title: PIKfyve in the SGK1 mediated regulation of the creatine transporter SLC6A8.
abstract: The Na(+),Cl(-),creatine transporter CreaT (SLC6A8) mediates concentrative cellular uptake of creatine into a wide variety of cells. Previous observations disclosed that SLC6A8 transport activity is enhanced by mammalian target of rapamycin (mTOR) at least partially through the serum and glucocorticoid inducible kinase isoforms SGK1 and SGK3. As SLC6A8 does not contain a putative SGK consensus motif, the mechanism linking SGK1 with SLC6A8 activity remained elusive. A candidate kinase is the mammalian phosphatidylinositol-3-phosphate-5-kinase PIKfyve (PIP5K3), which has previously been shown to regulate the glucose transporter GLUT4. The present experiments explored the possibility that SLC6A8 is regulated by PIKfyve. In Xenopus oocytes expressing SLC6A8 but not in water injected oocytes creatine induced a current which was significantly enhanced by coexpression of PIKfyve. The effect of PIKfyve on SLC6A8 was blunted by additional coexpression of the inactive mutant of the serum and glucocorticoid inducible kinase (K127N)SGK1. The stimulating effect of PIKfyve was abrogated by replacement of the serine in the SGK consensus sequence by alanine ((S318A)PIKfyve). Moreover, coexpression of ( S318A)PIKfyve blunted the effect of SGK1 on SLC6A8 activity. The observations suggest that SGK1 regulates the creatine transporter SLC6A8 at least partially through phosphorylation and activation of PIKfyve and subsequent formation of PI(3,5)P(2).
authors.affiliation: Department of Physiology I, University of Tubingen, Tubingen (Germany).
authors.forename: Nathalie
authors.initials: N
authors.lastname: Strutz-Seebohm
authors.forename: Manzar
authors.initials: M
authors.lastname: Shojaiefard
authors.forename: David
authors.initials: D
authors.lastname: Christie
authors.forename: Jeremy
authors.initials: J
authors.lastname: Tavare
authors.forename: Guiscard
authors.initials: G
authors.lastname: Seebohm
authors.forename: Florian
authors.initials: F
authors.lastname: Lang
mesh_terms: D019943:Amino Acid Substitution; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002417:Cattle; D016384:Consensus Sequence; D003401:Creatine / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D017874:Immediate-Early Proteins / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008954:Models, Biological; D018716:Molecular Mimicry / Q000187:drug effects; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D009865:Oocytes / Q000187:drug effects / Q000201:enzymology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D014981:Xenopus; D000099184:Serum-Glucocorticoid Regulated Kinases
chemical_list: D003401:Creatine; D017874:Immediate-Early Proteins; D026901:Membrane Transport Proteins; D050505:Mutant Proteins; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D000099184:Serum-Glucocorticoid Regulated Kinases; C080679:creatine transporter