1. Academic Validation
  2. Elevated glucosylsphingosine in Gaucher disease induced pluripotent stem cell neurons deregulates lysosomal compartment through mammalian target of rapamycin complex 1

Elevated glucosylsphingosine in Gaucher disease induced pluripotent stem cell neurons deregulates lysosomal compartment through mammalian target of rapamycin complex 1

  • Stem Cells Transl Med. 2021 Jul;10(7):1081-1094. doi: 10.1002/sctm.20-0386.
Manasa P Srikanth 1 Jace W Jones 2 Maureen Kane 2 Ola Awad 1 Tea Soon Park 3 Elias T Zambidis 3 Ricardo A Feldman 1
Affiliations

Affiliations

  • 1 Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
  • 2 Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, Maryland, USA.
  • 3 Johns Hopkins University School of Medicine, and Division of Pediatric Oncology, Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, Maryland, USA.
Abstract

Gaucher disease (GD) is a lysosomal storage disorder caused by mutations in GBA1, the gene that encodes lysosomal β-glucocerebrosidase (GCase). Mild mutations in GBA1 cause type 1 non-neuronopathic GD, whereas severe mutations cause types 2 and 3 neuronopathic GD (nGD). GCase deficiency results in the accumulation of glucosylceramide (GlcCer) and glucosylsphingosine (GlcSph). GlcSph is formed by deacylation of GlcCer by the lysosomal Enzyme acid Ceramidase. Brains from patients with nGD have high levels of GlcSph, a lipid believed to play an important role in nGD, but the mechanisms involved remain unclear. To identify these mechanisms, we used human induced pluripotent stem cell-derived neurons from nGD patients. We found that elevated levels of GlcSph activate mammalian target of rapamycin (mTOR) complex 1 (mTORC1), interfering with lysosomal biogenesis and Autophagy, which were restored by incubation of nGD neurons with mTOR inhibitors. We also found that inhibition of acid Ceramidase prevented both, mTOR hyperactivity and lysosomal dysfunction, suggesting that these alterations were caused by GlcSph accumulation in the mutant neurons. To directly determine whether GlcSph can cause mTOR hyperactivation, we incubated wild-type neurons with exogenous GlcSph. Remarkably, GlcSph treatment recapitulated the mTOR hyperactivation and lysosomal abnormalities in mutant neurons, which were prevented by coincubation of GlcSph with mTOR inhibitors. We conclude that elevated GlcSph activates an mTORC1-dependent pathogenic mechanism that is responsible for the lysosomal abnormalities of nGD neurons. We also identify acid Ceramidase as essential to the pathogenesis of nGD, providing a new therapeutic target for treating GBA1-associated neurodegeneration.

Keywords

drug target; experimental models; induced pluripotent stem cells; neural differentiation; neuropathy; signal transduction; stem/progenitor cell.

Figures
Products