Magnoni, R. | Search bioRxiv

bioRxiv2018

Arimoclomol as a potential therapy for neuronopathic Gaucher Disease

Gaucher Disease (GD) is caused by mutations of the GBA gene which encodes the lysosomal enzyme acid beta-glucosidase (GCase). GBA mutations commonly affect GCase function by perturbing its protein homeostasis rather than its catalytic activity. Heat shock proteins (HSPs) are well known cytoprotective molecules with numerous functions in protein homeostasis and lysosomal function and their manipulation has been suggested as a potential therapeutic strategy for GD. The investigational drug arimoclomol, which is currently in phase II/III clinical trials, is a well-characterized HSP amplifier and has been extensively clinically tested. Importantly, arimoclomol efficiently crosses the blood-brain-barrier hereby presenting an opportunity to target the neurological manifestations of GD, which remains without a disease modifying therapy.\n\nIn the present study, we found that arimoclomol induced relevant HSPs such as ER-resident HSP70 (BiP) and enhanced the folding, maturation, activity and correct cellular localization of mutated GCase across a number of genotypes including the common L444P and N370S mutations in primary cells from GD patients. These effects where recapitulated in a human neuronal model of GD obtained by differentiation of multipotent adult stem cells. Taken together, these data demonstrate the potential of HSP-targeting therapies in GCase-deficiencies and strongly support the clinical development of arimoclomol as a potential first therapeutic option for the neuronopathic forms of GD.\n\nSummaryThese studies provide proof-of-concept for the development of the Heat shock protein amplifier, arimoclomol, as a potential therapy for neuronopathic Gaucher disease as arimoclomol enhances folding, maturation, activity and correct localization of GCase in neuronopathic and non-neuronopathic Gaucher disease models.

neuroscience↗

bioRxiv2017

Intermolecular Disulfide-Bond Formation In Human FICD Modulates The Activity Of The Hyperactive E234G Mutant

Endoplasmic reticulum (ER) stress that leads to the accumulation of misfolded proteins in the ER initiates the unfolded protein response (UPR). This homeostatic response activates signaling pathways that seek to reinstate a proper ER protein folding balance or induce apoptosis if ER stress persists. Recently, we and others identified human FICD (Filamentation induced by cyclic AMP domain-containing protein), an enzyme with adenylyltransferase (aka AMPylation) activity, as a new UPR target. Here, we demonstrate that FICD is functionally linked to the UPR, as evidenced by the finding that the adenylyltransferase activity of the protein induces ER stress, while FICD silencing increases sensitivity to ER stress. We identify BiP, an abundant ER chaperone and key regulator of the UPR, as the main substrate of FICD AMPylation in ER-derived microsomes, further emphasizing close functional connection of FICD to the UPR and in line with recent reports that AMPylation inactivates BiP. Notably, BiP overexpression increased the levels of BiP AMPylation as well as FICD auto-AMPylation, suggesting a homeostatic response that balances the pool of active BiP to modulate its functions in protein folding as well as UPR signaling. Finally, we show that overexpressed FICD forms a disulfide-bonded homo-dimer through Cys51 and Cys75 and demonstrate that mutation of these two cysteines in the context of a hyperactive FICD mutant leads to increased BiP AMPylation. This latter finding opens up the possibility that FICD activity is redox regulated and closely connected with ER redox homeostasis.

molecular biology↗