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Lysosomes are major sites for intracellular, acidic hydrolase-mediated proteolysis and cellular degradation. The export of low-molecular-weight catabolic end-products is facilitated by polytopic transmembrane proteins mediating secondary active or passive transport. A number of these lysosomal transporters, however, remain enigmatic. We present a detailed analysis of MFSD1, a hitherto uncharacterized lysosomal family member of the major facilitator superfamily. MFSD1 is not N-glycosylated. It contains a dileucine-based sorting motif needed for its transport to lysosomes. Mfsd1 knockout mice develop splenomegaly and severe liver disease. Proteomics of isolated lysosomes from Mfsd1 knockout mice revealed GLMP as a critical accessory subunit for MFSD1. MFSD1 and GLMP physically interact. GLMP is essential for the maintenance of normal levels of MFSD1 in lysosomes and vice versa. Glmp knockout mice mimic the phenotype of Mfsd1 knockout mice. Our data reveal a tightly linked MFSD1/GLMP lysosomal membrane protein transporter complex., Competing Interests: DM, MT, FS, CT, AL, MS, IH, RL, WE, PS, MD No competing interests declared, (© 2019, Massa López et al.)

The vacuolar-type H + -translocating ATPase (v-H + -ATPase) has been implicated in the amino acid-dependent activation of the mechanistic target of rapamycin complex 1 (MTORC1), an important regulator of macroautophagy. To reveal the mechanistic links between the v-H + -ATPase and MTORC1, we destablilized v-H + -ATPase complexes in mouse liver cells by induced deletion of the essential chaperone ATP6AP2. ATP6AP2-mutants are characterized by massive accumulation of endocytic and autophagic vacuoles in hepatocytes. This cellular phenotype was not caused by a block in endocytic maturation or an impaired acidification. However, the degradation of LC3-II in the knockout hepatocytes appeared to be reduced. When v-H + -ATPase levels were decreased, we observed lysosome association of MTOR and normal signaling of MTORC1 despite an increase in autophagic marker proteins. To better understand why MTORC1 can be active when v-H + -ATPase is depleted, the activation of MTORC1 was analyzed in ATP6AP2-deficient fibroblasts. In these cells, very little amino acid-elicited activation of MTORC1 was observed. In contrast, insulin did induce MTORC1 activation, which still required intracellular amino acid stores. These results suggest that in vivo the regulation of macroautophagy depends not only on v-H + -ATPase-mediated regulation of MTORC1.

Unlabelled: A Disintegrin And Metalloprotease (ADAM) 10 exerts essential roles during organ development and tissue integrity in different organs, mainly through activation of the Notch pathway. However, only little is known about its implication in liver tissue physiology. Here we show that in contrast to its role in other tissues, ADAM10 is dispensable for the Notch2-dependent biliary tree formation. However, we demonstrate that expression of bile acid transporters is dependent on ADAM10. Consequently, mice deficient for Adam10 in hepatocytes, cholangiocytes and liver progenitor cells develop spontaneous hepatocyte necrosis and concomitant liver fibrosis. We furthermore observed a strongly augmented ductular reaction in 15-week old ADAM10(Δhep/Δch) mice and demonstrate that c-Met dependent liver progenitor cell activation is enhanced. Additionally, liver progenitor cells are primed to hepatocyte differentiation in the absence of ADAM10. These findings show that ADAM10 is a novel central node controlling liver tissue homeostasis., Highlights: Loss of ADAM10 in murine liver results in hepatocyte necrosis and concomitant liver fibrosis. ADAM10 directly regulates expression of bile acid transporters but is dispensable for Notch2-dependent formation of the biliary system. Activation of liver progenitor cells is enhanced through increased c-Met signalling, in the absence of ADAM10. Differentiation of liver progenitor cells to hepatocytes is augmented in the absence of ADAM10.

Objectives: To assess magnetic resonance imaging (MRI) with conventional chemical shift-based sequences with and without T2* correction for the evaluation of steatosis hepatitis (SH) in the presence of iron., Methods: Thirty-one patients who underwent MRI and liver biopsy because of clinically suspected diffuse liver disease were retrospectively analysed. The signal intensity (SI) was calculated in co-localised regions of interest (ROIs) using conventional spoiled gradient-echo T1 FLASH in-phase and opposed-phase (IP/OP). T2* relaxation time was recorded in a fat-saturated multi-echo-gradient-echo sequence. The fat fraction (FF) was calculated with non-corrected and T2*-corrected SIs. Results were correlated with liver biopsy., Results: There was significant difference (P < 0.001) between uncorrected and T2* corrected FF in patients with SH and concomitant hepatic iron overload (HIO). Using 5 % as a threshold resulted in eight false negative results with uncorrected FF whereas T2* corrected FF lead to true positive results in 5/8 patients. ROC analysis calculated three threshold values (8.97 %, 5.3 % and 3.92 %) for T2* corrected FF with accuracy 84 %, sensitivity 83-91 % and specificity 63-88 %., Conclusions: FF with T2* correction is accurate for the diagnosis of hepatic fat in the presence of HIO. Findings of our study suggest the use of IP/OP imaging in combination with T2* correction., Key Points: • Magnetic resonance helps quantify both iron and fat content within the liver • T2* correction helps to predict the correct diagnosis of steatosis hepatitis • "Fat fraction" from T2*-corrected chemical shift-based sequences accurately quantifies hepatic fat • "Fat fraction" without T2* correction underestimates hepatic fat with iron overload.

Histological, histochemical, and ultrastructural examinations were performed on pulmonary and hepatic tissues of rats after prolonged oral treatment with several tricyclic antidepressants and two neuroleptics, which are all of amphiphilic character. The antidepressants ipindole, imipramine, clomipramine, 1-chloro-amitriptyline, and 1-chloro-10,11-dehydro-amitriptyline were found to cause an accumulation of intraalveolar foam cells accompanied by the formation of abnormal lamellated and crystalloid cytoplasmic inclusions in most pulmonary and hepatic cell types. The ultrastructural and histochemical findings in both tissues point to generalized, abnormal intracellular storage of polar lipids, i.e. to drug-induced lipidosis. The foam cells are not regarded as an isolated pulmonary alteration but rather as an easily obtainable indication of generalized lipidosis, under the present conditions. They are thought to represent alveolar macrophages stuffed with non-digestible phospholipids. On the other hand, the tricyclic antidepressants noxiptiline and amitriptyline, and the neuroleptics chlorpromazine and thioridazine caused neither formation of foam cells nor of any lipidosis-like ultrastructural alterations. These negative results are tentatively ascribed to a more rapid biotransformation of the amphiphilic drug molecules into more hydrophilic metabolites which no longer have a high affinity to polar lipids. Two main conclusions can be drawn from the present ovservations: (1) Intraalveolar foam cells must not be regarded as a fortuitous alteration but rather as a first indication of generalized phospholipidosis, when they are found in animals treated with an amphiphilic drug. (2) Closely related compounds of amphiphilic character do not necessarily have the same potency to induce a phospholipidosis under in vivo conditions.

This ultrastructural investigation on renal collecting duct cells and hepatocytes of rats deals with the question of whether or not lipid-storage lysosomes as induced by cationic amphiphilic compounds retain their ability to fuse with autophagosomes/autolysosomes. These were recognized by their glycogen content which was made to persist by means of acarbose, an inhibitor of lysosomal alpha-glucosidase. To induce lipidosis, rats were pretreated for several weeks with chloroquine or chlorphentermine; they then received combined treatment with the lipidosis-inducing drug plus acarbose. In renal collecting duct cells, mixed storage lysosomes displaying the features of both lipidosis and glycogenosis were found to predominate, indicating that fusion between lipid-laden lysosomes and glycogen-containing autophagosomes/autolysosomes was efficient. Hepatocytes also displayed some mixed storage lysosomes; these were, however, regularly accompanied, within a given hepatocyte, by greater numbers of pure lipidosis-related inclusions and pure glycogen vacuoles. This observation indicates that in hepatocytes lipid-storage lysosomes were rather reluctant to fuse, thus displaying a feature of telolysosomes which are no longer capable of participating in cellular digestion.

The present paper describes an animal model of lysosomal glycogenosis as induced by a competitive inhibitor of alpha-glucosidase. Rats received intraperitoneal injections of the inhibitor, a pseudotetrasaccharide (Acarbose, Bay g 5421); liver tissue was examined by light and electron microscopy. Substrate-histochemical and enzyme-cytochemical methods were used to demonstrate intralysosomal glycogen storage within hepatocytes and Kupffer cells. The cytological picture closely resembled that occurring in glycogenosis type II (Pompe's disease) of humans. After cessation of drug treatment, the glycogen storage was slowly reversible. The present results point to the physiological role of the lysosomal apparatus for intracellular glycogen turnover. On the cellular level, this experimentally induced glycogenosis may be useful as a model of Pompe's disease.