SLAT promotes TCR-mediated, Rap1-dependent LFA-1 activation and adhesion through interaction of its PH domain with Rap1.
SLAT (also known as DEF6) promotes T cell activation and differentiation by regulating NFAT-Ca(2+) signaling. However, its role in TCR-mediated inside-out signaling, which induces integrin activation and T cell adhesion, a central process in T cell immunity and inflammation, has not been explored. Here, we show that SLAT is crucial for TCR-induced adhesion to ICAM-1 and affinity maturation of LFA-1 in CD4(+) T cells. Mechanistic studies revealed that SLAT interacts, through its PH domain, with a key component of inside-out signaling, namely the active form of the small GTPase Rap1 (which has two isoforms, Rap1A and Rap1B). This interaction has been further shown to facilitate the interdependent recruitment of Rap1 and SLAT to the T cell immunological synapse upon TCR engagement. Furthermore, a SLAT mutant lacking its PH domain drastically inhibited LFA-1 activation and CD4(+) T cell adhesion. Finally, we established that a constitutively active form of Rap1, which is present at the plasma membrane, rescues the defective LFA-1 activation and ICAM-1 adhesion in SLAT-deficient (Def6(-/-)) T cells. These findings ascribe a new function to SLAT, and identify Rap1 as a target of SLAT function in TCR-mediated inside-out signaling.
Division of Cell Biology, La Jolla Institute for Allergy & Immunology, La Jolla, CA 92037, USA.
Marjorie
M
Côte
Division of Cell Biology, La Jolla Institute for Allergy & Immunology, La Jolla, CA 92037, USA.
Camille
C
Fos
Division of Cell Biology, La Jolla Institute for Allergy & Immunology, La Jolla, CA 92037, USA.
Ann J
AJ
Canonigo-Balancio
Division of Inflammation Biology, La Jolla Institute for Allergy & Immunology, La Jolla, CA 92037, USA.
Klaus
K
Ley
Division of Cell Biology, La Jolla Institute for Allergy & Immunology, La Jolla, CA 92037, USA sbecart@its.jnj.com amnon@lji.org.
Stéphane
S
Bécart
Division of Cell Biology, La Jolla Institute for Allergy & Immunology, La Jolla, CA 92037, USA sbecart@its.jnj.com amnon@lji.org.
Amnon
A
Altman
D000818:Animals; D002448:Cell Adhesion / Q000502:physiology*; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors; D016169:Lymphocyte Function-Associated Antigen-1 / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011948:Receptors, Antigen, T-Cell / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D020668:rap GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020827:rap1 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; D020662:Guanine Nucleotide Exchange Factors; D016169:Lymphocyte Function-Associated Antigen-1; D009687:Nuclear Proteins; D011948:Receptors, Antigen, T-Cell; D020668:rap GTP-Binding Proteins; D020827:rap1 GTP-Binding Proteins; C473249:Def6 protein, mouse; C492136:Rap1b protein, mouse
Def6; Immunological synapse; Inside-out signaling; Integrin activation; Rap1; SLAT; T cell-adhesion