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Open Access Publications from the University of California

Scholarly Works (4 results)

  • Thesis
  • Peer Reviewed
UC Davis Electronic Theses and Dissertations (2021)

All living cells are enclosed by biological membranes, comprising of lipid bilayers formed by self-assembly of phospholipids, membrane proteins, cholesterol etc. Membrane active peptides (MAPs) are peptides that interact with the lipid bilayer, perturbing the structure and function of the biological membranes, impacting the function of the living cells. Antimicrobial peptides (AMPs), are a subset of MAPs that interact with pathogenic microbial membranes, disrupting the integrity of the lipid bilayer, using mechanisms such as pore formation, resulting in membrane leakage and cell death. Since MAPs interact directly with cell membranes, they are becoming increasingly important as a possible solution to multi-drug resistant pathogens. Multi-drug resistant fungal infections due to opportunistic and pathogenic fungi are one of the most common infections in the world. Millions of people across the globe are affected by these infections and about 1.5 million people each year succumb to this disease. Amphotericin B and azole drugs such as fluconazole and ketoconazole are common anti-fungal agents that have been used for many years but have a variety of short-term and long-term side effects and have induced widespread resistance in fungi. Therefore, there is dire need for the discovery of novel membrane active peptides with antimicrobial activities, and understanding how they interact with cell membranes. By applying this knowledge, we hope to develop highly selective antifungal membrane active peptides.In this dissertation, we report on the successful use of one-bead one-compound (OBOC) combinatorial library method to discover new MAPs with antifungal properties. To better understand the mechanism of action of these MAPs, we have used various methods to biochemically and biologically characterize these peptides.

    • Article
    • Peer Reviewed
    UC Davis Previously Published Works (2020)
    Membrane active peptides (MAPs) have gained wide interest due to their far reaching applications in drug discovery and drug delivery. The search for new MAPs, however, has been largely skewed with bias selecting for physicochemical parameters believed to be important for membrane activity, such as alpha helicity, cationicity and hydrophobicity. Here we carry out a search-and-find strategy to screen a 100,000-membered one-bead-one-compound (OBOC) combinatorial peptide library for lead compounds, agnostic of those physicochemical constraints. Such a synthetic strategy also permits expansion of our peptide repertoire to include unnatural amino acids. Using this approach, we discovered a structurally unique lead peptide LBF14, a linear 14-mer peptide, that induces gross morphological disruption of membranes, irrespective of membrane composition. Further, we demonstrate that the unique insertion mechanism of the peptide, visualized by spinning disc confocal microscopy and further analyzed by electron paramagnetic resonance measurements, may be the cause of this large scale membrane deformation. We also demonstrate the robustness, reproducibility, and potential application of this technique to discover and characterize new membrane active peptides that display activity by local insertion and subsequent allosteric effects leading to global membrane disruption.
      Cover page: Discovery and mechanistic characterization of a structurally-unique membrane active peptide
      • Article
      • Peer Reviewed
      UC Irvine Previously Published Works (2019)
      Ionizing radiation exposure to the brain is common for patients with a variety of CNS related malignancies. This exposure is known to induce structural and functional alterations to the brain, impacting dendritic complexity, spine density and inflammation. Over time, these changes are associated with cognitive decline. However, many of these impacts are only observable long after irradiation. Extracellular vesicles (EVs) are shed from cells in nearly all known tissues, with roles in many disease pathologies. EVs are becoming an important target for identifying circulating biomarkers. The aim of this study is to identify minimally invasive biomarkers of ionizing radiation damage to the CNS that are predictors of late responses that manifest as persistent cognitive impairments. Using a clinically relevant 9 Gy irradiation paradigm, we exposed mice to cranial (head only) irradiation. Using metabolomic and lipidomic profiling, we analyzed their plasma and plasma-derived EVs two days and two weeks post-exposure to detect systemic signs of damage. We identified significant changes associated with inflammation in EVs. Whole-plasma profiling provided further evidence of systemic injury. These studies are the first to demonstrate that profiling of plasma-derived EVs may be used to study clinically relevant markers of ionizing radiation toxicities to the brain.
        Cover page: Plasma-derived extracellular vesicles yield predictive markers of cranial irradiation exposure in mice
        • Article
        • Peer Reviewed
        UC Irvine Previously Published Works (2021)
        Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy wherein a majority of patients present metastatic disease at diagnosis. Although the role of epithelial to mesenchymal transition (EMT), mediated by transforming growth factor beta (TGFβ), in imparting an aggressive phenotype to PDAC is well documented, the underlying biochemical pathway perturbations driving this behaviour have not been elucidated. We used high-resolution mass spectrometry (HRMS) based molecular phenotyping approach in order to delineate metabolic changes concomitant to TGFβ-induced EMT in pancreatic cancer cells. Strikingly, we observed robust changes in amino acid and energy metabolism that may contribute to tumor invasion and metastasis. Somewhat unexpectedly, TGFβ treatment resulted in an increase in intracellular levels of retinoic acid (RA) that in turn resulted in increased levels of extracellular matrix (ECM) proteins including fibronectin (FN) and collagen (COL1). These findings were further validated in plasma samples obtained from patients with resectable pancreatic cancer. Taken together, these observations provide novel insights into small molecule dysregulation that triggers a molecular cascade resulting in increased EMT-like changes in pancreatic cancer cells, a paradigm that can be potentially targeted for better clinical outcomes.
          Cover page: TGFβ Drives Metabolic Perturbations during Epithelial Mesenchymal Transition in Pancreatic Cancer: TGFβ Induced EMT in PDAC
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