Kruppel-like transcription factor 5 promotes breast cell survival through pERK-mediated MKP-1 protein stabilization

Abstract #3019

Kruppel-like Factor 5 (KLF5) is a transcription factor promoting cell survival and tumorigenesis in multiple cancers. High level of KLF5 mRNA is associated with a shorter survival for breast cancer patients. However, the role of KLF5 and mechanism of KLF5 actions in breast cancer remain unclear. In this study, we found that KLF5 knockdown by siRNA in two basal type breast cell lines MCF10A and BT20 induces apoptosis, as indicated by loss of cell viability and cleaved PARP and caspase 3. Interestingly, a survival phosphotase, MKP-1, is downregulated at protein level by KLF5 ablation. Consistently, KLF5 over-expression increases the MKP-1 protein expression. However, MKP-1 is not a KLF5 direct target gene because the MKP-1 mRNA level is not regulated by KLF5. By the cycloheximide chase assays, we found that KLF5 decreases the MKP-1 protein degradation. However, KLF5 does not decrease the MKP-1 E3 ubiquitin ligase SKP2 expression. The ERK inhibitor U0126 specifically blocks the KLF5 induced MKP-1, suggesting that KLF5 up-regulates MKP-1 through activating ERK signaling. Finally, we demonstrated that MKP-1 over-expression blocks KLF5 knockdown induced apoptosis in MCF10A cells. These findings suggest that KLF5 is a survival factor which promotes breast cell survival partially through pERK-mediated MKP-1 stabilization. The KLF5-pERK-MKP-1 signaling axis may provide new therapeutic targets for invasive breast cancer.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3019.

Temperature-triggered gelation of aqueous laponite dispersions containing a cationic poly(N-isopropyl acrylamide) graft copolymer

In this work, temperature-triggered gelation of aqueous laponite dispersions containing a cationic poly(N-isopropylacrylamide) (PNIPAm) graft copolymer was investigated. The copolymer used was PDMA(+)(30)-g-(PNIPAm(210))(14) [Liu et al. Langmuir 2008, 24, 7099]. DMA(+) is quarternarized N,N-dimethylaminoethyl methacrylate. The presence of small concentrations of laponite enabled temperature-triggered gel formation to occur at low copolymer concentrations (e.g., 1 wt %). Dynamic rheological measurements of the gels showed that they had storage modulus values of up to 400 Pa when the total solid volume fraction (polymer and laponite) was only about 0.02. The storage modulus was dependent on both the temperature and the composition of the dispersion used for preparation. The key component that provided the temperature-triggered gels with their elasticity was found to be self-assembled nanocomposite (NC) sheets. These NC sheets spontaneously formed at room temperature upon addition of laponite to the copolymer solution. The NC sheets had lateral dimensions on the order of hundreds of micrometers and a thickness of a few micrometers. The NC sheets were present within the temperature-triggered gels and formed elastically effective chains. The NC sheets exhibited temperature-triggered contraction with a contraction onset temperature of 27 degrees C. A conceptual model is proposed to qualitatively explain the relationship between gel elasticity and dispersion composition.

Enzymatically inactive adenylate kinase 4 interacts with mitochondrial ADP/ATP translocase

Adenylate kinase 4 (AK4) is a unique member with no enzymatic activity in vitro in the adenylate kinase (AK) family although it shares high sequence homology with other AKs. It remains unclear what physiological function AK4 might play or why it is enzymatically inactive. In this study, we showed increased AK4 protein levels in cultured cells exposed to hypoxia and in an animal model of the neurodegenerative disease amyotrophic lateral sclerosis. We also showed that short hairpin RNA (shRNA)-mediated knockdown of AK4 in HEK293 cells with high levels of endogenous AK4 resulted in reduced cell proliferation and increased cell death. Furthermore, we found that AK4 over-expression in the neuronal cell line SH-SY5Y with low endogenous levels of AK4 protected cells from H(2)O(2) induced cell death. Proteomic studies revealed that the mitochondrial ADP/ATP translocases (ANTs) interacted with AK4 and higher amount of ANT was co-precipitated with AK4 when cells were exposed to H(2)O(2) treatment. In addition, structural analysis revealed that, while AK4 retains the capability of binding nucleotides, AK4 has a glutamine residue instead of a key arginine residue in the active site well conserved in other AKs. Mutation of the glutamine residue to arginine (Q159R) restored the adenylate kinase activity with GTP as substrate. Collectively, these results indicate that the enzymatically inactive AK4 is a stress responsive protein critical to cell survival and proliferation. It is likely that the interaction with the mitochondrial inner membrane protein ANT is important for AK4 to exert the protective benefits to cells under stress.

Crystal structure of human adenylate kinase 4 (L171P) suggests the role of hinge region in protein domain motion

It is well known that motion of LID and NMP-binding (NMP(bind)) domains in adenylate kinase (AK) is important in ligand binding and catalysis. However, the nature of such domain motions is poorly characterized. One of the critical hinge regions is hinge IV, which connects the CORE and LID domains. In addition, the hinge IV contains a strictly conserved residue, L171, in the AK family. To investigate the role of hinge IV, crystal structure of human adenylate kinase 4 (AK4) L171P mutant was determined. This mutation dramatically changes the orientation of the LID domain, which could be described as a novel twisted-and-closed conformation in contrast to the open and closed conformations in other AKs. This mutant provides a new example of domain motions in AK family.

Intensive glycemic control lowers plasma visfatin levels in patients with type 2 diabetes

Visfatin is an independent association factor for type 2 diabetes mellitus (T2DM). In order to evaluate the plasma visfatin levels and investigate whether plasma visfatin concentrations are altered by intensive glycemic control in patients with diabetes, we determined plasma visfatin concentrations and metabolic parameters in 53 newly diagnosed type 2 diabetic patients and 35 healthy controls. Visfatin levels were also investigated before and after intensive glycemic control for three months in subgroup of patients with T2DM. Plasma visfatin levels were significantly elevated in diabetic patients compared with healthy controls (p<0.001). Circulating visfatin concentration was associated with fasting plasma glucose (FPG), 2-hour OGTT plasma glucose (2hPG), HOMA-beta indexes (r=0.338, p=0.001; r=0.340, p=0.002; r=-0.296, p=0.006, respectively), but not with insulin sensitivity (HOMA-IR) or other metabolic or anthropometric parameters in all subjects. In addition, visfatin levels were also correlated with HbA1c levels in diabetic patients. Furthermore, visfatin concentrations reduced from 25.0+/-6.5 ng/ml at baseline to 20.3+/-4.7 ng/ml (p<0.01) after 3 months of intensive glycemic control, while HbA1c levels decreased from 9.0+/-1.8% to 6.2+/-0.7% (p<0.01). We conclude that the change of visfatin concentration may be a compensatory mechanism to ameliorate insulin deficiency due to pancreatic beta-cell dysfunction.

RAGE upregulation and nuclear factor-kappaB activation associated with ageing rat cardiomyocyte dysfunction

Evidence suggests that ageing is a major risk factor for cardiac dysfunction. Interactions between advanced glycation endproducts (AGEs) and the receptor for AGEs (RAGE) are known to cause chronic cellular activation, including activation of nuclear factor-kappaB (NF-kappaB), which has been implicated as a causal factor in the ageing process. To assess whether cardiomyocyte contractile function and the interaction of AGEs with RAGE in the heart are altered in ageing, 25- and 2-month-old male rats were compared. Mechanical properties were assessed in ventricular myocytes using an edge-detection system, including peak twitch amplitude (PTA), time-to-PTA (TPS), time-to-75% relengthening (TR75) and maximal velocity of shortening/relengthening (+/-dL/dt) in ventricular myocytes. AGEs were detected by using a fluorescence assay. The expression of RAGE and NF-kappaB was assessed through a Western blot analysis. Compared with young myocytes, aged myocytes displayed a prolonged TR75 at 1 Hz. With increasing stimulus frequency (from 2 to 4 Hz), aged myocytes' PTA was significantly reduced relative to young myocytes. Aged rat hearts displayed high level of AGEs, RAGE upregulation and NF-kappaB activation. These findings demonstrate impaired cardiomyocyte relaxation and reduced tolerance to increased stimulus frequency in aged rats, which might be associated with enhanced AGEs, RAGE expression, and NF-kappaB activation.

Cationic temperature-responsive poly(N-isopropyl acrylamide) graft copolymers: from triggered association to gelation

In this work temperature-triggered association and gel formation within aqueous solutions of a new family of cationic poly( N-isopropyl acrylamide) (PNIPAm) graft copolymers have been investigated. Five copolymers were synthesized using aqueous atom transfer radical polymerization (ATRP) involving a macroinitiator based on quaternarized N, N-dimethylaminoethyl methacrylate units (DMA+). The PDMA+) x - g-(PNIPAmn)y copolymers have x and y values that originate from the macroinitiator; values for n correspond to the PNIPAm arm length. The copolymer solutions exhibited temperature-triggered formation of nanometer-sized aggregates at the cloud point temperature, which was 33-34 degrees C. The aggregates were investigated using variable-temperature turbidity, hydrodynamic diameter, and electrophoretic mobility measurements. The aggregates were clearly evident using SEM and flowerlike or spherical morphologies were observed. Variable-temperature electrophoretic mobility measurements revealed that the zeta potentials of the aggregates increased with DMA+ content. A study of the effect of added NaNO3 showed that electrostatic interactions controlled the size of the aggregates. The concentrated graft copolymer solutions showed temperature-triggered gelation when the copolymer concentrations exceeded 5 wt %, Fluid-to-gel phase diagrams were constructed. It was found that electrostatic interactions also controlled the gelation temperature. A correlation was found between aggregate size and the minimum copolymer concentration needed to form a gel. A mechanism for the temperature-triggered structural changes leading to the formation of aggregates (in dilute solution) or gels (in concentrated solutions) is proposed.

Early postnatal development of rat brain: in vivo diffusion tensor imaging

Perinatal hypoxia is a major cause of neurodevelopmental deficits. Neuronal migration patterns are particularly sensitive to perinatal hypoxia/ischemia and are associated with the clinical deficits. The rat model of hypoxia/ischemia at P7 mimics that of perinatal injury in humans. Before assessing the effects of postnatal injury on brain development, it is essential to determine the normal developmental trajectories of various brain structures in individual animals. In vivo longitudinal diffusion tensor imaging (DTI) was performed from postnatal day 0 (P0) to P56 on Wistar rats. The DTI metrics, mean diffusivity (MD), fractional anisotropy (FA), axial (lambdal) and radial (lambdat) diffusivities, were determined for four gray matter and eight white matter structures. The FA of the cortical plate and the body of corpus callosum decreased significantly during the first 3 weeks after birth. The decrease in the cortical plate's FA value was associated mainly with an increase in lambdat. The initial decrease in FA of corpus callosum was associated with a significant decrease in lambdal. The FA of corpus callosum increased during the rest of the observational period, which was mainly associated with a decrease in lambdat. The FA of gray matter structures, hippocampus, caudate putamen, and cortical mantle did not show significant changes between P0 and P56. In contrast, the majority of white matter structures showed significant changes between P0 and P56. These temporal changes in the DTI metrics were related to the neuronal and axonal pruning and myelination that are known to occur in the developing brain.

Phosphorylated PP2A (tyrosine 307) is associated with Alzheimer neurofibrillary pathology

Down-regulation of protein phosphatase 2A (PP2A) is thought to play a critical role in tau hyperphosphorylation in Alzheimer's disease (AD). In vitro phosphorylation of PP2A catalytic subunit at Y307 efficiently inactivates PP2A. A specific antibody against phosphorylated (p) PP2A (Y307) (PP2Ac-Yp307) was used to investigate possible PP2A down-regulation by known pathophysiological changes associated with AD, such as Abeta accumulation and oestrogen deficiency. Immunohistochemistry and immunofluorescence confocal microscopy showed an aberrant accumulation of PP2Ac-Yp307 in neurons that bear pretangles or tangles in the susceptible brain regions, such as the entorhinal cortical cortex and the hippocampus. Experimentally, increased PP2Ac-Yp307 was observed in mouse N2a neuroblastoma cells that stably express the human amyloid precursor protein with Swedish mutation (APPswe) compared with wild-type, and in the brains of transgenic APPswe/ presenilin (PS1, A246E) mice, which corresponded to the increased tau phosphorylation. Treating N2a cells with Abeta25-35 mimicked the changes of PP2Ac-Yp307 and tau phosphorylation in N2a APPswe cells. Knockout of oestrogen receptor (ER) alpha or ERbeta gave similar changes of PP2Ac-Yp307 level and tau phosphorylation in the mouse brain. Taken together, these findings suggest that increased PP2A phosphorylation (Y307) can be mediated by Abeta deposition or oestrogen deficiency in the AD brain, and consequently compromise dephosphorylation of abnormally hyperphosphorylated tau, and lead to neurofibrillary tangle formation.

Crystallographic Studies of Human MitoNEET

MitoNEET was identified as an outer mitochondrial membrane protein that can potentially bind the anti-diabetes drug pioglitazone. The crystal structure of the cytoplasmic mitoNEET (residues 33-108) is determined in this study. The structure presents a novel protein fold and contains a [2Fe-2S] cluster-binding domain. The [2Fe-2S] cluster is coordinated to the protein by Cys-72, Cys-74, Cys-83, and His-87 residues. This coordination is also novel compared with the traditional [2Fe-2S] cluster coordinated by four cysteines or two cysteines and two histidines. The cytoplasmic mitoNEET forms homodimers in solution and in crystal. The dimerization is mainly mediated by hydrophobic interactions as well as hydrogen bonds coordinated by two water molecules binding at the interface. His-87 residue, which plays an important role in the coordination of the [2Fe-2S] cluster, is exposed to the solvent on the dimer surface. It is proposed that mitoNEET dimer may interact with other proteins via the surface residues in close proximity to the [2Fe-2S] cluster.

Application of a new leaf area index algorithm to China's landmass using MODIS data for carbon cycle research

An operational system was developed for mapping the leaf area index (LAI) for carbon cycle models from the moderate resolution imaging spectroradiometer (MODIS) data. The LAI retrieval algorithm is based on Deng et al. [2006. Algorithm for global leaf area index retrieval using satellite imagery. IEEE Transactions on Geoscience and Remote Sensing, 44, 2219-2229], which uses the 4-scale radiative transfer model [Chen, J.M., Leblancs, 1997. A 4-scale bidirectional reflection model based on canopy architecture. IEEE Transactions on Geoscience and Remote Sensing, 35, 1316-1337] to simulate the relationship of LAI with vegetated surface reflectance measured from space for various spectral bands and solar and view angles. This algorithm has been integrated to the MODISoft platform, a software system designed for processing MODIS data, to generate 250 m, 500 m and 1 km resolution LAI products covering all of China from MODIS MOD02 or MOD09 products. The multi-temporal interpolation method was implemented to remove the residual cloud and other noise in the final LAI product so that it can be directly used in carbon models without further processing. The retrieval uncertainties from land cover data were evaluated using five different data sets available in China. The results showed that mean LAI discrepancies can reach 27%. The current product was also compared with the NASA MODIS MOD15 LAI product to determine the agreement and disagreement of two different product series. LAI values in the MODIS product were found to be 21% larger than those in the new product. These LAI products were compared against ground TRAC measurements in forests in Qilian Mountain and Changbaishan. On average, the new LAI product agrees with the field measurement in Changbaishan within 2%, but the MODIS product is positively biased by about 20%. In Qilian Mountain, where forests are sparse, the new product is lower than field measurements by about 38%, while the MODIS product is larger by about 65%.

Identification of vip3A-type genes from Bacillus thuringiensis strains and characterization of a novel vip3A-type gene

AIMS

To search for novel Vip3A proteins for controlling insect pests.

METHODS AND RESULTS

A pair of universal primers was designed based on the conserved regions of five vip3A genes. Amplified products were digested with the HindIII and EcoR enzymes so as to confirm different restriction fragment length polymorphism (RFLP) patterns used to identify vip3A-type genes. The vip3A gene types of 606 Bacillus thuringiensis strains were screened and three patterns of RFLP were successfully identified. Two novel vip3A genes were found and one of these, vip3Aa19, was further characterized and its product was confirmed toxic to Spodoptera exigua, Helicoverpa armigera and Plutella xylostella larvae. Partial sequences of another novel vip3A-type gene were obtained that shared 83% homology with that of the vip3Af1 gene.

CONCLUSIONS

A polymerase chain reaction (PCR)-RFLP system we developed could be used for identifying novel vip3A-genes from B. thuringiensis strains. A novel Vip3A protein was found to have a broader insecticidal spectrum.

SIGNIFICANCE AND IMPACT OF THE STUDY

The reported method is a powerful tool to find novel Vip3A proteins from large-scale B. thuringiensis strains. The novel Vip3A protein may be used to control insect pests or resistant insect pests by constructing genetically engineered strains or transgenic plants.

Improving toxicity of Bacillus thuringiensis strain contains the cry8Ca gene specific to Anomala corpulenta larvae

The cry8C-type gene designated cry8Ca2, which was cloned and sequenced from a Bacillus thuringiensis isolate HBF-1 in China, consisted of an open reading frame of 3483 bp encoding a protein of 1160 amino-acid residues. Sequence analysis showed that the Cry8Ca2 protoxin of 130.5 kDa had 99.9% sequence homology with the previously reported Cry8Ca1 protein, with one mismatch between the two amino-acid sequences. When the Cry8Ca2 toxin was expressed in a crystal-negative strain of B. thuringiensis (HD-73(-)), elliptical crystals were produced. Cell extracts from this recombinant strain showed insecticidal activity against Anomala corpulenta larva. Mutant cry8Ca2 genes, produced by polymerase chain reaction amplification with Taq DNA polymerase, were used to develop recombinant B. thuringiensis strains. Mutants producing higher levels of insecticidal activity were identified by bioassay. Thirty-five mutants forming crystals were characterized, and two of them showed significantly increased insecticidal activity against A. corpulenta larva. The 50% lethality concentrations (LC(50)) of the two mutants were 0.2334 x 10(8) and 0.2591 x 10(8) colony-forming units g(-1), considerably lower than the LC(50) of the wild-type strain HBF-1 (0.9583 x 10(8) CFU g(-1)) and that of B. thuringiensis serovar japonensis strain Buibui (1.0752 x 10(8) CFU g(-1)).

Biologic effect and immunoisolating behavior of BMP-2 gene-transfected bone marrow-derived mesenchymal stem cells in APA microcapsules

We investigated the encapsulation of BMP-2 gene-modified mesenchymal stem cells (MSCs) in alginate-poly-L-lysine (APA) microcapsules for the persistent delivery of bone morphogenic protein-2 (BMP-2) to induce bone formation. An electrostatic droplet generator was employed to produce APA microcapsules containing encapsulated beta-gal or BMP-2 gene-transfected bone marrow-derived MSCs. We found that X-gal staining was still positive 28 days after encapsulation. Encapsulated BMP-2 gene-transfected cells were capable of constitutive delivery of BMP-2 proteins for at least 30 days. The encapsulated BMP-2 gene-transfected MSCs or the encapsulated non-gene transfer MSCs (control group) were cocultured with the undifferentiated MSCs. The gene products from the encapsulated BMP-2 cells could induce the undifferentiated MSCs to become osteoblasts that had higher alkaline phosphatase (ALP) activity than those in the control group (p<0.05). The APA microcapsules could inhibit the permeation of fluorescein isothiocyanate-conjuncted immunoglobulin G. Mixed lymphocyte reaction also indicates that the APA microcapsules could prevent the encapsulated BMP-2 gene-transfected MSCs from initiating the cellular immune response. These results demonstrated that the nonautologous BMP-2 gene-transfected stem cells are of potential utility for enhancement of bone repair and bone regeneration in vivo.