Biology subjects

Guette, C.

Publications and source records attributed to Guette, C..

5 recordsLinked to original sources

bioRxiv2024

Allosteric regulation of BH3-in-groove interactions by tail anchors of BCL-xL complexes limits BH3 mimetic antagonism.

In briefThe C terminal tail anchors of BCL-2 family proteins exert allosteric influence over the interface crucial for BH3 binding and cell survival. This is regulated by additional features taking place at the mitochondria membrane such as recruitment of the death executioner BAX, which, in response to BH3 binding antagonism, contributes to protein complex disruption. SummaryBCL-xL exerts an essential cell survival function which relies on its hydrophobic groove binding to BH3 domain of BH3-only initiators and downstream BAX/BAK executioners. Combining resonance energy transfer assays and molecular dynamics simulations, we unravel that the C-terminal tail mediated subcellular membrane anchoring of BCL-xL selectively advantages binding to membrane-anchored PUMA initiator over BH3 mimetic ligands of the groove. This is due to the combined allosteric effect on BH3-in-groove binding of BCL-xL and PUMA tail anchors. Moreover, doubly anchored PUMA / BCL-xL complexes recruit endogenous BAX, which favors their antagonism by BH3 mimetics. BAXs C-terminal tail anchor alone is sufficient to enhance BH3 mimetics induced death in cells expressing PUMA / BCL-xL. Thus, the survival function of BCL-xL is regulated by a complex interplay between its tail anchor and those of its interacting partners. This enables both resistance to pharmacological inhibitors and modulation by BAX, which functions as a crucial feedback disruptor of the BCL-xL network. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=80 SRC="FIGDIR/small/616265v1_ufig1.gif" ALT="Figure 1000"> View larger version (12K): org.highwire.dtl.DTLVardef@885687org.highwire.dtl.DTLVardef@e8eeaeorg.highwire.dtl.DTLVardef@8e09fborg.highwire.dtl.DTLVardef@1314d68_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsBH3 mimetic antagonism, and subsequent cell death, are limited when full length BCL-xL binds to some membrane-anchored BH3-only proteins such as PUMA. The BH3-in-groove interface is allosterically modulated by tail anchors of PUMA and BCL-xL. Binding to PUMA enriches BCL-xL interactome and recruits BAX. BAX counteracts the effects of tail anchors in BCL-xL complexes.

cell biology↗

bioRxiv2023

The YARS Tyrosyl tRNA Synthetase Regulates Senescence Induction and Escape Through the Transcriptional Control of LIN9, a Member of the DREAM Complex

Senescence is a tumor suppressor mechanism triggered by oncogene expression and chemotherapy treatment. It orchestrates a definitive cessation of cell proliferation through the activation of the p53-p21 and p16-Rb pathways, coupled with the compaction of proliferative genes within heterochromatin regions. Some cancer cells have the ability to elude this proliferative arrest but the signaling pathways involved in circumventing senescence remain to be characterized. We have recently described that malignant cells capable of evading senescence have an increased expression of specific tRNAs, such as tRNA-Leu-CAA and tRNA-Tyr-GTA, alongside the activation of their corresponding tRNA ligases, namely LARS and YARS. We have previously shown that YARS promotes senescence escape by activating proliferation and cell cycle genes but its functions during this proliferative arrest remain largely unknown. In this study, we have continued to characterize the functions of YARS, describing non-canonical transcriptional functions of the ligase. Our results show that YARS is present in the nucleus of growing and senescent cells and interacts with the Trim28 transcriptional regulator. Importantly, YARS binds to the LIN9 promoter, a critical member of the Dream complex responsible for regulating cell cycle transcription. YARS facilitates the binding and the phosphorylation of the type II RNA polymerase and promotes the deposit of activating epigenetic marks on the LIN9 promoter. Consequently, during senescence escape, YARS promotes LIN9 expression and both proteins are necessary to induce the proliferation of emergent cells. These results underscore the unconventional transcriptional functions of YARS in promoting senescence escape by activating LIN9 and likely influencing the functions of the Dream complex.

cancer biology↗

bioRxiv2023

NOXA/MCL-1 axis determines cell-death decision between apoptosis and pyroptosis and the inflammatory secretome of breast cancer cells treated with anti-mitotics.

Understanding how the malignant cells respond to chemotherapy is essential to prevent the development of resistance and to improve the efficiency of anti-cancer drugs. Recently, we established that, by intrinsic and paracrine mechanisms, taxol treatment in breast tumor cells increases NOXA a pro-apoptotic protein functioning as an endogenous inhibitor of survival protein MCL-1, thereby enhancing cytotoxic load on the compensatory survival protein BCL-xL. We herein sought to define the contribution of NOXA/MCL-1 to the modality of cell death secretome composition upon anti-mitotic treatment associated with a BCL-xL antagonist. We observed that genetic inactivation of NOXA (enforcing MCL-1 pro-survival activity) in cancer cells not only delays their death when exposed to taxol in combination with the BCL-xL antagonist A1331852, but also alters its morphological characteristics with the apparition of features evoking pyroptosis. We identified the Caspase3-GSDME axis as regulating pyroptotic-like features suggesting that NOXA may act as a negative regulator of this cell death process (and MCL-1 as a positive regulator for it). Furthermore, comparative analysis of secretomes from the NOXA proficient or deficient cancer cells treated by taxol reveals variations in inflammatory cytokine production including those of IL-1{beta} and IL-18. Thus, our results show that anti-mitotic treatments are able to induce death by apoptosis and/or pyroptosis depending on BCL-2 family balance in breast cancer cells. Furthermore, NOXA/MCL-1 ratio appears to control the communication between these two types of cell death and their associated extracellular inflammatory signals in coordination with the pore-forming gasdermin GSDME.

cancer biology↗

bioRxiv2022

BCL-xL antagonizes the deleterious effects of KRAS on mitochondrial scaffolding

In addition to its canonical role as a regulator of mitochondrial outer membrane permeabilization, BCL-xL exerts diverse non canonical functions contributing to cancer cell aggressiveness. In particular it regulates KRAS intracellular activation levels. We herein explored the mechanistic basis for this effect by a spatially restricted biotin-labelling proteomic approach designed to characterize proteins whose proximity to KRAS, used as a bait, is BCL-xL dependant. BCL-xL loss relocalizes KRAS to the vicinity of mitochondrial proteins. Proximal proteins include the mitochondrial scaffold prohibitin 2 (PHB2), which also interacts with BCL-xL and the downregulation of which prevents BCL-xL sensitive effects of KRAS induced contacts between mitochondria and endosomes, and mitochondrial mass decrease. These results argue that BCL-xL prevents a negative feedback regulation of KRAS canonical signaling by KRAS interference with mitochondrial quality control.

cell biology↗

bioRxiv2020

tRNA Biogenesis and Specific Aminoacyl-tRNA Synthetases Regulate Senescence Stability Under the Control of mTOR

Oncogenes or chemotherapy treatments trigger the induction of suppressive pathways such as apoptosis or senescence. Senescence was initially defined as a definitive arrest of cell proliferation but recent results have shown that this mechanism is also associated with cancer progression and chemotherapy resistance. Senescence is therefore much more heterogeneous than initially thought. How this response varies is not really understood, it has been proposed that its outcome relies on the secretome of senescent cells and on the maintenance of their epigenetic marks. Using experimental models of senescence escape, we now described that the stability of this suppression relies on specific tRNAs and aminoacyl-tRNA synthetases. Following chemotherapy treatment, the DNA binding of the type III RNA polymerase was reduced to prevent tRNA transcription and induce a complete cell cycle arrest. By contrast, during senescence escape, specific tRNAs such as tRNA-Leu-CAA and tRNA-Tyr-GTA were up-regulated. Reducing tRNA transcription appears necessary to control the strength of senescence since RNA pol III inhibition through BRF1 depletion maintained senescence and blocked cell persistence. mTOR inhibition also prevented CIS escape in association with a reduction of tRNA-Leu-CAA and tRNA-Tyr-GTA expression. Further confirming the role of the tRNA-Leu-CAA and tRNA-Tyr-GTA, their corresponding tRNA ligases, YARS and LARS, were necessary for senescence escape. This effect was specific since the CARS ligase had no effect on persistence. YARS and LARS inactivation reduced cell emergence and proteomic analysis indicated that this effect was associated with the down-regulation of E2F1 target genes. Overall, these findings highlight a new regulation of tRNA biology during senescence and suggest that specific tRNAs and ligases contribute to the strength and heterogeneity of this suppression.

cancer biology↗