dihydropyridines and Gaucher-Disease

Gaucher's disease (GD) is characterized by loss of lysosomal glucocerebrosidase (GC) activity. Mutations in the gene encoding GC destabilize the protein's native folding leading to ER-associated degradation (ERAD) of the misfolded enzyme. Enhancing the cellular folding capacity by remodeling the proteostasis network promotes native folding and lysosomal activity of mutated GC variants. However, proteostasis modulators reported so far, including ERAD inhibitors, trigger cellular stress and lead to induction of apoptosis. We show herein that lacidipine, an L-type Ca(2+) channel blocker that also inhibits ryanodine receptors on the ER membrane, enhances folding, trafficking and lysosomal activity of the most severely destabilized GC variant achieved via ERAD inhibition in fibroblasts derived from patients with GD. Interestingly, reprogramming the proteostasis network by combining modulation of Ca(2+) homeostasis and ERAD inhibition remodels the unfolded protein response and dramatically lowers apoptosis induction typically associated with ERAD inhibition.

Topics: Calcium; Cell Death; Cytoprotection; Cytosol; Dihydropyridines; Endoplasmic Reticulum; Endoplasmic Reticulum Chaperone BiP; Endoplasmic Reticulum-Associated Degradation; Fibroblasts; Gaucher Disease; Gene Silencing; Glucosylceramidase; Heat-Shock Proteins; Homeostasis; Humans; Lysosomes; Mutant Proteins; Mutation; Protein Folding; Protein Transport; Proto-Oncogene Proteins c-bcl-2; Unfolded Protein Response; Up-Regulation

The hallmark of Gaucher's disease cellular pathogenesis is the lysosomal accumulation of glucosylceramide, which is caused by misfolding of mutated glucocerebrosidase (GC) and loss of lysosomal GC activity, and leads to depletion of [Ca(2+)](ER). We demonstrate that modulation of Ca(2+) homeostasis and enhancement of the cellular folding capacity synergize to rescue the folding of mutated GC variants. Lacidipine, an L-type Ca(2+) channel blocker that also inhibits [Ca(2+)](ER) efflux, enhances folding, trafficking, and activity of degradation-prone GC variants. Lacidipine remodels mutated GC proteostasis by simultaneously activating a series of distinct molecular mechanisms, namely modulation of Ca(2+) homeostasis, upregulation of the ER chaperone BiP, and moderate induction of the unfolded protein response. However, unlike previously reported proteostasis regulators, lacidipine treatment is not cytotoxic but prevents apoptosis induction typically associated with sustained activation of the unfolded protein response.

Topics: Calcium; Calcium Channel Blockers; Calcium Channels, L-Type; Cells, Cultured; Dihydropyridines; Endoplasmic Reticulum Chaperone BiP; Fibroblasts; Gaucher Disease; Glucosylceramidase; Heat-Shock Proteins; Humans; Mutation; Protein Folding; Unfolded Protein Response