BACKGROUND: The mechanisms balancing proteostasis in glomerular cells are unknown. Mucolipidosis (ML) II and III are rare lysosomal storage disorders associated with mutations of the Golgi-resident GlcNAc-1-phosphotransferase, which generates mannose 6-phosphate residues on lysosomal enzymes. Without this modification, lysosomal enzymes are missorted to the extracellular space, which results in lysosomal dysfunction of many cell types. Patients with MLII present with severe skeletal abnormalities, multisystemic symptoms, and early death; the clinical course in MLIII is less progressive. Despite dysfunction of a major degradative pathway, renal and glomerular involvement is rarely reported, suggesting organ-specific compensatory mechanisms. METHODS: MLII mice were generated and compared with an established MLIII model to investigate the balance of protein synthesis and degradation, which reflects glomerular integrity. Proteinuria was assessed in patients. High-resolution confocal microscopy and functional assays identified proteins to deduce compensatory modes of balancing proteostasis. RESULTS: Patients with MLII but not MLIII exhibited microalbuminuria. MLII mice showed lysosomal enzyme missorting and several skeletal alterations, indicating that they are a useful model. In glomeruli, both MLII and MLIII mice exhibited reduced levels of lysosomal enzymes and enlarged lysosomes with abnormal storage material. Nevertheless, neither model had detectable morphologic or functional glomerular alterations. The models rebalance proteostasis in two ways: MLII mice downregulate protein translation and increase the integrated stress response, whereas MLIII mice upregulate the proteasome system in their glomeruli. Both MLII and MLIII downregulate the protein complex mTORC1 (mammalian target of rapamycin complex 1) signaling, which decreases protein synthesis. CONCLUSIONS: Severe lysosomal dysfunction leads to microalbuminuria in some patients with mucolipidosis. Mouse models indicate distinct compensatory pathways that balance proteostasis in MLII and MLIII.
BACKGROUND: The mechanisms balancing proteostasis in glomerular cells are unknown. Mucolipidosis (ML) II and III are rare lysosomal storage disorders associated with mutations of the Golgi-resident GlcNAc-1-phosphotransferase, which generates mannose 6-phosphate residues on lysosomal enzymes. Without this modification, lysosomal enzymes are missorted to the extracellular space, which results in lysosomal dysfunction of many cell types. Patients with MLII present with severe skeletal abnormalities, multisystemic symptoms, and early death; the clinical course in MLIII is less progressive. Despite dysfunction of a major degradative pathway, renal and glomerular involvement is rarely reported, suggesting organ-specific compensatory mechanisms. METHODS: MLII mice were generated and compared with an established MLIII model to investigate the balance of protein synthesis and degradation, which reflects glomerular integrity. Proteinuria was assessed in patients. High-resolution confocal microscopy and functional assays identified proteins to deduce compensatory modes of balancing proteostasis. RESULTS:Patients with MLII but not MLIII exhibited microalbuminuria. MLII mice showed lysosomal enzyme missorting and several skeletal alterations, indicating that they are a useful model. In glomeruli, both MLII and MLIII mice exhibited reduced levels of lysosomal enzymes and enlarged lysosomes with abnormal storage material. Nevertheless, neither model had detectable morphologic or functional glomerular alterations. The models rebalance proteostasis in two ways: MLII mice downregulate protein translation and increase the integrated stress response, whereas MLIII mice upregulate the proteasome system in their glomeruli. Both MLII and MLIII downregulate the protein complex mTORC1 (mammalian target of rapamycin complex 1) signaling, which decreases protein synthesis. CONCLUSIONS: Severe lysosomal dysfunction leads to microalbuminuria in some patients with mucolipidosis. Mouse models indicate distinct compensatory pathways that balance proteostasis in MLII and MLIII.
Authors: P Bifsha; K Landry; L Ashmarina; S Durand; V Seyrantepe; S Trudel; C Quiniou; S Chemtob; Y Xu; R A Gravel; R Sladek; A V Pshezhetsky Journal: Cell Death Differ Date: 2006-08-04 Impact factor: 15.828
Authors: K Kollmann; M Damme; S Markmann; W Morelle; M Schweizer; I Hermans-Borgmeyer; A K Röchert; S Pohl; T Lübke; J-C Michalski; R Käkelä; S U Walkley; T Braulke Journal: Brain Date: 2012-09 Impact factor: 13.501
Authors: Giorgia Di Lorenzo; Lena M Westermann; Timur A Yorgan; Julian Stürznickel; Nataniel F Ludwig; Luise S Ammer; Anke Baranowsky; Shiva Ahmadi; Elham Pourbarkhordariesfandabadi; Sandra R Breyer; Tim N Board; Anne Foster; Jean Mercer; Karen Tylee; Renata Voltolini Velho; Michaela Schweizer; Thomas Renné; Thomas Braulke; Dévora N Randon; Fernanda Sperb-Ludwig; Louise Lapagesse de Camargo Pinto; Carolina Araujo Moreno; Denise P Cavalcanti; Michael Amling; Kerstin Kutsche; Dominic Winter; Nicole M Muschol; Ida V D Schwartz; Tim Rolvien; Tatyana Danyukova; Thorsten Schinke; Sandra Pohl Journal: Genet Med Date: 2021-08-02 Impact factor: 8.822