bims-lymeca 2023-04-09 papers

Nat Cell Biol. 2023 Apr 06.

A lysosome membrane regeneration pathway depends on TBC1D15 and autophagic lysosomal reformation proteins.

Anshu Bhattacharya, Rukmini Mukherjee, Santosh Kumar Kuncha, Melinda Elaine Brunstein, Rajeshwari Rathore, Stephan Junek, Christian Münch, Ivan Dikic.

Acute lysosomal membrane damage reduces the cellular population of functional lysosomes. However, these damaged lysosomes have a remarkable recovery potential independent of lysosomal biogenesis and remain unaffected in cells depleted in TFEB and TFE3. We combined proximity-labelling-based proteomics, biochemistry and high-resolution microscopy to unravel a lysosomal membrane regeneration pathway that depends on ATG8, the lysosomal membrane protein LIMP2, the RAB7 GTPase-activating protein TBC1D15 and proteins required for autophagic lysosomal reformation, including dynamin-2, kinesin-5B and clathrin. Following lysosomal damage, LIMP2 acts as a lysophagy receptor to bind ATG8, which in turn recruits TBC1D15 to damaged membranes. TBC1D15 interacts with ATG8 proteins on damaged lysosomes and provides a scaffold to assemble and stabilize the autophagic lysosomal reformation machinery. This potentiates the formation of lysosomal tubules and subsequent dynamin-2-dependent scission. TBC1D15-mediated lysosome regeneration was also observed in a cell culture model of oxalate nephropathy.

DOI: https://doi.org/10.1038/s41556-023-01125-9

J Biol Chem. 2023 Mar 30. pii: S0021-9258(23)00305-8. [Epub ahead of print] 104663

Macrotubule associated protein MAP1LC3C regulates lysosomal exocytosis and induces zinc reprogramming in renal cancer cells.

Rita Verma, Parul Aggarwal, Megan E Bischoff, James Reigle, Dina Secic, Collin Wetzel, Katherine VandenHeuvel, Jacek Biesiada, Birgit Ehmer, Julio A Landero Figueroa, David R Plas, Mario Medvedovic, Jarek Meller, Maria F Czyzyk-Krzeska.

Microtubule Associated Protein 1 Light Chain 3 Gamma (MAP1LC3C or LC3C) is a member of the microtubule associated family of proteins that are essential in the formation of autophagosomes and lysosomal degradation of cargo. LC3C has tumor suppressing activity and its expression is dependent on kidney cancer tumor suppressors, such as von Hippel-Lindau protein (VHL) and folliculin (FLCN). Recently We demonstrated that LC3C autophagy is regulated by noncanonical upstream regulatory complexes and targets for degradation postdivision midbody rings associated with cancer cells stemness. Here we show that loss of LC3C leads to peripheral positioning of the lysosomes and lysosomal exocytosis (LE). This process is independent of the autophagic activity of LC3C. Analysis of isogenic cells with low and high LE shows substantial transcriptomic reprogramming with altered expression of Zn-related genes and activity of Polycomb Repressor Complex 2 (PRC2), accompanied by a robust decrease in intracellular Zn. Additionally, metabolomic analysis revealed alterations in amino acid steady-state levels. Cells with augmented LE show increased tumor initiation properties and form aggressive tumors in xenograft models. Immunocytochemistry identified high levels of Lysosomal Associated Membrane Protein 1 (LAMP1) on the plasma membrane of cancer cells in human clear cell renal cell carcinoma (ccRCC) and reduced levels of Zn, suggesting that LE occurs in ccRCC, potentially contributing to the loss of Zn. These data indicate that the reprogramming of lysosomal localization and Zn metabolism with implication for epigenetic remodeling in a subpopulation of tumor propagating cancer cells is an important aspect of tumor suppressing activity of LC3C.

Keywords: LC3C; exocytosis; lysosome; renal cancer; zinc

DOI: https://doi.org/10.1016/j.jbc.2023.104663

Physiol Rep. 2023 Apr;11(7): e15663

Sodium regulates PLC and IP3 R-mediated calcium signaling in invasive breast cancer cells.

Andrew D James, Katherine P Unthank, Isobel Jones, Nattanan Sajjaboontawee, Rebecca E Sizer, Sangeeta Chawla, Gareth J O Evans, William J Brackenbury.

Intracellular Ca2+ signaling and Na+ homeostasis are inextricably linked via ion channels and co-transporters, with alterations in the concentration of one ion having profound effects on the other. Evidence indicates that intracellular Na+ concentration ([Na+ ]i ) is elevated in breast tumors, and that aberrant Ca2+ signaling regulates numerous key cancer hallmark processes. The present study therefore aimed to determine the effects of Na+ depletion on intracellular Ca2+ handling in metastatic breast cancer cell lines. The relationship between Na+ and Ca2+ was probed using fura-2 and SBFI fluorescence imaging and replacement of extracellular Na+ with equimolar N-methyl-D-glucamine (0Na+ /NMDG) or choline chloride (0Na+ /ChoCl). In triple-negative MDA-MB-231 and MDA-MB-468 cells and Her2+ SKBR3 cells, but not ER+ MCF-7 cells, 0Na+ /NMDG and 0Na+ /ChoCl resulted in a slow, sustained depletion in [Na+ ]i that was accompanied by a rapid and sustained increase in intracellular Ca2+ concentration ([Ca2+ ]i ). Application of La3+ in nominal Ca2+ -free conditions had no effect on this response, ruling out reverse-mode NCX activity and Ca2+ entry channels. Moreover, the Na+ -linked [Ca2+ ]i increase was independent of membrane potential hyperpolarization (NS-1619), but was inhibited by pharmacological blockade of IP3 receptors (2-APB), phospholipase C (PLC, U73122) or following depletion of endoplasmic reticulum Ca2+ stores (cyclopiazonic acid). Thus, Na+ is linked to PLC/IP3 -mediated activation of endoplasmic reticulum Ca2+ release in metastatic breast cancer cells and this may have an important role in breast tumors where [Na+ ]i is perturbed.

Keywords: GPCR; IP3 receptor; breast cancer; calcium signaling; ion homeostasis; sodium

DOI: https://doi.org/10.14814/phy2.15663

Cancer Sci. 2023 Apr 03.

Autophagy and cancer: basic mechanisms and inhibitor development.

Yutaro Hama, Yuta Ogasawara, Nobuo N Noda.

Autophagy is a lysosomal degradation system of cytoplasmic components, and it contributes to cellular homeostasis through turnover of various biomolecules and organelles, often in a selective manner. Autophagy is closely related to cancer, but its roles in cancer are complicated. It works as either a promoter or suppressor, depending on the stage and type of cancer. In this review, we briefly summarize the basic mechanisms of autophagy and describe the complicated roles of autophagy in cancer. Moreover, we summarize the clinical trials of autophagy inhibitors targeting cancer and the development of more specific autophagy inhibitors for future clinical application.

Keywords: ATG; autophagy; cancer; chloroquine; inhibitor; mTORC1

DOI: https://doi.org/10.1111/cas.15803

J Cell Biol. 2023 Jun 05. pii: e202208155. [Epub ahead of print]222(6):

ClC-7 drives intraphagosomal chloride accumulation to support hydrolase activity and phagosome resolution.

Jing Ze Wu, Mariia Zeziulia, Whijin Kwon, Thomas J Jentsch, Sergio Grinstein, Spencer A Freeman.

Degradative organelles contain enzymes that function optimally at the acidic pH generated by the V-ATPase. The resulting transmembrane H+ gradient also energizes the secondary transport of several solutes, including Cl-. We report that Cl- influx, driven by the 2Cl-/H+ exchanger ClC-7, is necessary for the resolution of phagolysosomes formed by macrophages. Cl- transported via ClC-7 had been proposed to provide the counterions required for electrogenic H+ pumping. However, we found that deletion of ClC-7 had a negligible effect on phagosomal acidification. Instead, luminal Cl- was found to be required for activation of a wide range of phagosomal hydrolases including proteases, nucleases, and glycosidases. These findings argue that the primary role of ClC-7 is the accumulation of (phago)lysosomal Cl- and that the V-ATPases not only optimize the activity of degradative hydrolases by lowering the pH but, importantly, also play an indirect role in their activation by providing the driving force for accumulation of luminal Cl- that stimulates hydrolase activity allosterically.

DOI: https://doi.org/10.1083/jcb.202208155