title: Roles of major facilitator superfamily transporters in phosphate response in Drosophila.
abstract: The major facilitator superfamily (MFS) transporter Pho84 and the type III transporter Pho89 are responsible for metabolic effects of inorganic phosphate in yeast. While the Pho89 ortholog Pit1 was also shown to be involved in phosphate-activated MAPK in mammalian cells, it is currently unknown, whether orthologs of Pho84 have a role in phosphate-sensing in metazoan species. We show here that the activation of MAPK by phosphate observed in mammals is conserved in Drosophila cells, and used this assay to characterize the roles of putative phosphate transporters. Surprisingly, while we found that RNAi-mediated knockdown of the fly Pho89 ortholog dPit had little effect on the activation of MAPK in Drosophila S2R+ cells by phosphate, two Pho84/SLC17A1-9 MFS orthologs (MFS10 and MFS13) specifically inhibited this response. Further, using a Xenopus oocyte assay, we show that MSF13 mediates uptake of [(33)P]-orthophosphate in a sodium-dependent fashion. Consistent with a role in phosphate physiology, MSF13 is expressed highest in the Drosophila crop, midgut, Malpighian tubule, and hindgut. Altogether, our findings provide the first evidence that Pho84 orthologs mediate cellular effects of phosphate in metazoan cells. Finally, while phosphate is essential for Drosophila larval development, loss of MFS13 activity is compatible with viability indicating redundancy at the levels of the transporters.
authors.affiliation: Endocrine Unit, Massachusetts General Hospital, Boston, Massachusetts, United States of America. cbergwitz@partners.org
authors.forename: Clemens
authors.initials: C
authors.lastname: Bergwitz
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Rasmussen
authors.forename: Charles
authors.initials: C
authors.lastname: DeRobertis
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Wee
authors.forename: Sumi
authors.initials: S
authors.lastname: Sinha
authors.forename: Hway H
authors.initials: HH
authors.lastname: Chen
authors.forename: Joanne
authors.initials: J
authors.lastname: Huang
authors.forename: Norbert
authors.initials: N
authors.lastname: Perrimon
mesh_terms: D000818:Animals; D029721:Drosophila Proteins / Q000378:metabolism / Q000502:physiology*; D004331:Drosophila melanogaster / Q000235:genetics / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism*; D028081:Proton-Phosphate Symporters / Q000378:metabolism / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins; D050611:Sodium-Phosphate Cotransporter Proteins, Type III / Q000378:metabolism / Q000502:physiology*; D014018:Tissue Distribution
chemical_list: D029721:Drosophila Proteins; C105495:PHO84 protein, S cerevisiae; C493567:PHO89 protein, S cerevisiae; D010710:Phosphates; D028081:Proton-Phosphate Symporters; D029701:Saccharomyces cerevisiae Proteins; D050611:Sodium-Phosphate Cotransporter Proteins, Type III; D020928:Mitogen-Activated Protein Kinases