TY - JOUR
T1 - Folding defects in P-type ATP 8B1 associated with hereditary cholestasis are ameliorated by 4-phenylbutyrate
AU - van der Velden, L.M.
AU - Stapelbroek, J.M.
AU - Krieger, E.
AU - van den Berghe, P.V.E.
AU - Verhulst, P.M.
AU - Berger, R.
AU - Holthuis, J.C.M.
AU - Houwen, R.H.J.
AU - Klomp, L.W.J.
AU - van de Graaf, S.F.J.
PY - 2010
Y1 - 2010
N2 - Deficiency in P-type ATP8B1 is a severe and clinically highly variable hereditary disorder that is
primarily characterized by intrahepatic cholestasis. It presents either as a progressive (progressive
familial intrahepatic cholestasis type 1 [PFIC1]) or intermittent (benign recurrent intrahepatic cholestasis
type 1 [BRIC1]) disease.ATP8B1deficiency is caused by autosomal recessive mutations in the
gene encoding ATP8B1, a putative aminophospholipid-translocating P-type adenosine triphosphatase.
The exact pathogenesis of the disease is elusive, and no effective pharmacological therapy is
currently available. Here, the molecular consequences of six distinct ATP8B1 missense mutations
(p.L127P, p.G308V, p.D454G, p.D554N, p.I661T, and p.G1040R) and one nonsense mutation
(p.R1164X) associated with PFIC1 and/or BRIC1 were systematically characterized. Except for the
p.L127P mutation, all mutations resulted in markedly reduced ATP8B1 protein expression, whereas
messenger RNA expression was unaffected. Five of seven mutations resulted in (partial) retention of
ATP8B1 in the endoplasmic reticulum. Reduced protein expression was partially restored by culturing
the cells at 30°C and by treatment with proteasomal inhibitors, indicating protein misfolding and
subsequent proteosomal degradation. Protein misfolding was corroborated by predicting the consequences
of most mutations onto a homology model of ATP8B1. Treatment with 4-phenylbutyrate, a
clinically approved pharmacological chaperone, partially restored defects in expression and localization
of ATP8B1 substitutions G308V, D454G, D554N, and in particular I661T, which is the most
frequently identified mutation in BRIC1. Conclusion: A surprisingly large proportion of ATP8B1
mutations resulted in aberrant folding and decreased expression at the plasma membrane. These
effects were partially restored by treatment with 4-phenylbutyrate. We propose that treatment with
pharmacological chaperones may represent an effective therapeutic strategy to ameliorate the recurrent
attacks of cholestasis in patients with intermittent (BRIC1) disease
AB - Deficiency in P-type ATP8B1 is a severe and clinically highly variable hereditary disorder that is
primarily characterized by intrahepatic cholestasis. It presents either as a progressive (progressive
familial intrahepatic cholestasis type 1 [PFIC1]) or intermittent (benign recurrent intrahepatic cholestasis
type 1 [BRIC1]) disease.ATP8B1deficiency is caused by autosomal recessive mutations in the
gene encoding ATP8B1, a putative aminophospholipid-translocating P-type adenosine triphosphatase.
The exact pathogenesis of the disease is elusive, and no effective pharmacological therapy is
currently available. Here, the molecular consequences of six distinct ATP8B1 missense mutations
(p.L127P, p.G308V, p.D454G, p.D554N, p.I661T, and p.G1040R) and one nonsense mutation
(p.R1164X) associated with PFIC1 and/or BRIC1 were systematically characterized. Except for the
p.L127P mutation, all mutations resulted in markedly reduced ATP8B1 protein expression, whereas
messenger RNA expression was unaffected. Five of seven mutations resulted in (partial) retention of
ATP8B1 in the endoplasmic reticulum. Reduced protein expression was partially restored by culturing
the cells at 30°C and by treatment with proteasomal inhibitors, indicating protein misfolding and
subsequent proteosomal degradation. Protein misfolding was corroborated by predicting the consequences
of most mutations onto a homology model of ATP8B1. Treatment with 4-phenylbutyrate, a
clinically approved pharmacological chaperone, partially restored defects in expression and localization
of ATP8B1 substitutions G308V, D454G, D554N, and in particular I661T, which is the most
frequently identified mutation in BRIC1. Conclusion: A surprisingly large proportion of ATP8B1
mutations resulted in aberrant folding and decreased expression at the plasma membrane. These
effects were partially restored by treatment with 4-phenylbutyrate. We propose that treatment with
pharmacological chaperones may represent an effective therapeutic strategy to ameliorate the recurrent
attacks of cholestasis in patients with intermittent (BRIC1) disease
U2 - 10.1002/hep.23268
DO - 10.1002/hep.23268
M3 - Article
SN - 0270-9139
VL - 51
SP - 286
EP - 296
JO - Hepatology
JF - Hepatology
IS - 1
ER -