Biology subjects

Torgersen, M. L.

Publications and source records attributed to Torgersen, M. L..

3 recordsLinked to original sources

bioRxiv2022

ATPase activity of DFCP1 controls selective autophagy

Cellular homeostasis is governed by removal of damaged organelles and protein aggregates by selective autophagy mediated by cargo adaptors such as p62/SQSTM1. Autophagosomes can assemble in specialized cup-shaped regions of the endoplasmic reticulum (ER) known as omegasomes, which are characterized by the presence of the ER protein DFCP1/ZFYVE1. The function of DFCP1 is unknown, as are the mechanisms of omegasome formation and constriction. Here, we demonstrate that DFCP1 is an ATPase that dimerizes in an ATP-dependent fashion. Whereas depletion of DFCP1 had a minor effect on bulk autophagic flux, DFCP1 was required to maintain the autophagic flux of p62 under both fed and starved conditions, and this was dependent on its ability to bind and hydrolyse ATP. While DFCP1 mutants defective in ATP binding or hydrolysis localized to forming omegasomes, these omegasomes failed to constrict. Consequently, the release of nascent autophagosomes from omegasomes was markedly delayed. DFCP1 was found to associate with ubiquitinated proteins, and degradation of ubiquitinated cargoes such as protein aggregates, mitochondria and micronuclei was strongly inhibited when DFCP1 was knocked out or mutated. Thus, DFCP1 mediates ATPase-driven constriction of omegasomes to release autophagosomes for selective autophagy.

cell biology↗

bioRxiv2020

Physicochemical characterization, toxicity and in vivo biodistribution studies of a discoidal, lipid-based drug delivery vehicle: Lipodisq nanoparticles containing doxorubicin

Many promising pharmaceutically active compounds have low solubility in aqueous environments and their encapsulation into efficient drug delivery vehicles is crucial to increase their bioavailability. Lipodisq nanoparticles are approximately 10 nm in diameter and consist of a circular phospholipid bilayer, stabilized by an annulus of SMA (a hydrolysed copolymer of styrene and maleic anhydride). SMA is used extensively in structural biology to extract and stabilize integral membrane proteins for biophysical studies. Here, we assess the potential of these nanoparticles as drug delivery vehicles, determining their cytotoxicity and the in vivo excretion pathways of their polymer and lipid components. Doxorubicin-loaded Lipodisqs were cytotoxic across a panel of cancer cell lines, whereas nanoparticles without the drug had no effect on cell proliferation. Intracellular doxorubicin release from Lipodisqs in HeLa cells occurred in the low-pH environment of the endolysosomal system, consistent with the breakdown of the discoidal structure as the carboxylate groups of the SMA polymer become protonated. Biodistribution studies in mice showed that, unlike other nanoparticles injected intravenously, most of the Lipodisq components were recovered in the colon, consistent with rapid uptake by hepatocytes and excretion into bile. These data suggest that Lipodisqs have the potential to act as delivery vehicles for drugs and contrast agents.Competing Interest StatementThe authors have declared no competing interest.AbbreviationsDLPE1,2-dilauroyl-sn-glycero-3-phosphoethanolamineDLPE-Cy5Cy5 dye covalently conjugated to 1,2-dilauroyl-sn-glycero-3-phosphoethanolamineDLSdynamic light scatteringDMPC1,2-dimyristoyl-sn-glycero-3-phosphocholineDMPG1,2-dimyristoyl-sn-glycero-3-phospho-(1’-rac-glycerol)DOXDoxorubicinEPRenhanced permeability and retention effectLipodisqLQNMRnuclear magnetic resonanceNPnanoparticleRTroom temperatureSMAhydrolysed co-polymer of styrene and maleic anhydrideSMA-Cy5Cy5 dye covalently conjugated to a thiol derivative of SMASMAnhnon-hydrolysed co-polymer of styrene and maleic anhydrideSMAnh-SHthiol derivative of SMAnhSMA-SHthiol derivative of SMAView Full Text

pharmacology and toxicology↗

bioRxiv2018

The alkyl side chain of PACA nanoparticles dictates the impact on cellular stress responses and the mode of particle-induced cell death

For optimal exploitation of nanoparticles (NPs) in biomedicine, and to predict nanotoxicity, detailed knowledge on the cellular responses to cell-bound or internalized NPs is imperative. The outcome of NP-cell interaction is dictated by the type and magnitude of the NP insult and the cellular response. Here, we have systematically studied the impact of minor differences in NP composition on cellular stress responses and viability by using highly similar poly(alkylcyanoacrylate) (PACA) particles. Surprisingly, PACA particles differing only in their alkyl side chains; butyl (PBCA), ethylbutyl (PEBCA), or octyl (POCA), respectively, induced different stress responses and modes of cell death in human cell lines. POCA particles induced endoplasmic reticulum stress and apoptosis. In contrast, PBCA and PEBCA particles induced lipid peroxidation by depletion of the main cellular antioxidant glutathione (GSH), in a manner depending on the levels of the GSH precursor cystine, and transcription of the cystine transporter SLC7A11 regulated by ATF4 and Nrf2. Intriguingly, these particles activated the recently discovered cell death mechanism ferroptosis, which constitutes a promising alternative for targeting multidrug-resistant cancer stem-like cells. Of the two, PBCA was the strongest inducer. In summary, our findings highlight the cellular sensitivity to nanoparticle composition and have important implications for the choice of PACA monomer in therapeutical settings.

cell biology↗