Glutamine Produces Ammonium to Tune Lysosomal pH and Regulate Lysosomal Function
Glutamine is one of the most abundant amino acids in the cell. In mitochondria, glutaminases 1 and 2 (GLS1/2) hydrolyze glutamine to glutamate, which serves as the precursor of multiple metabolites. Here, we show that ammonium generated during GLS1/2-mediated glutaminolysis regulates lysosomal pH an...
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MDPI AG
2022-12-01
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| author | Jian Xiong Thi Thu Trang Luu Kartik Venkatachalam Guangwei Du Michael X. Zhu |
| author_facet | Jian Xiong Thi Thu Trang Luu Kartik Venkatachalam Guangwei Du Michael X. Zhu |
| author_sort | Jian Xiong |
| collection | DOAJ |
| description | Glutamine is one of the most abundant amino acids in the cell. In mitochondria, glutaminases 1 and 2 (GLS1/2) hydrolyze glutamine to glutamate, which serves as the precursor of multiple metabolites. Here, we show that ammonium generated during GLS1/2-mediated glutaminolysis regulates lysosomal pH and in turn lysosomal degradation. In primary human skin fibroblasts BJ cells and mouse embryonic fibroblasts, deprivation of total amino acids for 1 h increased lysosomal degradation capacity as shown by the increased turnover of lipidated microtubule-associated proteins 1A/1B light chain 3B (LC3-II), several autophagic receptors, and endocytosed DQ-BSA. Removal of glutamine but not any other amino acids from the culture medium enhanced lysosomal degradation similarly as total amino acid starvation. The presence of glutamine in regular culture media increased lysosomal pH by >0.5 pH unit and the removal of glutamine caused lysosomal acidification. GLS1/2 knockdown, GLS1 antagonist, or ammonium scavengers reduced lysosomal pH in the presence of glutamine. The addition of glutamine or NH<sub>4</sub>Cl prevented the increase in lysosomal degradation and curtailed the extension of mTORC1 function during the early time period of amino acid starvation. Our findings suggest that glutamine tunes lysosomal pH by producing ammonium, which regulates lysosomal degradation to meet the demands of cellular activities. During the early stage of amino acid starvation, the glutamine-dependent mechanism allows more efficient use of internal reserves and endocytosed proteins to extend mTORC1 activation such that the normal anabolism is not easily interrupted by a brief disruption of the amino acid supply. |
| first_indexed | 2024-03-11T10:05:40Z |
| format | Article |
| id | doaj.art-332d5943ca8a4db08de149661647448f |
| institution | Directory Open Access Journal |
| issn | 2073-4409 |
| language | English |
| last_indexed | 2024-03-11T10:05:40Z |
| publishDate | 2022-12-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Cells |
| spelling | doaj.art-332d5943ca8a4db08de149661647448f2023-11-16T15:05:47ZengMDPI AGCells2073-44092022-12-011218010.3390/cells12010080Glutamine Produces Ammonium to Tune Lysosomal pH and Regulate Lysosomal FunctionJian Xiong0Thi Thu Trang Luu1Kartik Venkatachalam2Guangwei Du3Michael X. Zhu4Department of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030, USADepartment of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030, USADepartment of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030, USADepartment of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030, USADepartment of Integrative Biology and Pharmacology, McGovern Medical School, The University of Texas Health Science Center at Houston, Houston, TX 77030, USAGlutamine is one of the most abundant amino acids in the cell. In mitochondria, glutaminases 1 and 2 (GLS1/2) hydrolyze glutamine to glutamate, which serves as the precursor of multiple metabolites. Here, we show that ammonium generated during GLS1/2-mediated glutaminolysis regulates lysosomal pH and in turn lysosomal degradation. In primary human skin fibroblasts BJ cells and mouse embryonic fibroblasts, deprivation of total amino acids for 1 h increased lysosomal degradation capacity as shown by the increased turnover of lipidated microtubule-associated proteins 1A/1B light chain 3B (LC3-II), several autophagic receptors, and endocytosed DQ-BSA. Removal of glutamine but not any other amino acids from the culture medium enhanced lysosomal degradation similarly as total amino acid starvation. The presence of glutamine in regular culture media increased lysosomal pH by >0.5 pH unit and the removal of glutamine caused lysosomal acidification. GLS1/2 knockdown, GLS1 antagonist, or ammonium scavengers reduced lysosomal pH in the presence of glutamine. The addition of glutamine or NH<sub>4</sub>Cl prevented the increase in lysosomal degradation and curtailed the extension of mTORC1 function during the early time period of amino acid starvation. Our findings suggest that glutamine tunes lysosomal pH by producing ammonium, which regulates lysosomal degradation to meet the demands of cellular activities. During the early stage of amino acid starvation, the glutamine-dependent mechanism allows more efficient use of internal reserves and endocytosed proteins to extend mTORC1 activation such that the normal anabolism is not easily interrupted by a brief disruption of the amino acid supply.https://www.mdpi.com/2073-4409/12/1/80amino acid starvationautophagyautophagosomeglutaminaseglutaminelysosomal pH |
| spellingShingle | Jian Xiong Thi Thu Trang Luu Kartik Venkatachalam Guangwei Du Michael X. Zhu Glutamine Produces Ammonium to Tune Lysosomal pH and Regulate Lysosomal Function Cells amino acid starvation autophagy autophagosome glutaminase glutamine lysosomal pH |
| title | Glutamine Produces Ammonium to Tune Lysosomal pH and Regulate Lysosomal Function |
| title_full | Glutamine Produces Ammonium to Tune Lysosomal pH and Regulate Lysosomal Function |
| title_fullStr | Glutamine Produces Ammonium to Tune Lysosomal pH and Regulate Lysosomal Function |
| title_full_unstemmed | Glutamine Produces Ammonium to Tune Lysosomal pH and Regulate Lysosomal Function |
| title_short | Glutamine Produces Ammonium to Tune Lysosomal pH and Regulate Lysosomal Function |
| title_sort | glutamine produces ammonium to tune lysosomal ph and regulate lysosomal function |
| topic | amino acid starvation autophagy autophagosome glutaminase glutamine lysosomal pH |
| url | https://www.mdpi.com/2073-4409/12/1/80 |
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