Development of human cGAS-specific small-molecule inhibitors for repression of dsDNA-triggered interferon expression.

Cyclic GMP-AMP synthase (cGAS) is the primary sensor for aberrant intracellular dsDNA producing the cyclic dinucleotide cGAMP, a second messenger initiating cytokine production in subsets of myeloid lineage cell types. Therefore, inhibition of the enzyme cGAS may act anti-inflammatory. Here we report the discovery of human-cGAS-specific small-molecule inhibitors by high-throughput screening and the targeted medicinal chemistry optimization for two molecular scaffolds. Lead compounds from one scaffold co-crystallize with human cGAS and occupy the ATP- and GTP-binding active site. The specificity and potency of these drug candidates is further documented in human myeloid cells including primary macrophages. These novel cGAS inhibitors with cell-based activity will serve as probes into cGAS-dependent innate immune pathways and warrant future pharmacological studies for treatment of cGAS-dependent inflammatory diseases.

Small misfolded Tau species are internalized via bulk endocytosis and anterogradely and retrogradely transported in neurons.

The accumulation of Tau into aggregates is associated with key pathological events in frontotemporal lobe degeneration (FTD-Tau) and Alzheimer disease (AD). Recent data have shown that misfolded Tau can be internalized by cells in vitro (Frost, B., Jacks, R. L., and Diamond, M. I. (2009) J. Biol. Chem. 284, 12845-12852) and propagate pathology in vivo (Clavaguera, F., Bolmont, T., Crowther, R. A., Abramowski, D., Frank, S., Probst, A., Fraser, G., Stalder, A. K., Beibel, M., Staufenbiel, M., Jucker, M., Goedert, M., and Tolnay, M. (2009) Nat. Cell Biol. 11, 909-913; Lasagna-Reeves, C. A., Castillo-Carranza, D. L., Sengupta, U., Guerrero-Munoz, M. J., Kiritoshi, T., Neugebauer, V., Jackson, G. R., and Kayed, R. (2012) Sci. Rep. 2, 700). Here we show that recombinant Tau misfolds into low molecular weight (LMW) aggregates prior to assembly into fibrils, and both extracellular LMW Tau aggregates and short fibrils, but not monomers, long fibrils, nor long filaments purified from brain extract are taken up by neurons. Remarkably, misfolded Tau can be internalized at the somatodendritic compartment, or the axon terminals and it can be transported anterogradely, retrogradely, and can enhance tauopathy in vivo. The internalized Tau aggregates co-localize with dextran, a bulk-endocytosis marker, and with the endolysosomal compartments. Our findings demonstrate that exogenous Tau can be taken up by cells, uptake depends on both the conformation and size of the Tau aggregates and once inside cells, Tau can be transported. These data provide support for observations that tauopathy can spread trans-synaptically in vivo, via cell-to-cell transfer.

Microbial community structure of hydrothermal deposits from geochemically different vent fields along the Mid-Atlantic Ridge.

To evaluate the effects of local fluid geochemistry on microbial communities associated with active hydrothermal vent deposits, we examined the archaeal and bacterial communities of 12 samples collected from two very different vent fields: the basalt-hosted Lucky Strike (37°17'N, 32°16.3'W, depth 1600-1750 m) and the ultramafic-hosted Rainbow (36°13'N, 33°54.1'W, depth 2270-2330 m) vent fields along the Mid-Atlantic Ridge (MAR). Using multiplexed barcoded pyrosequencing of the variable region 4 (V4) of the 16S rRNA genes, we show statistically significant differences between the archaeal and bacterial communities associated with the different vent fields. Quantitative polymerase chain reaction (qPCR) assays of the functional gene diagnostic for methanogenesis (mcrA), as well as geochemical modelling to predict pore fluid chemistries within the deposits, support the pyrosequencing observations. Collectively, these results show that the less reduced, hydrogen-poor fluids at Lucky Strike limit colonization by strict anaerobes such as methanogens, and allow for hyperthermophilic microaerophiles, like Aeropyrum. In contrast, the hydrogen-rich reducing vent fluids at the ultramafic-influenced Rainbow vent field support the prevalence of methanogens and other hydrogen-oxidizing thermophiles at this site. These results demonstrate that biogeographical patterns of hydrothermal vent microorganisms are shaped in part by large scale geological and geochemical processes.