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Open Access Publications from the University of California

Scholarly Works (3 results)

  • Thesis
  • Peer Reviewed
UC San Francisco Electronic Theses and Dissertations (2012)

This dissertation examines the role of ubiquitination in regulating the endocytic trafficking of opioid receptors, members of the large superfamily of seven-transmembrane receptors (7TMRs). The introduction provides a basic overview of 7TMR biology and diversity, examines the role of endocytic trafficking in modulating receptor-mediated signal strength and duration, presents current models for protein sorting in the endocytic pathway, and investigates various functions of ubiquitin in regulating trafficking decisions. The second and third chapters explore the role of ubiquitin in controlling the destruction of δ-opioid receptors after their sorting to lysosomes. In chapter four, a new function of ubiquitin is identified that allows μ-opioid receptors to control the dynamics of receptor-containing clathrin-coated pits and ultimately, their own endocytosis. The fifth chapter presents findings for an additional role of μ-opioid receptor ubiquitination later in the endocytic pathway, modulating receptor destruction after lysosomal sorting, that provides further support for models developed through study of the δ-opioid receptor. The included work used a combination of live-cell imaging, flow cytometric analysis, biochemistry, and genetic manipulations to address the role of ubiquitin in opioid receptor trafficking. Two additional studies that I contributed to during my graduate career, one published (Yudowski et al., 2009) and one under preparation, were excluded as they were beyond the main focus of this dissertation.

    Cover page: Elucidating the role of ubiquitin in controlling the endocytic trafficking of opioid receptors
    • Article
    • Peer Reviewed
    UCLA Previously Published Works (2024)
    LRRK2 polymorphisms (G2019S/N2081D) that increase susceptibility to Parkinsons disease and Crohns disease (CD) lead to LRRK2 kinase hyperactivity and suppress autophagy. This connection suggests that LRRK2 kinase inhibition, a therapeutic strategy being explored for Parkinsons disease, may also benefit patients with CD. Paneth cell homeostasis is tightly regulated by autophagy, and their dysfunction is a precursor to gut inflammation in CD. Here, we found that patients with CD and mice carrying hyperactive LRRK2 polymorphisms developed Paneth cell dysfunction. We also found that LRRK2 kinase can be activated in the context of interactions between genes (genetic autophagy deficiency) and the environment (cigarette smoking). Unexpectedly, lamina propria immune cells were the main intestinal cell types that express LRRK2, instead of Paneth cells as previously suggested. We showed that LRRK2-mediated pro-inflammatory cytokine release from phagocytes impaired Paneth cell function, which was rescued by LRRK2 kinase inhibition through activation of autophagy. Together, these data suggest that LRRK2 kinase inhibitors maintain Paneth cell homeostasis by restoring autophagy and may represent a therapeutic strategy for CD.
      Cover page: Macrophage LRRK2 hyperactivity impairs autophagy and induces Paneth cell dysfunction.
      • Article
      • Peer Reviewed
      UC San Francisco Previously Published Works (2021)
      GRN mutations cause frontotemporal dementia (GRN-FTD) due to deficiency in progranulin (PGRN), a lysosomal and secreted protein with unclear function. Here, we found that Grn-/- mice exhibit a global deficiency in bis(monoacylglycero)phosphate (BMP), an endolysosomal phospholipid we identified as a pH-dependent PGRN interactor as well as a redox-sensitive enhancer of lysosomal proteolysis and lipolysis. Grn-/- brains also showed an age-dependent, secondary storage of glucocerebrosidase substrate glucosylsphingosine. We investigated a protein replacement strategy by engineering protein transport vehicle (PTV):PGRN-a recombinant protein linking PGRN to a modified Fc domain that binds human transferrin receptor for enhanced CNS biodistribution. PTV:PGRN rescued various Grn-/- phenotypes in primary murine macrophages and human iPSC-derived microglia, including oxidative stress, lysosomal dysfunction, and endomembrane damage. Peripherally delivered PTV:PGRN corrected levels of BMP, glucosylsphingosine, and disease pathology in Grn-/- CNS, including microgliosis, lipofuscinosis, and neuronal damage. PTV:PGRN thus represents a potential biotherapeutic for GRN-FTD.
        Cover page: Rescue of a lysosomal storage disorder caused by Grn loss of function with a brain penetrant progranulin biologic
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