PML regulates apoptosis at endoplasmic reticulum by modulating calcium release.

The promyelocytic leukemia (PML) tumor suppressor is a pleiotropic modulator of apoptosis. However, the molecular basis for such a diverse proapoptotic role is currently unknown. We show that extranuclear Pml was specifically enriched at the endoplasmic reticulum (ER) and at the mitochondria-associated membranes, signaling domains involved in ER-to-mitochondria calcium ion (Ca(2+)) transport and in induction of apoptosis. We found Pml in complexes of large molecular size with the inositol 1,4,5-trisphosphate receptor (IP(3)R), protein kinase Akt, and protein phosphatase 2a (PP2a). Pml was essential for Akt- and PP2a-dependent modulation of IP(3)R phosphorylation and in turn for IP(3)R-mediated Ca(2+) release from ER. Our findings provide a mechanistic explanation for the pleiotropic role of Pml in apoptosis and identify a pharmacological target for the modulation of Ca(2+) signals.

High data output and automated 3D correlative light-electron microscopy method.

Correlative light/electron microscopy (CLEM) allows the simultaneous observation of a given subcellular structure by fluorescence light microscopy (FLM) and electron microscopy. The use of this approach is becoming increasingly frequent in cell biology. In this study, we report on a new high data output CLEM method based on the use of cryosections. We successfully applied the method to analyze the structure of rough and smooth Russell bodies used as model systems. The major advantages of our method are (i) the possibility to correlate several hundreds of events at the same time, (ii) the possibility to perform three-dimensional (3D) correlation, (iii) the possibility to immunolabel both endogenous and recombinantly expressed proteins at the same time and (iv) the possibility to combine the high data analysis capability of FLM with the high precision-accuracy of transmission electron microscopy in a CLEM hybrid morphometry analysis. We have identified and optimized critical steps in sample preparation, defined routines for sample analysis and retracing of regions of interest, developed software for semi/fully automatic 3D reconstruction and defined preliminary conditions for an hybrid light/electron microscopy morphometry approach.

Hypoxia modifies the transcriptome of primary human monocytes: modulation of novel immune-related genes and identification of CC-chemokine ligand 20 as a new hypoxia-inducible gene.

Peripheral blood monocytes migrate to and accumulate in hypoxic areas of inflammatory and tumor lesions. To characterize the molecular bases underlying monocyte functions within a hypoxic microenvironment, we investigated the transcriptional profile induced by hypoxia in primary human monocytes using high-density oligonucleotide microarrays. Profound changes in the gene expression pattern were detected following 16 h exposure to 1% O(2), with 536 and 677 sequences showing at least a 1.5-fold increase and decrease, respectively. Validation of this analysis was provided by quantitative RT-PCR confirmation of expression differences of selected genes. Among modulated genes, 74 were known hypoxia-responsive genes, whereas the majority were new genes whose responsiveness to hypoxia had not been previously described. The hypoxic transcriptome was characterized by the modulation of a significant cluster of genes with immunological relevance. These included scavenger receptors (CD163, STAB1, C1qR1, MSR1, MARCO, TLR7), immunoregulatory, costimulatory, and adhesion molecules (CD32, CD64, CD69, CD89, CMRF-35H, ITGB5, LAIR1, LIR9), chemokines/cytokines and receptors (CCL23, CCL15, CCL8, CCR1, CCR2, RDC1, IL-23A, IL-6ST). Furthermore, we provided conclusive evidence of hypoxic induction of CCL20, a chemoattractant for immature dendritic cells, activated/memory T lymphocytes, and naive B cells. CCL20 mRNA up-regulation was paralleled by increased protein expression and secretion. This study represents the first transcriptome analysis of hypoxic primary human monocytes, which provides novel insights into monocyte functional behavior within ischemic/hypoxic tissues. CCL20 up-regulation by hypoxia may constitute an important mechanism to promote recruitment of specific leukocyte subsets at pathological sites and may have implications for the pathogenesis of chronic inflammatory diseases.