title: Sphingosine-1-phosphate formation activates phosphatidylinositol-4 kinase in basolateral membranes from kidney cells: crosstalk in cell signaling through sphingolipids and phospholipids.
abstract: Sphingosine-1-phosphate (S1P) and phosphatidylinositol-4 phosphate [PtdIns(4)P] are important second messengers in various cellular processes. Here, we show that S1P and PtdIns(4)P are formed in purified basolateral membranes (BLM) derived from kidney proximal tubules, indicating the presence of a plasma membrane associated SPK (BLM-SPK) and phosphatidylinositol-4 kinase (PI-4K). We observed that S1P synthesis is linear with time, dependent on protein concentration, and saturable in the presence of increasing concentrations of sphingosine. Different from the observations on cytosolic SPKs, the formation of S1P by BLM-SPK is Mg(2+)-independent and insensitive to the classical inhibitor of the cytosolic SPKs, DL-threo-dihydrosphingosine. With sphingosine as substrate, the enzyme shows cooperative kinetics (n = 3.4) with a K(0.5) value of 0.12 mM, suggesting that BLM-SPK is different from the previously characterized cytosolic SPK. The formation of PtdIns(4)P markedly inhibits BLM-SPK activity. Conversely, a strong activation of PtdIns(4)P synthesis by the formation of S1P is observed. Taken together, these results indicate that (i) basolateral membranes from kidney cells harbor a SPK activity that potentially regulates renal epithelium function, and (ii) the formation of S1P mediated by SPK enhances PI-4K activity, while PtdIns(4)P in turn inhibits SPK, suggesting an interplay between these lipid signaling molecules. These findings suggest the possibility of crosstalk between sphingolipids and glycerolipids, which might be involved in the regulation of transepithelial fluxes across the BLM of kidney cells.
authors: Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-590, Brazil.
authors: Marcelo
authors: M
authors: Einicker-Lamas
authors: Leandro D
authors: LD
authors: Wenceslau
authors: Robson R
authors: RR
authors: Bernardo
authors: Luciana
authors: L
authors: Nogaroli
authors: Adilson
authors: A
authors: Guilherme
authors: Mecia M
authors: MM
authors: Oliveira
authors: Adalberto
authors: A
authors: Vieyra
mesh_terms: D019870:1-Phosphatidylinositol 4-Kinase / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D002855:Chromatography, Thin Layer; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004492:Edetic Acid; D007668:Kidney / Q000166:cytology* / Q000378:metabolism; D007700:Kinetics; D008246:Lysophospholipids / Q000378:metabolism*; D008274:Magnesium / Q000737:chemistry; D010743:Phospholipids / Q000378:metabolism; D010766:Phosphorylation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction; D013107:Sphingolipids / Q000378:metabolism; D013110:Sphingosine / Q000031:analogs & derivatives / Q000378:metabolism*; D013552:Swine; D013997:Time Factors; D000099157:Sphingosine Kinase
chemical_list: D019870:1-Phosphatidylinositol 4-Kinase; D004492:Edetic Acid; D008246:Lysophospholipids; D008274:Magnesium; D010743:Phospholipids; D017853:Phosphotransferases (Alcohol Group Acceptor); D013107:Sphingolipids; D013110:Sphingosine; D000099157:Sphingosine Kinase; C060506:sphingosine 1-phosphate