The long and arduous road to CRAC

Store-operated calcium (SOC) entry is the major route of calcium influx in non-excitable cells, especially immune cells. The best characterized store-operated current, I(CRAC), is carried by calcium release activated calcium (CRAC) channels. The existence of the phenomenon of store-operated calcium influx was proposed almost two decades ago. However, in spite of rigorous research by many laboratories, the identity of the key molecules participating in the process has remained a mystery. In all these years, multiple different approaches have been adopted by countless researchers to identify the molecular players in this fundamental process. Along the way, many crucial discoveries have been made, some of which have been summarized here. The last couple of years have seen significant breakthroughs in the field-identification of STIM1 as the store Ca(2+) sensor and CRACM1 (Orai1) as the pore-forming subunit of the CRAC channel. The field is now actively engaged in deciphering the gating mechanism of CRAC channels. We summarize here the latest progress in this direction.     

Cloning, expression, and catalytic triad of recombinant arylformamidase

Arylformamidase (AFMID) is the second enzyme of the kynurenine pathway metabolizing tryptophan to nicotinic acid and nicotinamide adenine dinucleotide cofactors. Inhibition of AFMID by organophosphorus insecticides in developing chicken embryos is correlated with lowered NAD levels and severe teratogenesis. The cDNA sequence previously identified for mouse liver AFMID (AF399717) (MW 34229) was cloned and expressed in Escherichia coli. Residues identified as potential catalytic triad members (S162, D247, and H279) through sequence motif and homology modeling were mutated to alanine to probe their contributions to enzyme activity. The wild-type and mutant AFMIDs were expressed as amino terminal 6 x His-tagged recombinant proteins to facilitate purification. Three chromatography steps isolated highly purified proteins for enzyme activity comparisons. Expressed AFMID showed high activity, 42+/-1 micromol/min/mg protein, for its natural substrate, N-formyl-l-kynurenine. The same K(m) (0.18--0.19 mM) was observed for expressed and native cytosolic AFMID. The single mutants (S162A, D247A, and H279A) lost essentially all (>99%) activity. The predicted catalytic triad of S162, D247, and H279 is therefore confirmed by site-directed mutagenesis.     

Killing, letting die and moral perception

There are a number of arguments that purport to show, in general terms, that there is no difference between killing and letting die. These are used to justify active euthanasia on the basis of the reasons given for allowing patients to die. I argue that the general and abstract arguments fail to take account of the complex and particular situations which are found in the care of those with terminal illness. When in such situations, there are perceptions and intuitions available that do not easily find propositional form but lead most of those whose practice is in the care of the dying to resist active euthanasia. I make a plea for their intuitions to be heeded above the sterile voice of abstract premises and arguments by examining the completeness of the outline form of the pro-euthanasia argument. In doing so, I make use of Nussbaum's discussion of moral perception and general claims to be found in the literature of moral particularism.     

Covert moral bioenhancement,public health,and autonomy

In a recent article in this journal, Parker Crutchfield argues that if moral bioenhancement ought to be compulsory, as some authors claim, then it ought to be covert, i.e., performed without the knowledge of the population that is being morally enhanced. Crutchfield argues that since the aim of compulsory moral bioenhancement is to prevent ultimate harm to the population, compulsory moral bioenhancement is best categorized as a public health issue, and should therefore be governed by the norms and values that apply in public health settings. In this article, I argue for two related claims. First, I question the extent to which compulsory moral enhancement should be considered a public health issue that ought to be governed by the norms and values that apply in public health settings. Second, I argue that Crutchfield's argument that covert moral bioenhancement would better respect people's autonomy than an overt program overlooks two important autonomy‐based reasons that, in fact, favor an overt moral enhancement program over a covert one.     

Environmental migrants,structural injustice,and moral responsibility

Climate change and environmental problems will force or induce millions of people to migrate. In this article, I describe environmental migration and articulate some of the ethical issues. To begin, I give an account of these migrants that overcomes misleading dichotomies. Then, I focus attention on two important ethical issues: justice and responsibility. Although we are all at risk of becoming environmental migrants, we are not equally at risk. Our risk depends on our temporal position, geographical location, social position, and the kind of society in which we live. We all contribute to environmental problems, but we do not contribute equally. About 11% of the world population is responsible for 50% of carbon emissions. These inequalities raise issues of justice because many of the people who are at high risk have contributed little to the problems. Since the issues of justice are relatively clear and compelling, I focus more attention on issues of responsibility. I use Iris Marion Young’s account of responsibility for structural injustice to address four key questions about moral responsibility and environmental migration.     

The caveolin triad: caveolae biogenesis, cholesterol trafficking, and signal transduction

Caveolins are a family of proteins that coat the cytoplasmic face of caveolae, vesicular invaginations of the plasma membrane. These proteins are central to the organization of the proteins and lipids that reside in caveolae. Caveolins transport cholesterol to and from caveolae, and they regulate the activity of signaling proteins that reside in caveolae. Through studying the genes encoding the caveolae coat proteins, we have learned much about how they perform these multiple functions.     

Mitochondria, calcium and cell death: A deadly triad in neurodegeneration

Mitochondrial Ca²⁺ accumulation is a tightly controlled process, in turn regulating functions as diverse as aerobic metabolism and induction of cell death. The link between Ca²⁺ (dys)regulation, mitochondria and cellular derangement is particularly evident in neurodegenerative disorders, in which genetic models and environmental factors allowed to identify common traits in the pathogenic routes. We will here summarize: i) the current view of mechanisms and functions of mitochondrial Ca²⁺ homeostasis, ii) the basic principles of organelle Ca²⁺ transport, iii) the role of Ca²⁺ in neuronal cell death, and iv) the new information on the pathogenesis of Alzheimer's, Huntington's and Parkinson's diseases, highlighting the role of Ca²⁺ and mitochondria.     

TIR, CARD and PYRIN: three domains for an antimicrobial triad

Innate immunity to microorganisms in mammals has gained a substantial interest during the last decade. The discovery of the Toll-like receptor (TLR) family has allowed the identification of a class of membrane-spanning receptors dedicated to microbial sensing. TLRs transduce downstream signaling via their intracellular Toll-interleukin-1 receptor (TIR) domain. More recently, the role of intracellular microbial sensors has been uncovered. These molecules include the Nod-like receptors Nod1, Nod2, Ipaf and Nalps, together with the helicase domain-containing antiviral proteins RIG-I and Mda-5. The intracellular microbial sensors lack the TIR domain, but instead transduce downstream signals via two domains also implicated in homophilic protein-protein interactions, the caspase activation and recruitment domain (CARD) and PYRIN domains. In light with these recent findings, we propose that TIR, CARD and PYRIN domains represent the three arms of innate immune detection of microorganisms in mammals.     

The evolution of moral progress and biomedical moral enhancement

In The Evolution of Moral Progress Allen Buchanan and Russell Powell advance an evolutionary explanation of moral progress by morality becoming more ‘inclusivist’. We are prepared to accept this explanation as far as it goes, but argue that it fails to explain how morality can become inclusivist in the fuller sense they intend. In fact, it even rules out inclusivism in their intended sense of moral progress, since they believe that human altruism and prosocial attitudes are essentially parochial. We also respond to their charge that the possibility of moral enhancement by biomedical means that we have defended in numerous publications assumes that moral attitudes are biologically hard‐wired to an extent that implies that they are resilient to the influence of cognitive or cultural factors. Quite the contrary, we think they are more open to such influence than they seem to do.     

Fundamental limits on wavelength, efficiency and yield of the charge separation triad

In an attempt to optimize a high yield, high efficiency artificial photosynthetic protein we have discovered unique energy and spatial architecture limits which apply to all light-activated photosynthetic systems. We have generated an analytical solution for the time behavior of the core three cofactor charge separation element in photosynthesis, the photosynthetic cofactor triad, and explored the functional consequences of its makeup including its architecture, the reduction potentials of its components, and the absorption energy of the light absorbing primary-donor cofactor. Our primary findings are two: First, that a high efficiency, high yield triad will have an absorption frequency more than twice the reorganization energy of the first electron transfer, and second, that the relative distance of the acceptor and the donor from the primary-donor plays an important role in determining the yields, with the highest efficiency, highest yield architecture having the light absorbing cofactor closest to the acceptor. Surprisingly, despite the increased complexity found in natural solar energy conversion proteins, we find that the construction of this central triad in natural systems matches these predictions. Our analysis thus not only suggests explanations for some aspects of the makeup of natural photosynthetic systems, it also provides specific design criteria necessary to create high efficiency, high yield artificial protein-based triads.     

Structural analysis of muscle development: transverse tubules, sarcoplasmic reticulum, and the triad.

Increased interest in the mechanism of excitation-contraction (E-C) coupling over the last few years has been accompanied by numerous investigations into the development of the underlying cellular structures. Areas of particular interest include: (1) the compartmentalization and specialization of an external and an internal membrane system, the T-tubules, and the sarcoplasmic reticulum, respectively; (2) interactions between the membrane proteins of both systems upon the formation of a junction, the triad; and (3) membrane-cytoskeletal interactions leading to the orderly arrangement of the triads with respect to the myofibrils. Structural studies using newly available specific molecular probes and a variety of in vivo and in vitro model systems have provided new insights into the cellular and molecular mechanisms involved in the development of the E-C coupling apparatus in skeletal muscle.     

The synergistic triad between microcin,colibactin, and salmochelin gene clusters in uropathogenic Escherichia coli

A functional synergy was previously demonstrated between microcin, salmochelin and colibactin islands in Escherichia coli strains from B2 phylogroup. We aimed to determine this association prevalence in uropathogenic E. coli, and whether it was predictive of the infection severity in a collection of 225 E. coli strains from urinary samples. The high prevalence of this triad, even if it wasn’t correlated with infection severity, suggested that it might not be a virulence factor per se within the urinary tract, but would promote its colonization. This triad would enable the strain to dominate the rectal reservoir with a minimal genetic cost.     

Transhumanism and moral equality

Conservative thinkers such as Francis Fukuyama have produced a battery of objections to the transhumanist project of fundamentally enhancing human capacities. This article examines one of these objections, namely that by allowing some to greatly extend their capacities, we will undermine the fundamental moral equality of human beings. I argue that this objection is groundless: once we understand the basis for human equality, it is clear that anyone who now has sufficient capacities to count as a person from the moral point of view will continue to count as one even if others are fundamentally enhanced; and it is mistaken to think that a creature which had even far greater capacities than an unenhanced human being should count as more than an equal from the moral point of view.