Activation of ataxia telangiectasia muted under experimental models and human Parkinson’s disease

In the present study we demonstrated that neurotoxin MPP<sup>+sup>-induced DNA damage is followed by ataxia telangiectasia muted (ATM) activation either in cerebellar granule cells (CGC) or in B65 cell line. In CGC, the selective ATM inhibitor KU-55933 showed neuroprotective effects against MPP<sup>+sup>-induced neuronal cell loss and apoptosis, lending support to the key role of ATM in experimental models of Parkinson’s disease. Likewise, we showed that knockdown of ATM levels in neuroblastoma B65 cells using an ATM-specific siRNA attenuates the phosphorylation of retinoblastoma protein without affecting other cell-cycle proteins involved in the G<sub>0sub>/G<sub>1sub> cell-cycle phase. Moreover, we demonstrated DNA damage, in human brain samples of PD patients. These findings support a model in which MPP<sup>+sup> leads to ATM activation with a subsequent DNA damage response and activation of pRb. Therefore, this study demonstrates a new link between DNA damage by MPP<sup>+sup> and cell-cycle re-entry through retinoblastoma protein phosphorylation.     

Role of the ubiquitin–proteasome system in the regulation of P2Y13 receptor expression: impact on hepatic HDL uptake

The protective effect of high density lipoproteins (HDL) against atherosclerosis is mainly attributed to their capacity to transport excess cholesterol from peripheral tissues back to the liver for further elimination into the bile, a process called reverse cholesterol transport (RCT). Recently, the importance of the P2Y<sub>13sub> receptor (P2Y<sub>13sub>-R) was highlighted in HDL metabolism since HDL uptake by the liver was decreased in P2Y<sub>13sub>-R deficient mice, which translated into impaired RCT. Here, we investigated for the first time the molecular mechanisms regulating cell surface expression of P2Y<sub>13sub>-R. When transiently expressed, P2Y<sub>13sub>-R was mainly detected in the endoplasmic reticulum (ER) and strongly subjected to proteasome degradation while its homologous P2Y<sub>12sub> receptor (P2Y<sub>12sub>-R) was efficiently targeted to the plasma membrane. We observed an inverse correlation between cell surface expression and ubiquitination level of P2Y<sub>13sub>-R in the ER, suggesting a close link between ubiquitination of P2Y<sub>13sub>-R and its efficient targeting to the plasma membrane. The C-terminus tail exchange between P2Y<sub>13sub>-R and P2Y<sub>12sub>-R strongly restored plasma membrane expression of P2Y<sub>13sub>-R, suggesting the involvement of the intra-cytoplasmic tail of P2Y<sub>13sub>-R in expression defect. Accordingly, proteasomal inhibition increased plasma membrane expression of functionally active P2Y<sub>13sub>-R in hepatocytes, and consequently stimulated P2Y<sub>13sub>-R-mediated HDL endocytosis. Importantly, proteasomal inhibition strongly potentiated HDL hepatic uptake (>200 %) in wild-type but not in P2Y<sub>13sub>-R-deficient mice, thus reinforcing the role of P2Y<sub>13sub>-R expression in regulating HDL metabolism. Therefore, specific inhibition of the ubiquitin–proteasome system might be a novel powerful HDL therapy to enhance P2Y<sub>13sub>-R expression and consequently promote the overall RCT.     

Molecular aspects of 2 human urinary glycoproteins with histocompatibility antigen (HLA) serological activity]

Two serologically active urinary glycoproteins (HLA-A 9 and HLA-B 12) were isolated from urine provided by a patient suffering from tubular proteinuria. Their N-terminal sequences were automatically determined. The latter were identical with the sequence of another urinary glycoprotein (protein HC). The relationship between protein HC and the serological activity is discussed.     

Ultra-remote stereocontrol by conformational communication of information along a carbon chain

Many receptors and allosteric proteins function through binding of a molecule to induce a conformational change, which then influences a remote active site. In synthetic systems, comparable intramolecular information transfer can be effected by using the shape of one part of a molecule to control the stereoselectivity of reactions occurring some distance away. However, the need for direct communication with the reaction site usually limits such remote stereocontrol to distances of not more than about five bond lengths. Cyclic structures overcome this problem by allowing the controlling centre and the reaction site to approach each other, but the information transfer spans only short absolute distances. Truly remote stereocontrol can, however, be achieved with rigid compounds containing amide groups: the conformation of the amides can be controlled by stereogenic centres and responds to that of neighbouring amide groups and in turn influences stereoselective reactions. This strategy has allowed remote stereocontrol spanning 8 (ref. 11) or 9 (ref. 12) bonds. Here we demonstrate stereocontrol over a reaction taking place more than 20 bond lengths from the controlling centre, corresponding to a linear distance of over 2.5 nm. This transmission of information, achieved by conformational changes relayed through the molecule, provides a chemical model of allostery and might serve as a molecular mechanism for communicating and processing information.     

Evidence for cultivar adoption and emerging complexity during the mid-Holocene in the La Plata basin

Multidisciplinary investigations at the Los Ajos archaeological mound complex in the wetlands of southeastern Uruguay challenge the traditional view that the La Plata basin was inhabited by simple groups of hunters and gatherers for much of the pre-Hispanic era. Here we report new archaeological, palaeoecological and botanical data indicating that during an increasingly drier mid-Holocene, at around 4,190 radiocarbon (14C) years before present (bp), Los Ajos became a permanent circular plaza village, and its inhabitants adopted the earliest cultivars known in southern South America. The architectural plan of Los Ajos during the following Ceramic Mound Period (around 3,000-500 14C yr bp) is similar to, but earlier than, settlement patterns demonstrated in Amazonia, revealing a new and independent architectural tradition for South America.     

The knockout mouse project

Mouse knockout technology provides a powerful means of elucidating gene function in vivo, and a publicly available genome-wide collection of mouse knockouts would be significantly enabling for biomedical discovery. To date, published knockouts exist for only about 10% of mouse genes. Furthermore, many of these are limited in utility because they have not been made or phenotyped in standardized ways, and many are not freely available to researchers. It is time to harness new technologies and efficiencies of production to mount a high-throughput international effort to produce and phenotype knockouts for all mouse genes, and place these resources into the public domain.     

Active fluidization of polymer networks through molecular motors

Entangled polymer solutions and melts exhibit elastic, solid-like resistance to quick deformations and a viscous, fluid-like response to slow deformations. This viscoelastic behaviour reflects the dynamics of individual polymer chains driven by brownian motion: since individual chains can only move in a snake-like fashion through the mesh of surrounding polymer molecules, their diffusive transport, described by reptation, is so slow that the relaxation of suddenly imposed stress is delayed. Entangled polymer solutions and melts therefore elastically resist deforming motions that occur faster than the stress relaxation time. Here we show that the protein myosin II permits active control over the viscoelastic behaviour of actin filament solutions. We find that when each actin filament in a polymerized actin solution interacts with at least one myosin minifilament, the stress relaxation time of the polymer solution is significantly shortened. We attribute this effect to myosin's action as a 'molecular motor', which allows it to interact with randomly oriented actin filaments and push them through the solution, thus enhancing longitudinal filament motion. By superseding reptation with sliding motion, the molecular motors thus overcome a fundamental principle of complex fluids: that only depolymerization makes an entangled, isotropic polymer solution fluid for quick deformations.