CD56 regulates human NK cell cytotoxicity through Pyk2.

Justin T Gunesch,Tasneem Am Ebrahim,Amera L Dixon,Tejas Kumar,Todd A Fehniger,Melissa M Berrien-Elliott,Emily M Mace,Swetha Tatineni,Everardo Hegewisch-Solloa

doi:10.7554/elife.57346

Abstract

Human natural killer (NK) cells are defined as CD56+CD3-. Despite its ubiquitous expression on human NK cells the role of CD56 (NCAM) in human NK cell cytotoxic function has not been defined. In non-immune cells, NCAM can induce signaling, mediate adhesion, and promote exocytosis through interactions with focal adhesion kinase (FAK). Here we demonstrate that deletion of CD56 on the NK92 cell line leads to impaired cytotoxic function. CD56-knockout (KO) cells fail to polarize during immunological synapse (IS) formation and have severely impaired exocytosis of lytic granules. Phosphorylation of the FAK family member Pyk2 at tyrosine 402 is decreased in NK92 CD56-KO cells, demonstrating a functional link between CD56 and signaling in human NK cells. Cytotoxicity, lytic granule exocytosis, and the phosphorylation of Pyk2 are rescued by the reintroduction of CD56. These data highlight a novel functional role for CD56 in stimulating exocytosis and promoting cytotoxicity in human NK cells.

Highlights

Natural killer (NK) cells are innate immune effectors that play an important role in the clearance of virally infected and tumorigenic cells and modulation of immune responses
CD56-negative YTS cells were isolated by FACS and the absence of CD56 protein was confirmed in both YTS and NK92 CD56-KO cell lines by Western blot analysis and flow cytometry (Figure 1A,B)
The extracellular domain of neural cell adhesion molecule (NCAM) can be post-translationally modified by the addition of polysialic acid (PSA), which affects the molecular weight of CD56 when detected by Western blotting

Summary

Introduction

Natural killer (NK) cells are innate immune effectors that play an important role in the clearance of virally infected and tumorigenic cells and modulation of immune responses. Human NK cells represent approximately 10% of circulating lymphocytes and can be defined within this population as CD56+CD3À cells. CD56bright and CD56dim NK cells have unique expression of cell surface receptors, transcription factors and intracellular effector molecules that contribute to their distinct phenotypic and functional capacities (Caligiuri, 2008; Freud and Caligiuri, 2006). Despite its conserved expression on human NK cells and its use as a phenotypic identifier, the role of CD56 in immune function is poorly defined. CD56 is the cluster of differentiation nomenclature for neural cell adhesion molecule (NCAM).

Methods

Results

Conclusion