Tsc1+ and tsc2+ regulate arginine uptake and metabolism in Schizosaccharomyces pombe.
Mutations in either TSC1 or TSC2 cause tuberous sclerosis complex, an autosomal dominant disorder characterized by seizures, mental retardation, and benign tumors of the skin, brain, heart, and kidneys. Homologs for the TSC1 and TSC2 genes have been identified in mouse, rat, Fugu, Drosophila, and in the yeast Schizosaccharomyces pombe. Here we show that S. pombe lacking tsc1+ or tsc2+ have similar phenotypes including decreased arginine uptake, decreased expression of three amino acid permeases, and low intracellular levels of four members of the arginine biosynthesis pathway. Recently, the small GTPase Rheb was identified as a target of the GTPase-activating domain of tuberin in mammalian cells and in Drosophila. We show that the defect in arginine uptake in cells lacking tsc2+ is rescued by the expression of a dominant negative form of rhb1+, the Rheb homolog in S. pombe, but not by expressing wild-type rhb1+. Expression of the tsc2+ gene with a patient-derived mutation within the GAP domain did not rescue the arginine uptake defect in tsc2+ mutant yeast. Taken together, these findings support a model in which arginine uptake is regulated through tsc1+, tsc2+, and rhb1+ in S. pombe and also suggest a role for the Tsc1 and Tsc2 proteins in amino acid biosynthesis and sensing.
van Slegtenhorst
Marjon
M
Department of Medical Oncology, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111, USA. Marjon.van.Slegtenhorst@fccc.edu
Carr
Erikka
E
Stoyanova
Radka
R
Kruger
Warren D
WD
Henske
Elizabeth Petri
EP
D000595:Amino Acid Sequence; D026905:Amino Acid Transport Systems / Q000096:biosynthesis; D001120:Arginine / Q000493:pharmacokinetics*; D015152:Blotting, Northern; D015153:Blotting, Western; D002172:Canavanine / Q000494:pharmacology; D015536:Down-Regulation; D029721:Drosophila Proteins; D020558:GTP Phosphohydrolases / Q000378:metabolism; D005799:Genes, Dominant; D005838:Genotype; D008969:Molecular Sequence Data; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism; D009154:Mutation; D020125:Mutation, Missense; D009479:Neuropeptides / Q000378:metabolism; D010641:Phenotype; D010957:Plasmids / Q000378:metabolism; D017434:Protein Structure, Tertiary; D000076205:Ras Homolog Enriched in Brain Protein; D012568:Schizosaccharomyces / Q000235:genetics*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics* / Q000502:physiology*; D013997:Time Factors; D015854:Up-Regulation
D026905:Amino Acid Transport Systems; D029721:Drosophila Proteins; D009479:Neuropeptides; D000076205:Ras Homolog Enriched in Brain Protein; C490212:Rheb protein, Drosophila; C490213:Rheb protein, mouse; D029702:Schizosaccharomyces pombe Proteins; C471572:Tsc1 protein, S pombe; C471573:Tsc2 protein, S pombe; D002172:Canavanine; D001120:Arginine; D020558:GTP Phosphohydrolases; D020559:Monomeric GTP-Binding Proteins