# A mechanism of lysosomal Calcium entry

> **NIH NIH R21** · UNIVERSITY OF CHICAGO · 2020 · $224,075

## Abstract

Lysosomes are highly acidic organelles that integrate important cellular processes in all cell types.
There is a preponderance of risk genes for neurological disorders associated with lysosome dysfunction.
In the lysosome, lumenal Ca2+ is critical to function, and defects in every known lysosomal Ca2+ release
channel leads to a distinct neurological disorder. Yet, dysregulated lysosomal Ca2+ can also arise due to
defective import. While much more known of mechanisms that release lysosomal Ca2+, there is a paucity
of information on the pathophysiology of Ca2+ import. Notably, the only known lysosomal Ca2+ importer in
animals, the P-type ATPase ATP13A2, was recently discovered by my laboratory using newly developed
reporter technology for lysosomal Ca2+ imaging. This importer was previously identified as a major risk
gene for Parkinson's disease. Thus, a structural level understanding of how by ATP13A2 imports Ca2+ into
the lysosome is highly significant.
 The premise of this proposal is that ATP13A2 function is mechanistically similar to that of SERCA but
with lower affinity and/or efficiency of Ca2+ transport. This premise is based on unpublished data from my
laboratory using homology modeling, which predicts very high similarity between ATP13A2 and SERCA.
SERCA (Sarco/Endoplasmic Reticulum Ca2+ ATPase) is one of the best studied P2-type ATPases. In
contrast, ATP13A2 is a P5-type ATPase, an ATPase sub-class yet to be mechanistically characterized.
 The steps outlined in this proposal will identify and study the molecular mechanism of how ATP13A2
drives lysosomal Ca2+ import by mapping lysosomal Ca2+ dynamics in real-time in live mammalian cells.
We plan to create and characterize a photostable lysosomal Ca2+ reporter and develop an assay to map
the kinetics of lysosomal Ca2+ import in situ in live cells. Preliminary data shows that we have identified the
relevant molecular components to make this photostable organellar Ca2+ reporter. Further, an initial
bioinformatics analysis and homology modeling has revealed a remarkable similarly between ATP13A2
and SERCA. This will allow us to pinpoint residues important to Ca2+ import by a P5-type ATPase. By
expressing various ATP13A2 mutants and using real-time Ca2+ mapping, we shall be able to identify
residues critical to the function of ATP13A2.
 Successful completion of this research will identify how a major risk gene for Parkinson's disease
imports lysosomal Ca2+ and elucidate the first structure-activity relationship in P5-type ATPases. Also, by
providing the first practical technology to quantitatively map lysosomal Ca2+ fluxes in live cells (in real-time),
we will be in a position to study new lysosomal Ca2+ importers and existing lysosome Ca2+ release channels
connected to various neurodegenerative diseases.

## Key facts

- **NIH application ID:** 10020204
- **Project number:** 5R21NS114428-02
- **Recipient organization:** UNIVERSITY OF CHICAGO
- **Principal Investigator:** Yamuna Krishnan
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $224,075
- **Award type:** 5
- **Project period:** 2019-09-30 → 2022-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10020204

## Citation

> US National Institutes of Health, RePORTER application 10020204, A mechanism of lysosomal Calcium entry (5R21NS114428-02). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10020204. Licensed CC0.

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