bims-raghud 2025-01-05 papers

Issue of 2025–01–05
three papers selected by
Irene Sambri, TIGEM

Sci Rep. 2024 Dec 30. 14(1): 31838

An AMBRA1, ULK1 and PP2A regulatory network regulates cytotoxic T cell differentiation via TFEB activation.

Loredana Migliore, Valentina Cianfanelli, Fabrizia Zevolini, Monica Gesualdo, Leandro Marzuoli, Laura Patrussi, Cristina Ulivieri, Giuseppe Marotta, Francesco Cecconi, Francesca Finetti, Cosima T Baldari.

The scaffold protein AMBRA1, which participates in the autophagy pathway, also promotes CD4+ T cell differentiation to Tregs independent of autophagy through its interactor PP2A. Here we have investigated the role of AMBRA1 in CD8+ T cell differentiation to cytotoxic T cells (CTL). AMBRA1 depletion in CD8+ T cells was associated with impaired expression of the transcription factors RUNX3 and T-BET that drive CTL differentiation and resulted in impaired acquisition of cytotoxic potential. These effects were recapitulated by pharmacological inhibition of the AMBRA1 activator ULK1 or its interactor PP2A. Based on the ability of PP2A to activate TFEB, we hypothesized a role for TFEB in the CTL differentiation program regulated by AMBRA1. We show that TFEB modulates RUNX3 and T-BET expression and the generation of killing-competent CTLs, and that AMBRA1 depletion, or ULK1 or PP2A inhibition, suppresses TFEB activity. These data highlight a role for AMBRA1, ULK1 and PP2A in CTL generation, mediated by TFEB, which we identify as a new pioneering transcription factor in the CTL differentiation program.

Keywords: AMBRA1; Cytotoxic T cell; Lytic granule /; PP2A / ULK1

DOI: https://doi.org/10.1038/s41598-024-82957-9

Sci Rep. 2025 Jan 02. 15(1): 325

Deficiency in NPC2 results in disruption of mitochondria-late endosome/lysosomes contact sites and endo-lysosomal lipid dyshomeostasis.

Raffaele Pastore, Lihang Yao, Nathan Hatcher, Martin Helley, Janet Brownlees, Radha Desai.

Dysfunction of the endo-lysosomal intracellular Cholesterol transporter 2 protein (NPC2) leads to the onset of Niemann-Pick Disease Type C (NPC), a lysosomal storage disorder. Metabolic and homeostatic mechanisms are disrupted in lysosomal storage disorders (LSDs) hence we characterized a cellular model of NPC2 knock out, to assess alterations in organellar function and inter-organellar crosstalk between mitochondria and lysosomes. We performed characterization of lipid alterations and confirmed altered lysosomal morphology, but no overt changes in oxidative stress markers. Using several techniques, we demonstrated that contacts between mitochondria and late endosomes/lysosomes are reduced in NPC2-/- HEK cells, we observed that the acidic compartments are swollen and lipid dense. Quantification of endogenous lipids in HEKNPC2-/- cells by mass spectrometry reveals accumulation of lipid species indicative of sphingolipid metabolic dysregulation within the lysosome. Specifically, HEK NPC2-/- cells exhibit marked elevation of glucosylsphingosine and glucosylceramides, substrates of beta glucocerebroside (GBA), as well as accumulation of sphingosine and sphingomyelins. Our studies suggest an involvement of NPC2 in the formation of contact sites between mitochondria and lysosomes and support the hypothesis of a role for NPC2 in the endo-lysosomal trafficking pathway and dynamic organellar crosstalk.

DOI: https://doi.org/10.1038/s41598-024-83460-x

FEBS Open Bio. 2024 Dec 30.

CDK5 interacts with MST2 and modulates the Hippo signalling pathway.

Mehak Passi, Jan B Stöckl, Thomas Fröhlich, Simone Moser, Angelika M Vollmar, Stefan Zahler.

MST2 (STK3) is a major upstream kinase in the Hippo signalling pathway, an evolutionary conserved pathway in regulation of organ size, self-renewal and tissue homeostasis. Its downstream effectors are the transcriptional regulators YAP and TAZ. This pathway is regulated by a variety of factors, such as substrate stiffness or cell-cell contacts. Using a yeast two-hybrid screen, we detected a novel interaction between the kinases MST2 and CDK5, which we further confirmed by co-immunoprecipitation experiments. Cyclin-dependent kinase 5 (CDK5) is an unusual member of the family of cyclin-dependent kinases, involved in tumour growth and angiogenesis. Although a link between CDK5 and Hippo has been previously postulated, the mode of action is still elusive. Here, we show that knockdown of CDK5 causes reduced transcriptional activity of YAP and that CDK5 influences the phosphorylation levels of the Hippo upstream kinase LATS1. Moreover, a phosphoproteomics approach revealed that CDK5 interferes with the phosphorylation of DLG5, another upstream kinase, which regulates the Hippo pathway. Hence, CDK5 seems to act as a signalling hub for integrating the Hippo pathway and other signalling cascades. These interactions might have important implications for the use of CDK5 inhibitors, which are already in clinical use for tumour diseases.

Keywords: CDK5; Hippo; TAZ; YAP; yeast‐two‐hybrid

DOI: https://doi.org/10.1002/2211-5463.13962