Biology subjects

Grallert, B.

Publications and source records attributed to Grallert, B..

3 recordsLinked to original sources

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↗

bioRxiv2018

Regulation of ATR activity by the RNA polymerase II phosphatase PNUTS-PP1

Ataxia telangiectasia mutated and Rad3-related (ATR) kinase is a key factor activated by DNA damage and replication stress. Here, we show that ATR signaling is increased in human cells after depletion of the RNAPII phosphatase PNUTS-PP1, which dephosphorylates RNAPII on Ser 5 of its carboxy-terminal domain (CTD) (pRNAPII S5). Increased ATR signaling was observed in the presence and absence of ionizing radiation or replication stress and even in G1 phase after depletion of PNUTS. Vice versa, ATR signaling was reduced, in a PNUTS dependent manner, after inhibition of the CDK7 kinase mediating pRNAPII S5. Furthermore, CDC73, a well-known RNAPII-CTD binding protein, was required for the high ATR signaling after depletion of PNUTS and co-immunoprecipitated with RNAPII and ATR. These results suggest a novel pathway involving RNAPII, PNUTS-PP1 and CDC73 in ATR signaling and give new insight into the diverse functions of ATR.

cancer biology↗

bioRxiv2018

Regulation of global translation during the cell cycle

It is generally accepted that global translation varies during the cell cycle and is low in mitosis. However, addressing this issue is challenging because it involves cell synchronization, which evokes stress responses which, in turn, affect translation rates. Here we have used two approaches to measure global translation rates in different cell-cycle phases. First, synchrony in different cell-cycle phases was obtained involving the same stress, by using temperature-sensitive mutants. Second, translation and DNA content were measured by flow cytometry in exponentially growing, single cells. We found no major variation in global translation rates through the cell cycle in either fission-yeast or mammalian cells. We also measured phosphorylation of eukaryotic initiation factor-2, an event thought to downregulate global translation in mitosis. In contrast with the prevailing view, eIF2 phosphorylation correlated poorly with downregulation of general translation and ectopically induced eIF2 phosphorylation inhibited general translation only at high levels.

cell biology↗