SOK1 translocates from the Golgi to the nucleus upon chemical anoxia and induces apoptotic cell death

SOK1 is a Ste20 protein kinase of the germinal center kinase (GCK) family that has been shown to be activated by oxidant stress and chemical anoxia, a cell culture model of ischemia. More recently, it has been shown to be localized to the Golgi apparatus, where it functions in a signaling pathway required for cell migration and polarization. Herein, we demonstrate that SOK1 regulates cell death after chemical anoxia, as its down-regulation by RNA interference enhances cell survival. Furthermore, expression of SOK1 elicits apoptotic cell death by activating the intrinsic pathway. We also find that a cleaved form of SOK1 translocates from the Golgi to the nucleus after chemical anoxia and that this translocation is dependent on both caspase activity and on amino acids 275-292, located immediately C-terminal to the SOK1 kinase domain. Furthermore, SOK1 entry into the nucleus is important for the cell death response since SOK1 mutants unable to enter the nucleus do not induce cell death. In summary, SOK1 is necessary to induce cell death and can induce death when overexpressed. Furthermore, SOK1 appears to play distinctly different roles in stressed versus non-stressed cells, regulating cell death in the former.     

Cytosolic glutamine synthetase and not nitrate reductase from the green alga Chlamydomonas reinhardtii is phosphorylated and binds 14-3-3 proteins

 The nitrate reductase activity from Chlamydomonas reinhardtii was not altered when extracts were incubated with yeast 14-3-3 proteins in the presence of Mg-ATP. However, the C. reinhardtii extracts contained 14-3-3 proteins capable of inhibiting the spinach nitrate reductase, raising the question of their physiological substrates. Two C. reinhardtii proteins of about 48 and 35 kDa were eluted from 14-3-3 affinity chromatography columns and bound to 14-3-3s in overlay assays. The 48-kDa protein corresponded to the cytosolic isoform of glutamine synthetase (GS1). The GS1 was phosphorylated by a Ca²⁺- and calmodulin-dependent protein kinase partially purified from the alga. However, neither phosphorylation nor 14-3-3 binding seemed to change GS catalytic activity. Received: 3 February 2000 / Accepted: 6 May 2000     

Laying the foundations for a human-predator conflict solution: assessing the impact of Bonelli's eagle on rabbits and partridges

Background

Predation may potentially lead to negative effects on both prey (directly via predators) and predators (indirectly via human persecution). Predation pressure studies are, therefore, of major interest in the fields of theoretical knowledge and conservation of prey or predator species, with wide ramifications and profound implications in human-wildlife conflicts. However, detailed works on this issue in highly valuable –in conservation terms– Mediterranean ecosystems are virtually absent. This paper explores the predator-hunting conflict by examining a paradigmatic, Mediterranean-wide (endangered) predator-two prey (small game) system.

Methodology/Principal Findings

We estimated the predation impact (‘kill rate’ and ‘predation rate’, i.e., number of prey and proportion of the prey population eaten, respectively) of Bonelli''s eagle Aquila fasciata on rabbit Oryctolagus cuniculus and red-legged partridge Alectoris rufa populations in two seasons (the eagle''s breeding and non-breeding periods, 100 days each) in SE Spain. The mean estimated kill rate by the seven eagle reproductive units in the study area was c. 304 rabbits and c. 262 partridges in the breeding season, and c. 237 rabbits and c. 121 partridges in the non-breeding period. This resulted in very low predation rates (range: 0.3–2.5%) for both prey and seasons.

Conclusions/Significance

The potential role of Bonelli''s eagles as a limiting factor for rabbits and partridges at the population scale was very poor. The conflict between game profitability and conservation interest of either prey or predators is apparently very localised, and eagles, quarry species and game interests seem compatible in most of the study area. Currently, both the persecution and negative perception of Bonelli''s eagle (the ‘partridge-eating eagle’ in Spanish) have a null theoretical basis in most of this area.     

Several Nuclear Events during Apoptosis Depend on Caspase-3 Activation but Do Not Constitute a Common Pathway

A number of nuclear events occur during apoptosis, including DNA laddering, nuclear lamina breakdown, phosphorylation of histones H2B and histone H2AX, and the tight binding to chromatin of HMGB1 and CAD, the nuclease responsible for DNA laddering. We have performed an epistasis analysis to investigate whether these events cluster together in pathways. We find that all depend directly or indirectly on caspase-3 activation. CAD activation, H2AX phosphorylation and DNA laddering cluster together into a pathway, but all other events appear to be independent of each other downstream of caspase-3, and likely evolved subject to different functional pressures.     

Catalyzed Reported Deposition-Fluorescence In Situ Hybridization Protocol To Evaluate Phagotrophy in Mixotrophic Protists

We describe a catalyzed reported deposition-fluorescence in situ hybridization (CARD-FISH) protocol particularly suited to assess the phagotrophy of mixotrophic protists on prokaryotes, since it maintains cell and plastid integrity, avoids cell loss and egestion of prey, and allows visualization of labeled prey against plastid autofluorescence. This protocol, which includes steps such as Lugol's-formaldehyde-thiosulfate fixation, agarose cell attachment, cell wall permeabilization with lysozyme plus achromopeptidase, and signal amplification with Alexa-Fluor 488, allowed us to detect almost 100% of planktonic prokaryotes (Bacteria and Archaea) and, for the first time, to show archaeal cells ingested by mixotrophic protists.     

Radial Dispersion of Neighbors and the Small-Scale Competitive Impact of Two Annual Grasses on a Native Perennial Grass

In California's Mediterranean type grasslands, native perennial grasses such as Nassella pulchra are surrounded by introduced annual species and these annuals are thought to have displaced natives through much of their range. Amongst other invaders, two grasses Lolium multiflorum and Bromus hordeaceus, commonly dominate portions of the grassland with potential for N. pulchra restoration. We hypothesized that competitor species differences and small‐scale gaps (150 cm²) could be important determinants of N. pulchra survival and performance on these sites. Lolium multiflorum and B. hordeaceus were planted in 20 cm diameter circular plots at a constant rate of 1 seed per cm² surrounding newly transplanted N. pulchra plants. Nassella pulchra showed no significant effect of the species of competitor or from the distribution of the competitors. Both interspersion of patches of bare ground and separation of competitors into patches did not increase N. pulchra pre‐dawn water potential, basal area change, number of seeds produced, or average weight of seeds. The presence of L. multiflorum was associated with a decrease in N. pulchra survival compared with plots with only B. hordeaceus. Plants with increases in basal area of less than 0.75 cm² during the growing season had 74% mortality compared with no mortality in plants with more growth. However, initial N. pulchra plant size was not a good predictor of mortality. Limiting competition from annuals may increase survival of N. pulchra plantings, but 60% of the plants survived for at least 1 year, despite being transplanted into soil containing substantial annual grass seed.     

The protistan microzooplankton community in the oligotrophicnorth-eastern Atlantic: large- and mesoscale patterns

We surveyed the oligotrophic waters of the north-eastern Atlanticsubtropical gyre to investigate the biomass, abundance, compositionand variability of the protistan microzooplankton community.Aloricate ciliates and gymnodinoid dinoflagellates dominatedthe community, which did not show broad seasonal variations.Large mixotrophic ciliates, with a high carbon content per cell,accounted for a substantial amount of the variability of thestanding stock. We found average values of microzooplanktonbiomass and abundance of 1.1 mg C m^-3 and 3.7 x 10³ cells l^-l,respectively, which are among the lowest measured in marinesystems, 5- to 10-fold lower than in the neighbouring watersof the North Atlantic Drift. The mesoscale structures surveyed,a cyclonic eddy and the hydrographical structures over a submarinemount, significantly enhanced microzooplankton biomass and sustainedthe presence of cells with a carbon content higher than in neighbouringwaters. Microzooplankton followed complex patterns of distributionthat did not correspond to the variability of primary productionor of chlorophyll a.     

Synthesis and evaluation of pharmacological profile of 1-aryl-6,7-dimethoxy-3,4-dihydroisoquinoline-2(1H)-sulfonamides

In previous studies we identified several 1-aryl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline derivatives displaying potent anticonvulsant effects in different animal models of epilepsy. With the aim to deepen the structure–activity relationships (SAR) for this class of compounds and identify novel anticonvulsant agents we synthesized a series of 1-aryl-6,7-dimethoxy-3,4-dihydroisoquinoline-2(1H)-sulfonamides. The new compounds incorporate the main features of the above-mentioned anticonvulsants and a sulfonamide function capable to inhibit the enzyme carbonic anhydrase (CA, EC 4.2.1.1), which represents an attractive target in epilepsy. Pharmacological effects were evaluated in vivo against audiogenic seizures in DBA/2 mice and in vitro against several CA isoforms. Some of the new molecules showed anticonvulsant properties better than topiramate, but weak inhibitory activity and low selectivity in enzymatic assay.