4 research outputs found
Correctors of mutant CFTR enhance subcortical cAMP-PKA signaling through modulating ezrin phosphorylation and cytoskeleton organization
The most common mutation of the cystic fibrosis transmembrane regulator (CFTR) gene, F508del, produces a misfolded protein resulting in its defective trafficking to the cell surface and an impaired chloride secretion. Pharmacological treatments partially rescue F508del CFTR activity either directly by interacting with the mutant protein and/or indirectly by altering the cellular protein homeostasis. Here, we show that the phosphorylation of ezrin together with its binding to phosphatidylinositol-4,5-bisphosphate (PIP2) tethers the F508del CFTR to the actin cytoskeleton, stabilizing it on the apical membrane and rescuing the sub-membrane compartmentalization of cAMP and activated PKA. Both the small molecules trimethylangelicin (TMA) and VX-809, which act as 'correctors' for F508del CFTR by rescuing F508del-CFTR-dependent chloride secretion, also restore the apical expression of phosphorylated ezrin and actin organization and increase cAMP and activated PKA submembrane compartmentalization in both primary and secondary cystic fibrosis airway cells. Latrunculin B treatment or expression of the inactive ezrin mutant T567A reverse the TMA and VX-809-induced effects highlighting the role of corrector-dependent ezrin activation and actin re-organization in creating the conditions to generate a sub-cortical cAMP pool of adequate amplitude to activate the F508del-CFTR-dependent chloride secretion
Emerging relationship between CFTR, actin and tight junction organization in cystic fibrosis airway epithelium
Cystic fibrosis (CF), one of the most
common genetic disorders affecting primarily
Caucasians, is due to mutations in the CF Transmembrane Conductance Regulator (CFTR) gene,
encoding for a chloride channel also acting as regulator
of other transmembrane proteins. In healthy subjects,
CFTR is maintained in its correct apical plasma
membrane location via the formation of a multiprotein
complex in which scaffold proteins (such as NHERF1)
and signaling molecules (such as cAMP and protein
kinases) guarantee its correct functioning. In CF, a
disorganized and dysfunctional airway epithelium brings
an altered flux of ions and water into the lumen of
bronchioles, consequent bacterial infections and an
enormous influx of inflammatory cells (mainly
polymorphonuclear neutrophils) into the airways. Recent
evidence in healthy airway cells supports the notion that
CFTR protein/function is strictly correlated with the
actin cytoskeleton and tight junctions status. In CF cells,
the most frequent CFTR gene mutation, F508del, has
been shown to be associated with a disorganized actin
cytoskeleton and altered tight junction permeability.
Thus, the correct localization of CFTR on the apical
plasma membrane domain through the formation of the
scaffolding and signaling complex is likely fundamental
to determine a physiological airway epithelium. The
correction of CFTR mutations by either gene or drug
therapies, as well as by stem cell-based interventions,
can determine the resumption of a physiological
organization of actin stress fibers and TJ structure and
barrier function, further indicating the close
interrelationship among these processes