Some ABCA3 mutations elevate ER stress and initiate apoptosis of lung epithelial cellsReport as inadecuate




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Respiratory Research

, 12:4

First Online: 01 December 2011Received: 15 April 2010Accepted: 07 January 2011

Abstract

BackgroundABCA3 transporter ATP-binding cassette transporter of the A subfamily is localized to the limiting membrane of lamellar bodies, organelles for assembly and storage of pulmonary surfactant in alveolar epithelial type II cells AECII. It transports surfactant phospholipids into lamellar bodies and absence of ABCA3 function disrupts lamellar body biogenesis. Mutations of the ABCA3 gene lead to fatal neonatal surfactant deficiency and chronic interstitial lung disease ILD of children. ABCA3 mutations can result in either functional defects of the correctly localized ABCA3 or trafficking-folding defects where mutated ABCA3 remains in the endoplasmic reticulum ER.

MethodsHuman alveolar epithelial A549 cells were transfected with vectors expressing wild-type ABCA3 or one of the three ABCA3 mutant forms, R43L, R280C and L101P, C-terminally tagged with YFP or hemagglutinin-tag. Localization-trafficking properties were analyzed by immunofluorescence and ABCA3 deglycosylation. Uptake of fluorescent NBD-labeled lipids into lamellar bodies was used as a functional assay. ER stress and apoptotic signaling were examined through RT-PCR based analyses of XBP1 splicing, immunoblotting or FACS analyses of stress-apoptosis proteins, Annexin V surface staining and determination of the intracellular glutathion level.

ResultsWe demonstrate that two ABCA3 mutations, which affect ABCA3 protein trafficking-folding and lead to partial R280C or complete L101P retention of ABCA3 in the ER compartment, can elevate ER stress and susceptibility to it and induce apoptotic markers in the cultured lung epithelial A549 cells. R43L mutation, resulting in a functional defect of the properly localized ABCA3, had no effect on intracellular stress and apoptotic signaling.

ConclusionOur data suggest that expression of partially or completely ER localized ABCA3 mutant proteins can increase the apoptotic cell death of the affected cells, which are factors that might contribute to the pathogenesis of genetic ILD.

List of abbreviationsABC transporterATP binding cassette transporter

AECIIalveolar epithelial type-II cells

ILDinterstitial lung disease

UPRunfolded protein response

ERendoplasmic reticulum

YFP-GFPyellow-green fluorescent protein

HAhemagglutinin

IPFidiopathic pulmonary fibrosis

SP-Csurfactant protein C

BiPbinding immunoglobulin protein

RT-PCRreverse-transcription PCR

XBP1X-box binding protein 1

TMtunicamycin

FACSfluorescence-activated cell sorting

NBD7-nitrobenz-2-oxa-1,3-diazole

PCphosphatidylcholine

PEphosphatidylethanolamine

LAMP3lysosomal-associated membrane protein 3

GSHglutathione

TNFαtumor necrosis factor α CFTR: cystic fibrosis conductance regulator.

Electronic supplementary materialThe online version of this article doi:10.1186-1465-9921-12-4 contains supplementary material, which is available to authorized users.

Nina Weichert, Eva Kaltenborn contributed equally to this work.

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Author: Nina Weichert - Eva Kaltenborn - Andreas Hector - Markus Woischnik - Andrea Schams - Andreas Holzinger - Sunčana Kern - Ma

Source: https://link.springer.com/







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