The adapter protein ADAP is required for selected dendritic cell functions

Togni Mauro, Engelmann Swen, Reinhold Dirk, Schraven Burkhart, Reinhold, Reinhold Annegret

Description

The cytosolic adaptor protein ADAP (adhesion and degranulation promoting adapter protein) is expressed by T cells, natural killer cells, myeloid cells and platelets. ADAP is involved in T-cell-receptor-mediated inside-out signaling, which leads to integrin activation, adhesion and reorganization of the actin cytoskeleton. However, little is known about the role of ADAP in myeloid cells. In the present study, we analyzed the function of ADAP in bone-marrow-derived dendritic cells (BMDCs) from ADAP-deficient mice. Results ADAP-deficient BMDCs showed almost normal levels of antigen uptake, adhesion, maturation, migration from the periphery to the draining lymph nodes, antigen-specific T-cell activation, and production of the proinflammatory cytokines IL-6 and TNF-∝. Furthermore, we provide evidence that the activation of signaling pathways after lipopolysaccharide (LPS) stimulation are not affected by the loss of ADAP. In contrast, ADAP-deficient BMDCs showed defects in CD11c-mediated cellular responses, with significantly diminished production of IL-6, TNF-∝ and IL-10. Actin polymerization was enhanced after CD11c integrin stimulation. Conclusions In summary, we propose that the adapter molecule ADAP is critical for selected CD11c integrin-mediated functions of dendritic cells.

Sujets

• Signal transducing adaptor protein
• ADAP
• Dendritic cell
• Integrin

Informations

• Publié par: biomed
• Publié le: 01 janvier 2012
• Nombre de lectures: 15
• Langue: English

Extrait

Togni et al. Cell Communication and Signaling 2012, 10:14
http://www.biosignaling.com/content/10/1/14
RESEARCH Open Access
The adapter protein ADAP is required for selected
dendritic cell functions
1 1 1 1,2 1*Mauro Togni , Swen Engelmann , Dirk Reinhold , Burkhart Schraven and Annegret Reinhold
Abstract
Background: The cytosolic adaptor protein ADAP (adhesion and degranulation promoting adapter protein) is
expressed by T cells, natural killer cells, myeloid cells and platelets. ADAP is involved in T-cell-receptor-mediated
inside-out signaling, which leads to integrin activation, adhesion and reorganization of the actin cytoskeleton.
However, little is known about the role of ADAP in myeloid cells. In the present study, we analyzed the function of
ADAP in bone-marrow-derived dendritic cells (BMDCs) from ADAP-deficient mice.
Results: ADAP-deficient BMDCs showed almost normal levels of antigen uptake, adhesion, maturation, migration
from the periphery to the draining lymph nodes, antigen-specific T-cell activation, and production of the
proinflammatory cytokines IL-6 and TNF-/. Furthermore, we provide evidence that the activation of signaling
pathways after lipopolysaccharide (LPS) stimulation are not affected by the loss of ADAP. In contrast, ADAP-deficient
BMDCs showed defects in CD11c-mediated cellular responses, with significantly diminished production of IL-6,
TNF-/ and IL-10. Actin polymerization was enhanced after CD11c integrin stimulation.
Conclusions: In summary, we propose that the adapter molecule ADAP is critical for selected CD11c integrin-mediated
functions of dendritic cells.
Keywords: Adapter protein, ADAP, Dendritic cell, Integrin, Inside-out signaling
Lay Abstract showed defects in integrin-mediated cellular responses.
Adapter molecules mediate protein-protein interactions in
Thesefindingshaveimportantimplicationsfortheundersignal transduction cascades. These signaling cascades standing of the role of ADAP in integrin-mediated
signaltranslate information from cell surface receptors into cellu- ing cascades in dendritic cells. This knowledge would also
larresponses.Wefocused ourresearchon theadaptermol- facilitate the therapeutic modulation of signal transduction
ecule ADAP (adhesion and degranulation promoting pathways in these cells.
adapter protein). To investigate the function of ADAP in
immune cells we used a genetically engineered mouse lack- Introduction
ing this molecule. It is known that ADAP plays a role in Adaptor proteins play a crucial role in organizing
signaintegrin-mediated signaling pathways leading to adhesion losomes, which are molecular complexes involved in
and motility in T lymphocytes. However, little is known signal transduction. Adaptor proteins are subdivided into
about the role of ADAP in dendritic cells, a special cell membrane-anchored adaptor molecules (transmembrane
population within the immune system linking the innate adaptor molecules) and cytosolic adaptor molecules [1].
and the adaptive immunity. Using their long dendrites,
ADAP(adhesionanddegranulationpromotingadaptorprothese cells capture and process antigen material and tein, previously designated SLAP-130 or Fyb) is a cytosolic
present it toother immune cells.Here,we provide evidence adaptor molecule expressed by T cells, natural killer
that most dendritic cell functions are not affected by the (NK) cells, myeloid cells and platelets [2,3]. ADAP is
lack of ADAP. Interestingly, ADAP-deficient dendritic cells expressed during the early stages of B cell development
in the bone marrow, but not in mature B cells [4]. On
the structural level, ADAP consists of a unique N-* Correspondence: [e-mail]
1Institute for Molecular and Clinical Immunology, Otto von Guericke terminal region, a proline-rich region, multiple
tyrosineUniversity Magdeburg, Leipziger Strasse 44, 39120 Magdeburg, Germany
based signaling motifs, two SH3 domains, two putative
Full list of author information is available at the end of the article
© 2012 Togni et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.Togni et al. Cell Communication and Signaling 2012, 10:14 Page 2 of 10
http://www.biosignaling.com/content/10/1/14
nuclear localisation sites, and an Ena-Vasp homology many T cells. This phase is followed by the establishment
(EVH1) domain binding site [2,3]. The adapter molecule of long-lasting contacts and the formation of an
immunoSKAP55 (expressed by T cells) and the ubiquitously logical synapse that eventually results in the activation and
expressed homolog SKAP-HOM constitutively bind to clonal expansion of naïveTcells[19].
ADAP. This interaction is predominantly mediated by In this study, we analyzed the functional consequences of
the proline-rich region of ADAP and the SH3 domain of the loss of ADAP on dendritic cell function. We report that
SKAP55/SKAP-HOM [5]. Disruption of the ADAP- ADAP-deficient BMDCs show normal levels of function in
SKAP55 module in T cells impairs conjugate formation antigen uptake, maturation, migration into the draining
between T cells and antigen-presenting cells (APCs), lymph nodes, antigen-specific T-cell activation, and
prolifand lymphocyte-function-associated antigen-1 (LFA-1)- eration. Importantly, however, following CD11c stimulation,
mediated adhesion [6,7]. ADAP was the first adapter the production of IL-6,TNF-α and IL-10 was diminished in
molecule to be identified that couples T-cell receptor ADAP-deficient BMDCs, whereas actin polymerization was
(TCR) stimulation to integrin activation and Tcell adhe- enhanced. These results suggest that ADAP is required for
sion (inside-out signaling) [8,9]. Recent work has estab- optimal CD11c integrin-mediated DC function.
lished that ADAP is also required in TCR-mediated
formation of the CARMA1-Bcl10-Malt1 (CBM) complex Results
and the subsequent activation of the nuclear factor (NF)-κB Normal levels of skin colonization, spontaneous motility
pathway [10]. Furthermore, ADAP shows a phosphoryl- and antigen-stimulated migration are seen in
ADAPation-dependent association with the SH2 domain of the deficient BMDCs
adapter molecule Nck [11,12]. Recently, a functional co- To investigate the function of dendritic cells in
ADAPoperation has been demonstrated between ADAP and Nck deficientmice,wefirstexaminedthedistributionofDCsin
in stabilizing the interaction of SLP-76 and Wiskott-Aldrich the epidermis, where they persist as Langerhans cells. Ear
syndrome protein (WASP). Thus, ADAP is also involved in skin explants were prepared and stained with anti-major
the regulation of actin cytoskeleton reorganization after histocompatibility complex (MHC) II antibodies, and no
TCR activation [13]. differences were found in the number of DCs colonizing
Ablation of ADAP in mice does not have a major impact the skin of wild-type mice or ADAP-deficient mice
on the development of NK cells [14]. However, it does (Figure 1A). In addition, when the explants were cultured
result in impaired positive and negative thymocyte selec- in vitro, the number of DCs that spontaneously emigrated
tion, as well as inefficient population of the peripheral from the epidermis was similar in ADAP-deficient mice
lymphoid organs [15]. ADAP-deficient TCR transgenic compared with wild-type mice (Figure 1B). To assess the
mice show a dramatically increased incidence of diabetes level of induced migration in response to dermal antigen
[16]. In a heart transplantation model, ADAP-deficient application in vivo, we used the hapten fluorescein
isothiomice showed prolonged survival after a heart graft; this cyanate (FITC) as a migration tracer. Twenty-four hours
allograft protection was accompanied by reduced infiltra- after FITC application, there was no significant difference
tion, proliferation, and activation of Tcells in the allograft in the percentage of FITC-positive, CD11c-positive cells in
[17]. In another transplantation model, the rejection of the draining lymph nodes of wild-type mice compared
intestinal allografts was ameliorated in ADAP-deficient with ADAP-deficient mice (Figure 1C). These data suggest
mice [18]. These in vivo studies focused on the role of that ADAP does not play a major role in skin colonization
ADAP in T-cell function, whereas the contribution of by DCs. Furthermore, ADAP does not appear to be
essenADAP-deficient APCs to T-cell function was not studied. tial for the migration of DCs from the skin to the draining
To our knowledge, there have been no published reports lymph nodes uponantigen uptake.
regarding the role of ADAP in dendritic cell (DC)
function. ADAP-deficient BMDCs show normal levels of antigen
DCs are the most efficient APCs, and they have the uptake, maturation and adhesion in vitro
unique capacity to activate naïve Tcells and to induce pri- Next, we measured antigen uptake and processing by
addmary immune responses. They originate in the bone mar- ing the fluorescent ovalbumin (OVA) analogue DQ-OVA to
row,fromwheretheymigratetotheperiphery,colonizeall the culture medium of wild-type and ADAP-deficient
organs, and continually sample the surroundings for patho- BMDCs. BMDCs lacking ADAP and wild-type BMDCs
gens. Pathogens activate immature DCs in the peripheral showed no differ