title: A1 adenosine receptor-stimulated exocytosis in bladder umbrella cells requires phosphorylation of ADAM17 Ser-811 and EGF receptor transactivation.
abstract: Despite the importance of ADAM17-dependent cleavage in normal biology and disease, the physiological cues that trigger its activity, the effector pathways that promote its function, and the mechanisms that control its activity, particularly the role of phosphorylation, remain unresolved. Using native bladder epithelium, in some cases transduced with adenoviruses encoding small interfering RNA, we observe that stimulation of apically localized A1 adenosine receptors (A1ARs) triggers a Gi-Gβγ-phospholipase C-protein kinase C (PKC) cascade that promotes ADAM17-dependent HB-EGF cleavage, EGFR transactivation, and apical exocytosis. We further show that the cytoplasmic tail of rat ADAM17 contains a conserved serine residue at position 811, which resides in a canonical PKC phosphorylation site, and is phosphorylated in response to A1AR activation. Preventing this phosphorylation event by expression of a nonphosphorylatable ADAM17(S811A) mutant or expression of a tail-minus construct inhibits A1AR-stimulated, ADAM17-dependent HB-EGF cleavage. Furthermore, expression of ADAM17(S811A) in bladder tissues impairs A1AR-induced apical exocytosis. We conclude that adenosine-stimulated exocytosis requires PKC- and ADAM17-dependent EGFR transactivation and that the function of ADAM17 in this pathway depends on the phosphorylation state of Ser-811 in its cytoplasmic domain.
authors.affiliation: Departments of Medicine and Cell Biology, University of Pittsburgh, Pittsburgh, PA 15261.
authors.forename: H Sandeep
authors.initials: HS
authors.lastname: Prakasam
authors.affiliation: Departments of Medicine and Cell Biology, University of Pittsburgh, Pittsburgh, PA 15261.
authors.forename: Luciana I
authors.initials: LI
authors.lastname: Gallo
authors.affiliation: Departments of Medicine and Cell Biology, University of Pittsburgh, Pittsburgh, PA 15261.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.affiliation: Departments of Medicine and Cell Biology, University of Pittsburgh, Pittsburgh, PA 15261.
authors.forename: Wily G
authors.initials: WG
authors.lastname: Ruiz
authors.affiliation: Departments of Medicine and Cell Biology, University of Pittsburgh, Pittsburgh, PA 15261.
authors.forename: Kenneth R
authors.initials: KR
authors.lastname: Hallows
authors.affiliation: Departments of Medicine and Cell Biology, University of Pittsburgh, Pittsburgh, PA 15261 gla6@pitt.edu.
authors.forename: Gerard
authors.initials: G
authors.lastname: Apodaca
mesh_terms: D051722:ADAM Proteins / Q000235:genetics / Q000378:metabolism*; D000072198:ADAM17 Protein; D000818:Animals; D004847:Epithelial Cells / Q000378:metabolism; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism*; D005089:Exocytosis / Q000235:genetics*; D006801:Humans; D010766:Phosphorylation; D051381:Rats; D043682:Receptor, Adenosine A1 / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation / Q000235:genetics; D001743:Urinary Bladder / Q000166:cytology / Q000378:metabolism
chemical_list: D043682:Receptor, Adenosine A1; D066246:ErbB Receptors; D051722:ADAM Proteins; D000072198:ADAM17 Protein; C000606462:ADAM17 protein, human; C000606464:Adam17 protein, rat