Cereblon regulates NK cell cytotoxicity and migration via Rac1 activation.

Cinzia Fionda,Giovanna Peruzzi,Helena Stabile,Angela Santoni,Angela Gismondi,Silvia Ruggeri,Alessandra Zingoni,Rossella Paolini,Marco Cippitelli,Cristina Capuano,Andrea Kosta,Alessandra Soriani,Rosa Molfetta

doi:10.1002/eji.202149269

Abstract

Rearrangement of the actin cytoskeleton is critical for cytotoxic and immunoregulatory functions as well as migration of natural killer (NK) cells. However, dynamic reorganization of actin is a complex process, which remains largely unknown. Here, we investigated the role of the protein Cereblon (CRBN), an E3 ubiquitin ligase complex co‐receptor and the primary target of the immunomodulatory drugs, in NK cells. We observed that CRBN partially colocalizes with F‐actin in chemokine‐treated NK cells and is recruited to the immunological synapse, thus suggesting a role for this protein in cytoskeleton reorganization. Accordingly, silencing of CRBN in NK cells results in a reduced cytotoxicity that correlates with a defect in conjugate and lytic synapse formation. Moreover, CRBN depletion significantly impairs the ability of NK cells to migrate and reduces the enhancing effect of lenalidomide on NK cell migration. Finally, we provided evidence that CRBN is required for activation of the small GTPase Rac1, a critical mediator of cytoskeleton dynamics. Indeed, in CRBN‐depleted NK cells, chemokine‐mediated or target cell–mediated Rac1 activation is significantly reduced. Altogether our data identify a critical role for CRBN in regulating NK cell functions and suggest that this protein may mediate the stimulatory effect of lenalidomide on NK cells.

Highlights

Natural Killer (NK) cells are innate lymphoid cells that play an important role in immune response against infection diseases and cancer, via contact-dependent cellular cytotoxicity and cytokine and chemokine production [1,2].NK cell cytotoxicity is a multistep and tightly controlled process
We initially demonstrated that CRBN is expressed at protein level in these lymphocytes both in cytosolic and nuclear compartment (Fig. 1A)
When visualized using confocal fluorescent microscopy, CRBN was found to accumulate at the interface with target cells (Fig. 1B and C and Supporting Information 1A) during the formation of mature NK cell immunological synapse (IS), which was identified by the accumulation of filamentous actin (F-actin) and the polarization of lytic granules [27]

Summary

Introduction

Natural Killer (NK) cells are innate lymphoid cells that play an important role in immune response against infection diseases and cancer, via contact-dependent cellular cytotoxicity and cytokine and chemokine production [1,2].NK cell cytotoxicity is a multistep and tightly controlled process. #These two authors contributed to this manuscript Step is NK cell conjugation with the target cell followed by formation of the immunological synapse (IS) at the contact site, lytic granule polarization, and degranulation. In particular the integrin lymphocyte function-associated antigen (LFA-1), play an essential role in these mechanisms. The engagement of LFA-1 with its ligand ICAM-1 mediates the firm adhesion to the target cell and drives the accumulation of filamentous actin (F-actin) as well as lytic granule convergence toward the microtubule organizing center (MTOC) and polarization at IS [3,4]. It is well established that cytoskeleton reorganization is necessary for the formation of IS and cytotoxic function [5,6]

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Conclusion