Project description:Hsp70 inhibition affects many signaling pathways. We established how these effects are translated into changes in gene expression. Hsp70 is a promising anti-cancer target, and several inhibitors of Hsp70 have been recently developed. Interest to Hsp70 inhibitors as drug prototypes is, however, somewhat hampered by potential similarity of their physiological effects to effects of already well-developed Hsp90 inhibitors. JG-98 series of inhibitors is unique in its ability to target an allosteric site in the ATPase domain of Hsp70, which disrupts its interaction with a co-chaperone Bag3 and affects a variety of signaling pathways important for cancer development and survival. Here, we used the Broad Institute Connectivity Map platform to evaluate physiological effects of JG-98, and found that these effects are dissimilar from effects of Hsp90 inhibitors, thus justifying further development of this compound series. Further, using gene expression data and ActivSignal IPAD platform, we identified pathways modulated by JG-98. Some of these pathways were affected by JG-98 in Bag3-dependent and some pathways in Bag3-independent manner, indicating multiple mechanisms of JG-98 action. Using pooled shRNA genetic screen, we established gene sets that modulate the response of cancer cells to JG-98. Based on genetic and gene expression information, we developed approaches to predict potent combinations of JG-98 with known drugs. These predictions were validated by demonstrating that proteasome, RNApol II, Akt and RTK inhibitors synergize with anti-cancer effects of JG-98. Overall, in this study we analyze unique effects of Hsp70 inhibitors of JG-98 series on cell physiology and define potential drug combinations for clinical use of these inhibitors.
Project description:The major heat shock protein Hsp70 has been shown to form a complex with a scaffold protein Bag3, linking it to multiple signaling pathways. Via these interactions, the Hsp70-Bag3 module functions as a proteotoxicity sensor that controls cell signaling. Here, as a tool to identify signaling pathways regulated by this complex, we utilized JG-98, an allosteric inhibitor of Hsp70 that blocks its interaction with Bag3. Gene expression profiling followed by the pathway analysis indicated that a set of signaling pathways including the unfolded protein response (UPR) was activated by JG-98. Surprisingly, only the translation initiation factor eIF2a-associated branch of the UPR was activated under these conditions, while other UPR branches mediating induction of ER chaperones were not induced, suggesting that the response was not related to ER proteotoxicity and thus to ER-associated kinase PERK1. Indeed, induction of the UPR genes under these conditions was dependent on activation of a distinct cytoplasmic eIF2a kinase, HRI. We demonstrated that the Hsp70-Bag3 complex directly interacted with HRI and regulated phosphorylation of eIF2a upon induction of cytoplasmic proteotoxicity. Therefore, we uncovered a novel signaling response, which regulates cell death upon the buildup of abnormal protein species in cytoplasm via an Hsp70-Bag3-HRI-eIF2a axis.
Project description:Gene expression profiling of immortalized human mesenchymal stem cells with hTERT/E6/E7 transfected MSCs. hTERT may change gene expression in MSCs. Goal was to determine the gene expressions of immortalized MSCs.
Project description:Transcriptional profiling of human mesenchymal stem cells comparing normoxic MSCs cells with hypoxic MSCs cells. Hypoxia may inhibit senescence of MSCs during expansion. Goal was to determine the effects of hypoxia on global MSCs gene expression.
Project description:Proteasome inhibitor (PI) resistance remains a central challenge in multiple myeloma. To identify pathways mediating resistance, we first mapped proteasome-associated genetic co-dependencies. We identified cytosolic heat shock protein 70 (HSP70) chaperones as potential targets, consistent with proposed mechanisms of myeloma tumor cells overcoming PI-induced stress. These results led us to explore allosteric HSP70 inhibitors (JG compounds) as myeloma therapeutics. We showed these compounds exhibit increased efficacy against acquired and intrinsic PI-resistant myeloma models, unlike HSP90 inhibition. Surprisingly, shotgun and pulsed-SILAC mass spectrometry found that JGs have the most pronounced effect on the proteome not through inhibiting cytosolic HSP70s but instead through mitochondrial-localized HSP70, HSPA9/mortalin, destabilizing the 55S mitoribosome. Analysis of myeloma patient data further supports strong effects of global proteostasis capacity, and particularly HSPA9 expression, on PI response. Our results characterize myeloma proteostasis networks under therapeutic pressure while motivating further investigation of HSPA9 as a specific vulnerability in PI-resistant disease.
Project description:Gene methylation profiling of immortalized human mesenchymal stem cells comparing HPV E6/E7-transfected MSCs cells with human telomerase reverse transcriptase (hTERT)- and HPV E6/E7-transfected MSCs. hTERT may increase gene methylation in MSCs. Goal was to determine the effects of different transfected genes on global gene methylation in MSCs.
Project description:Kynureninase is a member of a large family of catalytically diverse but structurally homologous pyridoxal 5'-phosphate (PLP) dependent enzymes known as the aspartate aminotransferase superfamily or alpha-family. The Homo sapiens and other eukaryotic constitutive kynureninases preferentially catalyze the hydrolytic cleavage of 3-hydroxy-l-kynurenine to produce 3-hydroxyanthranilate and l-alanine, while l-kynurenine is the substrate of many prokaryotic inducible kynureninases. The human enzyme was cloned with an N-terminal hexahistidine tag, expressed, and purified from a bacterial expression system using Ni metal ion affinity chromatography. Kinetic characterization of the recombinant enzyme reveals classic Michaelis-Menten behavior, with a Km of 28.3 +/- 1.9 microM and a specific activity of 1.75 micromol min-1 mg-1 for 3-hydroxy-dl-kynurenine. Crystals of recombinant kynureninase that diffracted to 2.0 A were obtained, and the atomic structure of the PLP-bound holoenzyme was determined by molecular replacement using the Pseudomonas fluorescens kynureninase structure (PDB entry 1qz9) as the phasing model. A structural superposition with the P. fluorescens kynureninase revealed that these two structures resemble the "open" and "closed" conformations of aspartate aminotransferase. The comparison illustrates the dynamic nature of these proteins' small domains and reveals a role for Arg-434 similar to its role in other AAT alpha-family members. Docking of 3-hydroxy-l-kynurenine into the human kynureninase active site suggests that Asn-333 and His-102 are involved in substrate binding and molecular discrimination between inducible and constitutive kynureninase substrates.
Project description:Gene expression profiling of immortalized human mesenchymal stem cells with hTERT/E6/E7 transfected MSCs. hTERT may change gene expression in MSCs. Goal was to determine the gene expressions of immortalized MSCs. One-condition experment, gene expression of 3A6