RT Journal Article SR Electronic T1 ESCRT-I fuels lysosomal degradation to restrict TFEB/TFE3 signaling via the Rag-mTORC1 pathway JF Life Science Alliance JO Life Sci. Alliance FD Life Science Alliance LLC SP e202101239 DO 10.26508/lsa.202101239 VO 5 IS 7 A1 Marta Wróbel A1 Jarosław Cendrowski A1 Ewelina Szymańska A1 Malwina Grębowicz-Maciukiewicz A1 Noga Budick-Harmelin A1 Matylda Macias A1 Aleksandra Szybińska A1 Michał Mazur A1 Krzysztof Kolmus A1 Krzysztof Goryca A1 Michalina Dąbrowska A1 Agnieszka Paziewska A1 Michał Mikula A1 Marta Miączyńska YR 2022 UL https://www.life-science-alliance.org/content/5/7/e202101239.abstract 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.