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Progressive familial intrahepatic cholestasis (PFIC) is a lethal inherited childhood cholestasis of hepatocellular origin. Different subtypes of PFIC have been described according to serum gamma‐glutamyl transpeptidase (GGT) activity. There is currently no effective medical therapy available for children with PFIC. We report on 39 patients with PFIC who received ursodeoxycholic acid (UDCA) orally (20‐30 mg/kg b.w./day) for a period of 2 to 4 years. Group 1 (n = 26) consisted of children with normal GGT activity, and group 2 (n = 13) of children with high GGT activity. Within group 1, liver tests normalized in 11 children, improved in 5, and stabilized or worsened in 10. Within group 2, liver tests normalized in six children, improved in four, and stabilized or worsened in three. Improvement of parameters was associated with an enrichment of the circulating pool of bile acids with UDCA. Hepatosplenomegaly and pruritus disappeared or diminished in children in whom liver tests normalized. In nine of these children, liver tests worsened and normalized again after stopping and restarting UDCA. Liver histology assessed in four children after normalization of liver tests and 2 years of treatment showed a decrease in fibrosis. We conclude that UDCA should be considered in the initial therapeutic management of children with PFIC, because it appears effective in resolving or improving the liver function and the clinical status of a fair proportion of children. Chronic UDCA therapy might thus avoid the need for liver transplantation in some children with PFIC.

ATP13A2 is a lysosomal P-type transport ATPase that has been implicated in Kufor-Rakeb syndrome and Parkinson's disease (PD), providing protection against α-synuclein, Mn 2+ , and Zn 2+ toxicity in various model systems. So far, the molecular function and regulation of ATP13A2 remains undetermined. Here, we demonstrate that ATP13A2 contains a unique N-terminal hydrophobic extension that lies on the cytosolic membrane surface of the lysosome, where it interacts with the lysosomal signaling lipids phosphatidic acid (PA) and phosphatidylinositol(3,5)bisphosphate [PI(3,5)P2]. We further demonstrate that ATP13A2 accumulates in an inactive autophosphorylated state and that PA and PI(3,5)P2 stimulate the autophosphorylation of ATP13A2. In a cellular model of PD, only catalytically active ATP13A2 offers cellular protection against rotenone-induced mitochondrial stress, which relies on the availability of PA and PI(3,5)P2. Thus, the N-terminal binding of PA and PI(3,5)P2 emerges as a key to unlock the activity of ATP13A2, which may offer a therapeutic strategy to activate ATP13A2 and thereby reduce α-synuclein toxicity or mitochondrial stress in PD or related disorders.mitochondria | lysosome | flippase | α-synuclein | P5-type ATPase N euronal fitness depends on optimal lysosomal function and efficient lysosomal delivery of proteins and organelles by autophagy for subsequent breakdown (1, 2). Kufor-Rakeb syndrome (KRS) is an autosomal recessive form of Parkinson's disease (PD) associated with dementia, which is caused by mutations in ATP13A2/PARK9 (3). Mutations in or knockdown (KD) of ATP13A2 lead to lysosomal dysfunctions, including reduced lysosomal acidification, decreased degradation of lysosomal substrates (4), impaired autophagosomal flux (4, 5), and accumulation of fragmented mitochondria (5, 6). By contrast, overexpression (OE) of Ypk9p (i.e., the yeast ATP13A2 ortholog) protects yeast against toxicity of α-synuclein (7), which is the major protein in Lewy bodies, the abnormal protein aggregates that develop inside nerve cells in PD. This protective effect of ATP13A2 on α-synuclein toxicity is conserved in yeast, Caenorhabditis elegans, and rat neuronal cells (7). Because ATP13A2 imparts resistance to Mn 2+ (7-9) and Zn 2+ (10-12), it was proposed that ATP13A2 may function as a Mn 2+ (7-9) and/or Zn 2+ transporter (10-12).ATP13A2 belongs to the P5 subfamily of the P-type ATPase superfamily, which comprises five subfamilies (P1-5) of membrane transporters. P-type ATPases hydrolyze ATP to actively transport inorganic ions across membranes or lipids between membrane leaflets (reviewed in ref. 13). During the transport cycle, a phosphointermediate is formed on a conserved aspartate residue (14). The human P5-type ATPases are divided into two groups, P5A (ATP13A1) and P5B (ATP13A2-5), but their transport specificity has not been established (14-16).P-type ATPases comprise a membrane-embedded core of six transmembrane (TM) helices (M1-6) that form the substrate binding site(s) and entrance/exit pathways for the transp...

Background-Saccharomyces boulardii is a non-pathogenic yeast which exerts trophic eVects on human and rat small intestinal mucosa. Aims-To examine the eVects of S boulardii on ileal adaptation after proximal enterectomy in rats. Methods-Wistar rats, aged eight weeks, underwent 60% proximal resection or transection and received by orogastric intubation either 1 mg/g body wt per day lyophilised S boulardii or the vehicle for seven days. The eVects on ileal mucosal adaptation were assessed eight days after surgery. Results-Compared with transection, resection resulted in mucosal hyperplasia with significant decreases in the specific and total activities of sucrase, lactase, and maltase. Treatment of resected animals with S boulardii had no eVect on mucosal hyperplasia but did upgrade disaccharidase activities to the levels of the transected group. Enzyme stimulation by S boulardii was associated with significant increases in diamine oxidase activity and mucosal polyamine concentrations. Likewise, sodium dependent D-glucose uptake by brush border membrane vesicles, measured as a function of time and glucose concentration in the incubation medium, was significantly (p<0.05) increased by 81% and three times respectively in the resected group treated with S boulardii. In agreement with this, expression of the sodium/glucose cotransporter-1 in brush border membranes of resected rats treated with S boulardii was enhanced twofold compared with resected controls. Conclusion-Oral administration of S boulardii soon after proximal enterectomy improves functional adaptation of the remnant ileum. (Gut 1999;45:89-96)

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The mechanism(s) by which rat immature enterocytes exhibit increased responsiveness to insulin before weaning is unknown. Therefore, we have analyzed the distribution, ontogeny, and molecular properties of insulin receptors (IR) and of related substrates in immature and mature enterocytes. IR were studied by radioligand binding assays, cross-linking labeling, immunohistochemistry, and in vitro phosphorylated substrates by immunoprecipitation. Regardless of age, 125I-insulin binding to IR was five times higher in crypt cells than in villus cells and two times higher in the ileum than in the jejunum. Binding capacity to villus cells from sucklings (day 14) exceeded three times that of older animals (day 30 and day 60). Scatchard analysis of equilibrium binding data confirmed an age-related decrease in low- and high-affinity receptor classes without change in affinity constants. In concordance, both alpha- and beta-IR subunits were more abundant in immature than in mature membranes. In vitro, insulin elicited the phosphorylation of three membrane proteins (96, 60 and 42 kDa), whose signals were virtually inhibited by preincubating membranes with antireceptor monoclonal antibodies. By immunoprecipitation, the 60-kDa signal was rapidly detected as a tyrosine-phosphorylated protein, expressed in mature and immature membranes, and identified as a receptor substrate phosphorylated in vitro by the IR tyrosine kinase. In conclusion, 1) increased responsiveness of rat immature enterocytes to insulin could be related to high membrane concentrations of IR and 2) normal rat enterocytes express a 60-kDa phosphotyrosine protein identified as a direct substrate of the IR tyrosine kinase.

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Cell swelling triggers in most cell types an outwardly rectifying anion current, I Cl,swell, via volume-regulated anion channels (VRACs). We have previously demonstrated in calf pulmonary artery endothelial (CPAE) cells that inhibition of the Rho/Rho kinase/myosin light chain phosphorylation pathway reduces the swelling-dependent activation of I Cl,swell. However, these experiments did not allow us to discriminate between a direct activator role or a permissive effect. We now show that the Rho pathway did not affect VRAC activity if this pathway was activated by transfecting CPAE cells with constitutively active isoforms of Gα (a Rho activating heterotrimeric G protein subunit), Rho, or Rho kinase. Furthermore, biochemical and morphological analysis failed to demonstrate activation of the Rho pathway during hypotonic cell swelling. Finally, manipulating the Rho pathway with either guanosine 5′- O-(3-thiotriphosphate) or C3 exoenzyme had no effect on VRACs in caveolin-1-expressing Caco-2 cells. We conclude that the Rho pathway exerts a permissive effect on VRACs in CPAE cells, i.e., swelling-induced opening of VRACs requires a functional Rho pathway, but not an activation of the Rho pathway.