Precision Medicine for Lysosomal Disorders

Precision medicine (PM) is an emerging approach for disease treatment and prevention that accounts for the individual variability in the genes, environment, and lifestyle of each person. Lysosomal diseases (LDs) are a group of genetic metabolic disorders that include approximately 70 monogenic conditions caused by a defect in lysosomal function. LDs may result from primary lysosomal enzyme deficiencies or impairments in membrane-associated proteins, lysosomal enzyme activators, or modifiers that affect lysosomal function. LDs are heterogeneous disorders, and the phenotype of the affected individual depends on the type of substrate and where it accumulates, which may be impacted by the type of genetic change and residual enzymatic activity. LDs are individually rare, with a combined incidence of approximately 1:4000 individuals. Specific therapies are already available for several LDs, and many more are in development. Early identification may enable disease course prediction and a specific intervention, which is very important for clinical outcome. Driven by advances in omics technology, PM aims to provide the most appropriate management for each patient based on the disease susceptibility or treatment response predictions for specific subgroups. In this review, we focused on the emerging diagnostic technologies that may help to optimize the management of each LD patient and the therapeutic options available, as well as in clinical developments that enable customized approaches to be selected for each subject, according to the principles of PM.

Mechanism-based enzyme activating compounds

Compared to inhibitors, which constitute the vast majority of today’s drugs, enzyme activators have considerable advantages, especially in the context of enzymes that regulate reactive flux through metabolic pathways associated with chronic, age-related diseases and lifespan. Across all families of enzymes, only a dozen or so distinct classes of small molecule activators have been characterized. Enzyme activators that are not based on naturally evolved allosteric mechanisms are much more difficult to design than inhibitors, because enzymatic catalysis has been optimized over billions of years of evolution. Here, we introduce modes of enzyme activation based on the catalytic reaction mechanisms of enzymes for which naturally evolved activators may not exist. We establish biophysical properties of small molecule modulators that are necessary to achieve desired changes in the steady state and non-steady state parameters of these enzymes, including changes in local conformational degrees of freedom conducive to the enhancement of catalytic activity that can be identified through computational modeling of their active sites. We illustrate how the modes of action of several compounds reported to activate enzymes without known allosteric sites may be understood using the framework presented. We also present simulations and new experimental results in support of this framework, including identification of the mechanism of a compound that activates the human SIRT3 enzyme, which does not contain a known allosteric site, under physiologically relevant conditions.

The Appearance of a Leptin Effect on Glucose Absorption in Caco2 Cells Depends on Their Differentiation Level

Backdround/Aims: The aim of this work was to study the effect and mechanism of action of leptin added apically, on glucose absorption, using Caco-2 cells as a model. Methods: Cells were grown on inserts and treated with leptin, at different time points after confluence. Radiolabelled glucose was added to the upper chamber and samples from the lower chamber were collected and assayed for radioactivity. Results: Glucose absorption increased with an increase in the level of differentiation and was associated with an increase in the protein expression level of glucose transporters. Leptin reduced glucose absorption only by day 16 after confluence, the time at which apical leptin receptors started appearing. This inhibitory effect became higher the longer the post confluence period, and was prominent on day 23. The hormone effect was found to be mediated via a decrease in the number of glucose transporters (SGLT1 and GLUT2) and a decrease in the activity of the Na+/K+ ATPase which was assayed by measuring the amount of inorganic phosphate liberated in presence and absence of enzyme activators. Conclusion: It was concluded that by day 23 post confluence, Caco-2 cells are differentiated and are appropriate to use as a model for intestinal transport studies.

Peptide-Modulated Activity Enhancement of Acidic Protease Cathepsin E at Neutral pH

Enzymes are regulated by their activation and inhibition. Enzyme activators can often be effective tools for scientific and medical purposes, although they are more difficult to obtain than inhibitors. Here, using the paired peptide method, we report on protease-cathepsin-E-activating peptides that are obtained at neutral pH. These selected peptides also underwent molecular evolution, after which their cathepsin E activation capability improved. Thus, the activators we obtained could enhance cathepsin-E-induced cancer cell apoptosis, which indicated their potential as cancer drug precursors.