Disruption of the vacuolar-type H-ATPase complex in liver causes MTORC1-independent accumulation of autophagic vacuoles and lysosomes

TY - JOUR

T1 - Disruption of the vacuolar-type H-ATPase complex in liver causes MTORC1-independent accumulation of autophagic vacuoles and lysosomes

AU - Kissing, Sandra

AU - Rudnik, Sönke

AU - Damme, Markus

AU - Lüllmann-Rauch, Renate

AU - Ichihara, Atsuhiro

AU - Kornak, Uwe

AU - Eskelinen, Eeva-Liisa

AU - Jabs, Sabrina

AU - Heeren, Jörg

AU - De Brabander, Jef K

AU - Haas, Albert

AU - Saftig, Paul

PY - 2017/4/3

Y1 - 2017/4/3

N2 - 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.

AB - 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.

KW - Amino Acids

KW - Animals

KW - Autophagy

KW - Cells, Cultured

KW - Embryo, Mammalian

KW - Endocytosis

KW - Endosomes

KW - Fibroblasts

KW - Hepatocytes

KW - Insulin

KW - Liver

KW - Lysosomes

KW - Mechanistic Target of Rapamycin Complex 1

KW - Mice, Knockout

KW - Proton-Translocating ATPases

KW - Receptors, Cell Surface

KW - Vacuoles

KW - Journal Article

U2 - 10.1080/15548627.2017.1280216

DO - 10.1080/15548627.2017.1280216

M3 - SCORING: Journal article

C2 - 28129027

VL - 13

SP - 670

EP - 685

JO - AUTOPHAGY

JF - AUTOPHAGY

SN - 1554-8627

IS - 4

ER -