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| Subject Categories: Membranes & Transport |
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| The EMBO Journal
(2006) 25, 1590–1602, doi:10.1038/sj.emboj.7601067 Published online 6 April 2006 |
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| GGA function is required for maturation of neuroendocrine secretory granules |
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| Or Kakhlon1, Prabhat Sakya2, Banafshe Larijani2, Rose Watson3 and Sharon A Tooze1 |
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1 Secretory Pathway Laboratories, Cancer Research UK, London Research Institute, London, UK 2 Cell Biophysics, Cancer Research UK, London Research Institute, London, UK 3 Electron Microscopy Laboratories, Cancer Research UK, London Research Institute, London, UK To whom correspondence should be addressed Sharon A Tooze, Secretory Pathway Laboratories, Cancer Research UK, London Research Institute, 44 Lincoln's Inn Fields, London WC2A 3PX, UK. Tel.: +44 207 269 3122; Fax: +44 207 269 3417; E-mail: sharon.tooze@cancer.org.uk Received 6 October 2005; Accepted 8 March 2006; Published online 6 April 2006. |
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| Abstract |
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Secretory granule (SG) maturation has been proposed to involve formation of clathrin-coated vesicles (CCVs) from immature SGs (ISGs). We tested the effect of inhibiting CCV budding by using the clathrin adaptor GGA (Golgi-associated,  -ear-containing, ADP-ribosylation factor-binding protein) on SG maturation in neuroendocrine cells. Overexpression of a truncated, GFP-tagged GGA, VHS (Vps27, Hrs, Stam)-GAT (GGA and target of myb (TOM))-GFP led to retention of MPR, VAMP4, and syntaxin 6 in mature SGs (MSGs), suggesting that CCV budding from ISGs is inhibited by the SG-localizing VHS-GAT-GFP. Furthermore, VHS-GAT-GFP-overexpression disrupts prohormone convertase 2 (PC2) autocatalytic cleavage, processing of secretogranin II to its product p18, and the correlation between PC2 and p18 levels. All these effects were not observed if full-length GGA1-GFP was overexpressed. Neither GGA1-GFP nor VHS-GAT-GFP perturbed SG protein budding from the TGN, or homotypic fusion of ISGs. Reducing GGA3 levels by using short interfering (si)RNA also led to VAMP4 retention in SGs, and inhibition of PC2 activity. Our results suggest that inhibition of CCV budding from ISGs downregulates the sorting from the ISGs and perturbs the intragranular activity of PC2. |
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| Keywords: clathrin-coated vesicles, GGA, granule maturation, secretory granules |
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Top of page MORE ARTICLES LIKE THISThese links to content published by NPG are automatically generated NEWS AND VIEWSSingle-handed recognition of a sorting traffic motif by the GGA proteins Nature Structural Biology News and Views (01 Apr 2002) The long and short of adaptor appendages Nature Structural Biology News and Views (01 Aug 2003) RESEARCHThe EMBO Journal Article (15 Aug 1997) Divalent interaction of the GGAs with the Rabaptin-5?Rabex-5 complex The EMBO Journal Article (02 Jan 2003) |
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