Biology subjects

Castets, M.

Publications and source records attributed to Castets, M..

4 recordsLinked to original sources

bioRxiv2023

Lysosomal MLKL is balanced by ESCRT to control cell death

Mixed lineage kinase-like (MLKL) is activated by RHIM-domain containing kinase (RIPK)3 to permeabilize the plasma-membrane and execute necroptosis, a form of regulated necrosis. We found that MLKL is activated in an atypical, RIPK3- and necroptosis-independent manner downstream of Toll-like receptor 3, resulting in its translocation to lysosomes and lysosomal membrane permeabilization. Damaged lysosomes then undergo exocytosis, leading to the integration of lysosomal MLKL into the plasma-membrane to trigger cell death. The ESCRT-machinery can repair damaged lysosomes and counteract cell death by packing lysosomal MLKL into intraluminal vesicles, which are subsequently released as extracellular vesicles. In this way, ESCRT-machinery balances life and death decisions by preventing lysosomal MLKL to reach its killing destination, which is the plasma-membrane.

cell biology↗

bioRxiv2022

Fusion-negative Rhabdomyosarcoma 3D-organoids as an innovative model to predict resistance to cell death inducers

Rhabdomyosarcoma (RMS) is the main form of soft-tissue sarcoma in children and adolescents. For 20 years, and despite international clinical trials, its cure rate has not really improved, and remains stuck at 20% in case of relapse. The definition of new effective therapeutic combinations is hampered by the lack of reliable models, which complicate the transposition of promising results obtained in pre-clinical studies into efficient solutions for young patients. Inter-patient heterogeneity, particularly in the so-called fusion-negative group (FNRMS), adds an additional level of difficulty in optimizing the clinical management of children and adolescents with RMS. Here, we describe an original 3D-organoid model derived from relapsed FNRMS and show that it finely mimics the characteristics of the original tumor, including inter- and intra-tumoral heterogeneity. Moreover, we have established the proof-of-concept of their preclinical potential by re-evaluating the therapeutic opportunities of targeting apoptosis in FNRMS from a streamlined approach based on the exploitation of bulk and single-cell omics data.

cancer biology↗

bioRxiv2020

Low expression of ANT1 confers oncogenic properties to rhabdomyosarcoma tumor cells via modulating metabolism and death pathways.

Rhabdomyosarcoma (RMS) is the most frequent form of pediatric soft-tissue sarcoma. It is divided into 2 main subtypes: ERMS (embryonal) and ARMS (alveolar). Current treatments are based on chemotherapy, surgery and radiotherapy. 5-year survival rate remains of 70% since 2000, despite several clinical trials. RMS cells are thought to derive from muscle lineage precursors. During development, myogenesis is characterized by primary expansion of myoblasts, elimination of those in excess by cell death and the differentiation of the remaining ones into myotubes and myofibers. The idea that these processes could be hijacked by tumor cells to sustain their oncogenic transformation has emerged, while RMS is being considered as the Mister Hydes side of myogenesis. Thus, focusing on myogenic developmental programs could help understanding RMS molecular aetiology. Following this idea, we decided to concentrate on ANT1, which is involved in myogenesis and is the underlying cause of genetic disorders associated with muscle degeneration. ANT1 is a mitochondrial protein, which has a functional duality, as it is involved both in metabolism via regulation of ATP/ADP release from mitochondria, but also in apoptosis as part as the mitochondria Permeability Transition Pore (mPTP). By bioinformatic analysis of transcriptomic datasets, we observed that ANT1 is expressed at low levels in RMS. Using CRISPR-Cas9 technology, we showed that decreased ANT1 expression confers selective advantages to RMS cells in terms of proliferation and resistance to stress-induced death. These effects result notably from a metabolic switch. Restoration of ANT1 expression using a Tet-On system is sufficient to prime tumor cells to death and to increase their sensitivity to chemotherapies. Thus, modulation of ANT1 activity could appear as an appealing therapeutic approach in RMS management.

cancer biology↗

bioRxiv2020

Caspase-8 deficiency induces a switch from TLR3 induced apoptosis to lysosomal cell death in neuroblastoma cell lines

TLR3 converts in cancer cells from an inflammatory to a death receptor and TLR3-induced cell death activates the extrinsic apoptosis pathway. Here, we demonstrate that activation of TLR3 triggers a form lysosomal cell death. Following the combinational treatment of IFN-1/poly(I:C) of the Caspase-8 deficient neuroblastoma cell line SH-SY5Y, lysosomes enlarge and accumulate before cells display characteristic apoptotic morphologies. However, caspases are not involved in signalling from TLR3 to the lysosome as 25 M did not inhibit cell death. However, increasing zVAD concentrations to 50 M which is known to inhibit cathepsins, as well as a specific cathepsin B inhibitor reduced TLR3-induced lysosomal cell death. Thus lysosomal cathepsins have a role in cell death execution and overtake the role of caspase-8 in inducing the apoptotic caspase cascade. Further in the caspase-8 positive neuroblastoma cell line SK-N-AS, knockdown of caspase-8 induces a switch from TLR3-induced apoptosis to lysosomal cell death. Taken together our data suggest that lysosomal cell death represents a default death mechanism, when caspase-8 is absent.

molecular biology↗