The small heat shock protein B8 (HSPB8) confers resistance to bortezomib by promoting autophagic removal of misfolded proteins in multiple myeloma cells.

Velcade is one of the inescapable drug to treat patient suffering from multiple myeloma (MM) and resistance to this drug represents a major drawback for patients. However, the mechanisms underlying velcade resistance remain incompletely understood. We derived several U266 MM cell clones that resist to velcade.

Severe thymic atrophy in a mouse model of skin inflammation accounts for impaired TNFR1 signaling.

Transgenic mice expressing the caspase-cleaved form of the tyrosine kinase Lyn (LynΔN) develop a TNFα-dependent skin disease that accurately recapitulates human psoriasis. Participation of lymphocytes in this disease was confirmed by backcrossing LynΔN mice on a Rag-1 deficient background. The present study was therefore conducted to analyze whether modification of lymphocyte homeostasis does occur and participate in the phenotype of LynΔN mice.

The caspase 6 derived N-terminal fragment of DJ-1 promotes apoptosis via increased ROS production.

In pathological conditions, the amount of DJ-1 determines whether a cell can survive or engage a cell death program. This is exemplified in epithelial cancers, in which DJ-1 expression is increased, while autosomal recessive early onset Parkinson's disease mutations of DJ-1 generally lead to decreased stability and expression of the protein. We have shown previously that DJ-1 is cleaved by caspase-6 during induction of apoptosis.

The anti-apoptotic Bcl-B protein inhibits BECN1-dependent autophagic cell death.

Bcl-2 family members are key modulators of apoptosis that have recently been shown to also regulate autophagy. It has been previously reported that Bcl-2 and Bcl-X(L) bind and inhibit BECN1, an essential mediator of autophagy. Bcl-B is an anti-apoptotic member of the Bcl-2 family that possesses the four BH (Bcl-2 homology) domains (BH1, BH2, BH3 and BH4) and a predicted C-terminal trans-membrane domain.

Mechanisms of AXL overexpression and function in Imatinib-resistant chronic myeloid leukemia cells.

AXL is a receptor tyrosine kinase of the TAM family, the function of which is poorly understood. We previously identified AXL overexpression in Imatinib (IM)-resistant CML cell lines and patients. The present study was conducted to investigate the role of AXL and the mechanisms underlying AXL overexpression in Tyrosine Kinase Inhibitor (TKI)-resistant CML cells.

Acadesine kills chronic myelogenous leukemia (CML) cells through PKC-dependent induction of autophagic cell death.

CML is an hematopoietic stem cell disease characterized by the t(9;22) (q34;q11) translocation encoding the oncoprotein p210BCR-ABL. The effect of acadesine (AICAR, 5-Aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside) a compound with known antileukemic effect on B cell chronic lymphoblastic leukemia (B-CLL) was investigated in different CML cell lines. Acadesine triggered loss of cell metabolism in K562, LAMA-84 and JURL-MK1 and was also effective in killing imatinib-resistant K562 cells and Ba/F3 cells carrying the T315I-BCR-ABL mutation.

The caspase-cleaved form of LYN mediates a psoriasis-like inflammatory syndrome in mice.

We showed previously that Lyn is a substrate for caspases, a family of cysteine proteases, involved in the regulation of apoptosis and inflammation. Here, we report that expression of the caspase-cleaved form of Lyn (LynDeltaN), in mice, mediates a chronic inflammatory syndrome resembling human psoriasis. Genetic ablation of TNF receptor 1 in a LynDeltaN background rescues a normal phenotype, indicating that LynDeltaN mice phenotype is TNF-alpha-dependent.

Imatinib mesylate-resistant human chronic myelogenous leukemia cell lines exhibit high sensitivity to the phytoalexin resveratrol.

Imatinib is successfully used in the treatment of chronic myelogenous leukemia (CML), and the main mechanisms of resistance in refractory patients are now partially understood. In the present study, we investigated the mechanism of action of resveratrol in imatinib-sensitive (IM-S) and -resistant (IM-R) CML cell lines. Resveratrol induced loss of viability and apoptosis in IM-S and IM-R in a time- and dose-dependent fashion.

Effect of caspase inhibition on thymic apoptosis in hemorrhagic shock.

In hemorrhagic shock (HS) an increased thymic apoptosis (TA) was described. The aim of this study was to evaluate the effect of administration of the caspase inhibitor N-benzyloxy-carbonil-Val-Ala-Asp-fluoromethylketone (Z-VAD-FMK) during the resuscitation phase on TA, organ dysfunctions, and tumor necrosis factor (TNF)-alpha release in HS. Forty rats were randomly assigned to four groups: no HS/resuscitation (sham); HS/resuscitation with shed blood and normal saline (control); HS/resuscitation with shed blood and phosphate-buffered solution (PBS) (vehicle); and HS/resuscitation with shed blood and Z-VAD-FMK (inhibitor).

Apoptosis and erythroid differentiation triggered by Bcr-Abl inhibitors in CML cell lines are fully distinguishable processes that exhibit different sensitivity to caspase inhibition.

Imatinib targets the Bcr-Abl oncogene that causes chronic myelogenous leukemia (CML) in humans. Recently, we demonstrated that besides triggering apoptosis in K562 cells, imatinib also mediated their erythroid differentiation. Although both events appear to proceed concomitantly, it is not known at present whether or not imatinib-induced apoptosis and differentiation are interdependent processes.

A survey of the signaling pathways involved in megakaryocytic differentiation of the human K562 leukemia cell line by molecular and c-DNA array analysis.

The K562 cell line serves as a model to study the molecular mechanisms associated with leukemia differentiation. We show here that cotreatment of K562 cells with PMA and low doses of SB202190 (SB), an inhibitor of the p38 MAPK pathway, induced a majority of cells to differentiate towards the megakaryocytic lineage. Electronic microscopy analysis showed that K562 cells treated with PMA+SB exhibited characteristic features of physiological megakaryocytic differentiation including the presence of vacuoles and demarcation membranes.

Cleavage of Mcl-1 by caspases impaired its ability to counteract Bim-induced apoptosis.

Mcl-1 is an antiapoptotic member of the Bcl-2 family that can promote cell viability. We report here that Mcl-1 is a new substrate for caspases during induction of apoptosis. Mcl-1 cleavage occurs after Asp127 and Asp157 and generates four fragments of 24, 19, 17 and 12 kDa in both intact cells and in vitro, an effect prevented by selective caspase inhibitors.

Focal adhesion kinase pp125FAK interacts with the large conductance calcium-activated hSlo potassium channel in human osteoblasts: potential role in mechanotransduction.

Unlabelled: Molecular events of mechanotransduction in osteoblasts are poorly defined. We show that the mechanosensitive BK channels open and recruit the focal adhesion kinase FAK in osteoblasts on hypotonic shock. This could convert mechanical signals in biochemical events, leading to osteoblast activation.

Active stromelysin-3 (MMP-11) increases MCF-7 survival in three-dimensional Matrigel culture via activation of p42/p44 MAP-kinase.

Stromelysin-3 (ST3) has the characteristic structure of matrix metalloproteinases (MMP), but its substrate specificity and pattern of expression differ markedly from that of other MMP family members. ST3 was originally isolated on the basis of its expression in primary breast cancers and has been shown to be overexpressed in virtually all primary carcinomas, suggesting that ST3 participates in the initial development of epithelial malignancies. Recent data using murine models reported that ST3 expression was able to increase tumor take by suppressing cell apoptosis.

Differential requirements for ERK1/2 and P38 MAPK activation by thrombin in T cells. Role of P59Fyn and PKCepsilon.

Activation of the mitogen-activated protein kinase (MAPK) cascade is a well documented mechanism for the G-protein-coupled receptors. Here, we have analysed the requirements for ERKs and p38 MAPK activation by thrombin in Jurkat T cells. We show that thrombin-mediated ERKs activation requires both PTK and PKC activities, whereas p38 MAPK activation is dependent only on PTKs.

Differential expression of the Kell blood group and CD10 antigens: two related membrane metallopeptidases during differentiation of K562 cells by phorbol ester and hemin.

The erythroleukemic cell line K562 can undergo further differentiation in erythroid or megakaryocytic lineage depending on the nature of the stimulus. Phorbol ester (PMA) stimulates megakaryocytic development whereas hemin promotes erythroid differentiation of these cells. We have examined the effect of PMA and hemin on the expression of the Kell blood group and CD10 antigens, two related proteins that belong to a family of membrane-bound neutral metalloendopeptidases.

CD10 is expressed on human thymic epithelial cell lines and modulates thymopentin-induced cell proliferation.

Thymic hormones such as thymopoietin (TP) have been shown to regulate thymocyte differentiation and lymphocyte activation. However, it is not known whether thymopoietin affects thymic epithelial cell (TEC) functions. In this study we have examined the effect of a five amino acid active peptide (TP5), corresponding to amino acids 32-36 of TP, on the proliferation of nontransformed clones of human TEC.

Endopeptidase 24.11 (CD10/NEP) is required for phorbol ester-induced growth arrest in Jurkat T cells.

Jurkat T cells express a functional endopeptidase 24.11 that is involved in the regulation of T cell activation. We have analyzed the effect of ectopic CD10 expression in mutant Jurkat cell clones that fail to express CD10 and, unlike wild-type cells, are resistant to the growth-inhibitory effects of the protein kinase C activator, PMA.

CD10 plays a specific role in early thymic development.

Development of T lymphocyte is a complex process that depends on both thymocytestromal cell interactions and the production of soluble factors such as cytokines, peptides, and hormones. In many tissues, the concentration of active biological peptides is regulated locally by a specialized family of enzymes: the ectopeptidases. We show here that treatment of fetal thymic organ cultures (FTOC) with the specific CD10 (endopeptidase 24.

CD10 (endopeptidase 24.11) is a thymic peptide-degrading enzyme possibly involved in the regulation of thymocyte functions.

Human immature thymocytes express significant levels of the CD10 (endopeptidase 24.11) cell surface antigen. We report here that IOB5, an anti-CD10 mAb, as well as the phorbol ester PMA down-regulate CD10 activity at the surface of human thymocytes.

Thrombin and trypsin-induced Ca(2+) mobilization in human T cell lines through interaction with different protease-activated receptors.

This study was conducted to determine whether serine proteinases may induce [Ca(2+)]i mobilization in different hematopoietic cell lines and to analyze their mechanisms of action. We show that in addition to thrombin and thrombin receptor agonist peptide (TRP, SFLLRN), trypsin induced [Ca(2+)]i mobilization in a highly thrombin-sensitive Jurkat T cell clone. Thrombin, TRP, and trypsin were found to induce [Ca(2+)]i release in three different Jurkat T cell clones differing in the level of T cell receptor expression.

High levels of functional endopeptidase 24.11 (CD10) activity on human thymocytes: preferential expression on immature subsets.

Although it is now well established that cells of the immune system express most of the exopeptidases described so far, little information is available concerning the identification and the characterization of the peptidases associated with the surface of human thymocytes. In the present study we have focused on CD10 expression on thymocytes using both FACS and enzymatic analysis. Unfractionated intact human thymocytes were shown to express significant levels of CD10-specific enzymatic activity, as assessed by the hydrolysis of the neutral endopeptidase (NEP) substrate Suc-Ala-Ala-Phe-pNA and of D-Ala2-Leu-enkephalin, a typical NEP substrate.

Thrombin and thrombin receptor agonist peptide induce early events of T cell activation and synergize with TCR cross-linking for CD69 expression and interleukin 2 production.

Thrombin stimulation of the T leukemic cell line Jurkat induced a transient increase in [Ca2+]i. Proteolytic activity of the enzyme was required for this effect since diisopropyl fluorophosphate-thrombin failed to increase [Ca2+]i. Furthermore, hirudin and anti-thrombin III inhibited the thrombin-induced [Ca2+]i rise in Jurkat T cells.