PT - JOURNAL ARTICLE AU - Marta Wróbel AU - Jarosław Cendrowski AU - Ewelina Szymańska AU - Malwina Grębowicz-Maciukiewicz AU - Noga Budick-Harmelin AU - Matylda Macias AU - Aleksandra Szybińska AU - Michał Mazur AU - Krzysztof Kolmus AU - Krzysztof Goryca AU - Michalina Dąbrowska AU - Agnieszka Paziewska AU - Michał Mikula AU - Marta Miączyńska TI - ESCRT-I fuels lysosomal degradation to restrict TFEB/TFE3 signaling via the Rag-mTORC1 pathway AID - 10.26508/lsa.202101239 DP - 2022 Jul 01 TA - Life Science Alliance PG - e202101239 VI - 5 IP - 7 4099 - https://www.life-science-alliance.org/content/5/7/e202101239.short 4100 - https://www.life-science-alliance.org/content/5/7/e202101239.full SO - Life Sci. Alliance2022 Jul 01; 5 AB - Within the endolysosomal pathway in mammalian cells, ESCRT complexes facilitate degradation of proteins residing in endosomal membranes. Here, we show that mammalian ESCRT-I restricts the size of lysosomes and promotes degradation of proteins from lysosomal membranes, including MCOLN1, a Ca2+ channel protein. The altered lysosome morphology upon ESCRT-I depletion coincided with elevated expression of genes annotated to biogenesis of lysosomes due to prolonged activation of TFEB/TFE3 transcription factors. Lack of ESCRT-I also induced transcription of cholesterol biosynthesis genes, in response to inefficient delivery of cholesterol from endolysosomal compartments. Among factors that could possibly activate TFEB/TFE3 signaling upon ESCRT-I deficiency, we excluded lysosomal cholesterol accumulation and Ca2+-mediated dephosphorylation of TFEB/TFE3. However, we discovered that this activation occurs due to the inhibition of Rag GTPase–dependent mTORC1 pathway that specifically reduced phosphorylation of TFEB at S122. Constitutive activation of the Rag GTPase complex in cells lacking ESCRT-I restored S122 phosphorylation and prevented TFEB/TFE3 activation. Our results indicate that ESCRT-I deficiency evokes a homeostatic response to counteract lysosomal nutrient starvation, that is, improper supply of nutrients derived from lysosomal degradation.