Modulation of STIM1 and capacitative Ca2+ entry by the endoplasmic reticulum luminal oxidoreductase ERp57

STIM1 is an endoplasmic reticulum (ER) membrane Ca(2+) sensor responsible for activation of store-operated Ca(2+) influx. We discovered that STIM1 oligomerization and store-operated Ca(2+) entry (SOC) are modulated by the ER oxidoreductase ERp57. ERp57 interacts with the ER luminal domain of STIM1, with this interaction involving two conserved cysteine residues, C(49) and C(56). SOC is accelerated in the absence of ERp57 and inhibited in C(49) and C(56) mutants of STIM1. We show that ERp57, by ER luminal interaction with STIM1, has a modulatory role in capacitative Ca(2+) entry. This is the first demonstration of a protein involved in ER intraluminal regulation of STIM1.     

Smallpox vaccine-induced antibodies are necessary and sufficient for protection against monkeypox virus

Vaccination with live vaccinia virus affords long-lasting protection against variola virus, the agent of smallpox. Its mode of protection in humans, however, has not been clearly defined. Here we report that vaccinia-specific B-cell responses are essential for protection of macaques from monkeypox virus, a variola virus ortholog. Antibody-mediated depletion of B cells, but not CD4+ or CD8+ T cells, abrogated vaccine-induced protection from a lethal intravenous challenge with monkeypox virus. In addition, passive transfer of human vaccinia-neutralizing antibodies protected nonimmunized macaques from severe disease. Thus, vaccines able to induce long-lasting protective antibody responses may constitute realistic alternatives to the currently available smallpox vaccine (Dryvax).     

E3 ubiquitin ligases and their control of T cell autoreactivity

A loss of T cell tolerance underlies the development of most autoimmune diseases. The design of therapeutic strategies to reinstitute immune tolerance, however, is hampered by uncertainty regarding the molecular mechanisms involved in the inactivation of potentially autoreactive T cells. Recently, E3 ubiquitin ligases have been shown to mediate the development of a durable state of unresponsiveness in T cells called clonal anergy. In this review, we will discuss the mechanisms used by E3 ligases to control the activation of T cells and prevent the development of autoimmunity.     

On the number of New World founders: a population genetic portrait of the peopling of the Americas

The founding of New World populations by Asian peoples is the focus of considerable archaeological and genetic research, and there persist important questions on when and how these events occurred. Genetic data offer great potential for the study of human population history, but there are significant challenges in discerning distinct demographic processes. A new method for the study of diverging populations was applied to questions on the founding and history of Amerind-speaking Native American populations. The model permits estimation of founding population sizes, changes in population size, time of population formation, and gene flow. Analyses of data from nine loci are consistent with the general portrait that has emerged from archaeological and other kinds of evidence. The estimated effective size of the founding population for the New World is fewer than 80 individuals, approximately 1% of the effective size of the estimated ancestral Asian population. By adding a splitting parameter to population divergence models it becomes possible to develop detailed portraits of human demographic history. Analyses of Asian and New World data support a model of a recent founding of the New World by a population of quite small effective size.     

Fine-needle aspiration of the thyroid: an overview

Thyroid nodules (TN) are a common clinical problem. Fine needle aspiration (FNA) of the thyroid now is practiced worldwide and proves to be the most economical and reliable diagnostic procedure to identify TNs that need surgical excision and TNs that can be managed conservatively. The key for the success of thyroid FNA consists of an adequate or representative cell sample and the expertise in thyroid cytology. The FNA cytologic manifestations of TNs may be classified into seven working cytodiagnostic groups consisting of a few heterogenous lesions each to facilitate the differential diagnosis. Recent application of diagnostic molecular techniques to aspirated thyroid cells proved to be useful in separating benign from malignant TNs in several cases of indeterminate lesions.     

Aggregated LDL and lipid dispersions induce lysosomal cholesteryl ester accumulation in macrophage foam cells

Macrophage foam cells in atherosclerotic lesions accumulate substantial cholesterol stores within large, swollen lysosomes. Previous studies with mildly oxidized low density lipoprotein (OxLDL)-treated THP-1 macrophages suggest an initial buildup of free cholesterol (FC), followed by an inhibition of lysosomal cholesteryl ester (CE) hydrolysis and a subsequent lysosomal accumulation of unhydrolyzed lipoprotein CE. We examined whether other potential sources of cholesterol found within atherosclerotic lesions could also induce similar lysosomal accumulation. Biochemical analysis combined with microscopic analysis showed that treatment of THP-1 macrophages with aggregated low density lipoprotein (AggLDL) or CE-rich lipid dispersions (DISP) produced a similar lysosomal accumulation of both FC and CE. Co-treatment with an ACAT inhibitor, CP113,818, confirmed that the CE accumulation was primarily the result of the inhibition of lysosomal CE hydrolysis. The rate of unhydrolyzed CE buildup was more rapid with DISP than with AggLDL. However, with both treatments, FC appeared to accumulate in lysosomes before the inhibition in hydrolysis and CE accumulation, a sequence shared with mildly OxLDL. Thus, lysosomal accumulation of FC and CE can be attributable to more general mechanisms than just the inhibition of hydrolysis by oxidized lipids.     

The identification and structure of the membrane-spanning domain of the Clostridium septicum alpha toxin

Alpha toxin (AT) is a pore-forming toxin produced by Clostridium septicum that belongs to the unique aerolysin-like family of pore-forming toxins. The location and structure of the transmembrane domains of these toxins have remained elusive. Using deletion mutagenesis, cysteine-scanning mutagenesis and multiple spectrofluorimetric methods a membrane-spanning amphipathic beta-hairpin of AT has been identified. Spectrofluorimetric analysis of cysteine-substituted residues modified with an environmentally sensitive fluorescent probe via the cysteine sulfydryl showed that the side chains of residues 203-232 alternated between the aqueous milieu and the membrane core when the AT oligomer was inserted into membranes, consistent with the formation of an amphipathic transmembrane beta-hairpin. AT derivatives that contained deletions that removed up to 90% of the beta-hairpin did not form a pore but were similar to native toxin in all other aspects of the mechanism. Furthermore, a mutant of AT that contained an engineered disulfide, predicted to restrict the movement of the beta-hairpin, functioned similarly to native toxin except that it did not form a pore unless the disulfide bond was reduced. Together these studies revealed the location and structure of the membrane-spanning domain of AT.