WNT1-inducible signaling pathway protein-1 activates diverse cell survival pathways and blocks doxorubicin-induced cardiomyocyte death

The anthracycline antibiotic doxorubicin (DOX) is a potent cancer chemotherapeutic agent that exerts both acute and chronic cardiotoxicity. Here we show that in adult mouse cardiomyocytes, DOX activates (i) the pro-apoptotic p53, (ii) p38MAPK and JNK, (iii) Bax translocation, (iv) cytochrome c release, and (v) caspase 3. Further, it (vi) inhibits expression of anti-apoptotic Akt, Bcl-2 and Bcl-xL, and (vii) induces internucleosomal degradation and cell death. WNT1-inducible signaling pathway protein-1 (WISP1), a CCN family member and a matricellular protein, inhibits DOX-mediated cardiomyocyte death. WISP1 inhibits DOX-induced p53 activation, p38 MAPK and JNK phosphorylation, Bax translocation to mitochondria, and cytochrome c release into cytoplasm. Additionally, WISP1 reverses DOX-induced suppression of Bcl-2 and Bcl-xL expression and Akt inhibition. The pro-survival effects of WISP1 were recapitulated by the forced expression of mutant p53, wild-type Bcl-2, wild-type Bcl-xL, or constitutively active Akt prior to DOX treatment. WISP1 also induces the pro-survival factor Survivin via PI3K/Akt signaling. Overexpression of wild-type, but not mutant Survivin, blunts DOX cytotoxicity. Further, WISP1 stimulates PI3K–Akt-dependent GSK3β phosphorylation and β-catenin nuclear translocation. Importantly, WISP1 induces its own expression. Together, these results provide important insights into the cytoprotective effects of WISP1 in cardiomyocytes, and suggest a potential therapeutic role for WISP1 in DOX-induced cardiotoxicity.     

Pretreatment with Bacopa monnieri extract offsets 3-nitropropionic acid induced mitochondrial oxidative stress and dysfunctions in the striatum of prepubertal mouse brain

The present investigation was designed to determine the efficacy of Bacopa monnieri (Brahmi; BM) to offset 3-nitropropionic acid (3-NPA) induced oxidative stress and mitochondrial dysfunction in dopaminergic (N27) cells and prepubertal mouse brain. Pretreatment of N27 cells with BM ethanolic extract (BME) significantly attenuated 3-NPA-induced cytotoxicity. Further, we determined the degree of oxidative stress induction, redox status, enzymic antioxidants, and protein oxidation in the striatal mitochondria of mice given BME prophylaxis followed by 3-NPA challenge. While 3-NPA-induced marked oxidative stress in the mitochondria of the striatum, BME prophylaxis markedly prevented 3-NPA-induced oxidative dysfunctions and depletion of reduced glutathione and thiol levels. The activities of antioxidant enzymes (superoxide dismutase, glutathione peroxidase, glutathione reductase, thioredoxin reductase), Na(+),K(+)-ATPase, and citric acid cycle enzymes in the striatum discernible among 3-NPA mice were significantly restored with BME prophylaxis. Interestingly, BME offered protection against 3-NPA-induced mitochondrial dysfunctions as evidenced by the restoration of the activities of ETC enzymes (NADH:ubiquinone oxidoreductase, NADH:cytochrome c reductase, succinate-ubiquinone oxidoreductase, and cytochrome c oxidase) and mitochondrial viability. We hypothesize that the neuroprotective effects of BME may be wholly or in part related to its propensity to scavenge free radicals, maintain redox status, and upregulate antioxidant machinery in striatal mitochondria.     

Coordination of cell proliferation and anterior-posterior axis establishment in the mouse embryo

During development, the growth of the embryo must be coupled to its patterning to ensure correct and timely morphogenesis. In the mouse embryo, migration of the anterior visceral endoderm (AVE) to the prospective anterior establishes the anterior-posterior (A-P) axis. By analysing the distribution of cells in S phase, M phase and G2 from the time just prior to the migration of the AVE until 18 hours after its movement, we show that there is no evidence for differential proliferation along the A-P axis of the mouse embryo. Rather, we have identified that as AVE movements are being initiated, the epiblast proliferates at a much higher rate than the visceral endoderm. We show that these high levels of proliferation in the epiblast are dependent on Nodal signalling and are required for A-P establishment, as blocking cell division in the epiblast inhibits AVE migration. Interestingly, inhibition of migration by blocking proliferation can be rescued by Dkk1. This suggests that the high levels of epiblast proliferation function to move the prospective AVE away from signals that are inhibitory to its migration. The finding that initiation of AVE movements requires a certain level of proliferation in the epiblast provides a mechanism whereby A-P axis development is coordinated with embryonic growth.     

Copper alters aggregation behavior of prion protein and induces novel interactions between its N- and C-terminal regions

Copper is reported to promote and prevent aggregation of prion protein. Conformational and functional consequences of Cu(2+)-binding to prion protein (PrP) are not well understood largely because most of the Cu(2+)-binding studies have been performed on fragments and truncated variants of the prion protein. In this context, we set out to investigate the conformational consequences of Cu(2+)-binding to full-length prion protein (PrP) by isothermal calorimetry, NMR, and small angle x-ray scattering. In this study, we report altered aggregation behavior of full-length PrP upon binding to Cu(2+). At physiological temperature, Cu(2+) did not promote aggregation suggesting that Cu(2+) may not play a role in the aggregation of PrP at physiological temperature (37 °C). However, Cu(2+)-bound PrP aggregated at lower temperatures. This temperature-dependent process is reversible. Our results show two novel intra-protein interactions upon Cu(2+)-binding. The N-terminal region (residues 90-120 that contain the site His-96/His-111) becomes proximal to helix-1 (residues 144-147) and its nearby loop region (residues 139-143), which may be important in preventing amyloid fibril formation in the presence of Cu(2+). In addition, we observed another novel interaction between the N-terminal region comprising the octapeptide repeats (residues 60-91) and helix-2 (residues 174-185) of PrP. Small angle x-ray scattering studies of full-length PrP show significant compactness upon Cu(2+)-binding. Our results demonstrate novel long range inter-domain interactions of the N- and C-terminal regions of PrP upon Cu(2+)-binding, which might have physiological significance.     

Cg2091 encodes a polyphosphate/ATP-dependent glucokinase of Corynebacterium glutamicum

The Corynebacterium glutamicum gene cg2091 is encoding a polyphosphate (PolyP)/ATP-dependent glucokinase (PPGK). Previous work demonstrated the association of PPGK to PolyP granules. The deduced amino acid sequence of PPGK shows 45% sequence identity to PolyP/ATP glucomannokinase of Arthrobacter sp. strain KM and 50% sequence identity to PolyP glucokinase of Mycobacterium tuberculosis H37Rv. PPGK from C. glutamicum was purified from recombinant Escherichia coli. PolyP was highly preferred over ATP and other NTPs as substrate and with respect to the tested PolyPs differing in chain length; the protein was most active with PolyP₇₅. Gel filtration analysis revealed that PolyP supported the formation of homodimers of PPGK and that PPGK was active as a homodimer. A ppgK deletion mutant (ΔppgK) showed slowed growth in minimal medium with maltose as sole carbon source. Moreover, in minimal medium containing 2 to 4% (w/v) glucose as carbon source, ΔppgK grew to lower final biomass concentrations than the wild type. Under phosphate starvation conditions, growth of ΔppgK was reduced, and growth of a ppgK overexpressing strain was increased as compared to wild type and empty vector control, respectively. Thus, under conditions of glucose excess, the presence of PPGK entailed a growth advantage.     

Prioritizing Tiger Conservation through Landscape Genetics and Habitat Linkages

Even with global support for tiger (Panthera tigris) conservation their survival is threatened by poaching, habitat loss and isolation. Currently about 3,000 wild tigers persist in small fragmented populations within seven percent of their historic range. Identifying and securing habitat linkages that connect source populations for maintaining landscape-level gene flow is an important long-term conservation strategy for endangered carnivores. However, habitat corridors that link regional tiger populations are often lost to development projects due to lack of objective evidence on their importance. Here, we use individual based genetic analysis in combination with landscape permeability models to identify and prioritize movement corridors across seven tiger populations within the Central Indian Landscape. By using a panel of 11 microsatellites we identified 169 individual tigers from 587 scat and 17 tissue samples. We detected four genetic clusters within Central India with limited gene flow among three of them. Bayesian and likelihood analyses identified 17 tigers as having recent immigrant ancestry. Spatially explicit tiger occupancy obtained from extensive landscape-scale surveys across 76,913 km² of forest habitat was found to be only 21,290 km². After accounting for detection bias, the covariates that best explained tiger occupancy were large, remote, dense forest patches; large ungulate abundance, and low human footprint. We used tiger occupancy probability to parameterize habitat permeability for modeling habitat linkages using least-cost and circuit theory pathway analyses. Pairwise genetic differences (F_ST) between populations were better explained by modeled linkage costs (r>0.5, p<0.05) compared to Euclidean distances, which was in consonance with observed habitat fragmentation. The results of our study highlight that many corridors may still be functional as there is evidence of contemporary migration. Conservation efforts should provide legal status to corridors, use smart green infrastructure to mitigate development impacts, and restore habitats where connectivity has been lost.     

Structural insights into the EB1-APC interaction

EB1 proteins bind to microtubule ends where they act in concert with other components, including the adenomatous polyposis coli (APC) tumor suppressor, to regulate the microtubule filament system. We find that EB1 is a stable dimer with a parallel coiled coil and show that dimerization is essential for the formation of its C-terminal domain (EB1-C). The crystal structure of EB1-C reveals a highly conserved surface patch with a deep hydrophobic cavity at its center. EB1-C binds two copies of an APC-derived C-terminal peptide (C-APCp1) with equal 5 microM affinity. The conserved APC Ile2805-Pro2806 sequence motif serves as an anchor for the interaction of C-APCp1 with the hydrophobic cavity of EB1-C. Phosphorylation of the conserved Cdc2 site Ser2789-Lys2792 in C-APCp1 reduces binding four-fold, indicating that the interaction APC-EB1 is post-translationally regulated in cells. Our findings provide a basis for understanding the dynamic crosstalk of EB1 proteins with their molecular targets in eukaryotic organisms.     

Contrasting effects of natural selection on human and chimpanzee CC chemokine receptor 5

Human immunodeficiency virus type 1 (HIV-1) evolved via cross-species transmission of simian immunodeficiency virus (SIVcpz) from chimpanzees (Pan troglodytes). Chimpanzees, like humans, are susceptible to infection by HIV-1. However, unlike humans, infected chimpanzees seldom develop immunodeficiency when infected with SIVcpz or HIV-1. SIVcpz and most strains of HIV-1 require the cell-surface receptor CC chemokine receptor 5 (CCR5) to infect specific leukocyte subsets, and, subsequent to infection, the level of CCR5 expression influences the amount of HIV-1 entry and the rate of HIV-1 replication. Evidence that variants in the 5' cis-regulatory region of CCR5 (5'CCR5) affect disease progression in humans suggests that variation in CCR5 might also influence the response of chimpanzees to HIV-1/SIVcpz. To determine whether patterns of genetic variation at 5'CCR5 in chimpanzees are similar to those in humans, we analyzed patterns of DNA sequence variation in 37 wild-born chimpanzees (26 P. t. verus, 9 P. t. troglodytes, and 2 P. t. schweinfurthii), along with previously published 5'CCR5 data from 112 humans and 50 noncoding regions in the human and chimpanzee genomes. These analyses revealed that patterns of variation in 5'CCR5 differ dramatically between chimpanzees and humans. In chimpanzees, 5'CCR5 was less diverse than 80% of noncoding regions and was characterized by an excess of rare variants. In humans, 5'CCR5 was more diverse than 90% of noncoding regions and had an excess of common variants. Under a wide range of demographic histories, these patterns suggest that, whereas human 5'CCR5 has been subject to balancing selection, chimpanzee 5'CCR5 has been influenced by a selective sweep. This result suggests that chimpanzee 5'CCR5 might harbor or be linked to functional variants that influence chimpanzee resistance to disease caused by SIVcpz/HIV-1.