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Open Access Publications from the University of California

Scholarly Works (109 results)

  • Thesis
  • Peer Reviewed
UC San Diego Electronic Theses and Dissertations (2019)

All cell types express heparan sulfate proteoglycans (HSPGs) where they are embedded into the cell membrane or released into the extracellular matrix. To identify novel membrane bound heparan sulfate binding proteins (HSBPs), we utilized limited proteolysis to liberate ectodomains of cell surface proteins expressed on human umbilical vein endothelial cells. Chromatography over heparin-Sepharose and mass spectrometry yielded several known HSBPs while also isolating the heparin binding domain. Novel endothelial HSPBs were identified including PTPRB, CLEC14A, CLEC2B, CD93, and GDF15. We mapped the heparin-binding domain of CLEC14A by mutagenesis and showed that the binding site resides in the C-type lectin domain. Recombinant CLEC14A ectodomain bound with high affinity heparin oligosaccharides of ≥dp6. Binding occurred in 1:1 stoichiometry and led to increased thermal stability of CLEC14A. Overexpression of membrane bound wild-type CLEC14A or the ectodomain had no effect on in vitro angiogenic sprouting, whereas the CLEC14A heparin binding deficient mutant protein inhibited sprouting. To determine how heparin binding mediates CLEC14A function, we then used chemical cross-linkers to identify CLEC14A endothelial protein binding partners and to test if heparin can alter CLEC14A protein-protein interactions. Mass spectrometry identified over 15 CLEC14A binding partners including MMRN2, ITIH5, NRP1, TXLNA, and EFEMP1. Heparin blocked binding of CLEC14A to MMRN2, but mutation of a key residue in the heparin-binding domain did not interfere with binding. A model is proposed in which heparan sulfate modulates CLEC14A-protein interactions resulting in altered angiogenesis.

  • 4 supplemental ZIPs
Cover page: Proteomic-Based Screening of the Endothelial Heparan-Sulfate Interactome
  • Article
  • Peer Reviewed
UC San Diego Previously Published Works (2014)
Numerous proteins, including cytokines and chemokines, enzymes and enzyme inhibitors, extracellular matrix proteins, and membrane receptors, bind heparin. Although they are traditionally classified as heparin-binding proteins, under normal physiological conditions these proteins actually interact with the heparan sulfate chains of one or more membrane or extracellular proteoglycans. Thus, they are more appropriately classified as heparan sulfate-binding proteins (HSBPs). This review provides an overview of the various modes of interaction between heparan sulfate and HSBPs, emphasizing biochemical and structural insights that improve our understanding of the many biological functions of heparan sulfate.
    Cover page: Demystifying heparan sulfate-protein interactions.
    • Article
    • Peer Reviewed
    UC San Diego Previously Published Works (2016)
    Idiopathic autism spectrum disorders (ASDs) are neurodevelopmental disorders with unknown etiology. An estimated 1:68 children in the U.S. are diagnosed with ASDs, making these disorders a substantial public health issue. Recent advances in genome sequencing have identified numerous genetic variants across the ASD patient population. Many genetic variants identified occur in genes that encode glycosylated extracellular proteins (proteoglycans or glycoproteins) or enzymes involved in glycosylation (glycosyltransferases and sulfotransferases). It remains unknown whether "glycogene" variants cause changes in glycosylation and whether they contribute to the etiology and pathogenesis of ASDs. Insights into glycan susceptibility factors are provided by studies in the normal brain and congenital disorders of glycosylation, which are often accompanied by ASD-like behaviors. The purpose of this review is to present evidence that supports a contribution of extracellular glycans and glycoconjugates to the etiology and pathogenesis of idiopathic ASDs and other types of pervasive neurodevelopmental disorders.
      Cover page: Glycan susceptibility factors in autism spectrum disorders
      • Article
      • Peer Reviewed
      UC San Diego Previously Published Works (2016)
      Idiopathic autism spectrum disorders (ASDs) are neurodevelopmental disorders with unknown etiology. An estimated 1:68 children in the U.S. are diagnosed with ASDs, making these disorders a substantial public health issue. Recent advances in genome sequencing have identified numerous genetic variants across the ASD patient population. Many genetic variants identified occur in genes that encode glycosylated extracellular proteins (proteoglycans or glycoproteins) or enzymes involved in glycosylation (glycosyltransferases and sulfotransferases). It remains unknown whether "glycogene" variants cause changes in glycosylation and whether they contribute to the etiology and pathogenesis of ASDs. Insights into glycan susceptibility factors are provided by studies in the normal brain and congenital disorders of glycosylation, which are often accompanied by ASD-like behaviors. The purpose of this review is to present evidence that supports a contribution of extracellular glycans and glycoconjugates to the etiology and pathogenesis of idiopathic ASDs and other types of pervasive neurodevelopmental disorders.
        • Article
        • Peer Reviewed
        UC San Diego Previously Published Works (2014)
        Numerous proteins, including cytokines and chemokines, enzymes and enzyme inhibitors, extracellular matrix proteins, and membrane receptors, bind heparin. Although they are traditionally classified as heparin-binding proteins, under normal physiological conditions these proteins actually interact with the heparan sulfate chains of one or more membrane or extracellular proteoglycans. Thus, they are more appropriately classified as heparan sulfate-binding proteins (HSBPs). This review provides an overview of the various modes of interaction between heparan sulfate and HSBPs, emphasizing biochemical and structural insights that improve our understanding of the many biological functions of heparan sulfate.
          Cover page: Demystifying Heparan Sulfate–Protein Interactions
          • Article
          • Peer Reviewed
          UC San Diego Previously Published Works (2020)
            • Article
            • Peer Reviewed
            UC San Diego Previously Published Works (2018)
            Heparan sulfate proteoglycans are found at the cell surface and in the extracellular matrix, where they interact with a plethora of proteins involved in lipid homeostasis and inflammation. Over the last decade, new insights have emerged regarding the mechanism and biological significance of these interactions in the context of cardiovascular disease. The majority of cardiovascular disease-related deaths are caused by complications of atherosclerosis, a disease that results in narrowing of the arterial lumen, thereby reducing blood flow to critical levels in vital organs, such as the heart and brain. Here, we discuss novel insights into how heparan sulfate proteoglycans modulate risk factors such as hyperlipidemia and inflammation that drive the initiation and progression of atherosclerotic plaques to their clinical critical endpoint.
              Cover page: The heparan sulfate proteoglycan grip on hyperlipidemia and atherosclerosis
              • Article
              • Peer Reviewed
              UC San Diego Previously Published Works (2015)
              GNeosomes, lysosomotropic lipid vesicles decorated with guanidinoneomycin, can encapsulate and facilitate the cellular internalization and lysosomal delivery of cargo ranging from small molecules to high molecular weight proteins, in a process that is exclusively dependent on cell surface glycosaminoglycans. Their cellular uptake mechanism and co-localization with lysosomes, as well as the delivery, release, and activity of internalized cargo, are quantified. GNeosomes are proposed as a universal platform for lysosomal delivery with potential as a basic research tool and a therapeutic vehicle.
                • Article
                • Peer Reviewed
                UC San Diego Previously Published Works (2014)
                Guanidinium-rich scaffolds facilitate cellular translocation and delivery of bioactive cargos through biological barriers. Although impressive uptake has been demonstrated for nonoligomeric and nonpept(o)idic guanidinylated scaffolds in cell cultures and animal models, the fundamental understanding of these processes is lacking. Charge pairing and hydrogen bonding with cell surface counterparts have been proposed, but their exact role remains putative. The impact of the number and spatial relationships of the guanidinium groups on delivery and organelle/organ localization is yet to be established.
                  • Article
                  • Peer Reviewed
                  UC San Diego Previously Published Works (2015)
                  Macrophages are important mediators of diseases associated with metabolic inflammation such as obesity and atherosclerosis. In this Stimulus we discuss recent findings showing that heparan sulfate proteoglycans on macrophages serve as an important inflammatory rheostat. This observation has significant implications as the degree of macrophage proteoglycan sulfation can determine and possibly predict disease outcomes of metabolic inflammatory disorders.
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