# Discovering the mechanisms and functions of signaling by the calcineurin beta1 isoform

> **NIH NIH R01** · STANFORD UNIVERSITY · 2020 · $391,496

## Abstract

Project Summary
Comprehensive mapping and monitoring of signaling pathways are essential for achieving the
goals of precision medicine. Calcineurin (CN), the serine/threonine protein phosphatase and
target of immunosuppressants, FK506 and CysA, is a critical mediator of Ca2+-dependent
signaling with multiple functions relevant to human health. However, many CN-regulated
substrates and processes remain to be elucidated. This proposal focuses on CNb1, a CN
isoform with unique properties and functions that is conserved in vertebrates and broadly
expressed in human tissues, but significantly under-studied. By addressing fundamental gaps in
knowledge about CNb1, this research will discover novel CN-regulated signaling pathways,
elucidate roles for CNb1 in healthy and diseased cells, and ultimately identify methods to
therapeutically manipulate the enzyme. Our studies show that its unique C-tail, generated by
alternative 3’ end mRNA processing, confers distinct regulation and localization to CNb1: In
vitro, maximal phosphatase activity of CNb1 in the presence of Ca2+/calmodulin is significantly
lower than that of canonical CNb2, due to a unique C-terminal auto-inhibitory sequence that
occludes an essential substrate binding site. In vivo, CNb1 localizes to membrane
compartments, including the plasma membrane and Golgi, in contrast to canonical CN isoforms,
which are primarily cytosolic. We show that lipidation of conserved cysteines in the CNAb1 C-tail
promotes membrane association and that palmitoylation of CNAb1 is dynamic, suggesting a
novel mechanism for regulating its distribution and activity in cells that will be examined in Aim
1. CNb1 does not dephosphorylate NFAT transcription factors and its substrates are currently
unknown. Our central hypothesis is that by mapping CNb1-regulated signaling pathways we will
uncover unique functions for CN at membranes and provide critical new insights into CN
regulation in a broad range of tissues and processes. Our preliminary data, which suggests that
CNb1 regulates synthesis of phosphatidylinositol 4-phosphate (PI4P) at the PM during GPCR
signaling by dephosphorylating FAM126A, whose genetic disruption gives rise to
hypomyelination and congenital cataracts (HCC), supports this hypothesis, which is further
tested in Aim 2. We also propose innovative approaches, coupling TurboID for proximity
labeling over fast time frames with computational identification of CN-binding peptides, to
systematically discover additional CNb1 substrates and thus map this enzymes’s unique
signaling network in Aim 3. We anticipate that this knowledge will have therapeutic applications
for pathologies to which CN signaling contributes, and will create a critical new resource for
researchers studying Ca2+- or phosphorylation-dependent signaling.

## Key facts

- **NIH application ID:** 9921418
- **Project number:** 5R01GM129236-02
- **Recipient organization:** STANFORD UNIVERSITY
- **Principal Investigator:** Martha S. Cyert
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $391,496
- **Award type:** 5
- **Project period:** 2019-05-01 → 2021-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9921418

## Citation

> US National Institutes of Health, RePORTER application 9921418, Discovering the mechanisms and functions of signaling by the calcineurin beta1 isoform (5R01GM129236-02). Retrieved via AI Analytics 2026-05-28 from https://api.ai-analytics.org/grant/nih/9921418. Licensed CC0.

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