ADAP plays a pivotal role in CD4+ T cell activation but is only marginally involved in CD8+ T cell activation, differentiation, and immunity to pathogens

Abstract

The adhesion and degranulation promoting adaptor protein (ADAP) is a multifunctional scaffold involved in many different signaling pathways that are important for the function of T cells, including the inside-out and outside-in signaling of integrins, the activation of NF-κB, and the subsequent production of proinflammatory cytokines (e.g., IFN-γ and IL-2). Strikingly, despite its well-established role in T cells, previous studies did not distinguish between CD4 and CD8 T cells, and thus, it is unknown whether ADAP fulfills equally important functions in both T cell subsets. We show here that despite comparable ADAP expression levels in CD4 and CD8 T cells, their function is differentially dependent on ADAP. Whereas in vitro TCR-stimulation experiments revealed that activation, proliferation, and adhesion are severely compromised in CD4 T cells lacking ADAP, their CD8 counterparts are hardly affected by ADAP deficiency. Accordingly, antigen-specific in vivo stimulation of adoptively transferred CD8 T cells during Listeria monocytogenes (Lm) and influenza A virus (IAV) infection revealed only moderate effects of ADAP deficiency in terms of CD8 T cell activation, proliferation, and differentiation, which, however, did not impair pathogen-specific immunity. Thus, we show for the first time that ADAP fulfills different functions in CD4 and CD8 T cells, with CD8 T cells being less dependent on ADAP. Our data identify ADAP as a potential molecular target for T cell subset-specific therapeutic interventions.

Filamin A Phosphorylation at Serine 2152 by the Serine/Threonine Kinase Ndr2 Controls TCR-Induced LFA-1 Activation in T Cells

“…Cells were then allowed to adhere for 30 min at 37°C, unbound cells were carefully washed off with Hanks buffered saline (HBSS, Biochrom AG). Bound cells were counted and calculated as percentage of input (2 × 10 5 Jurkat T cells or 1 × 10 6 mouse T cells) in duplicates or triplicates (47, 48). Conjugate formation was performed as previously described (24, 49).…”

ADAP Promotes Degranulation and Migration of NK Cells Primed During in vivo Listeria monocytogenes Infection in Mice

“…The Listeria monocytogenes (Lm) strain 10403S expressing ovalbumin was used for mouse infection experiments as described before (6,41). Frozen stocks of Lm were thawed and subsequently diluted in brain heart infusion medium (BHI) followed by overnight growth on agar plates.…”

“…In vivo infection of mice with Lm is known to induce effective NK cell activation (33,34) in a process involving a complex cellular network of macrophages, neutrophils, and dendritic cells as well as a plethora of soluble mediators derived from these cells (35,36). Thus, Lm infection, that is well-established in our laboratory (6), represents a suitable tool to study the role of ADAP in NK cell priming, cytokine production and cytotoxicity during in vivo infection.…”

“…Moreover, ADAP plays an important role in T cell receptor-and chemokine receptor-mediated activation of integrins (inside-out signaling) and mediates signals derived from the interaction of integrins on T cells with ligands on target cells (outside-in signaling) (4,5). ADAP-deficient T cells show reduced migration toward chemokines (6), impaired formation of the immunological synapse (4,5) and impaired activation, differentiation and resident memory formation during acute infections (6,7).…”

Adap

“…The role of ADAP specifically in CD8+ T cell function in pathogen clearance has been tested in mice with inconclusive results. In one study, by Li et al, loss of ADAP in mice led to increased Influenza virus A-induced mortality, whereas in another study, the ability of ADAP À/À CD8+ T cells to clear similar infection was unimpaired (Parzmair et al 2017). Finally, the ADAP/SKAP1 module can reduce cytotoxicity of CD8+ T cells through positive regulation of the inhibitory molecule, PD-1.…”