Gabriel Pineda
University of California, San Diego
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Featured researches published by Gabriel Pineda.
Nature | 2009
Zongping Xia; Lijun Sun; Xiang Chen; Gabriel Pineda; Xiaomo Jiang; Anirban Adhikari; Wenwen Zeng; Zhijian J. Chen
TRAF6 is a ubiquitin ligase that is essential for the activation of NF-κB and MAP kinases in several signalling pathways, including those emanating from the interleukin 1 and Toll-like receptors. TRAF6 functions together with a ubiquitin-conjugating enzyme complex consisting of UBC13 (also known as UBE2N) and UEV1A (UBE2V1) to catalyse Lys 63-linked polyubiquitination, which activates the TAK1 (also known as MAP3K7) kinase complex. TAK1 in turn phosphorylates and activates IκB kinase (IKK), leading to the activation of NF-κB. Although several proteins are known to be polyubiquitinated in the IL1R and Toll-like receptor pathways, it is not clear whether ubiquitination of any of these proteins is important for TAK1 or IKK activation. By reconstituting TAK1 activation in vitro using purified proteins, here we show that free Lys 63 polyubiquitin chains, which are not conjugated to any target protein, directly activate TAK1 by binding to the ubiquitin receptor TAB2 (also known as MAP3K7IP2). This binding leads to autophosphorylation and activation of TAK1. Furthermore, we found that unanchored polyubiquitin chains synthesized by TRAF6 and UBCH5C (also known as UBE2D3) activate the IKK complex. Disassembly of the polyubiquitin chains by deubiquitination enzymes prevented TAK1 and IKK activation. These results indicate that unanchored polyubiquitin chains directly activate TAK1 and IKK, suggesting a new mechanism of protein kinase regulation.
Advances in Experimental Medicine and Biology | 2007
Gabriel Pineda; Chee Kwee Ea; Zhijian J. Chen
Ubiquitin (Ub) is a highly conserved small polypeptide that is ubiquitously expressed in all eukaryotic cells. The best-known function of ubiquitin is to target protein degradation through covalent attachment of this polypeptide on protein substrates. 1, 2, 3This covalent modification, known as ubiquitination, is carried out via a three-step enzymatic cascade. In the first step, Ub is activated by the Ub-activating enzyme (E1) in an ATP-dependent reaction to form an E1-Ub thioester. In the second step, the activated Ub is transferred to a cysteine residue in the active site of a Ub-conjugating enzyme (Ubc or E2) to form an E2-Ub thioester. Finally, in the presence of a Ub-protein ligase (E3), ubiquitin is conjugated to a protein substrate by forming an isopeptide bond between the carboxyl terminus of ubiquitin and the e-amino group of a lysine residue on the protein target. After Ub is conjugated to a protein substrate, Ub itself can be conjugated by another Ub through one of its seven lysines, typically lysine-48. This process reiterates itself in a highly processive manner to form a polyubiquitin chain, which is then recruited to a large ATP-dependent protease complex called the 26S proteasome. The polyubiquitinated protein substrates are degraded inside the proteasome, whereas the polyubiquitin chains are cleaved to monomeric ubiquitin, which is recycled.
Cell Stem Cell | 2016
Maria Anna Zipeto; Angela C. Court; Anil Sadarangani; Nathaniel Delos Santos; Larisa Balaian; Hye-Jung Chun; Gabriel Pineda; Sheldon R. Morris; Cayla N. Mason; Ifat Geron; Christian L. Barrett; Daniel Goff; Russell Wall; Maurizio Pellecchia; Mark D. Minden; Kelly A. Frazer; Marco A. Marra; Leslie Crews; Qingfei Jiang; Catriona Jamieson
Post-transcriptional adenosine-to-inosine RNA editing mediated by adenosine deaminase acting on RNA1 (ADAR1) promotes cancer progression and therapeutic resistance. However, ADAR1 editase-dependent mechanisms governing leukemia stem cell (LSC) generation have not been elucidated. In blast crisis chronic myeloid leukemia (BC CML), we show that increased JAK2 signaling and BCR-ABL1 amplification activate ADAR1. In a humanized BC CML mouse model, combined JAK2 and BCR-ABL1 inhibition prevents LSC self-renewal commensurate with ADAR1 downregulation. Lentiviral ADAR1 wild-type, but not an editing-defective ADAR1(E912A) mutant, induces self-renewal gene expression and impairs biogenesis of stem cell regulatory let-7 microRNAs. Combined RNA sequencing, qRT-PCR, CLIP-ADAR1, and pri-let-7 mutagenesis data suggest that ADAR1 promotes LSC generation via let-7 pri-microRNA editing and LIN28B upregulation. A small-molecule tool compound antagonizes ADAR1s effect on LSC self-renewal in stromal co-cultures and restores let-7 biogenesis. Thus, ADAR1 activation represents a unique therapeutic vulnerability in LSCs with active JAK2 signaling.
Journal of Translational Medicine | 2015
Anil Sadarangani; Gabriel Pineda; Kathleen M. Lennon; Hye Jung E Chun; Alice Shih; Annelie E. Schairer; Angela C. Court; Daniel Goff; Sacha L. Prashad; Ifat Geron; Russell Wall; John D. McPherson; Richard A. Moore; Minya Pu; Lei Bao; Amy Jackson-Fisher; Michael John Munchhof; Todd VanArsdale; Tannishtha Reya; Sheldon R. Morris; Mark D. Minden; Karen Messer; Hanna Mikkola; Marco A. Marra; Thomas J. Hudson; Catriona Jamieson
BackgroundDormant leukemia stem cells (LSC) promote therapeutic resistance and leukemic progression as a result of unbridled activation of stem cell gene expression programs. Thus, we hypothesized that 1) deregulation of the hedgehog (Hh) stem cell self-renewal and cell cycle regulatory pathway would promote dormant human LSC generation and 2) that PF-04449913, a clinical antagonist of the GLI2 transcriptional activator, smoothened (SMO), would enhance dormant human LSC eradication.MethodsTo test these postulates, whole transcriptome RNA sequencing (RNA-seq), microarray, qRT-PCR, stromal co-culture, confocal fluorescence microscopic, nanoproteomic, serial transplantation and cell cycle analyses were performed on FACS purified normal, chronic phase (CP) chronic myeloid leukemia (CML), blast crisis (BC) phase CML progenitors with or without PF-04449913 treatment.ResultsNotably, RNA-seq analyses revealed that Hh pathway and cell cycle regulatory gene overexpression correlated with leukemic progression. While lentivirally enforced GLI2 expression enhanced leukemic progenitor dormancy in stromal co-cultures, this was not observed with a mutant GLI2 lacking a transactivation domain, suggesting that GLI2 expression prevented cell cycle transit. Selective SMO inhibition with PF-04449913 in humanized stromal co-cultures and LSC xenografts reduced downstream GLI2 protein and cell cycle regulatory gene expression. Moreover, SMO inhibition enhanced cell cycle transit and sensitized BC LSC to tyrosine kinase inhibition in vivo at doses that spare normal HSC.ConclusionIn summary, while GLI2, forms part of a core HH pathway transcriptional regulatory network that promotes human myeloid leukemic progression and dormant LSC generation, selective inhibition with PF-04449913 reduces the dormant LSC burden thereby providing a strong rationale for clinical trials predicated on SMO inhibition in combination with TKIs or chemotherapeutic agents with the ultimate aim of obviating leukemic therapeutic resistance, persistence and progression.
Nature Communications | 2017
Elisa Lazzari; Phoebe K. Mondala; Nathaniel Delos Santos; Amber Miller; Gabriel Pineda; Qingfei Jiang; Heather Leu; Shawn Ali; Anusha Preethi Ganesan; Christina N. Wu; Caitlin Costello; Mark D. Minden; Raffaella Chiaramonte; A. Keith Stewart; Leslie Crews; Catriona Jamieson
Despite novel therapies, relapse of multiple myeloma (MM) is virtually inevitable. Amplification of chromosome 1q, which harbors the inflammation-responsive RNA editase adenosine deaminase acting on RNA (ADAR)1 gene, occurs in 30–50% of MM patients and portends a poor prognosis. Since adenosine-to-inosine RNA editing has recently emerged as a driver of cancer progression, genomic amplification combined with inflammatory cytokine activation of ADAR1 could stimulate MM progression and therapeutic resistance. Here, we report that high ADAR1 RNA expression correlates with reduced patient survival rates in the MMRF CoMMpass data set. Expression of wild-type, but not mutant, ADAR1 enhances Alu-dependent editing and transcriptional activity of GLI1, a Hedgehog (Hh) pathway transcriptional activator and self-renewal agonist, and promotes immunomodulatory drug resistance in vitro. Finally, ADAR1 knockdown reduces regeneration of high-risk MM in serially transplantable patient-derived xenografts. These data demonstrate that ADAR1 promotes malignant regeneration of MM and if selectively inhibited may obviate progression and relapse.The treatment of multiple myeloma is challenging due to high relapse rates. Here the authors show that expression of ADAR1 correlates with poor patient outcomes, and that ADAR1-mediated editing of GLI1 is a mechanism relevant in the context of multiple myeloma progression and drug resistance.
Cancer Research | 2017
Elisa Lazzari; Nathaniel Delos Santos; Christina Wu; Heather Leu; Gabriel Pineda; Shawn Ali; Caitlin Costello; Mark D. Minden; Raffaella Chiaramonte; Leslie Crews; Catriona Jamieson
Introduction: Despite novel therapies, most of multiple myeloma (MM) patients relapse as a result of clonal evolution in inflammatory microenvironments. Adenosine-to-inosine (A-to-I) RNA editing, driven by inflammatory cytokine-responsive adenosine deaminase acting on RNA1 (ADAR1), promotes cancer progression by enhancing survival and self-renewal of malignant progenitor cells. Amplifications of chromosome 1q21, containing IL-6R and ADAR1 loci, occur frequently in high-risk MM patients, who frequently develop secondary plasma cell leukemia (PCL) and have shorter survival. While increased IL-6 signaling has been linked to relapse and A-to-I editing contributes to therapeutic resistance in a broad array of malignancies, the role of ADAR1 in MM pathogenesis has not been elucidated. This study aimed to investigate whether pro-inflammatory cues in MM activate ADAR1 editing thereby promoting malignant regeneration. Procedures: Publicly available primary patient datasets were analyzed and validated in a separate cohort of biobanked primary samples and human myeloma cell lines. Lentiviral vector-mediated activation or knockdown of ADAR1, or treatment with extrinsic pro-inflammatory stimuli, was utilized to probe the functional impact of RNA editing activity in MM models. Site-specific qPCR was used to quantify RNA editing in specific cancer stem cell-associated loci. Functional effects of ADAR1 activity were assessed in in vitro survival and self-renewal assays, and in novel in vivo PCL xenografts. Results: Patients harboring 1q21 amplification showed significant and stage-dependent increases in ADAR1 expression. In a set of separate primary PCL samples, aberrant RNA editing in the coding region of the Hedgehog (Hh) pathway transcription factor GLI1 was observed in high ADAR1-expressing samples. Notably, increased GLI1 editing, previously reported to have increased capacity to activate its transcriptional targets, was detected in serially transplantable, patient-derived xenograft models. Furthermore, abolition of ADAR1 editase activity impaired GLI1 editing. Lastly, in vitro pro-inflammatory IL-6 stimulation, or continuous exposure to the immunomodulatory drug lenalidomide led to increased ADAR1 mRNA and protein levels, with a concomitant induction of RNA editing activity. Conclusions: In MM, 1q21 amplification has been linked to progression. We provide new evidence linking expression and activity of ADAR1, located on 1q21, and disease stage. Because ADAR1 induces transcript recoding, A-to-I editing could contribute to the marked transcriptomic diversity typical of advanced MM. While the Hh pathway has been linked to cancer stem cell generation in human MM, here we identified a primate-specific mechanism of Hh pathway activation in MM through RNA editing-dependent stabilization of GLI1. Together, both genetic and microenvironmental factors modulate epitranscriptomic deregulation of cancer stem cell pathways in MM. Citation Format: Elisa Lazzari, Nathaniel Delos Santos, Christina Wu, Heather Leu, Gabriel Pineda, Shawn Ali, Caitlin Costello, Mark Minden, Raffaella Chiaramonte, Leslie Crews, Catriona Jamieson. Aberrant RNA editing of GLI1 promotes malignant regeneration in multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3351. doi:10.1158/1538-7445.AM2017-3351
BMC Research Notes | 2015
Gabriel Pineda; Zhouxin Shen; Claudio P. Albuquerque; Eduardo Reynoso; Jeffrey E. Chen; Chi‑Chiang Tu; Wingchung Tang; Steve Briggs; Huilin Zhou; Jean Y. J. Wang
AbstractBackgroundEukaryotic RNA polymerase II contains a C-terminal repeated domain (CTD) consisting of 52 consensus heptad repeats of Y1S2P3T4S5P6S7 that mediate interactions with many cellular proteins to regulate transcription elongation, RNA processing and chromatin structure. A number of CTD-binding proteins have been identified and the crystal structures of several protein-CTD complexes have demonstrated considerable conformational flexibility of the heptad repeats in those interactions. Furthermore, phosphorylation of the CTD at tyrosine, serine and threonine residues can regulate the CTD-protein interactions. Although the interactions of CTD with specific proteins have been elucidated at the atomic level, the capacity and specificity of the CTD-interactome in mammalian cells is not yet determined.ResultsA proteomic study was conducted to examine the mammalian CTD-interactome. We utilized six synthetic peptides each consisting of four consensus CTD-repeats with different combinations of serine and tyrosine phosphorylation as affinity-probes to pull-down nuclear proteins from HeLa cells. The pull-down fractions were then analyzed by MUDPIT mass spectrometry, which identified 100 proteins with the majority from the phospho-CTD pull-downs. Proteins pulled-down by serine-phosphorylated CTD-peptides included those containing the previously defined CTD-interacting domain (CID). Using SILAC mass spectrometry, we showed that the in vivo interaction of RNA polymerase II with the mammalian CID-containing RPRD1B is disrupted by CID mutation. We also showed that the CID from four mammalian proteins interacted with pS2-phosphorylated but not pY1pS2-doubly phosphorylated CTD-peptides. However, we also found proteins that were preferentially pulled-down by pY1pS2- or pY1pS5-doubly phosphorylated CTD-peptides. We prepared an antibody against tyrosine phosphorylated CTD and showed that ionizing radiation (IR) induced a transient increase in CTD tyrosine phosphorylation by immunoblotting. Combining SILAC and IMAC purification of phospho-peptides, we found that IR regulated the phosphorylation at four CTD tyrosine sites in different ways.ConclusionUpon phosphorylation, the 52 repeats of the CTD have the capacity to generate a large number of binding sites for cellular proteins. This study confirms previous findings that serine phosphorylation stimulates whereas tyrosine phosphorylation inhibits the protein-binding activity of the CTD. However, tyrosine phosphorylation of the CTD can also stimulate other CTD-protein interactions. The CTD-peptide affinity pull-down method described here can be adopted to survey the mammalian CTD-interactome in various cell types and under different biological conditions.
Cancer Research | 2018
Leslie Crews; Elisa Lazzari; Phoebe K. Mondala; Nathaniel Delos Santos; Amber Miller; Gabriel Pineda; Qingfei Jiang; Anusha-Preethi Ganesan; Christina Wu; Caitlin Costello; Mark D. Minden; Raffaella Chiaramonte; A. Keith Stewart; Catriona Jamieson
Introduction: Representing 10% of hematologic malignancies, multiple myeloma (MM) is typified by clonal plasma cell proliferation in the bone marrow (BM) and may progress to therapy-resistant plasma cell leukemia (PCL). Despite many novel therapies, relapse rates remain high as a result of malignant regeneration (self-renewal) of MM cells in inflammatory microenvironments. In addition to recurrent DNA mutations and epigenetic deregulation, inflammatory cytokine-responsive adenosine deaminase associated with RNA (ADAR1)-mediated adenosine to inosine (A-to-I) RNA editing has emerged as a key driver of cancer relapse and progression. In MM, copy number amplification of chromosome 1q21, which contains both ADAR1 and interleukin-6 receptor (IL-6R) gene loci, portends a poor prognosis. Thus, we hypothesized that ADAR1 copy number amplification combined with inflammatory cytokine activation of ADAR1 stimulates malignant regeneration of MM and therapeutic resistance. Methods and Results: Analysis of MMRF CoMMpass RNA sequencing (RNA-seq) data revealed that high ADAR1 expression (n=162 patients) correlated with significantly reduced progression-free and overall survival compared with a low ADAR1 subset (n=159 patients). In contrast to lentiviral ADAR1 shRNA knockdown and overexpression of an editase defective ADAR1 mutant (ADAR1 E912A ), lentiviral wild-type ADAR1 overexpression enhanced editing of GLI1, a Hedgehog (Hh) pathway transcriptional activator and self-renewal agonist. Editing of GLI1 transcripts enhanced GLI transcriptional activity in luciferase reporter assays, and promoted lenalidomide resistance in vitro. Finally, lentiviral shRNA ADAR1 knockdown reduced regeneration of high-risk MM in humanized serial transplantation mouse models, indicative of reduced malignant self-renewal capacity. Whole-transcriptome RNA-sequencing of primary samples after lentiviral shRNA knockdown of ADAR1 revealed specific modulation of extracellular and immune response genes, while overexpression of wild-type versus edited GLI1 elicited distinct gene expression changes in human myeloma cells analyzed using NanoString nCounter assays. These data demonstrate that ADAR1 promotes malignant self-renewal of MM and, if selectively inhibited, may prevent progression and relapse through modulation of extracellular and immune response genes. Conclusions: Deregulated RNA editing, driven by aberrant ADAR1 activation, represents a unique source of transcriptomic and proteomic diversity, resulting in self-renewal of MM cells in inflammatory microenvironments. In summary, both genetic (1q21 amplification) and microenvironmental factors (inflammatory cytokines, IMiDs) combine to drive GLI1-dependent malignant regeneration in MM. Thus, ADAR1 represents both a vital prognostic biomarker and therapeutic target in MM. Citation Format: Leslie A. Crews, Elisa Lazzari, Phoebe K. Mondala, Nathaniel Delos Santos, Amber Miller, Gabriel Pineda, Qingfei Jiang, Anusha-Preethi Ganesan, Christina Wu, Caitlin Costello, Mark Minden, Raffaella Chiaramonte, A. Keith Stewart, Catriona H. M. Jamieson. Down-modulation of ADAR1-mediated GLI1 editing alters extracellular and immune response genes in multiple myeloma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4437.
Scientific Reports | 2016
Gabriel Pineda; Kathleen M. Lennon; Nathaniel Delos Santos; Florence Lambert-Fliszar; Gennarina L. Riso; Elisa Lazzari; Marco A. Marra; Sheldon R. Morris; Asako Sakaue-Sawano; Atsushi Miyawaki; Catriona Jamieson
While implicated in therapeutic resistance, malignant progenitor cell cycle kinetics have been difficult to quantify in real-time. We developed an efficient lentiviral bicistronic fluorescent, ubiquitination-based cell cycle indicator reporter (Fucci2BL) to image live single progenitors on a defined niche coupled with cell cycle gene expression analysis. We have identified key differences in cell cycle regulatory gene expression and transit times between normal and chronic myeloid leukemia progenitors that may inform cancer stem cell eradication strategies.
Clinical Cancer Research | 2015
Gabriel Pineda; Kathleen M. Lennon; Florence Lambert-Fliszar; Gennarina L. Riso; Catriona Jamieson
Human leukemia stem cells (LSC) are quiescent self-renewing cells that drive leukemic transformation of myeloproliferative neoplasms and myelodysplastic syndromes. Currently, there are few methods to quantitatively visualize cell cycle progression in (LSC) and to interrogate stem cell cycle gene regulatory networks in live cells. Human LSC are characterized as quiescent self-renewing cells and current methods require sequential transduction and clonal selection. These methods and conditions are not feasible for studying primary patient samples and LSC, which are generally limited in cell numbers. To alleviate this challenge, we generated a lentiviral biscistronic vector encoding FUCCI2 (fluorescent ubiquitination-based cell-cycle indicator) probes. We characterized the fidelity of the cell cycle by confirming normal cell division and distinct nuclear staining of either green or red fluorescence in both transiently and stably transduced 293 cells. Further, analysis by flow cytometry of 293 cell confirmed that S/G2/M and G1/G0 phases of cell cycle correlate with expression of fluorescent reporters expressed from the bicistronic lentiviral vector and recapitulate FACS based analysis using traditional Ki67 and 7AAD staining. Recently, using this lentiviral biscistronic reporter we succeeded in tracking cell cycle progression in CD34+ cells from CML primary patient samples co-cultured with SL/M2 cells. Time-lapse confocal imaging of these samples reveals distinct differences within the population of CML cells. In summary using this new Dual FUCCI2 lentiviral reporter makes it possible to track real time cell cycle kinetics in cancer stem cells. Future studies will include measuring LSC, cell cycle gene regulatory networks in live cells at different stages of the cell cycle. Citation Format: Gabriel Pineda, Kathleen M. Lennon, Florence Lambert-Fliszar, Gennarina L. Riso, Catriona Jamieson. Real time niche tracking of cancer stem cell cycle kinetics using a novel bi-cistronic lentiviral reporter. [abstract]. In: Proceedings of the AACR Special Conference on Hematologic Malignancies: Translating Discoveries to Novel Therapies; Sep 20-23, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(17 Suppl):Abstract nr A46.