4.Cells sense internal amino acid levels to couple their metabolic state with their gene expres-sion programs. One key regulatory switch that amino acid levels control is expression of the genesrequired for ribosome biogenesis – all the proteins and RNA molecules that required to generate thesmall and large ribosomal subunits. Ribosome biogenesis is one of the most resource-intensive pro-cesses in proliferating cells. In order to couple ri-bosome biogenesis – which entails high level syn-thesis of hundreds of proteins – with the availabil-ity of amino acid precursors required to makethose proteins, cells evolved a signaling networkthat converges on a key protein complex in thecell known as MTOR complex 1 (MTORC1). Thenet result of the signaling network shown in thediagram is that mTORC1 is ultimately activatedby the presence of leucine and arginine in the cell(the blunt arrows represent inhibitory interactions;the details are not important here). WhenMTORC1 is active, cells induce the gene expres-sion program required for ribosome biogenesis.arginineleucineCASTORISestrin2GATOR2GATOR1TSCcomplexKICSTORRagARagu-MTORC1V-ATPase latorRagCRhebSLC38A9(a) MTORC1 is specifically activated by arginine.Describe the synthesis of arginine including pre-cursors, key intermediates and other metabolicpathways we have learned about.lysosomeaminoarginineacidsWolfson and Sabatini, 2017, Cell Metabolism (b) In addition to arginine, mTORC1 also senses leucine. Monitoring leucine and arginine levels pro-vides mTORC1 with key information about different classes of amino acids as well as two other keymetabolic processes in addition to amino acid synthesis. What are the two classes of amino acids, andwhy might it be advantageous for mTORC1 to receive information about both of these classes? Whatare the other two processes and how does mTORC1 indirectly sense them?(c) Given its role in regulating ribosome biogenesis, propose a speculative argument for why it mightbe useful for mTORC1 to specifically sense arginine rather than other amino acids.

Name: 4.Cells sense internal amino acid levels to couple their metabolic st
Uploaded: 2024-03-20T06:42:41.000Z
Channel: Bartleby
Description: 4.Cells sense internal amino acid levels to couple their metabolic state with their gene expres-sion programs. One key regulatory switch that amino acid levels control is expression of the genesrequired for ribosome biogenesis – all the proteins and