Cells facing environmental threats have developed numerous coping mechanisms, and HypOxystation users Tim Audas and Stephen Lee have uncovered a fascinating new cellular strategy to remain viable under stress and restore homeostasis when the crisis ends. In their recent paper “Adaptation to Stressors by Systemic Protein Amyloidogenesis”, they describe a physiological process of amyloidogenesis which cells activate under stress conditions, such as hypoxia and acidosis, to remove copious amounts of heterogeneous proteins from circulation, enabling cells to survive in a dormant state. This discovery expands our current view of amyloids as a rare and pathological phenomenon associated with neuropathies such as Alzheimer’s and Parkinson’s diseases, and exposes a novel post-translational, regulatory form of protein organization.
Using a combination of Congo red staining, proteinase K digestion, and OC antibody detection on cells exposed to a variety of stimuli, Audas et al. were able to identify nuclear foci consisting of immobilized, insoluble protein in a crossed β-sheet conformation which they named A-Bodies. In amyloidogenic proteins such as VHL and RNF8, an ACM (amyloid-converting motif) containing arginine and histidine was identified as essential for capture specifically in the A-bodies; a similar motif was also identified in the pathological β-amyloid associated with Alzheimer’s disease. Upon environmental insult, the ACM interacts with ribosomal intergenic spacer RNA (rIGSRNA) to concentrate the proteins and trigger their polymerization in the A-bodies allowing the cells to enter a dormant state.
Audas et al. exerted this type of severe stress on the cells through incubation at pH 6.0 and 1% oxygen in the H35 HypOxystation by Don Whitley Scientific. The HypOxystation’s closed workstation format and rigorous control of oxygen, CO2, temperature and humidity facilitate accurate regulation of cell culture conditions as the in vivo situation of adverse environmental stimuli is simulated. Upon reversion to standard growth conditions (21% oxygen and pH 7.4), the A-bodies dissipated within 4 hours and protein was refolded into the native conformation. The hypoxic and acidotic conditions simulated in the HypOxystation are also characteristic of the tumor microenvironment, where mouse xenograft assays identified the same process of rIGSRNA-mediated A-body formation causing cancer cell dormancy.
The ubiquitous nature of A-bodies in stressed cells indicates that physiological amyloidogenesis may be a common form of protein organization for the purpose of reversible sequestration under harsh conditions. Another HypOxystation user, Violaine See at the University of Liverpool, recently described research into the distribution of HIF’s in nuclear speckles, but Audas et al. note the unique amyoidogenic properties of the A-bodies. For all these simulations of hypoxic conditions in cell culture, Dr. Audas notes that “The workstation is critical because it allows us to manipulate the cells within a low oxygen environment and, unlike an incubator, maintains the O2 levels when cells are taken in and out, avoiding spikes of normoxia“.
from: Audas et al. “Adaptation to Stressors by Systemic Protein Amyloidogenesis”2016: Developmental Cell 39, 155–168