Namrita Kaur

• Kaur, Namrita; Carlsson, Sven R. & Lystad, Alf Håkon Lohsen (2025). Lysosome-associated CASM: from upstream triggers to downstream effector mechanisms. Frontiers in Cell and Developmental Biology. 13. doi: 10.3389/fcell.2025.1559125. Fulltekst i vitenarkiv Vis sammendrag

  Lysosomes are dynamic organelles critical for cellular degradation and signaling, safeguarded by a limiting membrane that prevents leakage of harmful contents into the cytoplasm. Upon lysosomal damage, cells deploy defensive mechanisms, including a key process called CASM (conjugation of ATG8 to single membranes), which lipidates ATG8 proteins onto the limiting membrane to support protective pathways. CASM operates through two pathways: VAIL, induced by lysosomal pH changes via V-ATPase and ATG16L1, and STIL, triggered by sphingomyelin exposure and mediated by TECPR1. This review examines CASM’s role in lysosomal damage responses, exploring the mechanisms of damaging agents, distinctions between VAIL and STIL, and the downstream effects of decorating lysosomes with ATG8, including effector recruitment for membrane repair or removal.

• Kaur, Namrita; Carlsson, Sven R & Lystad, Alf Håkon Lohsen (2023). The separate axes of TECPR1 and ATG16L1 in CASM. Autophagy. ISSN 1554-8627. s. 1–2. doi: 10.1080/15548627.2023.2255462. Fulltekst i vitenarkiv Vis sammendrag

  Conjugation of ATG8 to single membranes (CASM) is a fundamental cellular process that entails the conjugation of mammalian Atg8 homologs, here referred to as ATG8, to phosphatidylethanolamine (PE) and phosphatidylserine (PS) on endolysosomal compartments. Our current research, together with recent reports from the Randow, Wu, and Wileman labs, has uncovered yet another layer to this process. We discovered that, in addition to ATG16L1-containing complexes, TECPR1 (tectonin beta-propeller repeat containing 1)-containing ATG12–ATG5 E3 complexes can facilitate CASM, thereby providing a broader understanding of this pathway.

• Kaur, Namrita; Ballina, Laura R de la; Haukaas, Håvard Styrkestad; Torgersen, Maria Lyngaas; Radulovic, Maja & Munson, Michael J [Vis alle 11 forfattere av denne artikkelen] (2023). TECPR1 is activated by damage-induced sphingomyelin exposure to mediate noncanonical autophagy. EMBO Journal. ISSN 0261-4189. 42(17), s. 1–19. doi: 10.15252/embj.2022113105. Fulltekst i vitenarkiv Vis sammendrag

  Abstract Cells use noncanonical autophagy, also called conjugation of ATG8 to single membranes (CASM), to label damaged intracellular compartments with ubiquitin‐like ATG8 family proteins in order to signal danger caused by pathogens or toxic compounds. CASM relies on E3 complexes to sense membrane damage, but so far, only the mechanism to activate ATG16L1‐containing E3 complexes, associated with proton gradient loss, has been described. Here, we show that TECPR1‐containing E3 complexes are key mediators of CASM in cells treated with a variety of pharmacological drugs, including clinically relevant nanoparticles, transfection reagents, antihistamines, lysosomotropic compounds, and detergents. Interestingly, TECPR1 retains E3 activity when ATG16L1 CASM activity is obstructed by the Salmonella Typhimurium pathogenicity factor SopF. Mechanistically, TECPR1 is recruited by damage‐induced sphingomyelin (SM) exposure using two DysF domains, resulting in its activation and ATG8 lipidation. In vitro assays using purified human TECPR1‐ATG5‐ATG12 complex show direct activation of its E3 activity by SM, whereas SM has no effect on ATG16L1‐ATG5‐ATG12. We conclude that TECPR1 is a key activator of CASM downstream of SM exposure.

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