Hafner, M. et al. Inhibition of cytohesins by SecinH3 leads to hepatic insulin resistance. Nature 444, 941-944

LIMES Program Unit Chemical Biology & Medicinal Chemistry, c/o Kekulé Institut für Organische Chemie und Biochemie, University of Bonn, Germany.
Nature (Impact Factor: 41.46). 01/2007; 444(7121):941-4. DOI: 10.1038/nature05415
Source: PubMed


G proteins are an important class of regulatory switches in all living systems. They are activated by guanine nucleotide exchange factors (GEFs), which facilitate the exchange of GDP for GTP. This activity makes GEFs attractive targets for modulating disease-relevant G-protein-controlled signalling networks. GEF inhibitors are therefore of interest as tools for elucidating the function of these proteins and for therapeutic intervention; however, only one small molecule GEF inhibitor, brefeldin A (BFA), is currently available. Here we used an aptamer displacement screen to identify SecinH3, a small molecule antagonist of cytohesins. The cytohesins are a class of BFA-resistant small GEFs for ADP-ribosylation factors (ARFs), which regulate cytoskeletal organization, integrin activation or integrin signalling. The application of SecinH3 in human liver cells showed that insulin-receptor-complex-associated cytohesins are required for insulin signalling. SecinH3-treated mice show increased expression of gluconeogenic genes, reduced expression of glycolytic, fatty acid and ketone body metabolism genes in the liver, reduced liver glycogen stores, and a compensatory increase in plasma insulin. Thus, cytohesin inhibition results in hepatic insulin resistance. Because insulin resistance is among the earliest pathological changes in type 2 diabetes, our results show the potential of chemical biology for dissecting the molecular pathogenesis of this disease.

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Available from: Markus Hafner, Mar 27, 2014
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    • "The depletion of cytohesin 2 has been shown to prevent the activation of ARF6, but not ARF1, during preadipocyte migration, indicating that ARF6 is the substrate for cytohhesin 2 GEF activity [3]. To determine the role of cytohesin 2 and ARF6 in preadipocyte migration, we first studied the effect of various concentrations (6.25–50 mM) of SecinH3, a chemical inhibitor for the ARF6 activation by cytohesins, on 3T3-L1 preadipocyte migration over 24 h [7]. SecinH3 inhibited the migration significantly at 6.25 mM (53.65% AE 3.072 vs. 87.50% "
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    ABSTRACT: Preadipocyte migration is vital for the development of adipose tissue, which plays a crucial role in lipid metabolism. ADP-ribosylation factor 6 (ARF6) small GTPase, which regulates membrane trafficking, is activated by GTP-exchange factors (GEFs) such as cytohesin 2. Cytohesin 2 and ARF6 have previously been implicated in the regulation of 3T3-L1 preadipocyte migration. We investigated here the molecular mechanism underlying the cytohesin 2 and ARF6 mediated regulation of preadipocyte migration. Preadipocyte migration and the activation of ARF6 and ERK1/2 were studied by using a number of approaches, including pharmacological inhibitors, siRNA and the inhibitory peptides. The siRNA mediated down regulation of ARF6 and cytohesin 2 expression confirmed the requirement of both for migration of preadipocytes. Phosphatidylinositol 3-kinase (PI3 K) and PI 4,5-bisphosphate (PIP2) have also found to be essential for the cytohesin 2/ARF6 induced preadipocyte migration. Pharmacological inhibition of the activation of ARF6, ERK1/2 or dynamin led to significant reduction in migration of 3T3-L1 preadipocytes. Furthermore, our study revealed the activation of ARF6 and ERK1/2 during migration of preadipocytes. In the migrating preadipocytes, ARF6 activation was inhibited with SecinH3 (cytohesin inhibitor) and LY294002 (PI3 K inhibitor) whereas the ERK1/2 phosphorylation was inhibited with SecinH3, LY294002, PBP10 (a PIP2 sequester peptide) and PD98059 (MAPKK inhibitor). However, dynosore (dynamin inhibitor) had inhibited neither ARF6 activation nor ERK1/2 phosphorylation during preadipocyte migration. These results together suggest that cytohesin 2 activates ARF6 in a PI3 K dependent manner and then the active ARF6 causes phosphorylation of ERK1/2 during preadipocyte migration.
    Biochemical Pharmacology 10/2014; 92(4). DOI:10.1016/j.bcp.2014.09.023 · 5.01 Impact Factor
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    • "In cells, it is primarily Arf6 that recruits PIP5K to the plasma membrane to generate PtdIns(4,5)P 2 , which, in turn, stimulates plasma membrane ruffling (Honda et al., 1999). Arf proteins are positive activators of the insulin signaling pathway through their activation of PtdIns(4,5)P 2 (Fuss et al., 2006; Hafner et al., 2006; Lim et al., 2010). At the Golgi, Arf1 recruits and stimulates the activity of phosphatidylinositol 4- kinase, forming PtdIns4P, an important regulator of sterol trafficking in cells (Mesmin et al., 2013). "
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    ABSTRACT: The Arf small G proteins regulate protein and lipid trafficking in eukaryotic cells through a regulated cycle of GTP binding and hydrolysis. In their GTP-bound form, Arf proteins recruit a specific set of protein effectors to the membrane surface. These effectors function in vesicle formation and tethering, non-vesicular lipid transport and cytoskeletal regulation. Beyond fundamental membrane trafficking roles, Arf proteins also regulate mitosis, plasma membrane signaling, cilary trafficking and lipid droplet function. Tight spatial and temporal regulation of the relatively small number of Arf proteins is achieved by their guanine nucleotide-exchange factors (GEFs) and GTPase-activating proteins (GAPs), which catalyze GTP binding and hydrolysis, respectively. A unifying function of Arf proteins, performed in conjunction with their regulators and effectors, is sensing, modulating and transporting the lipids that make up cellular membranes. In this Cell Science at a Glance article and the accompanying poster, we discuss the unique features of Arf small G proteins, their functions in vesicular and lipid trafficking in cells, and how these functions are modulated by their regulators, the GEFs and GAPs. We also discuss how these Arf functions are subverted by human pathogens and disease states.
    Journal of Cell Science 08/2014; 127(19). DOI:10.1242/jcs.144899 · 5.43 Impact Factor
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    • "Cytohesin-2 and cytohesin-3 contribute to β1 integrin recycling [7] [8]. Most importantly, cytohesins are supported to be cytoplasmic activators of receptor tyrosine kinase signaling by the epidermal growth factor receptor (EGFR) [9] and insulin receptor (IR), respectively [10] [11]. It is well known that the EGFR and IGFR signaling pathways play pivotal roles in carcinogenesis and cancer progression, especially in HCC [12] [13] [14]. "
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    ABSTRACT: Hepatocellular carcinoma (HCC) is a malignant tumor with high morbidity and mortality, and is characterized by high potential for metastasis and recurrence. The outcome of it is still poor due to lacking of targeted therapeutic strategies. There is an urgent need to find new therapeutic targets for interventions against HCC metastasis and recurrence. In the present study, we found cytohesin-3, a member of the cytohesin family, was upregulated in HCC tissues, and its expression was negatively correlated with the overall survival and relapse-free survival of HCC patients. Further clinicopathological correlation analysis revealed that cytohesin-3 expression was related with tumor size and vascular invasion. And in vitro studies revealed that knock-down of cytohesin-3 suppressed HCC cells proliferation and migration. These results suggest that cytohesin-3 may act as a novel prognostic factor of HCC, and it might also be useful to exploit targeted therapeutic drugs against HCC growth and metastasis.
    International journal of clinical and experimental pathology 06/2014; 7(5):2123-32. · 1.89 Impact Factor
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