rate of β-phase formation in the ether lipids 1-O-alkylglycerols have been investigated at various temperatures. The concentrations of the phases vs. time in 1-O-hexadecylglycerol (C₁₆G) were measured using automatic X-ray powder diffraction peak area measurements. In 1-O-decylglycerol (C₁₆G) the rate was estimated using the heat evolved during the transition. At least two factors are important for the low transition rate. At higher temperatures the rate appears to be limited by a low probability of β crystallite formation (nucleation). As the temperature is decreased, crystallite formation probably increases. A second factor involves an activation of the metastable lattice. The activation process results in a lower rate at decreased temperatures. The two factors together give the highest transition rate at the α ? sub-α-phase transition temperature.     

Dynamic relocation of the TORC1–Gtr1/2–Ego1/2/3 complex is regulated by Gtr1 and Gtr2

TORC1 regulates cellular growth, metabolism, and autophagy by integrating various signals, including nutrient availability, through the small GTPases RagA/B/C/D in mammals and Gtr1/2 in budding yeast. Rag/Gtr is anchored to the lysosomal/vacuolar membrane by the scaffold protein complex Ragulator/Ego. Here we show that Ego consists of Ego1 and Ego3, and novel subunit Ego2. The ∆ego2 mutant exhibited only partial defects both in Gtr1-dependent TORC1 activation and Gtr1 localization on the vacuole. Ego1/2/3, Gtr1/2, and Tor1/Tco89 were colocalized on the vacuole and associated puncta. When Gtr1 was in its GTP-bound form and TORC1 was active, these proteins were preferentially localized on the vacuolar membrane, whereas when Gtr1 was in its GDP-bound form, they were mostly localized on the puncta. The localization of TORC1 to puncta was further facilitated by direct binding to Gtr2, which is involved in suppression of TORC1 activity. Thus regulation of TORC1 activity through Gtr1/Gtr2 is tightly coupled to the dynamic relocation of these proteins.     

Binding of Subdomains 1/2 of PfEMP1-DBL1α to Heparan Sulfate or Heparin Mediates Plasmodium falciparum Rosetting

The capacity of Plasmodium falciparum parasitized erythrocytes (pRBC) to adhere to the endothelial lining in the microvasculature and to red blood cells (RBC) is associated with the virulence of the parasite, the pathogenesis and development of severe malaria. Rosetting, the binding of uninfected RBC to pRBC, is frequently observed in individuals with severe malaria and is mediated by the N-terminal NTS-DBL1α domain of the adhesin Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) expressed at the surface of the pRBC. Heparan sulfate has been suggested to be an important receptor for the NTS-DBL1α variant IT4_var60 expressed by the parasite FCR3S1.2. Here, we have determined the binding site of NTS-DBL1α (IT4_var60) to the RBC and heparin using a set of recombinant, mutated proteins expressed in and purified from E. coli. All the variants were studied for their ability to bind to RBC, their capacities to disrupt FCR3S1.2 rosettes, their affinities for heparin and their binding to rosette-disruptive mAbs. Our results suggest that NTS-DBL1α mediates binding to RBC through a limited number of basic amino acid residues localized on the surface of subdomains 1 (SD1) and 2 (SD2). The SD2-binding site is localized in close proximity to one of two previously identified binding sites in the rosetting PfEMP1 of the parasite PaloAlto-varO. The binding site in SD2 of NTS-DBL1α could represent a template for the development of anti-rosetting drugs.     

Structure of Smad1 MH1/DNA complex reveals distinctive rearrangements of BMP and TGF-β effectors

Smad1 is a downstream effector of the BMP signaling pathway that binds regulatory DNA to execute gene expression programs leading to, for example, the maintenance of pluripotency in mice. On the contrary, the TGF-β-activated Smad3 triggers strikingly different programs such as mesodermal differentiation in early development. Because Smad1 and Smad3 contain identical amino acids at the DNA contact interface it is unclear how they elicit distinctive bioactivities. Here, we report the crystal structure of the MH1 domain of Smad1 bound to a palindromic Smad binding element. Surprisingly, the DNA contact interface of Smad1 is drastically rearranged when compared to Smad3. The N-terminal helix 1 of Smad1 is dislodged from its intramolecular binding site and adopts a domain swapped arrangement with a symmetry-related molecule. As a consequence, helix 2 kinks away from the double helix disabling several key phosphate backbone interactions. Thermal melting analysis corroborates a decompacted conformation of Smad1 and DNA binding assays indicate a lower overall affinity of Smad1 to DNA but increased cooperativity when binding to palindromic DNA motifs. These findings suggest that Smad1 and Smad3 evolved differential qualities to assemble on composite DNA elements and to engage in co-factor interactions by remodeling their N-termini.     

TGF-β1 increases invasiveness of SW1990 cells through Rac1/ROS/NF-κB/IL-6/MMP-2

Human pancreatic cancer invasion and metastasis have been found to correlate with increased levels of active matrix metalloproteinase 2 (MMP-2). The multifunctional cytokine transforming growth factor beta 1 (TGF-β1) has been shown to increase both secretion of MMP-2 and invasion by several pancreatic cancer cell types. In the present study, we investigated the signaling pathway involved in TGF-β1-promoted MMP-2 secretion and invasion by human pancreatic cancer cells SW1990. Using specific inhibitors, we found that stimulation of these tumor cells with TGF-β1 induced secretion and activation of the collagenase MMP-2, which was required for TGF-β1-stimulated invasion. Our results also indicate that signaling events involved in TGF-β1-enhanced SW1990 invasiveness comprehend activation of Rac1 followed by generation of reactive oxygen species through nicotinamide adenine dinucleotide phosphate-oxidase, activation of nuclear factor-kappa beta, release of interleukin-6, and secretion and activation of MMP-2.