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Kim, Wookhyun

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Kim

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Wookhyun

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Kim, Wookhyun

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2011 - 20162

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Author's Publications: search.filters.isAuthorOfPublication.bb72401b-d7a9-443a-80c9-72a40faa84b1

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    In situ regeneration of bioactive coatings enabled by an evolved Staphylococcus aureus sortase A
    (Nature Publishing Group, 2016) Ham, Hyun Ok; Qu, Zheng; Haller, Carolyn; Dorr, Brent M.; Dai, Erbin; Kim, Wookhyun; Liu, David; Chaikof, Elliot
    Surface immobilization of bioactive molecules is a central paradigm in the design of implantable devices and biosensors with improved clinical performance capabilities. However, in vivo degradation or denaturation of surface constituents often limits the long-term performance of bioactive films. Here we demonstrate the capacity to repeatedly regenerate a covalently immobilized monomolecular thin film of bioactive molecules through a two-step stripping and recharging cycle. Reversible transpeptidation by a laboratory evolved Staphylococcus aureus sortase A (eSrtA) enabled the rapid immobilization of an anti-thrombogenic film in the presence of whole blood and permitted multiple cycles of film regeneration in vitro that preserved its biological activity. Moreover, eSrtA transpeptidation facilitated surface re-engineering of medical devices in situ after in vivo implantation through removal and restoration film constituents. These studies establish a rapid, orthogonal and reversible biochemical scheme to regenerate selective molecular constituents with the potential to extend the lifetime of bioactive films.
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    Cannabinoids Inhibit Insulin Receptor Signaling in Pancreatic \(\beta\)-Cells
    (American Diabetes Association, 2011) Doyle, Máire E.; Liu, Zhuo; Lao, Qizong; Shin, Yu-Kyong; Carlson, Olga D.; Thomas, Sam; Napora, Joshua K.; Moaddel, Ruin; Maudsley, Stuart; Martin, Bronwen; Egan, Josephine M.; Kim, Wookhyun; Kim, Hee Seung; Lee, Eun-Kyung; Wang, Yan; Kulkarni, Rohit
    Objective: Optimal glucose homeostasis requires exquisitely precise adaptation of the number of insulin-secreting \(\beta\)-cells in the islets of Langerhans. Insulin itself positively regulates \(\beta\)-cell proliferation in an autocrine manner through the insulin receptor (IR) signaling pathway. It is now coming to light that cannabinoid 1 receptor (CB1R) agonism/antagonism influences insulin action in insulin-sensitive tissues. However, the cells on which the CB1Rs are expressed and their function in islets have not been firmly established. We undertook the current study to investigate if intraislet endogenous cannabinoids (ECs) regulate \(\beta\)-cell proliferation and if they influence insulin action. Research Design and Methods: We measured EC production in isolated human and mouse islets and \(\beta\)-cell line in response to glucose and KCl. We evaluated human and mouse islets, several \(\beta\)-cell lines, and CB1R-null (CB1R\(^{−/−}\)) mice for the presence of a fully functioning EC system. We investigated if ECs influence \(\beta\)-cell physiology through regulating insulin action and demonstrated the therapeutic potential of manipulation of the EC system in diabetic (db/db) mice. Results: ECs are generated within \(\beta\)-cells, which also express CB1Rs that are fully functioning when activated by ligands. Genetic and pharmacologic blockade of CB1R results in enhanced IR signaling through the insulin receptor substrate 2-AKT pathway in \(\beta\)-cells and leads to increased \(\beta\)-cell proliferation and mass. CB1R antagonism in db/db mice results in reduced blood glucose and increased \(\beta\)-cell proliferation and mass, coupled with enhanced IR signaling in \(\beta\)-cells. Furthermore, CB1R activation impedes insulin-stimulated IR autophosphorylation on \(\beta\)-cells in a G\(\alpha_i\)-dependent manner. Conclusions: These findings provide direct evidence for a functional interaction between CB1R and IR signaling involved in the regulation of \(\beta\)-cell proliferation and will serve as a basis for developing new therapeutic interventions to enhance \(\beta\)-cell function and proliferation in diabetes.