Mitogenic signals through CD28 activate the protein kinase Ctheta-NF-kappaB pathway in primary peripheral T cells.
Mitogenic anti-CD28 antibody stimulates all peripheral T cells to proliferate in the absence of TCR ligation, providing an exception to the two-signal requirement of T cell responses. This antibody preferentially recognizes a mobilized signaling-competent form of CD28, normally induced following TCR ligation, thus providing a unique non-physiological tool to dissect CD28-specific signals leading to T cell proliferation. The protein kinase C (PKC)theta-NF-kappaB pathway has recently been shown to integrate TCR- and CD28-derived signals in co-stimulation. We now demonstrate that this pathway is activated by mitogenic anti-CD28 antibody stimulation. In contrast to conventional anti-CD28 antibody, mitogenic anti-CD28 antibody induced activation of phospholipase Cgamma and Ca(2+) flux in peripheral rat T cells despite no or low levels of inducible tyrosine phosphorylation of TCRzeta chain, TCRzeta-associated protein of 70 kDa (ZAP-70) or linker for activation of T cells (LAT)-critical components of the TCR signaling machinery. Nevertheless, PKCtheta kinase activity in vitro was increased following mitogenic anti-CD28 antibody stimulation, as was membrane association of both PKCtheta and Bcl10. As downstream targets of PKCtheta activation, NF-kappaB components translocated to the nucleus at levels comparable to those after TCR-CD28 co-stimulation. NF-kappaB translocation was diminished by PKCtheta inhibition, as was induction of the NF-kappaB/AP-1 responsive activation marker CD69. We propose that co-stimulation is a sequential process in which appropriate TCR engagement is required to mobilize CD28 into a signaling-competent form which then activates the PKCtheta-NF-kappaB pathway necessary for IL-2 production and proliferation.
Dennehy
Kevin M
KM
Institute for Virology and Immunobiology, University of Würzburg, 97078 Würzburg, Germany.
Kerstan
Andreas
A
Bischof
Astrid
A
Park
Jung-Hyun
JH
Na
Shin-Young
SY
Hünig
Thomas
T
D000818:Animals; D018106:CD28 Antigens / Q000276:immunology / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D020033:Protein Isoforms; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D011948:Receptors, Antigen, T-Cell / Q000378:metabolism; D013601:T-Lymphocytes / Q000378:metabolism*; D051746:ZAP-70 Protein-Tyrosine Kinase
D018106:CD28 Antigens; D016328:NF-kappa B; D020033:Protein Isoforms; D011948:Receptors, Antigen, T-Cell; D011505:Protein-Tyrosine Kinases; D051746:ZAP-70 Protein-Tyrosine Kinase; D011493:Protein Kinase C