title: Polarized membrane traffic and cell polarity development is dependent on dihydroceramide synthase-regulated sphinganine turnover.
abstract: Sphingoid bases have been implicated in various cellular processes including cell growth, apoptosis and cell differentiation. Here, we show that the regulated turnover of sphingoid bases is crucial for cell polarity development, i.e., the biogenesis of apical plasma membrane domains, in well-differentiated hepatic cells. Thus, inhibition of dihydroceramide synthase or sphinganine kinase activity with fumonisin B1 or N,N-dimethylsphingosine, respectively, dramatically perturbs cell polarity development, which is due to increased levels of sphinganine. Consistently, reduction of free sphinganine levels stimulates cell polarity development. Moreover, dihydroceramide synthase, the predominant enzyme responsible for sphinganine turnover, is a target for cell polarity stimulating cAMP/protein kinase A (PKA) signaling cascades. Indeed, electrospray ionization tandem mass spectrometry analyses revealed a significant reduction in sphinganine levels in cAMP/PKA-stimulated cells. These data suggest that sphinganine turnover is critical for and is actively regulated during HepG2 cell polarity development. Previously, we have identified an apical plasma membrane-directed trafficking pathway from the subapical compartment. This transport pathway, which is part of the basolateral-to-apical transcytotic itinerary, plays a crucial role in apical plasma membrane biogenesis. Here, we show that, as a part of the underlying mechanism, the inhibition of dihydroceramide synthase activity and ensuing increased sphinganine levels specifically perturb the activation of this particular pathway in the de novo apical membrane biogenesis.
authors.affiliation: Department of Cell Biology/Section Membrane Cell Biology, University of Groningen, 9713-AV Groningen, The Netherlands. s.c.d.van.ijzendoorn@med.rug.nl
authors.forename: Sven C D
authors.initials: SC
authors.lastname: Van IJzendoorn
authors.forename: Johanna M
authors.initials: JM
authors.lastname: Van Der Wouden
authors.forename: Gerhard
authors.initials: G
authors.lastname: Liebisch
authors.forename: Gerd
authors.initials: G
authors.lastname: Schmitz
authors.forename: Dick
authors.initials: D
authors.lastname: Hoekstra
mesh_terms: D001693:Biological Transport, Active; D002451:Cell Compartmentation; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D016764:Cell Polarity / Q000502:physiology*; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D037341:Fumonisins / Q000494:pharmacology; D006801:Humans; D008954:Models, Biological; D010088:Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D037341:Fumonisins; C056933:fumonisin B1; D000242:Cyclic AMP; D010088:Oxidoreductases; C473786:dihydroceramide synthase; D017853:Phosphotransferases (Alcohol Group Acceptor); C022647:sphinganine kinase; D017868:Cyclic AMP-Dependent Protein Kinases; C061800:N,N-dimethylsphingosine; D013110:Sphingosine; C005682:safingol