Cytoskeleton disruption in J774 macrophages: Consequences for lipid droplet formation and cholesterol flux

Abstract

Macrophages store excess unesterified cholesterol (free, FC) in the form of cholesteryl ester (CE) in cytoplasmic lipid droplets. The hydrolysis of droplet-CE in peripheral foam cells is critical to HDL-promoted reverse cholesterol transport because it represents the first step in cellular cholesterol clearance, as only FC is effluxed from cells to HDL. Cytoplasmic lipid droplets move within the cell utilizing the cytoskeletal network, but, little is known about the influence of the cytoskeleton on lipid droplet formation. To understand this role we employed cytochalasin D (cyt.D) to promote actin depolymerization in J774 macrophages. Incubating J774 with acetylated LDL creates foam cells having a 4-fold increase in cellular cholesterol content (30-40% cholesterol present as cholesteryl ester (CE)) in cytoplasmic droplets. Lipid droplets formed in the presence of cyt.D are smaller in diameter. CE-deposition and -hydrolysis are decreased when cells are cholesterol-enriched in the presence of cyt.D or latrunculin A, another cytoskeleton disrupting agent. However, when lipid droplets formed in the presence of cyt.D are isolated and incubated with an exogenous CE hydrolase, the CE is more rapidly metabolized compared to droplets from control cells. This is apparently due to the smaller size and altered lipid composition of the droplets formed in the presence of cyt.D. Cytoskeletal proteins found on CE droplets influence droplet lipid composition and maturation in model foam cells. In J774 macrophages, cytoskeletal proteins are apparently involved in facilitating the interaction of lipid droplets and a cytosolic neutral CE hydrolase and may play a role in foam cell formation.

Role for formin-like 1-dependent acto-myosin assembly in lipid droplet dynamics and lipid storage

“…This revealed several actin-binding proteins (Supplementary Table 1), including NMIIa (encoded by the MYH9 gene), a structural component of contractile actin filaments. NMIIa has earlier been identified in the LD proteome of several organisms101112, but its functional role at LDs remains unknown.…”

“…Actin and actin-binding proteins have been reported to be associated with LDs101112. In murine macrophages, pharmacological disruption of the actin cytoskeleton reduces LD size and lipid storage10 and in 3T3-L1 cells, inhibition of actin dynamics through cofilin-1 depletion disrupts adipogenesis and lipid storage13.…”

“…In murine macrophages, pharmacological disruption of the actin cytoskeleton reduces LD size and lipid storage10 and in 3T3-L1 cells, inhibition of actin dynamics through cofilin-1 depletion disrupts adipogenesis and lipid storage13. At the organismal level, pharmacological perturbation of acto-myosin turnover in zebrafish affects the recruitment of LDs from the yolk-blastodisc to the animal pole14.…”

Intramuscular preadipocytes impede differentiation and promote lipid deposition of muscle satellite cells in chickens

“…[ 58 ]. In addition, several studies suggest that cell junction-related pathways are also involved in lipid deposition [ 52 , 59 , 60 ].…”

Transcriptional insights into key genes and pathways controlling muscle lipid metabolism in broiler chickens

“…Additionally, DEGs were also significantly enriched ( p < 0.05) in calcium signaling pathway and junction-related pathways (focal adhesions, cell adhesion, gap junction, tight junction, regulation of actin cytoskeleton and ECM-receptor interaction). Many studies have shown that the cell junction-related pathways may contribute to lipid deposition [9, 53, 54]. These results indicated that the above pathways might be the key pathways for lipid deposition in chicken pectoralis muscle tissue and a possible molecular regulatory network was constructed (Fig.…”