title: Differential effect of extracellular acidosis on the release and dispersal of soluble and membrane proteins secreted from the Weibel-Palade body.
abstract: Proteins secreted from Weibel-Palade bodies (WPBs) play important roles in regulating inflammatory and hemostatic responses. Inflammation is associated with the extracellular acidification of tissues and blood, conditions that can alter the behavior of secreted proteins. The effect of extracellular pH (pH(o)) on the release of von Willebrand factor (VWF), the VWF-propolypeptide (Proregion), interleukin-8, eotaxin-3, P-selectin, and CD63 from WPBs was investigated using biochemical approaches and by direct optical analysis of individual WPB fusion events in human endothelial cells expressing green or red fluorescent fusions of these different cargo proteins. Between pH(o) 7.4 and 7.0, ionomycin-evoked WPB exocytosis was characterized by the adhesion of VWF to the cell surface and the formation of long filamentous strands. The rapid dispersal of Proregion, interleukin-8, and eotaxin-3 into solution, and of P-selectin and CD63 into the plasma membrane, was unaltered over this pH(o) range. At pH(o) 6.8 or lower, Proregion remained associated with VWF, in many cases WPB failed to collapse fully and VWF failed to form filamentous strands. At pH(o) 6.5 dispersal of interleukin-8, eotaxin-3, and the membrane protein CD63 remained unaltered compared with that at pH(o) 7.4; however, P-selectin dispersal into the plasma membrane was significantly slowed. Thus, extracellular acidification to levels of pH(o) 6.8 or lower significantly alters the behavior of secreted VWF, Proregion, and P-selectin while rapid release of the small pro-inflammatory mediators IL-8 and eotaxin-3 is essentially unaltered. Together, these data suggest that WPB exocytosis during extracellular acidosis may favor the control of inflammatory processes.
authors.affiliation: MRC National Institute for Medical Research, Mill Hill, London NW7 1AA, United Kingdom.
authors.forename: Victor
authors.initials: V
authors.lastname: Babich
authors.forename: Laura
authors.initials: L
authors.lastname: Knipe
authors.forename: Lindsay
authors.initials: L
authors.lastname: Hewlett
authors.forename: Athinoula
authors.initials: A
authors.lastname: Meli
authors.forename: John
authors.initials: J
authors.lastname: Dempster
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Hannah
authors.forename: Tom
authors.initials: T
authors.lastname: Carter
mesh_terms: D015703:Antigens, CD; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D000075906:Chemokine CCL26; D019742:Chemokines, CC / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology / Q000378:metabolism*; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D016209:Interleukin-8 / Q000378:metabolism; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D019007:P-Selectin / Q000378:metabolism; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism; D060149:Tetraspanin 30; D020302:Weibel-Palade Bodies / Q000378:metabolism*; D014841:von Willebrand Factor / Q000378:metabolism
chemical_list: D015703:Antigens, CD; C120429:CCL26 protein, human; C554586:CD63 protein, human; C508606:CXCL8 protein, human; D000075906:Chemokine CCL26; D019742:Chemokines, CC; D016209:Interleukin-8; D007476:Ionophores; D019007:P-Selectin; D010980:Platelet Membrane Glycoproteins; D060149:Tetraspanin 30; D014841:von Willebrand Factor; D015759:Ionomycin