Two ABCB4 mutations involving two strategic NBD-motifs do not prevent the targeting to the plasma membrana but promote MDR3 dysfunction
Poster
Data di Pubblicazione:
2012
Citazione:
Two ABCB4 mutations involving two strategic NBD-motifs do not prevent the targeting to the plasma membrana but promote MDR3 dysfunction / D. Degiorgio, P.A. Corsetto, A.M. Rizzo, C. Colombo, M. Seia, L. Costantino, G. Montorfano, L. Castellano, A. Ragozzino, G. Castaldo, M.P. Rastaldi, D.A. Coviello. - In: EUROPEAN JOURNAL OF HUMAN GENETICS. - ISSN 1018-4813. - 20:suppl. 1(2012 Sep), pp. 290-290. (Intervento presentato al convegno European human genetics conference tenutosi a Nürnberg nel 2012).
Abstract:
MDR3 protein translocates phosphatidylcoline (PC) from the inner to the outer leaflet of the
hepatocanalicular membrane; its deficiency, related to ABCB4 mutations, favours the formation of
“toxic bile”. A continuum of hepatobiliary diseases have been associated with ABCB4 mutations but,
for most of them, the detrimental effect on the protein is speculative only. The functional relevance
of two strategic mutations within the N-terminal Nucleotide-Binding-Domain was examined with
stably transfected HUH28-cell-lines expressing wild type and mutant MDR3 proteins by westernblotting,
immunocytochemistry and chromatographic quantification of lipids, collected from culture
medium after sodium-taurocholate (NaTC) stimulation. As suggested by our three-dimensional
model of MDR3 (Degiorgio D et al., 2007), the p.Y403H mutation involves the A-loop while the
p.L481R mutation is contained into the Q-loop. Our results show that both MDR3-mutant proteins
were expressed in a comparable way to the MDR3-wild-type protein: a molecular mass of 160KDa
associated with a green fluorescent signal, intenser and sharper in the plasma membranes, was
constantly identified. However, compared to the stably transfected HUH28-cell-line expressing
wild-type-MDR3 protein in the presence of NaTC 3mM, the lipid dosage into culture medium has
shown (with five indipendent experiments) that
i) the efflux of PC is reduced (p<0.01) from cell lines expressing p.Y403H and p.L481R mutant
proteins;
ii) the efflux of cholesterol is increased (p<0.01) from cell line expressing the p.Y403H mutant
protein.
In conclusion these mutations could promote in vivo formation of toxic bile with reduced amounts of
PC (p.L481R) or with reduced amounts of PC and increased level of cholesterol (p.Y403H).
Tipologia IRIS:
01 - Articolo su periodico
Elenco autori:
D. Degiorgio, P.A. Corsetto, A.M. Rizzo, C. Colombo, M. Seia, L. Costantino, G. Montorfano, L. Castellano, A. Ragozzino, G. Castaldo, M.P. Rastaldi, D.A. Coviello
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