The Tsc/Rheb signaling pathway controls basic amino acid uptake via the Cat1 permease in fission yeast.
The Tsc/Rheb signaling pathway plays critical roles in the control of growth and cell cycle. Studies in fission yeast have also implicated its importance in the regulation of amino acid uptake. Disruption of tsc2+, one of the tsc+ genes, has been shown to result in decreased arginine uptake and resistance to canavanine. A similar effect is also seen with other basic amino acids. We have identified a permease responsible for the uptake of basic amino acids by genetic complementation and disruption. SPAC869.11 (termed Cat1 for cationic amino acid transporter) contains 12 predicted transmembrane domains and its overexpression in wild type fission yeast leads to the increased uptake of basic amino acids and sensitivity to canavanine. Disruption of cat1+ in the deltatsc2 background interfered with the suppression of the canavanine-resistant phenotype of Atsc2 mutants by a dominant negative Rheb. In deltatsc2 mutant strains, the amount of Cat1 was not altered, but instead was mislocalized. This mislocalization was suppressed by the expression of dominant negative Rheb. In addition, we found that the loss of the E3 ubiquitin ligase, Pub1, also restores proper localization. These results provide a crucial link between Tsc/Rheb signaling and the regulation of the basic amino acid permease in fission yeast.
Aspuria
Paul-Joseph
PJ
Department of Microbiology, Immunology and Molecular Genetics, Jonsson Comprehensive Cancer Center, Molecular Biology Institute, University of California, Los Angeles, 1602 Molecular Sciences Building, Los Angeles, CA 90095-1489, USA.
Tamanoi
Fuyuhiko
F
D000595:Amino Acid Sequence; D026905:Amino Acid Transport Systems / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D024361:Amino Acids, Basic / Q000378:metabolism*; D002172:Canavanine / Q000494:pharmacology; D025141:Drug Resistance, Fungal / Q000235:genetics; D015966:Gene Expression Regulation, Fungal; D008954:Models, Biological; D008969:Molecular Sequence Data; D020559:Monomeric GTP-Binding Proteins / Q000502:physiology*; D030781:Organisms, Genetically Modified; D010802:Phylogeny; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology
D026905:Amino Acid Transport Systems; D024361:Amino Acids, Basic; C530694:Cat1 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; C471572:Tsc1 protein, S pombe; C471573:Tsc2 protein, S pombe; D002172:Canavanine; D020559:Monomeric GTP-Binding Proteins; C530693:Rheb protein, S pombe