Disturbance of endoplasmic reticulum (ER) homoeostasis induces ER stress and leads to activation of the unfolded protein response (UPR), which is an adaptive reaction that promotes cell survival or triggers apoptosis, when homoeostasis is not restored. DDRGK1 is an ER membrane protein and a critical component of the ubiquitin-fold modifier 1 (Ufm1) system. However, the functions and mechanisms of DDRGK1 in ER homoeostasis are largely unknown. Here, we show that depletion of DDRGK1 induces ER stress and enhances ER stress-induced apoptosis in both cancer cells and hematopoietic stem cells (HSCs). Depletion of DDRGK1 represses IRE1α-XBP1 signalling and activates the PERK-eIF2α-CHOP apoptotic pathway by targeting the ER-stress sensor IRE1α. We further demonstrate that DDRGK1 regulates IRE1α protein stability via its interaction with the kinase domain of IRE1α, which is dependent on its ufmylation modification. Altogether, our results provide evidence that DDRGK1 is essential for ER homoeostasis regulation.
Crystallization
kinetics of phase change materials (PCMs) at high
temperatures is of key importance for the extreme speed of data writing
and erasing. In this work, the crystallization behavior of one of
the typical PCMs, GeTe, has been studied using ultrafast differential
scanning calorimetry (DSC) at high heating rates up to 4 × 104 K s–1. A strong non-Arrhenius temperature-dependent
viscosity has been observed. We considered two viscosity models for
estimating the crystal growth kinetics coefficient (U
kin). The results showed that the MYEGA model was more
suitable to describe the temperature-dependent viscosity and the crystal
growth kinetics for supercooled liquid GeTe. The glass transition
temperature (T
g) and fragility m were estimated to be 432.1 K and 130.7, respectively.
The temperature-dependent crystal growth rates, which were extrapolated
by the MYEGA model, were in line with the experimental results that
were measured by in situ transmission electron microscopy at a given
temperature. The crystal growth rate reached a maximum of 3.5 m s–1 at 790 K. These results based on ultrafast DSC with
the MYEGA model offer a revelation for crystallization kinetics of
supercooled liquid GeTe.
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