bims-lysosi Biomed News
on Lysosomes and signaling
Issue of 2022‒07‒10
two papers selected by
Stephanie Fernandes
Max Planck Institute for Biology of Ageing
  1. Secretory autophagy during lysosome inhibition (SALI).
  2. Multiparameter phenotypic screening for endogenous TFEB and TFE3 translocation identifies novel chemical series modulating lysosome function.
  1. Autophagy. 2022 Jul 04.
    Secretory autophagy during lysosome inhibition (SALI).
    Jayanta Debnath, Andrew M Leidal.
      Both macroautophagy/autophagy and extracellular vesicle (EV) secretion pathways converge upon the endolysosome system. Although lysosome impairment leads to defects in autophagic degradation, the impact of such dysfunction on EV secretion remains poorly understood. Recently, we uncovered a novel secretory autophagy pathway that employs EVs and nanoparticles (EVPs) for the secretion of autophagy cargo receptors outside the cell when either autophagosome maturation or lysosomal function is blocked. We term this process secretory autophagy during lysosome inhibition (SALI). SALI functionally requires multiple steps in classical autophagosome formation and the small GTPase RAB27A. Because the intracellular accumulation of autophagy cargo receptors perturbs cell signaling and quality control pathways, we propose that SALI functions as a failsafe mechanism to preserve protein and cellular homeostasis when autophagic or lysosomal degradation is impaired.
    Keywords:  Autophagy cargo receptors; extracellular vesicles; lysosome; proteostasis; secretory autophagy; vesicular trafficking
    DOI:  https://doi.org/10.1080/15548627.2022.2095788
  2. Autophagy. 2022 Jul 04.
    Multiparameter phenotypic screening for endogenous TFEB and TFE3 translocation identifies novel chemical series modulating lysosome function.
    Phillippa J Carling, Brent J Ryan, William McGuinness, Shikha Kataria, Stewart W Humble, Stefan Milde, James A Duce, Nirav Kapadia, William J Zuercher, John B Davis, Elena Di Daniel, Richard Wade-Martins.
      The accumulation of toxic protein aggregates in multiple neurodegenerative diseases is associated with defects in the macroautophagy/autophagy-lysosome pathway. The amelioration of disease phenotypes across multiple models of neurodegeneration can be achieved through modulating the master regulator of lysosome function, TFEB (transcription factor EB). Using a novel multi-parameter high-throughput screen for cytoplasmic:nuclear translocation of endogenous TFEB and the related transcription factor TFE3, we screened the Published Kinase Inhibitor Set 2 (PKIS2) library as proof of principle and to identify kinase regulators of TFEB and TFE3. Given that TFEB and TFE3 are responsive to cellular stress we have established assays for cellular toxicity and lysosomal function, critical to ensuring the identification of hit compounds with only positive effects on lysosome activity. In addition to AKT inhibitors which regulate TFEB localization, we identified a series of quinazoline-derivative compounds that induced TFEB and TFE3 translocation. A novel series of structurally-related analogs was developed, and several compounds induced TFEB and TFE3 translocation at higher potency than previously screened compounds. KINOMEscan and cell-based KiNativ kinase profiling revealed high binding for the PRKD (protein kinase D) family of kinases, suggesting good selectivity for these compounds. We describe and utilize a cellular target-validation platform using CRISPRi knockdown and orthogonal PRKD inhibitors to demonstrate that the activity of these compounds is independent of PRKD inhibition. The more potent analogs induced subsequent upregulation of the CLEAR gene network and cleared pathological HTT protein in a cellular model of proteinopathy, demonstrating their potential to alleviate neurodegeneration-relevant phenotypes.
    Keywords:  High-content screening; PKIS2; TFEB; lysosome activity; lysosome biogenesis; protein aggregation
    DOI:  https://doi.org/10.1080/15548627.2022.2095834
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