# Mechanism underlying regulation of Ca2+ signaling in local effector T cells

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA LOS ANGELES · 2020 · $227,499

## Abstract

PROJECT SUMMARY
CRAC (Ca2+ release-activated Ca2+) channels are pivotal for activation of the Ca2+-NFAT (nuclear factor of
activated T cells) signaling pathway in T cells. Defects in the Ca2+-NFAT pathway lead to immune deficiency in
humans. In addition, blockers for this pathway including cyclosporin A and FK506 are widely used to suppress
T cell functions in the clinic, further emphasizing the importance of this pathway. The major problem with
therapeutic exploitation of the Ca2+-NFAT pathway is that inhibition of this pathway leads to systemic immune
suppression due to its broad role in T cell functions. Our goal is to elucidate mechansims regulating CRAC
channels specifically in local effector T cells that are already migrated to the tissue and develop a therapeutic
method to selectively suppress cytokine production in those cells. During the onset of autoimmunity, naïve T
cells are primed and differentiate to effector T cells at the lymph nodes. Primed effector T cells then migrate to
the site of inflammation, where they encounter self-antigen-enriched milieu and produce maximal levels of
inflammatory cytokines including IFN-gamma, IL-17 and GM-CSF. Our preliminary data now reveal a novel
mechanism underlying regulation of CRAC channels selectively in local effector T cell responses, not in T cell
priming. We find that surface expression of ORAI1, the pore subunit of CRAC channels is limited and a large
fraction of the protein (60%) is intracellularly trapped within vesicles. In effector T cells, T cell receptor (TCR)
stimulation triggers trafficking of ORAI1+ vesicles to the plasma membrane, which is important for sustained
Ca2+ entry and thereby robust effector T cell response. From a targeted screen, we have identified two
components of these ORAI1+ vesicles, NKD2 (naked cuticle homolog 2), a signaling adaptor, and Rab44, a
novel Rab GTPase. Mechanistically, NKD2 gets activated upon TCR stimulation and orchestrates ORAI1+
vesicle trafficking via Rab44. Both NKD2 and Rab44 are abundantly expressed in effector T cells and deletion
of Nkd2 specifically decreased local effector T cell responses without influencing T cell development and
priming in vivo. Taken together, the main hypothesis of the current proposal is that ORAI1 trafficking from the
intracellular pool to the plasma membrane is crucial for high and sustained Ca2+ signaling required for local
effector T cell responses. The specific objectives of this proposal are 1) uncover the role of TCR signals in
triggering of ORAI1+ vesicle trafficking, 2) identify the molecular machinery involved in trafficking of the
ORAI1/NKD2+ vesicles, that includes Rab44, and 3) elucidate the physiological role of ORAI1+ vesicle
trafficking in local effector T cell responses using animal models of neuronal inflammation.

## Key facts

- **NIH application ID:** 9969751
- **Project number:** 1R01AI146615-01A1
- **Recipient organization:** UNIVERSITY OF CALIFORNIA LOS ANGELES
- **Principal Investigator:** Yousang Gwack
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $227,499
- **Award type:** 1
- **Project period:** 2020-03-05 → 2025-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9969751

## Citation

> US National Institutes of Health, RePORTER application 9969751, Mechanism underlying regulation of Ca2+ signaling in local effector T cells (1R01AI146615-01A1). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9969751. Licensed CC0.

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