Anti-HSP90 Antibody [D7A] (A305112)

The transmembrane semaphorin, Sema6A, has important roles in axon guidance, cell migration and neuronal connectivity in multiple regions of the nervous system, mediated by context-dependent interactions with plexin receptors, PlxnA2 and PlxnA4. Here, we demonstrate that Sema6A can also signal cell-autonomously, in two modes, constitutively, or in response to higher-order clustering mediated by either PlxnA2-binding or chemically induced multimerisation. Sema6A activation stimulates recruitment of Abl to the cytoplasmic domain of Sema6A and phos¡phorylation of this cytoplasmic tyrosine kinase, as well as phosphorylation of additional cytoskeletal regulators. Sema6A reverse signaling affects the surface area and cellular complexity of non-neuronal cells and aggregation and neurite formation of primary neurons in vitro. Sema6A also interacts with PlxnA2 in cis, which reduces binding by PlxnA2 of Sema6A in trans but not vice versa. These experiments reveal the complex nature of Sema6A biochemical functions and the molecular logic of the context-dependent interactions between Sema6A and PlxnA2.

TRAIL is involved in immune tumor surveillance and is considered a promising anti-cancer agent owing to its limited side effects on healthy cells. However, some cancer cells display resistance, or become resistant to TRAIL-induced cell death. Hyperthermia can enhance sensitivity to TRAIL-induced cell death in various resistant cancer cell lines, including lung, breast, colon or prostate carcinomas. Mild heat shock treatment has been proposed to restore Fas ligand or TRAIL-induced apoptosis through c-FLIP degradation or the mitochondrial pathway. We demonstrate here that neither the mitochondria nor c-FLIP degradation are required for TRAIL-induced cell death restoration during hyperthermia. Our data provide evidence that insolubilization of c-FLIP, alone, is sufficient to enhance apoptosis induced by death receptors. Hyperthermia induced c-FLIP depletion from the cytosolic fraction, without apparent degradation, thereby preventing c-FLIP recruitment to the TRAIL DISC and allowing efficient caspase-8 cleavage and apoptosis. Hyperthermia-induced c-FLIP depletion was independent of c-FLIP DED2 FL chain assembly motif or ubiquitination-mediated c-FLIP degradation, as assessed using c-FLIP point mutants on lysine 167 and 195 or threonine 166, a phosphorylation site known to regulate ubiquitination of c-FLIP. Rather, c-FLIP depletion was associated with aggregation, because addition of glycerol not only prevented the loss of c-FLIP from the cytosol but also enabled c-FLIP recruitment within the TRAIL DISC, thus inhibiting TRAIL-induced apoptosis during hyperthermia. Altogether our results demonstrate that c-FLIP is a thermosensitive protein whose targeting by hyperthermia allows restoration of apoptosis induced by TNF ligands, including TRAIL. Our findings suggest that combining TRAIL agonists with whole-body or localized hyperthermia may be an interesting approach in cancer therapy.

Several complex molecular events are involved in tumorigenesis of hepatocellular carcinoma (HCC). The interactions of these molecules may constitute the HCC imbalanced network. Gansui Banxia Tang (GSBXT), as a classic Chinese herbal formula, is a popular complementary and alternative medicine modality for treating HCC. In order to investigate the therapeutic effects and the pharmacological mechanisms of GSBXT on reversing HCC imbalanced network, we in the current study developed a comprehensive systems approach of integrating disease-specific and drug-specific networks, and successfully revealed the relationships of the ingredients in GSBXT with their putative targets, and with HCC significant molecules and HCC related pathway systems for the first time. Meanwhile, further experimental validation also demonstrated the preventive effects of GSBXT on tumor growth in mice and its regulatory effects on potential targets.

The heat shock protein 90 (Hsp90) plays a crucial role in the stability of several proteins that are essential for malignant transformation. Hsp90 is therefore an interesting therapeutic target for cancer therapy. In this paper, we investigated whether an oxidative stress generated during ascorbate-driven menadione redox cycling (ascorbate/menadione), affects Hsp90 leading to the degradation of some critical proteins and cell death. Unlike 17-AAG, which inhibits Hsp90 but enhances Hsp70 levels, ascorbate/menadione-treated cells present an additional Hsp90 protein band of about 70kDa as shown by Western blot analysis, suggesting Hsp90 cleavage. This Hsp90 cleavage seems to be a selective phenomenon since it was observed in a large panel of cancer cell lines but not in non-transformed cells. Antibodies raised against either the N-terminus or the C-terminus domains of Hsp90 suggest that the site of cleavage should be located at its N-terminal part. Furthermore, antibodies raised against either the alpha- or the beta-Hsp90 isoform show that Hsp90beta is cleaved while the alpha isoform is down-regulated. We have further shown that different Hsp90 client proteins like Bcr-Abl (a chimerical protein expressed in K562 leukemia cells), RIP and Akt, were degraded when K562 cells were exposed to an oxidative stress. Both Hsp90 cleavage and Bcr-Abl degradation were observed by incubating K562 cells with another H(2)O(2)-generating system (glucose/glucose oxidase) and by incubating KU812 cells (another leukemia cell line) with ascorbate/menadione. Due to the major role of Hsp90 in stabilizing oncogenic and mutated proteins, these results may have potential clinical applications.

Immunoprecipitation of unactivated avian progesterone receptor results in the copurification of hsp90, hsp70, and three additional proteins, p54, p50, and p23. p23 is also present in immunoaffinity-purified hsp90 complexes along with hsp70 and another protein, p60. Antibody and cDNA probes for p23 were prepared in an effort to elucidate the significance and function of this protein. Antibodies to p23 detect similar levels of p23 in all tissues tested and cross-react with a protein of the same size in mice, rabbits, guinea pigs, humans, and Saccharomyces cerevisiae, indicating that p23 is a conserved protein of broad tissue distribution. These antibodies were used to screen a chicken brain cDNA library, resulting in the isolation of a 468-bp partial cDNA clone encoding a sequence containing four sequences corresponding to peptide fragments isolated from chicken p23. This partial clone was subsequently used to isolate a full-length human cDNA clone. The human cDNA encodes a protein of 160 amino acids that does not show homology to previously identified proteins. The chicken and human cDNAs are 88% identical at the DNA level and 96.3% identical at the protein level. p23 is a highly acidic phosphoprotein with an aspartic acid-rich carboxy-terminal domain. Bacterially overexpressed human p23 was used to raise several monoclonal antibodies to p23. These antibodies specifically immunoprecipitate p23 in complex with hsp90 in all tissues tested and can be used to immunoaffinity isolate progesterone receptor complexes from chicken oviduct cytosol.