Torbett Laboratory


Hexokinases - Their Role in Differentiation, Metabolism and Autophagy (Kristina Seiler)

Kristina-Project-Pic.pngHexokinases (HKs) are rate-limiting enzymes that catalyze the phosphorylation of glucose to glucose-6-phosphate, the first step of glycolysis. They promote and sustain a concentration gradient that facilitates glucose entry, which ensures the initiation of glucose dependent pathways. In general, HKs have a cytoprotective role that is highlighted by enhanced sensitivity of cancer cells to drugs when Hks were inhibited. Of the different HK isoforms, HK3 expression is significantly reduced in patient acute myeloid leukemia (AML) cells, particulraly in acute promyelocytic leukemia (APL) celss expressing the PML-RARA oncofusion protein. Interestingly, while HK1 and HK2 levels remain stable during all stages of myeloid diffrentiation, HK3 mRNA levels significantly increase. The same pattern of HK mRNA expression was seen in NB4 APL and HL60 AML cell lines differentiated towards granulocytes and monocytes using all-trans retinoic acid (ATRA) and vitamin D3, respectively. We now aim to report about the catalytic and potential regulatory functions of HK3 during normal and aberrant myeloid hematopoiesis.

CD46 Null Packaging Cell Line Improves Measles Lentiviral Vector Production and Gene Delivery to Hematopoietic Stem and Progenitor Cells (Stosh Ozog)

stoshprojectpicDevelopment of methodologies for the improvement of lentiviral vector-mediated gene delivery for anti-HIV prophylaxis. Identification of intrinsic immune factors that limit efficient gene delivery to hematopoietic stem cells. Cellular restriction factors are overcome through viral envelope pseudotyping and pharmacologic modulation. Anti-HIV prophylaxis is pursued through vector delivery of broadly neutralizing immunoadhesins to mature B cells and hematopoietic stem cells.

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A Small Molecule Approach for Investigating Lentiviral Vector Transduction Resistance in Hematopoietic Stem Cells (Kip Hermann)

kipprojpicInefficient gene transfer of hematopoietic stem cells (HSCs) by lentivirus has hindered the efficient clinical application of many therapies. We are investigating various small molecules that have been found to have an effect on lentiviral transduction of HSCs and the underlying mechanism of these effects. Our goal is to improve lentiviral transduction of HSCs by better understanding and manipulating the pathways revealed from these small molecule studies.

Regulation of HIV by the Host Ubiquitin-Proteasome System (Johanna Heideker)

johannaprojpic2My main interest is elucidating the role of the ubiquitin proteasome system in the modulation of HIV infectivity, replication, particle assembly and latency and its crosstalk with the opioid signaling system. It is well established that cellular immune responses are heavily regulated by the ubiquitin proteasome system. Current pharmacological interventions in ubiquitin biology have enabled advances in anticancer treatments and are actively pursued to expand anticancer therapy options. I hope to combine the insights from these studies to identify new ways of interfering with the HIV life cycle. In addition I support all protein purification and proteomics efforts related to HIV research by the San Diego Center for AIDS Research (CFAR). Current collaborations include structural studies of HIV core assembly and Gag - Alix interactions.

Identification and Characterization of Host Factors Involved in Gag Assembly and Trafficking (Shentian Zhuang)

shentianprojectpicHIV has to depend on cellular proteins and pathways to complete its replication cycle. On the other hand, host cells use restriction factors to defend themselves against HIV-1 infection. Therefore, cellular proteins that are hijacked by HIV in order to complete its replication cycle, form attractive new targets for anti-retroviral therapy. Gag is the key structural protein mediating assembly of HIV particle in infected cells. Although Gag is capable os self-assembly in vitro, it has become generally accepted that host factors play a decisive role for Gag efficient assembly and trafficking in living cells. Several host factors that associate with Gag have been identified previously, however, understanding of Gag-host factor interactions remains incomplete. So, we aim to use affinity purification or proximity-dependent biotin labelling coupled with mass spectrometry to identify novel Gag-interacting proteins and then perform further biochemical and virological validations of the candidates.

The Role of PU.1 in Alternative Splicing of the Anti-Apoptotic cFLIP (Nicolas Niklaus)


The formation of mature hematopietic cells is regulated by a complex interpaly between transcription factors, which regulate key processes of differentiation in response to external signals. One of these trasnscription factors involved throughout hematopoietic differentiation is the ETS-transcription factor PU.1. This tumor suppressor gene is needed particularly to activate genes, which orchestrate terminal differentiation of macrophages, neutrophils, B-cells, and TH9 cells, but little is known about the role of PU.1 during cell death mechanisms. Depletion of PU.1 specifically increases levels of the short isoform of the anti-apoptotic protein cFLIP, but reduces the levels of the full length isoform, while induction of PU.1 by an inducible system showed the opposite effect. Interestingly, PU.1 is associated with alternative splicing and not only binds DNA but also RNA. Thus, it is likely that PU.1 is involved in the splicing mechanisms of cFLIP leading to increased apoptosis.



Department of Immunology and Microbiology

The Scripps Research Institute

Director, Molecular Basis of Viral Pathogenesis Training Program

Director, CFAR Protein Expression and Proteomics (PEP) Core

Co-Director, HIV Interaction and Viral Evolution (HIVE) Center

Co-Director, UCSD Center for AIDS Research (CFAR)


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