title: Cholangiocyte primary cilia are chemosensory organelles that detect biliary nucleotides via P2Y12 purinergic receptors.
abstract: Cholangiocytes, the epithelial cells lining intrahepatic bile ducts, contain primary cilia, which are mechano- and osmosensory organelles detecting changes in bile flow and osmolality and transducing them into intracellular signals. Here, we asked whether cholangiocyte cilia are chemosensory organelles by testing the expression of P2Y purinergic receptors and components of the cAMP signaling cascade in cilia and their involvement in nucleotide-induced cAMP signaling in the cells. We found that P2Y(12) purinergic receptor, adenylyl cyclases (i.e., AC4, AC6, and AC8), and protein kinase A (i.e., PKA RI-beta and PKA RII-alpha regulatory subunits), exchange protein directly activated by cAMP (EPAC) isoform 2, and A-kinase anchoring proteins (i.e., AKAP150) are expressed in cholangiocyte cilia. ADP, an endogenous agonist of P2Y(12) receptors, perfused through the lumen of isolated rat intrahepatic bile ducts or applied to the ciliated apical surface of normal rat cholangiocytes (NRCs) in culture induced a 1.9- and 1.5-fold decrease of forskolin-induced cAMP levels, respectively. In NRCs, the forskolin-induced cAMP increase was also lowered by 1.3-fold in response to ATP-gammaS, a nonhydrolyzed analog of ATP but was not affected by UTP. The ADP-induced changes in cAMP levels in cholangiocytes were abolished by chloral hydrate (a reagent that removes cilia) and by P2Y(12) siRNAs, suggesting that cilia and ciliary P2Y(12) are involved in nucleotide-induced cAMP signaling. In conclusion, cholangiocyte cilia are chemosensory organelles that detect biliary nucleotides through ciliary P2Y(12) receptors and transduce corresponding signals into a cAMP response.
authors.affiliation: Mayo Clinic Coll. of Medicine, Department of Internal Medicine, 200 1st St. SW, Rochester, MN 55905, USA.
authors.forename: Anatoliy I
authors.initials: AI
authors.lastname: Masyuk
authors.forename: Sergio A
authors.initials: SA
authors.lastname: Gradilone
authors.forename: Jesus M
authors.initials: JM
authors.lastname: Banales
authors.forename: Bing Q
authors.initials: BQ
authors.lastname: Huang
authors.forename: Tatyana V
authors.initials: TV
authors.lastname: Masyuk
authors.forename: Seung-Ok
authors.initials: SO
authors.lastname: Lee
authors.forename: Patrick L
authors.initials: PL
authors.lastname: Splinter
authors.forename: Angela J
authors.initials: AJ
authors.lastname: Stroope
authors.forename: Nicholas F
authors.initials: NF
authors.lastname: Larusso
mesh_terms: D054758:A Kinase Anchor Proteins / Q000502:physiology; D000227:Adenine Nucleotides / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000378:metabolism; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D001646:Bile / Q000378:metabolism*; D001653:Bile Ducts, Intrahepatic / Q000648:ultrastructure*; D002923:Cilia / Q000502:physiology*; D000242:Cyclic AMP / Q000502:physiology*; D020662:Guanine Nucleotide Exchange Factors / Q000502:physiology; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D058925:Receptors, Purinergic P2Y12; D015398:Signal Transduction / Q000502:physiology
chemical_list: D054758:A Kinase Anchor Proteins; D000227:Adenine Nucleotides; C415703:Akap5 protein, rat; D020662:Guanine Nucleotide Exchange Factors; C553058:P2ry12 protein, rat; C531571:Rapgef4 protein, rat; D018048:Receptors, Purinergic P2; D058925:Receptors, Purinergic P2Y12; D000244:Adenosine Diphosphate; D000242:Cyclic AMP; D000262:Adenylyl Cyclases