Gliotoxin Induces Cofilin Phosphorylation to Promote Actin Cytoskeleton Dynamics and Internalization of Aspergillus fumigatus Into Type II Human Pneumocyte Cells

Abstract

Aspergillus fumigatus is able to internalize into lung epithelial cells to escape from immune attack for further dissemination. We previously reported that gliotoxin, a major mycotoxin of A. fumigatus , promotes this internalization; however, the mechanism remained unclear. Here, we report that gliotoxin is able to induce cofilin phosphorylation in A549 type II human pneumocytes. Either too high or too low a level of cofilin phosphorylation blocked the gliotoxin-induced actin cytoskeleton rearrangement and A. fumigatus internalization. LIM domain kinase 1 (LIMK1) and its upstream small GTPases (Cdc42 and RhoA, but not Rac1) predominantly mediated the gliotoxin-induced cofilin phosphorylation and A. fumigatus internalization. Simultaneously, gliotoxin significantly stimulated an increase in cAMP; however, adding an antagonist of PKA did not block gliotoxin-induced A. fumigatus internalization. In vivo , exogenous gliotoxin helped gliotoxin synthesis deficient strain gliPΔ invade into the lung tissue and the lung fungal burden increased markedly in immunosuppressed mice. In conclusion, these data revealed a novel role of gliotoxin in inducing cofilin phosphorylation mostly through the Cdc42/RhoA-LIMK1 signaling pathway to promote actin cytoskeleton rearrangement and internalization of A. fumigatus into type II human pneumocytes.

In vitro study on aspects of molecular mechanisms underlying invasive aspergillosis caused by gliotoxin and fumagillin, alone and in combination

“…Further, reduced dithiol form of GT has the ability to chelate Zn 2+ ions from intracellular metalloenzymes and target thioredoxin redox system 47,48 . Also, GT is involved in activation of phospholipase D which catalyzes hydrolysis to produce the signal molecule phosphatidic acid, soluble choline and actin cytoskeleton rearrangement 49,50 . On the other hand in case of FUM, total glutathione content is significantly higher in cell lines insensitive (human umbilical vein endothelial cells) to FUM than in sensitive cell lines (human colon cancer cell line) 51 .…”

Fungal Toxins and Host Immune Responses

“…The germination of A. fumigatus conidia and subsequent invasion into the respiratory epithelium is a critical step which promotes infection. Gliotoxin promotes cytoskeletal remodelling in human alveolar epithelial cells in vitro which facilitates the internalisation of A. fumigatus conidia (Jia et al, 2014;Zhang et al, 2019). Fungal burdens present in the lung tissue of immunosuppressed mice infected with an A. fumigatus gliP mutant unable to produce gliotoxin were significantly reduced compared with wild-type fungus, and the invasive capacity of the gliP mutant was partially restored following the addition of exogenous gliotoxin which correlated with increased mortality (Jia et al, 2014;Zhang et al, 2019).…”

Rocking the Boat: The Decisive Roles of Rho Kinases During Oocyte, Blastocyst, and Stem Cell Development

“…Cofilin in turn promotes actin polymerization and stability. Recent works by Zhang et al (2019) and Morales-Quinones et al (2020) have clearly explained how LIMK implicates cytoskeletal organization and muscle contraction through the Rho pathway. The disruption of LIMK activities resulted in the loss of muscle contraction and vasoconstriction reducing cofilin phosphorylation and stiffening of arterial muscle ( Morales-Quinones et al, 2020 ).…”