# The Molecular Mechanism of the CD19-CD81 B Cell Co-Receptor Complex

> **NIH NIH F31** · HARVARD UNIVERSITY · 2020 · $37,464

## Abstract

Abstract
The tetraspanins comprise a class of four-pass transmembrane proteins that have acquired a variety of
discrete, yet poorly understood, functions in mammalian physiology, playing essential roles in the immune,
nervous, cardiovascular, reproductive, and auditory systems, as well as in infectious disease processes, tumor
metastasis, and the development of organ systems. The functions of tetraspanins are mediated through their
direct interaction with partner proteins, and one of the most critical functions of a tetraspanin is the regulation of
B cell signaling via the interaction between the tetraspanin cluster of differentiation 81 (CD81) and the B cell
co-receptor, cluster of differentiation 19 (CD19). Altered expression and signaling of CD19 causes defects in B
cell development and has been implicated in the development of immunodeficiency, B cell malignancies, and
autoimmunity. However, the mechanism by which CD81 regulates the trafficking and signaling of CD19 is
unclear, largely due to a lack of structural and biochemical data. Therefore, I propose to investigate the
molecular mechanism of tetraspanin regulation of CD19 through: i) structural characterization of the CD19-
CD81 complex, and ii) functional studies of CD19 trafficking to the cell surface and signaling after B cell
activation in cell-based assays. A better understanding of the molecular mechanism underlying CD19-CD81
function will have broad biomedical implications, offering novel insights into B cell biology and signal
transduction mechanisms, tetraspanin function, and how to better target the B cell signaling pathway for novel
therapeutics.
Under the F31 fellowship award, I will receive exceptional training in structural biology, membrane protein
biochemistry, and assay development under the guidance of Dr. Kruse and Dr. Blacklow at Harvard Medical
School. My technical training will be accompanied by training in experimental design, mentorship, public
speaking, biomedical ethics, scientific writing, and opportunities to present my research at scientific meetings.
This training plan is designed to lead to a successful and productive graduate education and will provide an
outstanding foundation for achieving my long-term goal of becoming an independent researcher focused on
transmembrane signaling.

## Key facts

- **NIH application ID:** 9972746
- **Project number:** 5F31HL147459-02
- **Recipient organization:** HARVARD UNIVERSITY
- **Principal Investigator:** Katherine Julia Susa
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $37,464
- **Award type:** 5
- **Project period:** 2019-07-01 → 2022-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9972746

## Citation

> US National Institutes of Health, RePORTER application 9972746, The Molecular Mechanism of the CD19-CD81 B Cell Co-Receptor Complex (5F31HL147459-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9972746. Licensed CC0.

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