Condensed desmin and actin cytoskeletal communication in lipid droplets

Abstract

The interplay between intermediate filaments (IFs) and other cytoskeletal components is important for the integrity and motility of cells. The impact of IF assembly on other components and cell morphology is not yet fully understood. Therefore, we examined the effects of combined desmin and actin assembly on cytoskeletal network arrangement in artificial cell‐sized droplets. Fluorescently labeled desmin, with or without actin, was enclosed in droplets prepared with 1,2‐dioleoyl‐sn‐glycero‐3‐phosphoethanolamine (DOPE) using the water‐in‐oil method. Protein networks were observed using fluorescence microscopy in the presence of 150 mM KCl, 20 mM imidazole–HCl (pH 7.4), 2 mM MgCl2, and 1 mM adenosine 5'‐triphosphate for both desmin and actin assembly. As desmin alone can assemble into filaments within seconds, desmin networks mainly localizing at the inner margins of the droplets were observed within 10 min after assembly initiation. Subsequently, deformations of droplets appeared. Furthermore, a portion of droplets formed desmin‐rich protrusions of several micrometers. Notably, actin alone rarely formed protrusions under the same conditions. When 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine was used instead of DOPE, protrusions became less frequent. The combination of desmin and actin increased the number of deformed droplets in which the proteins were considerably colocalized. The assembly process of desmin facilitated colocalization. Atomic force microscopy failed to reveal interactions between the two filament types. These results suggest that the mechanical properties of desmin networks may influence the behavior of actin networks, as well as membrane morphology, possibly reflecting the mechanical function of desmin filaments in muscle cells.

Woven bone formation and mineralization by rat mesenchymal stromal cells imply increased expression of the intermediate filament desmin

“…In our cell model, this hypothesis was initially substantiated by the evidence that DES co-localized with the two cytoskeletal proteins vimentin and F-actin, and the osteogenic transcription factor runx2. DES, vimentin, actin, and runx2 all exhibited an intracellular topography that varied in relation to the cell morphotype, with patterns of immunocytochemical staining reciprocally conforming to changes in the cell geometry, a property described for changes from elongated, to polygonal, to spread cytoplasms and related organelles arrangements, as a result of reciprocal reassembly of DES, vimentin, and actin filaments ( 67 – 69 ). Since this reassembly has been shown relevant to bring about runx2 expression ( 62 , 70 – 73 ), we reasoned that knowledge of the cytoskeletal proteins and related enzymes/chaperones/signaling molecules detectable in our rBMSCs could be of utility to collect a panel of molecular information suitable for the eventual construction of a protein -protein interaction (PPI) network or interactome ( 74 ), focused on the potential role of DES in osteogenesis.…”

Multiscale architecture: Mechanics of composite cytoskeletal networks

“…Moving toward synthetic cell research, composite actin-IF networks within lipid vesicles were studied: in the vesicles, desmin and actin filaments are colocalized at the droplet periphery as observed by epifluorescence microscopy. 96 Both filament types deform the droplets, but the composite network with equal concentrations (measured in g/l) of actin and desmin exhibits twice as many deformations as the single-component networks with the same total protein concentration. AFM experiments revealed that there is no explicit interaction between the filaments, so that likely the interaction of both proteins with the lipid membrane and a physical mechanism such as depletion forces cause the interaction between desmin and actin filaments.…”

Research Progress in Skin Aging, Metabolism, and Related Products

“…Impaired desmin can compromise lipid metabolism, impacting the synthesis and transport of lipids that are essential for skin health. This disruption can affect lipid synthesis and storage within skin cells, potentially leading to skin-related issues, including impaired skin barrier function [70].…”