Potentiation of ABCA3 lipid transport function by ivacaftor and genistein.

Susanna Kinting,Matthias Griese,Florent Delhommel,Maria Forstner,Yang Li,Michael Sattler

doi:10.1111/jcmm.14397

Abstract

ABCA3 is a phospholipid transporter implicated in pulmonary surfactant homoeostasis and localized at the limiting membrane of lamellar bodies, the storage compartment for surfactant in alveolar type II cells. Mutations in ABCA3 display a common genetic cause for diseases caused by surfactant deficiency like respiratory distress in neonates and interstitial lung disease in children and adults, for which currently no causal therapy exists. In this study, we investigated the effects of ivacaftor and genistein, two potentiators of the cystic fibrosis transmembrane conductance regulator (CFTR), on ABCA3‐specific lipid transport function. Wild‐type (WT) and functional ABCA3 mutations N568D, F629L, G667R, T1114M and L1580P were stably expressed in A549 cells. Three‐dimensional modelling predicted functional impairment for all five mutants that was confirmed by in vitro experiments (all <14% of WT functional activity). Treatment with potentiators rescued the mutants N568D (up to 114% of WT), F629L (up to 47% of WT), and G667R (up to 60% of WT), the latter variation needing higher concentrations of genistein, showing reduced affinity of the potentiator to the mutant protein. Our results present a first proof that functional ABCA3 mutations are rescued by CFTR potentiators, making them a potential therapeutical option for patients suffering from surfactant deficiency due to ABCA3 mutations.

Highlights

Pulmonary surfactant is a lipoprotein complex that lines the alveo‐ lar spaces and is synthesized, stored and secreted by alveolar type II (ATII) cells
Functional impairment of ABCA3 due to mutations may lead to fatal or chronic disturbances of ATII cells and surfactant homoeostasis re‐ sulting in pulmonary diseases like neonatal respiratory distress syn‐ drome and chronic interstitial lung disease
We showed impaired phospholipid transport function of ABCA3 due to distinct disease causing functional mutations that can be rescued by the CFTR potentiators ivacaftor and genistein for mutations located in the NBD1 of the protein

Summary

| INTRODUCTION

Pulmonary surfactant is a lipoprotein complex that lines the alveo‐ lar spaces and is synthesized, stored and secreted by alveolar type II (ATII) cells. Adenosine triphosphate (ATP)‐binding cassette subfam‐ ily A member 3 (ABCA3), a lipid transporter involved in surfactant homoeostasis, is localized at the outer membrane of lamellar bod‐ ies.[5,6,7,8] Like all ABC transporters it is composed of two transmem‐ brane domains (TMDs) that form a pore and two nucleotide‐binding domains (NBDs) that bind and hydrolyse ATP to generate the energy to transport surfactant lipids into the lumen of LBs.[9,10]. For ABCA3 we showed that a treatment with correctors rescued processing, trafficking, localization and function of misfolding muta‐ tions.[23] Since a lot of ABCA3 mutations are classified as functional mutations, the main goal of this study was to evaluate the effect of potentiators on the lipid transport function of those mutations. G667R is located in the NBD1 con‐ served ABC signature motif, affected in G551D in CFTR It was selected because a rare variant has been described in humans in this position.[27]. The results presented here might pave the way for muta‐ tion‐group specific treatment of pulmonary diseases caused by ABCA3 mutations

| MATERIALS AND METHODS

| DISCUSSION

Findings

CONFLICT OF INTEREST