LCDR maintains the integrity of lysosomal membrane by hnRNP K-stabilized LAPTM5 transcript and promotes cell survival
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ABSTRACT:
PROVIDER: PRJNA727295 | ENA |
REPOSITORIES: ENA
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Project description:Lysosome plays important roles in cellular homeostasis and its dysregulation is associated with cancer. However, the regulation and underlying mechanism of lysosome in cancer survival remain incompletely understood. Here, we reveal a role for a histone acetylation-regulated long non-coding RNA termed as lysosome cell death regulator (LCDR) in lung cancer cell survival, knockdown of which promotes apoptosis. Mechanistically, LCDR binds to heterogenous nuclear ribonucleoprotein K (hnRNP K) to regulate the stability of lysosomal-associated protein transmembrane 5 (LAPTM5) transcript that maintain integrity of lysosomal membrane. Consequently, knockdown of LCDR, hnRNP K or LAPTM5 promotes lysosomal membrane permeabilization and lysosomal cell death-mediated apoptosis. LAPTM5 overexpression or cathepsin B inhibitor partially restores the effects of this axis on lysosomal cell death. Clinically, LCDR/hnRNP K/LAPTM5 are upregulated in lung cancer tissues and coexpression of this axis shows the increased diagnostic value for lung cancer. These findings shed light on LCDR/hnRNP K/LAPTM5 as potential therapeutic targets and targeting lysosome is a promising strategy in cancer treatment.
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Project description:Oxidative stress has been implicated in the pathogenesis of age-related macular degeneration, the leading cause of blindness in older adults, with retinal pigment epithelium (RPE) cells playing a key role. To better understand the cytotoxic mechanisms underlying oxidative stress, we used a mouse model of iron overload, as iron can catalyze reactive oxygen species formation in the RPE. In a liver-specific Hepc (Hamp) knockout murine model of systemic iron overload, RPE cells accumulated lipid peroxidation adducts and lysosomes, developed progressive hypertrophy, and underwent cell death. Proteomic and lipidomic analyses revealed accumulation of lysosomal proteins, ceramide biosynthetic enzymes, and ceramides. The proteolytic enzyme cathepsin D had impaired maturation. A large proportion of lysosomes were galectin-3 positive, suggesting cytotoxic lysosomal membrane permeabilization. RNA sequencing was performed and did not show evidence of upregulation of CLEAR network genes, suggesting that the lysosomal accumulation was due to decreased lysosomal turnover and not increased lysosomal biogenesis. Collectively, these results demonstrate that iron overload induces lysosomal accumulation and impairs lysosomal function, likely owing to iron-induced lipid peroxides that can inhibit lysosomal enzymes.
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Project description:hnRNP UL1 plays an important function in cell nuclei, where it is recruited to DNA damage sites and is involved in the repair of DNA double strand breaks. Furthermore, this protein is known as a transcriptional repressor of RNA polymerase II genes. In the present study, we have shown that hnRNP UL1 is also localized in the nucleoli. Revealing its function, we figured out that hnRNP UL1 stimulates rDNA gene transcription and may be involved in the transport of the proteins between the nucleolus and the nucleoplasm. Moreover, we observed that cells with hnRNP UL1 silencing are more sensitive to DNA damage, suggesting its role in rDNA repair pathways and nucleolar genome integrity. Indeed, we confirmed that hnRNP UL1 interacts with yH2A.X, RPA32, XRCC1, and Chk1 in cell nucleoli, suggesting its involvement in repairing of DNA damages.
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Project description:Within the endolysosomal pathway in mammalian cells, ESCRT complexes facilitate degradation of membrane proteins from limiting membranes of late endosomes. Recent studies revealed that yeast ESCRT proteins also sort for degradation, ubiquitinated proteins from vacuolar membrane. However, whether mammalian ESCRTs perform similar function at lysosomes remained unknown. Here, we studied the involvement of mammalian ESCRT-I in maintaining lysosomal membrane homeostasis and its implication in lysosome-related signaling. We show that ESCRT-I restricts the size of lysosomes and promotes degradation of lysosomal Ca2+ channel, MCOLN1 protein. ESCRT-I depletion induced transcriptional response related to MiT-TFE signaling and cholesterol biosynthesis, pointing to lysosomal dysfunction. The lack of ESCRT-I promoted abnormal cholesterol accumulation on lysosomes and activated TFEB/TFE3 transcription factors in Ca2+-MCOLN1-dependent, but lipid-independent manner. Hence, our study provides evidence that ESCRT-I maintains lysosomal homeostasis and elucidates MiT-TFE regulatory mechanism activated in response to ESCRT-I deprivation
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Project description:This experiment identifies hnRNP A1 binding sites transcriptome-wide in Hela cells. HeLa cells with inducible expression of T7-tagged hnRNP A1 were grown to approximately 90% confluence and then subject to iCLIP analysis (following the protocol from Huppertz et al. 2014 (iCLIP: protein-RNA interactions at nucleotide resolution)). The iCLIP library was sequenced using Illumina's HighSeq 1500
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