# Pathogenic Mechanisms of Lysosomal Disease

> **NIH NIH R01** · GREENWOOD GENETIC CENTER · 2022 · $306,339

## Abstract

PROJECT SUMMARY
Maintaining normal activity of lysosomes is essential for human health, as evidenced by the many rare
disorders caused by defects in lysosomal biogenesis and function. How lysosomal dysfunction leads to the
tissue-specific phenotypes associated with lysosomal storage disorders (LSDs) is poorly understood. Our long-
term goal is to define these pathogenic mechanisms, and use this information to identify new therapeutic
strategies. Our recent efforts have focused on the investigation of secreted proteases as key initiators of
disease in mucolipidosis II (MLII). In MLII, the enzyme (GlcNAc-1-phosphotransferase) that synthesizes the
carbohydrate-based tag needed for receptor-mediated lysosomal targeting is missing. This causes cathepsin
proteases to be secreted outside the cell where they become activated. Using powerful zebrafish tools, we
established that these secreted cathepsin proteases alter the key signaling events that control normal cartilage
and cardiac development. The current proposal will extend these studies and test the central hypothesis that
cathepsin-mediated mechanisms are pathogenic drivers across multiple LSDs with different etiologies. This
effort is premised on observations that demonstrate: i) cathepsin activity is altered in other LSDs including
sialidosis (NEU1) and MPSIVA (GALNS), ii) increased lysosomal exocytosis is associated with altered
cathepsin activity, and iii) extracellular cathepsin K (Ctsk) activity is modulated by specific glycosaminoglycans
(GAGs). We will use a unique and innovative set of tools in the zebrafish system to investigate the protease-
mediated pathogenesis in cartilage, with the goal of identifying novel disease mechanisms for these LSDs. We
believe this will point to new modes of treatment for disorders like MLII and sialidosis (where no approved
therapies exist), and for MPSIVA (where enzyme replacement has limited efficacy in cartilage and bone).
Understanding how extracellular cathepsin activity impacts different tissues is also crucial since there are a
growing number of proposed therapies aimed at increasing lysosomal exocytosis as a means of resolving
lysosomal storage. Such therapies may positively impact certain tissues but release of lysosomal enzymes in
other tissues may have unexpected and detrimental consequences. To address the central hypothesis, we will
profile cathepsin activity and TGFß related growth factor signaling in sialidosis and MPSIVA zebrafish (AIM 1)
and address whether changes in the abundance or type of GAGs present can tune this protease-dependent
pathogenic cascade (AIM 2). Next, we will define the extent to which lysosomal exocytosis drives cartilage
pathology in these disorders and ask if modulating exocytosis improves or exacerbates phenotypes (AIM 3).
We will also investigate the neuronal pathogenesis associated with NUS1 (NogoB receptor; NgBR) deficiency,
a newly characterized disorder with lysosomal dysfunction and cholesterol storage. Here we...

## Key facts

- **NIH application ID:** 10519229
- **Project number:** 9R01NS128907-14
- **Recipient organization:** GREENWOOD GENETIC CENTER
- **Principal Investigator:** Richard Steet
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $306,339
- **Award type:** 9
- **Project period:** 2009-01-01 → 2026-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10519229

## Citation

> US National Institutes of Health, RePORTER application 10519229, Pathogenic Mechanisms of Lysosomal Disease (9R01NS128907-14). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10519229. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*