Summary Gaucher disease, the most common lysosomal storage disorder, is caused by the defective activity of the lysosomal enzyme, acid‐β‐glucosidase (GlcCerase), leading to accumulation of glucosylceramide (GlcCer), particularly in cells of the macrophage lineage. Nearly 200 mutations in GlcCerase have been described, but for the most part, genotype‐phenotype correlations are weak, and little is known about the down‐stream biochemical changes that occur upon GlcCer accumulation that result in cell and tissue dysfunction. In contrast, the clinical course of Gaucher disease has been well described, and at least one treatment is available, namely enzyme replacement therapy. One other treatment, substrate reduction therapy, has recently been marketed, and others are in early stages of development. This review, after discussing pathological mechanisms, evaluates the advantages and disadvantages of existing therapies.

Enzyme replacement therapy is the standard of care for symptomatic Gaucher disease. Velaglucerase alfa is a human ␤-glucocerebrosidase produced in a wellcharacterized human cell line. A 9-month phase 1/2 open-label, single-center trial and ongoing extension study were conducted to evaluate safety and efficacy of velaglucerase alfa. Twelve symptomatic adult type 1 Gaucher patients (intact spleens) received velaglucerase alfa (60 U/kg per infusion) during phase 1/2. An extension study was offered to patients completing the trial; step-wise dose reduction (to 30 U/kg per infusion) was instituted. Eleven patients completed phase 1/2; 10 entered the extension; 9 patients reached 39 months of extension. No drug-related serious adverse events or withdrawals, and no antibodies were observed. Home therapy was successfully implemented during the extension. Statistically significant improvements (P < .004) were noted in mean percentage change from baseline to 9 months and baseline to 48 months for hemoglobin (؉19.2%, ؉21.7%, respectively), platelet counts (؉67.6%, ؉157.8%, respectively), normalized liver volume (؊18.2%, ؊42.8%, respectively), and normalized spleen volume (؊49.5%, ؊79.3%, respectively).

Endocrine cells produce large amounts of one or more peptides. The post-translational control of selective production of a single protein is often unknown. We used 3 unrelated approaches to diminish PKCepsilon in rat islets to evaluate its role in preferential glucose-mediated insulin production. Transfection with siRNA (siR-PKCepsilon) or expression of inactive PKCepsilon (PKCepsilon-KD) resulted in a significant reduction in insulin response to glucose (16.7 mmol/l). Glucose stimulation resulted in concentration of PKCepsilon in the perinuclear region, an area known to be rich in ER-Golgi systems, associated with insulin-containing structures. ss'COP1 (RACK2) is the anchoring protein for PKCepsilon. Glucose-stimulated proinsulin production was diminished by 50% in islets expressing PKCepsilon-KD, and 60% in islets expressing RACK2 binding protein (epsilonV1-2); total protein biosynthesis was not affected. In islets expressing epsilonV1-2, a chase period following glucose stimulus resulted in a reduced proinsulin conversion to mature insulin. We propose that PKCepsilon plays a specific role in mediating the glucose-signal into insulin production: binding to ss'COP1 localizes the activated enzyme to the RER where it modulates the shuttling of proinsulin to the TGN. Subsequently the enzyme may be involved in anterograde trafficking of the prohormone or in its processing within the TGN.