Stress-Induced Membraneless Organelles in Eukaryotes and Prokaryotes: Bird’s-Eye View

Abstract

Stress is an inevitable part of life. An organism is exposed to multiple stresses and overcomes their negative consequences throughout its entire existence. A correlation was established between life expectancy and resistance to stress, suggesting a relationship between aging and the ability to respond to external adverse effects as well as quickly restore the normal regulation of biological processes. To combat stress, cells developed multiple pro-survival mechanisms, one of them is the assembly of special stress-induced membraneless organelles (MLOs). MLOs are formations that do not possess a lipid membrane but rather form as a result of the “liquid–liquid” phase separation (LLPS) of biopolymers. Stress-responsive MLOs were found in eukaryotes and prokaryotes, they form as a reaction to the acute environmental conditions and are dismantled after its termination. These compartments function to prevent damage to the genetic and protein material of the cell during stress. In this review, we discuss the characteristics of stress-induced MLO-like structures in eukaryotic and prokaryotic cells.

Reorganization of Cell Compartmentalization Induced by Stress

“…There is evidence that nSBs may be involved in the regulation of mRNA splicing. For example, an increased import of SR proteins into nSBs was detected in response to stress [ 6 ]. Additionally, nSBs components positively impact cell survival, thus HSF1 and SAFB knockdowns promoted apoptosis [ 6 ].…”

“…Revolutionary changes in the ideas about the organization of the intracellular space that occurred in the mid-2010s made it possible to form a unified view on the molecular mechanisms underlying cell physiology [ 5 ]. First, it became obvious that adaptive, fast, and reversible reprogramming of regulatory pathways in response to a stimulus is achieved with the help of the formation/disassembly of liquid-droplet compartments and, secondly, the concentration of proteins via phase separation is necessary for this mechanism [ 6 ]. Intrinsically disordered proteins play a central role in these processes.…”

“…A clear illustration of that is fast reorganization of cellular compartmentalization under stress conditions. [ 6 ]. Initially, the majority of studies devoted to stress-induced MLOs focused on cytoplasmic compartments, especially stress-granules.…”

“…However, an increasing number of reports have been published demonstrating a multiple nuclear MLOs sensitive to stress and potentially involved in stress-response mechanisms. Some MLOs are stress-induced and form de novo in response to stress, whereas others exist and function in unstressed cells and during stress-response undergo adaptive structural and functional changes (( Table 1 , Figure 1 ) [ 6 , 11 ]. Stress-induced MLOs have been found across eukarya and bacteria life domains advocating early evolutionary development of this cell survival strategy ( Table 1 , Table 2 and Table 3 ).…”

Pathological and Functional Amyloid Fibrils—Part I

“…To the extremely interesting observations and generalizations of the authors, we would like to add that the studies reviewed by the authors do not explain how the local increase in protein concentration which is necessary for the initiation of amyloidogenesis occurs. At the same time, it is now known that the local concentration of proteins can occur in membraneless organelles, dynamic coacervates, which also emerge in response to stress as a result of liquid-liquid phase separation [ 6 ]. The coverage of the role of non-membrane organelles in the formation of amyloid fibrils would be a logical continuation of the review by Galkin and Sysoev.…”