Browsing by Author "Popp, Lauren"

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    CLN8 is an endoplasmic reticulum cargo receptor that regulates lysosome biogenesis
    (Springer Nature, 2018) di Ronza, Alberto; Bajaj, Lakshya; Sharma, Jaiprakash; Sanagasetti, Deepthi; Lotfi, Parisa; Adamski, Carolyn Joy; Collette, John; Palmieri, Michela; Amawi, Abdallah; Popp, Lauren; Chang, Kevin Tommy; Meschini, Maria Chiara; Leung, Hon-Chiu Eastwood; Segatori, Laura; Simonati, Alessandro; Sifers, Richard Norman; Santorelli, Filippo Maria; Sardiello, Marco; Bioengineering; Biosciences; Chemical and Biomolecular Engineering
    Organelle biogenesis requires proper transport of proteins from their site of synthesis to their target subcellular compartment1,2,3. Lysosomal enzymes are synthesized in the endoplasmic reticulum (ER) and traffic through the Golgi complex before being transferred to the endolysosomal system4,5,6, but how they are transferred from the ER to the Golgi is unknown. Here, we show that ER-to-Golgi transfer of lysosomal enzymes requires CLN8, an ER-associated membrane protein whose loss of function leads to the lysosomal storage disorder, neuronal ceroid lipofuscinosis 8 (a type of Batten disease)7. ER-to-Golgi trafficking of CLN8 requires interaction with the COPII and COPI machineries via specific export and retrieval signals localized in the cytosolic carboxy terminus of CLN8. CLN8 deficiency leads to depletion of soluble enzymes in the lysosome, thus impairing lysosome biogenesis. Binding to lysosomal enzymes requires the second luminal loop of CLN8 and is abolished by some disease-causing mutations within this region. Our data establish an unanticipated example of an ER receptor serving the biogenesis of an organelle and indicate that impaired transport of lysosomal enzymes underlies Batten disease caused by mutations in CLN8.
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    The autophagic response to polystyrene nanoparticles is mediated by transcription factor EB and depends on surface charge
    (BioMed Central, 2015) Song, Wensi; Popp, Lauren; Yang, Justin; Kumar, Ayushi; Gangoli, Varun S.; Segatori, Laura
    Background: A number of engineered nanoparticles induce autophagy, the main catabolic pathway that regulates bulk degradation of cytoplasmic material by the lysosomes. Depending on the specific physico-chemical properties of the nanomaterial, however, nanoparticle-induced autophagy may have different effects on cell physiology, ranging from enhanced autophagic degradation to blockage of autophagic flux. To investigate the molecular mechanisms underlying the impact of nanoparticle charge on the nature of the autophagic response, we tested polystyrene nanoparticles (50 nm) with neutral, anionic, and cationic surface charges. Results: We found all polystyrene nanoparticles investigated in this study to activate autophagy. We showed that internalization of polystyrene nanoparticles results in activation of the transcription factor EB, a master regulator of autophagy and lysosome biogenesis. Autophagic clearance, however, was observed to depend specifically on the charge of the nanoparticles. Particularly, we found that the autophagic response to polystyrene nanoparticles presenting a neutral or anionic surface involves enhanced clearance of autophagic cargo. Cell exposure to polystyrene nanoparticles presenting a cationic surface, on the other hand, results in transcriptional upregulation of the pathway, but also causes lysosomal dysfunction, ultimately resulting in blockage of autophagic flux. Conclusions: This study furthers our understanding of the molecular mechanisms that regulate the autophagic response to nanoparticles, thus contributing essential design criteria for engineering benign nanomaterials.
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    Zinc Oxide Particles Induce Activation of the Lysosome–Autophagy System
    (American Chemical Society, 2019) Popp, Lauren; Segatori, Laura; Bioengineering; Chemical and Biomolecular Engineering
    Metal-oxide-based materials are highly versatile and used in a wide variety of applications ranging from medical technology to personal care products. Generally recognized as safe by the US Food and Drug Administration, zinc oxide (ZnO) has been increasingly used in pharmaceutical, cosmetic, food, and commodity chemical industries. As a result, exposure to nano- and micron-sized ZnO particles through occupational processes and consumer products is increasing and has raised concerns over the health effects associated with the large-scale production and commercialization of ZnO-based materials. It is therefore important to investigate the interaction of ZnO particles with biological systems and elucidate the consequent effect on cell physiology. Of particular interest is the autophagic response to zinc oxide particles, as autophagy is the first line of defense activated in response to the uptake of foreign materials. As the main cellular catabolic pathway, the lysosome–autophagy system plays an important homeostatic function and defects or deficiency of this degradation system is associated with the cellular pathogenesis of a number of human diseases, ranging from neurodegenerative disorders to cancer. In this study, we investigated the response of the lysosome–autophagy system to three relevant types of ZnO particles, namely, a polydisperse mixture of bare, micron-sized particles (100–1000 nm) and monodisperse, bare, and coated (with triethoxycaprylylsilane) ZnO nanoparticles (85 nm). To investigate the molecular mechanisms mediating the response of the lysosome–autophagy system to these ZnO particles, we examined a complete set of markers of this pathway and characterized each step, from transcriptional activation to clearance of autophagic cargo. To evaluate the effect of the different types of ZnO particles on the lysosome–autophagy system, biological assays were conducted under conditions that do not cause considerable cytotoxicity. All three types of ZnO particles were found to result in activation of the transcription factor EB, a master regulator of autophagy and lysosomal biogenesis. Cellular exposure to bare and coated nano-sized ZnO enhanced the formation and turnover of autophagosomes and cellular clearance. Cellular exposure to the polydisperse mixture of ZnO particles, however, resulted in enhancement of autophagosome formation, but also in blockage of the autophagic flux. Results from this study underscore the importance of characterizing the autophagic response to ZnO-based materials and contribute significant engineering principles for the future design of nano- and micron-sized ZnO materials with the desired autophagy-modulating properties.