Proteolysis of cystatin C by cathepsin D in the breast cancer microenvironment.: Proteolysis of cystatin C by cathepsin D

International audienceThe aspartic protease cathepsin D, a poor prognostic indicator of breast cancer, is abundantly secreted as procathepsin D by human breast cancer cells and self-activates at low pH in vitro, giving rise to catalytically active cathepsin D. Due to a lower extracellular pH in tumor microenvironments compared to normal tissues, cathepsin D may cleave pathophysiological substrates contributing to cancer progression. Here, we show by yeast 2-hybrid and degradomics analyses that cystatin C, the most potent natural secreted inhibitor of cysteine cathepsins, both binds to and is a substrate of extracellular procathepsin D. The amount of cystatin C in the extracellular environment is reduced in the secretome of mouse embryonic fibroblasts stably transfected with human cathepsin D. Cathepsin D extensively cleaved cystatin C in vitro at low pH. Cathepsin D secreted by breast cancer cells also processed cystatin C at the pericellular pH of tumors and so enhancing extracellular proteolytic activity of cysteine cathepsins. Thus, tumor derived cathepsin D assists breast cancer progression by reducing cystatin C activity, which, in turn, enhances cysteine cathepsin proteolytic activity, revealing a new link between protease classes in the protease web

Direct and indirect CeO2 nanoparticles toxicity for Escherichia coli and Synechocystis

International audiencePhysico-chemical interactions between nanoparticles and cell membranes play a crucial role in determining the cytotoxicity of nanoparticles, which may thereby vary depending on the nature of the target microorganisms. We investigated the responses of two different models of unicellular bacteria to cerium oxide (CeO2) nanoparticles. These organisms are: Synechocystis PCC6803 a representative of environmentally important cyanobacterial organisms (producer of biomass for aquatic food chains), and Escherichia coli a representative of intestine-colonizing bacteria. Coupling physico-chemical (adsorption isotherms and electrophoretic mobility), biological (survival tests), microscopical (SEM, TEM and EDS) and spectroscopic (XANES) methods, we enlightened two distinct mechanisms for the CeO2 nanoparticles toxicological impact: A 'direct' mechanism that requires a close contact between nanoparticles and cell membranes, and an 'indirect' influence elicited by the acidity of nanoparticles stabilizing agents. We showed that E. coli is sensitive to the 'direct' effects of nanoparticles, whereas Synechocystis being protected by extracellular polymeric substances preventing direct cellular contacts is sensitive only to the 'indirect' mechanism. Consequently, our findings demonstrate the importance of the 'direct/indirect' effects of nanoparticles on cell fitness, a phenomenon that should be systematically investigated with appropriate techniques and dose metrics to make meaningful environmental and/or health recommendations

Clonal architecture of chronic myelomonocytic leukemias.

International audienceGenomic studies in chronic myeloid malignancies, including myeloproliferative neoplasms (MPN), myelodysplastic syndromes (MDS), and MPN/MDS, have identified common mutations in genes encoding signaling, epigenetic, transcription, and splicing factors. In the present study, we interrogated the clonal architecture by mutation-specific discrimination analysis of single-cell-derived colonies in 28 patients with chronic myelomonocytic leukemias (CMML), the most frequent MPN/MDS. This analysis reveals a linear acquisition of the studied mutations with limited branching through loss of heterozygosity. Serial analysis of untreated and treated samples demonstrates a dynamic architecture on which most current therapeutic approaches have limited effects. The main disease characteristics are early clonal dominance, arising at the CD34(+)/CD38(-) stage of hematopoiesis, and granulomonocytic differentiation skewing of multipotent and common myeloid progenitors. Comparison of clonal expansions of TET2 mutations in MDS, MPN, and CMML, together with functional invalidation of TET2 in sorted progenitors, suggests a causative link between early clonal dominance and skewed granulomonocytic differentiation. Altogether, early clonal dominance may distinguish CMML from other chronic myeloid neoplasms with similar gene mutations