Isp7 is a novel regulator of amino acid uptake in the TOR signaling pathway

We show that the sensitivity of tsc mutant cells to rapamycin is mediated by TORC1 and can be suppressed by overexpression of the 2-oxoglutarate-Fe(II) dependent oxygenase, Isp7. We show that Isp7 is a novel regulator of amino acids uptake that acts via regulation of gene expression, both upstream and downstream of TOR signaling. suppressed by overexpression of the putative 2-oxoglutarate-Fe(II) dependent oxygenase, Isp7. We show that Isp7 is a novel master regulator of amino acids uptake that acts via regulation of gene expression, both upstream and downstream of TOR signaling. TOR proteins reside in two distinct complexes, TOR complex 1 and 2 (TORC1 and TORC2) that are central for the regulation of cellular growth, proliferation and survival. TOR is also the target for the immunosuppressive and anti-cancer drug rapamycin. In Schizosaccharaomyces pombe, disruption of the TSC complex, mutations in which can lead to the Tuberous Sclerosis syndrome in humans, results in a rapamycin sensitive phenotype under poor nitrogen conditions. We show here that the sensitivity to rapamycin is mediated via inhibition of TORC1 and suppressed by overexpression of isp7+, a member of the family of 2-oxoglutarate-Fe(II) dependent oxygenases. The transcript level of isp7+ is negatively regulated by TORC1 but positively regulated by TORC2. Yet, we find extensive similarity between the transcriptome of cells disrupted for isp7+ and cells mutated in the catalytic subunit of TORC1. Moreover, Isp7 regulates amino acid permease expression similarly to TORC1 and in contrast to TORC2. Overexpression of isp7+ induces TORC1-dependent phosphorylation of ribosomal protein Rps6, while inhibiting TORC2-dependent phosphorylation and activation of the AGC-like kinase Gad8. Taken together, our findings suggest a central role for Isp7 in amino acid homeostasis and the presence of isp7+-dependent regulatory loops that affect both TORC1 and TORC2. 6 Samples (arrays) were performed. We generated pairwise comparison between DISP7 and WT, using Partek Genomics Suite. Genes with p≤5%[FDR] and a fold-change difference of ≥2\1.5 or <-2\-1.5 were selected.