Structural and functional investigation of human chemokines and applications of human chemokines in blocking HIV-1 entry

Chemokines are important mediators of leukocyte migration. Chemokines bind to G protein–coupled receptors (GPCR) and cause conformational changes that trigger intracellular signaling pathways involved in inflammation, injury healing, cancer, metastasis, and HIV infections. No direct structural information about any chemokine receptor is available, but the structure of chemokines has been well studied. Structural studies of chemokines coupled with cell-biological investigations may lead to a better understanding of the mechanisms of chemokine-receptor interactions. In this Ph.D. project, I studied the structural and functional relationship between chemokines and chemokine receptors using NMR, X-ray crystallography, and mutagenesis approaches, coupled with several different cell-biology assays. We found that the conserved “chemokine fold” can support different dimerization types in the chemokines family, although changing the dimers from CC- to CXC-type fold is not readily accomplished. I also used an engineered covalently-bound dimer of the MIP-1β mutant, MIP-1β-A10C, to study the relationship between dimerization of chemokines and their interaction with the CCR5 receptor. My results suggest that MIP-1β dimer neither bind nor activate the CCR5 receptor. I also studied the biophysical properties of one N-terminal awkward mutant of P2-RANTES, which was originally selected by others from a phage display using CCR5-expressing cells. Although the NMR and X-ray crystal studies revealed that the wild type RANTES is a tight homodimer, analytical ultracentrifugation reveals that P2-RANTES is a monomer in solution, the 1.7 Å resolution X-ray crystal structure of P2-RANTES was found to be a packed tetramer. The mutated N-terminal residues play a very important role in the tetramerization in the X-ray crystal structure. Finally I used the HIV-1 env mediated cell-cell fusion assay to study the combination of chemokines or chemokine variants with anti-HIV peptides C37 or/and T-20. A surprisingly synergistic effect was found between P2-RANTES and C37 or T-20. This combination stratagem may lead to further useful drug combinations or drug delivery for more potent anti-HIV treatments

What Does Stock Ownership Breadth Measure?

Using holdings data on a representative sample of all Shanghai Stock Exchange investors, we show that increases in ownership breadth (the fraction of market participants who own a stock) predict low returns: highest change quintile stocks underperform lowest quintile stocks by 23% per year. Small retail investors drive this result. Retail ownership breadth increases appear to be correlated with overpricing. Among institutional investors, however, the opposite holds: Stocks in the top decile of wealth-weighted institutional breadth change outperform the bottom decile by 8% per year, consistent with prior work that interprets breadth as a measure of short-sales constraints.

Protein Modifications as Potential Biomarkers in Breast Cancer

A variety of post-translational protein modifications (PTMs) are known to be altered as a result of cancer development. Thus, these PTMs are potentially useful biomarkers for breast cancer. Mass spectrometry, antibody microarrays and immunohistochemistry techniques have shown promise for identifying changes in PTMs. In this review, we summarize the current literature on PTMs identified in the plasma and tumor tissue of breast-cancer patients or in breast cell lines. We also discuss some of the analytical techniques currently being used to evaluate PTMs

Structural and functional investigation of human chemokines and applications of human chemokines in blocking HIV-1 entry

Chemokines are important mediators of leukocyte migration. Chemokines bind to G protein–coupled receptors (GPCR) and cause conformational changes that trigger intracellular signaling pathways involved in inflammation, injury healing, cancer, metastasis, and HIV infections. No direct structural information about any chemokine receptor is available, but the structure of chemokines has been well studied. Structural studies of chemokines coupled with cell-biological investigations may lead to a better understanding of the mechanisms of chemokine-receptor interactions. In this Ph.D. project, I studied the structural and functional relationship between chemokines and chemokine receptors using NMR, X-ray crystallography, and mutagenesis approaches, coupled with several different cell-biology assays. We found that the conserved “chemokine fold” can support different dimerization types in the chemokines family, although changing the dimers from CC- to CXC-type fold is not readily accomplished. I also used an engineered covalently-bound dimer of the MIP-1β mutant, MIP-1β-A10C, to study the relationship between dimerization of chemokines and their interaction with the CCR5 receptor. My results suggest that MIP-1β dimer neither bind nor activate the CCR5 receptor. I also studied the biophysical properties of one N-terminal awkward mutant of P2-RANTES, which was originally selected by others from a phage display using CCR5-expressing cells. Although the NMR and X-ray crystal studies revealed that the wild type RANTES is a tight homodimer, analytical ultracentrifugation reveals that P2-RANTES is a monomer in solution, the 1.7 Å resolution X-ray crystal structure of P2-RANTES was found to be a packed tetramer. The mutated N-terminal residues play a very important role in the tetramerization in the X-ray crystal structure. Finally I used the HIV-1 env mediated cell-cell fusion assay to study the combination of chemokines or chemokine variants with anti-HIV peptides C37 or/and T-20. A surprisingly synergistic effect was found between P2-RANTES and C37 or T-20. This combination stratagem may lead to further useful drug combinations or drug delivery for more potent anti-HIV treatments

Informed Trading and Expected Returns

Does information asymmetry affect the cross-section of expected stock returns? We explore this question using representative portfolio holdings data from the Shanghai Stock Exchange. We show that institutional investors have a strong information advantage, and that past aggressiveness of institutional trading in a stock positively predicts institutions’ future information advantage in this stock. Sorting stocks on this predictor and controlling for other correlates of expected returns, we find that the top quintile’s average annualized return in the next month is 10.8% higher than the bottom quintile’s, indicating that information asymmetry increases expected returns

Comparison of [11C]TZ1964B and [18F]MNI659 for PET imaging brain PDE10A in nonhuman primates

Phosphodiesterase 10A (PDE10A) inhibitors show therapeutic effects for diseases with striatal pathology. PET radiotracers have been developed to quantify in vivo PDE10A levels and target engagement for therapeutic interventions. The aim of this study was to compare two potent and selective PDE10A radiotracers, [(11)C]TZ1964B and [(18)F]MNI659 in the nonhuman primate (NHP) brain. Double scans in the same cynomolgus monkey on the same day were performed after injection of [(11)C]TZ1964B and [(18)F]MNI659. Specific uptake was determined in two ways: nondisplaceable binding potential (BP(ND)) was calculated using cerebellum as the reference region and the PDE‐10A enriched striatum as the target region of interest (ROI); the area under the time–activity curve (AUC) for the striatum to cerebellum ratio was also calculated. High‐performance liquid chromatography (HPLC) analysis of solvent‐extracted NHP plasma identified the percentage of intact tracer versus radiolabeled metabolites samples post injection of each radiotracer. Both radiotracers showed high specific accumulation in NHP striatum. [(11)C]TZ1964B has higher striatal retention and lower specific striatal uptake than [(18)F]MNI659. The BP(ND) estimates of [(11)C]TZ1964B were 3.72 by Logan Reference model (LoganREF) and 4.39 by simplified reference tissue model (SRTM); the BP(ND) estimates for [(18)F]MNI659 were 5.08 (LoganREF) and 5.33 (SRTM). AUC ratios were 5.87 for [(11)C]TZ1964B and 7.60 for [(18)F]MNI659. Based on BP(ND) values in NHP striatum, coefficients of variation were ~10% for [(11)C]TZ1964B and ~30% for [(18)F]MNI659. Moreover, the metabolism study showed the percentage of parent compounds were ~70% for [(11)C]TZ1964B and ~50% for [(18)F]MNI659 60 min post injection. These data indicate that either [(11)C]TZ1964B or [(18)F]MNI659 could serve as suitable PDE10A PET radiotracers with distinguishing features for particular clinical application

Delivery of MicroRNA-10b with Polylysine Nanoparticles for Inhibition of Breast Cancer Cell Wound Healing

Recent studies revealed that micro RNA-10b (mir-10b) is highly expressed in metastatic breast cancer cells and positively regulates breast cancer cell migration and invasion through inhibition of HOXD10 target synthesis. In this study we designed anti-mir-10b molecules and combined them with poly L-lysine (PLL) to test the delivery effectiveness. An RNA molecule sequence exactly matching the mature mir-10b minor antisense showed strong inhibition when mixed with PLL in a wound-healing assay with human breast cell line MDA-MB-231. The resulting PLL-RNA nanoparticles delivered the anti-microRNA molecules into cytoplasm of breast cancer cells in a concentration-dependent manner that displayed sustainable effectiveness