Research
I. The bioenergetics of B lymphocyte growth and survival responses
We are interested in understanding the bioenergetics underlying B lymphocyte growth and survival responses. Current projects seek to understand the role of glucose energy metabolism in naïve B lymphocyte growth and proliferation following antigen receptor ligation. We are determining the biological role of glucose catabolism, pathways that mediate glucose catabolism, and the signal transduction pathways that link antigen receptors to changes in glucose energy metabolism. We incorporate elements of cell biology (e.g., confocal microscopy and flow cytometry), biochemistry (e.g., NMR and enzymology), and molecular biology to investigate these questions. Our recent findings suggest that PI-3K/Akt link antigen receptor ligation to increased Glut1 expression, glucose transport and glycolytic catabolism in order to provide glycolytic intermediates to support de novo macromolecular biosynthesis and ATP production (Blood 107: 4458).
IA. A metabolomic approach using 2D-gHSQC to identify novel 13C-glucose-derived metabolites in activated macrophages.
An ongoing collaboration with Drs. Robert (Chemistry Department, Boston College) and Rabinowitz (Princeton University, Department of Chemistry) is focused on identifying novel metabolites that exhibit immunomodulatory activities. Shown here is the identification of itaconic acid in VM-M3 murine tumor cells (a) and in RAW 264.7 cells (b) subsequently stimulated with LPS (c) or primary murine macrophages (d) stimulated with IFN-gamma plus LPS (e).
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II. Insights into the Cytotoxicity of 3-Deoxyphosphatidylinositols
An ongoing project seeks to understand the structural specificity and mechanism of cytotoxic D-3-Deoxyphosphatidylinositol derivates. In collaboration with Dr. Scott Miller (Yale University, Chemistry Department) and Dr. Mary Roberts (Boston College, Chemistry Department) we have synthesized a series of 3-deoxydioctanoylphosphatidylinositol (3-deoxy-diC8PI) derivates with altered chirality of the inositol ring and/or additional modification (deoxygenation or phosphorylation) at the inositol C5 atom (J. Am. Chem. Soc. 130:7747:2008). Shown here is the viability of U937 cells in the presence of different concentrations of 3-deoxy-diC8PI compounds: D-3-deoxy-diC8PI (dark circle), L-3-deoxy-diC8PI (opened circles), and D-3-diC8PI(5)P (x).
III. Cell cycle regulation
A second project in the laboratory seeks to understand the regulation of the cell cycle in splenic B-2 and peritoneal B-1a cells, as these two B-cell subsets have distinct requirements for cell cycle entry and S-phase commitment. Here, we use a variety of approaches to understand the contribution of cyclins D2 and D3 to B cell cycle, including TAT-mediated transduction of cell cycle inhibitors (e.g., p16), into primary ex vivo B cell cultures (A), which disrupts D-type cyclin:cdk4 complexes (B) as well as evaluating mice deficient in cyclins D2 or D3 for proliferative responses (C) and lymphocyte subsets (D) (J. Immunol. 177: 787).
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IV. Mechanisms underlying IL-4 mediated B cell survival
A third project seeks to understand the role of Stat6 in linking IL-4 receptor stimulation to metabolic pathways that promote naïve B cell survival. We make use of several knock out models for IRS-2, p85a subunit of PI-3K, and Stat6 in order to elucidate the signaling pathway that link IL-4 receptors to Stat6-dependent glucose energy metabolism. Our recent findings indicate that survival of naïve B cells by IL-4 requires increased glycolysis and that glycolysis is enhanced via a Stat6-dependent mechanism that increases the expression of genes encoding rate-limiting glycolytic enzymes (J. Immunol. 179: 4953-4957).
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V. Therapeutic strategies to inhibit the growth of human diffuse large B-cell lymphoma cells
The laboratory is interested in identifying therapeutic strategies to inhibit the growth of human diffuse large B-cell lymphoma cells (DLBCLs). We are currently evaluating the mechanisms of action of two small molecules cdk inhibitors, seliciclib and CVT-313, which block cell growth and induce apoptosis in a variety of human DLBCLs, including LY-3, LY-8, and LY-18 (Cell Cycle 6(23): 2982; Biochem. Pharmacol. 72 : 1246).
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VI. Developing novel carbon nanotube structures for the delivery of macromolecules into primary mammalian cell cultures
In an ongoing collaboration with faculty from the Physics Department (Drs. Ren and Kempa), our group has pioneered the use of novel carbon nanotube structures for the delivery of macromolecules into primary mammalian cell cultures. Vertically aligned carbon nanotubes grown by plasma-enhanced chemical vapor deposition (PECVD) (A, B) have ferromagnetic catalyst nickel particles enclosed in their tips. This structure makes the nanotubes respond to magnetic agitation, the momentum of the carbon nanotubes has been used to penetrate cell membranes (C) and thereby shuttling macromolecular cargo immobilized on the carbon nanotube into cells (Nature Methods 2: 449).
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VII. Fabricating molecular nanosensors for detection of cancer biomarkers
A major project ongoing in the laboratory centers on fabricating molecular imprint-based nanosensors using carbon nanotubes (CNTs) for the detection of cancer biomarkers. This project represents an integrated effort with Drs. Cai, Naughton (Physics Department), and Ren (Physics Department).
Molecular Imprint Recognition of Macromolecules e.g. proteins (Nature Nanotech. 5:597:2010).
Figure A shows conformational-dependent imprint recognition of calmodulin; Figure B shows imprint recognition of E7 oncoprotein.
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