title: Phospholipase D2 mediates signaling by ATPase class I type 8B membrane 1.
abstract: Functional defects in ATPase class I type 8B membrane 1 (ATP8B1 or familial intrahepatic cholestasis 1, FIC1) lead to cholestasis by mechanism(s) that are not fully understood. One proposed pathophysiology involves aberrant signaling to the bile acid sensor, the farnesoid X receptor (FXR), via protein kinase C ζ (PKCζ). The following cell line-based studies investigated whether phospholipase D2 may transduce a signal from FIC1 to FXR. PLD2 gain of function led to activation of the bile salt export pump (BSEP) promoter, a well-characterized FXR response. BSEP activation by PLD2 could be blocked by abrogating either PKCζ or FXR signaling. PLD2 loss of function led to a reduction in BSEP promoter activity. In addition, a variety of proteins that are activated by FXR, including BSEP, were reduced in HepG2 cells treated with PLD2 siRNA. Similar effects were observed in freshly isolated human hepatocytes. Activation of BSEP by FIC1 gain of function was blocked when PLD2 but not PLD1 was silenced. Overexpression of wild-type but not Byler mutant FIC1 led to an increase in membrane associated PLD activity. An intermediate level of activation of PLD activity was induced when a benign recurrent intrahepatic cholestasis FIC1 mutant construct was expressed. These studies show that FIC1 signals to FXR via a signaling pathway including PLD2 and PKCζ.
authors.affiliation: Division of Pediatric Gastroenterology, Hepatology and Nutrition, Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
authors.forename: Frank
authors.initials: F
authors.lastname: Chen
authors.forename: Ayantika
authors.initials: A
authors.lastname: Ghosh
authors.forename: Benjamin L
authors.initials: BL
authors.lastname: Shneider
mesh_terms: D000074020:ATP Binding Cassette Transporter, Subfamily B, Member 11; D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D020868:Gene Silencing; D056945:Hep G2 Cells; D006801:Humans; D010739:Phospholipase D / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011493:Protein Kinase C / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D015398:Signal Transduction; D000099221:Protein Kinase C zeta; D000099150:Receptor, Farnesoid X-Activated
chemical_list: D000074020:ATP Binding Cassette Transporter, Subfamily B, Member 11; D018528:ATP-Binding Cassette Transporters; D000251:Adenosine Triphosphatases; D010739:Phospholipase D; D011493:Protein Kinase C; D018160:Receptors, Cytoplasmic and Nuclear; D000099221:Protein Kinase C zeta; D000099150:Receptor, Farnesoid X-Activated; C093491:ABCB11 protein, human; C105606:phospholipase D2; C111067:ATP8B1 protein, human