Defective CFTR induces aggresome formation and lung inflammation in cystic fibrosis through ROS-mediated autophagy inhibition

Abstract

Accumulation of unwanted/misfolded proteins in aggregates has been observed in airways of patients with cystic fibrosis (CF), a life-threatening genetic disorder caused by mutations in the gene encoding the cystic fibrosis transmembrane conductance regulator (CFTR). Here we show how the defective CFTR results in defective autophagy and decreases the clearance of aggresomes. Defective CFTR-induced upregulation of reactive oxygen species (ROS) and tissue transglutaminase (TG2) drive the crosslinking of beclin 1, leading to sequestration of phosphatidylinositol-3-kinase (PI(3)K) complex III and accumulation of p62, which regulates aggresome formation. Both CFTR knockdown and the overexpression of green fluorescent protein (GFP)-tagged-CFTR(F508del) induce beclin 1 downregulation and defective autophagy in non-CF airway epithelia through the ROS-TG2 pathway. Restoration of beclin 1 and autophagy by either beclin 1 overexpression, cystamine or antioxidants rescues the localization of the beclin 1 interactome to the endoplasmic reticulum and reverts the CF airway phenotype in vitro, in vivo in Scnn1b-transgenic and Cftr(F508del) homozygous mice, and in human CF nasal biopsies. Restoring beclin 1 or knocking down p62 rescued the trafficking of CFTR(F508del) to the cell surface. These data link the CFTR defect to autophagy deficiency, leading to the accumulation of protein aggregates and to lung inflammation.

Depletion of the Ubiquitin-binding Adaptor Molecule SQSTM1/p62 from Macrophages Harboring cftr ΔF508 Mutation Improves the Delivery of Burkholderia cenocepacia to the Autophagic Machinery

“…This is due to both the self-oligomerization and ubiquitin-binding nature of p62 (1,2,10,37,38). Similar aggregates have been identified in various neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and cancer (1,2,43,44). Impaired turnover of p62 is a major cause of the pathogenic changes seen in the autophagy-deficient mice, as the loss of Atg7 in mouse livers results in severe p62 accumulation.…”

“…Macrophages-A growing body of evidence indicates that BECN1 is sequestered within the mutant CFTR aggresomes (1,2). BECN1/Atg6 is a member of the class III PI3K complex and is essential for the early stages of autophagosome formation (5,39).…”

“…The most common CFTR mutation results in a deletion of phenylalanine at position 508 (⌬F508), which affects the processing of the CFTR protein in such way that it cannot reach the epithelial cell surface. This mutation results in an aggresome-prone protein that forms intracellular aggregates (1)(2)(3)(4).…”

Autophagy: for better or for worse

“…In this condition, ROS accumulation causes TG2-dependent crosslinking of Beclin-1 and the sequestration of the PIK3C3 complex in perinuclear aggregates, which prevents the PIK3C3 complex from fulfilling its autophagic function at its proper locations [205].…”

Identification of autophagy signaling network that contributes to stroke in the ischemic rodent brain via gene expression

“…Cerebral ischemia-induced microglial autophagy contributes to ischemic neuronal inflammation and injury. Autophagy is a process for the intracellular bulk degradation of cellular constituents that has multiple effects on immunity [12][13][14] . Blocking autophagy in epithelial cells enhances host cell death and finally leads to tissue destruction and infl ammation [15] .…”