title: Ceramide is a potent activator of plasma membrane Ca2+-ATPase from kidney-promixal tubule cells with protein kinase A as an intermediate.
abstract: The kidney-proximal tubules are involved in reabsorbing two-thirds of the glomerular ultrafiltrate, a key Ca(2+)-modulated process that is essential for maintaining homeostasis in body fluid compartments. The basolateral membranes of these cells have a Ca(2+)-ATPase, which is thought to be responsible for the fine regulation of intracellular Ca(2+) levels. In this paper we show that nanomolar concentrations of ceramide (Cer(50) = 3.5 nm), a natural product derived from sphingomyelinase activity in biological membranes, promotes a 50% increase of Ca(2+)-ATPase activity in purified basolateral membranes. The stimulatory effect of ceramide occurs through specific and direct (cAMP-independent) activation of a protein kinase A (blocked by 10 nm of the specific inhibitor of protein kinase A (PKA), the 5-22 peptide). The activation of PKA by ceramide results in phosphorylation of the Ca(2+)-ATPase, as detected by an anti-Ser/Thr specific PKA substrate antibody. It is observed a straight correlation between increase of Ca(2+)-ATPase activity and PKA-mediated phosphorylation of the Ca(2+) pump molecule. Ceramide also stimulates phosphorylation of renal Ca(2+)-ATPase via protein kinase C, but stimulation of this pathway, which inhibits the Ca(2+) pump in kidney cells, is counteracted by the ceramide-triggered PKA-mediated phosphorylation. The potent effect of ceramide reveals a new physiological activator of the plasma membrane Ca(2+)-ATPase, which integrates the regulatory network of glycerolipids and sphingolipids present in the basolateral membranes of kidney cells.
authors.affiliation: Laboratório de Físico-Química Biológica Aída Hassón-Voloch, Universidade Federal do Rio de Janeiro, 21949-900, Rio de Janeiro, Brazil.
authors.forename: Lindsey M P
authors.initials: LM
authors.lastname: Cabral
authors.forename: Mira
authors.initials: M
authors.lastname: Wengert
authors.forename: Alexandre A A
authors.initials: AA
authors.lastname: da Ressurreição
authors.forename: Pedro H P
authors.initials: PH
authors.lastname: Feres-Elias
authors.forename: Fernando G
authors.initials: FG
authors.lastname: Almeida
authors.forename: Adalberto
authors.initials: A
authors.lastname: Vieyra
authors.forename: Celso
authors.initials: C
authors.lastname: Caruso-Neves
authors.forename: Marcelo
authors.initials: M
authors.lastname: Einicker-Lamas
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D002518:Ceramides / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D007668:Kidney / Q000378:metabolism; D007684:Kidney Tubules / Q000378:metabolism*; D021962:Membrane Microdomains / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D013107:Sphingolipids / Q000378:metabolism; D013552:Swine
chemical_list: D002518:Ceramides; D013107:Sphingolipids; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D002118:Calcium