Publications by authors named "Kathryn P Trogden"

4 Publications

  • Page 1 of 1

Regulation of Glucose-Dependent Golgi-Derived Microtubules by cAMP/EPAC2 Promotes Secretory Vesicle Biogenesis in Pancreatic β Cells.

Curr Biol 2019 07 11;29(14):2339-2350.e5. Epub 2019 Jul 11.

Department of Cell and Developmental Biology, Vanderbilt University, Nashville, TN 37235, USA. Electronic address:

The microtubule (MT) network is an essential regulator of insulin secretion from pancreatic β cells, which is central to blood-sugar homeostasis. We find that when glucose metabolism induces insulin secretion, it also increases formation of Golgi-derived microtubules (GDMTs), notably with the same biphasic kinetics as insulin exocytosis. Furthermore, GDMT nucleation is controlled by a glucose signal-transduction pathway through cAMP and its effector EPAC2. Preventing new GDMT nucleation dramatically affects the pipeline of insulin production, storage, and release. There is an overall reduction of β-cell insulin content, and remaining insulin becomes retained within the Golgi, likely because of stalling of insulin-granule budding. While not preventing glucose-induced insulin exocytosis, the diminished granule availability substantially blunts the amount secreted. Constant dynamic maintenance of the GDMT network is therefore critical for normal β-cell physiology. Our study demonstrates that the biogenesis of post-Golgi carriers, particularly large secretory granules, requires ongoing nucleation and replenishment of the GDMT network.
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http://dx.doi.org/10.1016/j.cub.2019.06.032DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6698911PMC
July 2019

An image-based small-molecule screen identifies vimentin as a pharmacologically relevant target of simvastatin in cancer cells.

FASEB J 2018 05 18;32(5):2841-2854. Epub 2018 Jan 18.

Department of Cell Biology and Physiology, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina, USA.

Vimentin is a cytoskeletal intermediate filament protein that is expressed in mesenchymal cells and cancer cells during the epithelial-mesenchymal transition. The goal of this study was to identify vimentin-targeting small molecules by using the Tocriscreen library of 1120 biochemically active compounds. We monitored vimentin filament reorganization and bundling in adrenal carcinoma SW13 vimentin-positive (SW13-vim) cells via indirect immunofluorescence. The screen identified 18 pharmacologically diverse hits that included 2 statins-simvastatin and mevastatin. Simvastatin induced vimentin reorganization within 15-30 min and significant perinuclear bundling within 60 min (IC = 6.7 nM). Early filament reorganization coincided with increased vimentin solubility. Mevastatin produced similar effects at >1 µM, whereas the structurally related pravastatin and lovastatin did not affect vimentin. In vitro vimentin filament assembly assays revealed a direct targeting mechanism, as determined biochemically and by electron microscopy. In SW13-vim cells, simvastatin, but not pravastatin, reduced total cell numbers (IC = 48.1 nM) and promoted apoptosis after 24 h. In contrast, SW13-vim cell viability was unaffected by simvastatin, unless vimentin was ectopically expressed. Simvastatin similarly targeted vimentin filaments and induced cell death in MDA-MB-231 (vim), but lacked effect in MCF7 (vim) breast cancer cells. In conclusion, this study identified vimentin as a direct molecular target that mediates simvastatin-induced cell death in 2 different cancer cell lines.-Trogden, K. P., Battaglia, R. A., Kabiraj, P., Madden, V. J., Herrmann, H., Snider, N. T. An image-based small-molecule screen identifies vimentin as a pharmacologically relevant target of simvastatin in cancer cells.
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http://dx.doi.org/10.1096/fj.201700663RDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5901388PMC
May 2018

Identifying Regulators of Morphogenesis Common to Vertebrate Neural Tube Closure and Caenorhabditis elegans Gastrulation.

Genetics 2016 Jan 4;202(1):123-39. Epub 2015 Oct 4.

Department of Biology, University of North Carolina at Chapel Hill, North Carolina 27599 Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, North Carolina 27599 Curriculum in Genetics and Molecular Biology, University of North Carolina at Chapel Hill, North Carolina 27599.

Neural tube defects including spina bifida are common and severe congenital disorders. In mice, mutations in more than 200 genes can result in neural tube defects. We hypothesized that this large gene set might include genes whose homologs contribute to morphogenesis in diverse animals. To test this hypothesis, we screened a set of Caenorhabditis elegans homologs for roles in gastrulation, a topologically similar process to vertebrate neural tube closure. Both C. elegans gastrulation and vertebrate neural tube closure involve the internalization of surface cells, requiring tissue-specific gene regulation, actomyosin-driven apical constriction, and establishment and maintenance of adhesions between specific cells. Our screen identified several neural tube defect gene homologs that are required for gastrulation in C. elegans, including the transcription factor sptf-3. Disruption of sptf-3 in C. elegans reduced the expression of early endodermally expressed genes as well as genes expressed in other early cell lineages, establishing sptf-3 as a key contributor to multiple well-studied C. elegans cell fate specification pathways. We also identified members of the actin regulatory WAVE complex (wve-1, gex-2, gex-3, abi-1, and nuo-3a). Disruption of WAVE complex members reduced the narrowing of endodermal cells' apical surfaces. Although WAVE complex members are expressed broadly in C. elegans, we found that expression of a vertebrate WAVE complex member, nckap1, is enriched in the developing neural tube of Xenopus. We show that nckap1 contributes to neural tube closure in Xenopus. This work identifies in vivo roles for homologs of mammalian neural tube defect genes in two manipulable genetic model systems.
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http://dx.doi.org/10.1534/genetics.115.183137DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4701080PMC
January 2016

TOG Proteins Are Spatially Regulated by Rac-GSK3β to Control Interphase Microtubule Dynamics.

PLoS One 2015 25;10(9):e0138966. Epub 2015 Sep 25.

Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, United States of America; Carolina Center for Genome Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, United States of America; Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, 27599, United States of America.

Microtubules are regulated by a diverse set of proteins that localize to microtubule plus ends (+TIPs) where they regulate dynamic instability and mediate interactions with the cell cortex, actin filaments, and organelles. Although individual +TIPs have been studied in depth and we understand their basic contributions to microtubule dynamics, there is a growing body of evidence that these proteins exhibit cross-talk and likely function to collectively integrate microtubule behavior and upstream signaling pathways. In this study, we have identified a novel protein-protein interaction between the XMAP215 homologue in Drosophila, Mini spindles (Msps), and the CLASP homologue, Orbit. These proteins have been shown to promote and suppress microtubule dynamics, respectively. We show that microtubule dynamics are regionally controlled in cells by Rac acting to suppress GSK3β in the peripheral lamellae/lamellipodium. Phosphorylation of Orbit by GSK3β triggers a relocalization of Msps from the microtubule plus end to the lattice. Mutation of the Msps-Orbit binding site revealed that this interaction is required for regulating microtubule dynamic instability in the cell periphery. Based on our findings, we propose that Msps is a novel Rac effector that acts, in partnership with Orbit, to regionally regulate microtubule dynamics.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0138966PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4583408PMC
May 2016