Cell spreading distinguishes the mechanism of augmentation of T cell activation by integrin-associated protein/CD47 and CD28

Abstract

Integrin-associated protein (IAP/CD47) is a 50 kDa transmembrane protein initially defined as a regulator of beta3 integrin-mediated functions in neutrophils. IAP also can synergize with the TCR in T cell activation independent of beta3 integrins. To analyze the mechanism for IAP synergy with TCR, we expressed in Jurkat cells a chimeric molecule, consisting of the CD16 extracellular domain, the CD7 transmembrane domain and the TCR zeta chain cytoplasmic tail (CD16-7-zeta), which on its own is unable to induce IL-2 production. Ligation of IAP acted in synergy with TCR to induce IL-2 transcription and synthesis, but failed to synergize with the signal generated by CD16-7-zeta, while CD28 was a potent co-stimulator with both TCR and CD16-7-zeta. The failure of IAP to activate Jurkat together with CD16-7-zeta correlated with a lack of c-Jun N-terminal kinase, but not extracellular-signal-regulated kinase activation. Jurkat adhesion to anti-IAP, but not anti-CD28, induced cell spreading and the same domains of IAP required for augmentation of T cell activation were required to induce cell spreading. IAP synergy with TCR signaling likely results from its ability to stimulate adhesion to a ligand-expressing surface or antigen-presenting cell (APC), rather than from initiation of a novel signaling cascade. We conclude that a major role for ligation of IAP in T cell activation is to enhance the efficiency of TCR signaling by causing T cells to spread on an APC or surface.

Phylogenetic Divergence of CD47 Interactions with Human Signal Regulatory Protein α Reveals Locus of Species Specificity

“…Adhesion and Spreading Processes Involving CD47-CD47-SIRP␣ interactions can clearly mediate adhesion (4,6,25), but here we show that adhesion is followed by dynamic cell spreading (Fig. 3, A-C) that could contribute, for example, to cell-cell interactions between a T-cell and an antigenpresenting cell (52).…”

CD47 deficiency confers cell and tissue radioprotection by activation of autophagy

“…Jurkat T lymphoma cells and the CD47-deficient (CD47 − ) Jurkat somatic mutant clone JinB8 22 were routinely cultured in RPMI 1640 (Invitrogen, 11875-093) medium supplemented with 10% FBS (Gemini BioProducts, GBP-100106), penicillin/streptomycin and glutamine (Invitrogen, 15070-063, complete growth medium) at 37°C and 5% CO 2 . Human umbilical vein endothelial cells (HUVEC) and murine lung endothelial cells from WT and CD47 null mice were grown in endothelial cell growth medium-2 in a humidified 37°C incubator with 5% CO 2 .…”

“…Because the CD47 − Jurkat cell line was generated by chemical mutagenesis 22 we wanted to confirm that the altered LC3 puncta components such as vacuoles and membranes as well as mitochondria, that have not fused with a lysosome. 19 We observed more than a 2-fold increase in autophagosome number in sections of irradiated CD47 − Jurkat T cells when compared with WT irradiated counterparts ( Fig.…”

The Mechanism of CD47-Dependent Killing of T Cells: Heterotrimeric Gi-Dependent Inhibition of Protein Kinase A

“…Both JE6.1 (CD47 ϩ/ϩ ) and JINB8 (CD47 Ϫ/Ϫ ) have been described previously (32). The Jurkat T cells were cultured in Iscove's medium supplemented with 10% FBS, penicillin (100 U/ml), and streptomycin (100 g/ ml).…”