title: Aftiphilin and gamma-synergin are required for secretagogue sensitivity of Weibel-Palade bodies in endothelial cells.
abstract: Formation of secretory organelles requires the coupling of cargo selection to targeting into the correct exocytic pathway. Although the assembly of regulated secretory granules is driven in part by selective aggregation and retention of content, we recently reported that adaptor protein-1 (AP-1) recruitment of clathrin is essential to the initial formation of Weibel-Palade bodies (WPBs) at the trans-Golgi network. A selective co-aggregation process might include recruitment of components required for targeting to the regulated secretory pathway. However, we find that acquisition of the regulated secretory phenotype by WPBs in endothelial cells is coupled to but can be separated from formation of the distinctive granule core by ablation of the AP-1 effectors aftiphilin and gamma-synergin. Their depletion by small interfering RNA leads to WPBs that fail to respond to secretagogue and release their content in an unregulated manner. We find that these non-responsive WPBs have density, markers of maturation, and highly multimerized von Willebrand factor similar to those of wild-type granules. Thus, by also recruiting aftiphilin/gamma-synergin in addition to clathrin, AP-1 coordinates formation of WPBs with their acquisition of a regulated secretory phenotype.
authors.affiliation: MRC Laboratory of Molecular Cell Biology, Cell Biology Unit and Department of Cell and Developmental Biology, University College London, London WC1E 6BT, United Kingdom.
authors.forename: Winnie W Y
authors.initials: WW
authors.lastname: Lui-Roberts
authors.forename: Francesco
authors.initials: F
authors.lastname: Ferraro
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Nightingale
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Cutler
mesh_terms: D033961:Adaptor Protein Complex 1 / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002966:Clathrin / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D005089:Exocytosis / Q000502:physiology; D005260:Female; D006801:Humans; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D011247:Pregnancy; D011487:Protein Conformation; D034622:RNA Interference; D055571:Secretory Pathway / Q000502:physiology*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D020302:Weibel-Palade Bodies / Q000378:metabolism*; D014841:von Willebrand Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: C538998:AFTPH protein, human; D033961:Adaptor Protein Complex 1; D015415:Biomarkers; D002352:Carrier Proteins; D002966:Clathrin; D009419:Nerve Tissue Proteins; C121510:SYNRG protein, human; D018808:Transcription Factor AP-1; D014841:von Willebrand Factor