TY - JOUR
T1 - Targeted knock-in mice expressing mutations of CD28 reveal an essential pathway for costimulation
AU - Dodson, Lindzy F.
AU - Boomer, Jonathan S.
AU - Deppong, Christine M.
AU - Shah, Dulari D.
AU - Sim, Julia
AU - Bricker, Traci L.
AU - Russell, John H.
AU - Green, Jonathan M.
PY - 2009/7
Y1 - 2009/7
N2 - Despite extensive study, the role of phosphatidylinositol 3-kinase (PI3-kinase) activation in CD28 function has been highly contentious. To definitively address this question, we generated knock-in mice expressing mutations in two critical domains of the cytoplasmic tail of CD28. Mutation of the proximal tyrosine motif interrupted PI3-kinase binding and prevented CD28-dependent phosphorylation of protein kinase B (PKB)/ Akt; however, there was no detectable effect on interleukin-2 (IL-2) secretion, expression of Bcl-XL, or on T-cell function in vivo. Furthermore, we demonstrate that signaling initiated by the C-terminal proline motif is directly responsible for tyrosine phosphorylation of phosphoinosotide-dependent kinase 1, protein kinase Cβ, and glycogen synthase kinase 3β, as well as contributing to threonine phosphorylation of PKB. T cells mutated in this domain were profoundly impaired in IL-2 secretion, and the mice had marked impairment of humoral responses as well as less severe disease manifestations in experimental allergic encephalomyelitis. These data demonstrate that the distal proline motif initiates a critical nonredundant signaling pathway, whereas direct activation of PI3-kinase by the proximal tyrosine motif of CD28 is not required for normal T-cell function.
AB - Despite extensive study, the role of phosphatidylinositol 3-kinase (PI3-kinase) activation in CD28 function has been highly contentious. To definitively address this question, we generated knock-in mice expressing mutations in two critical domains of the cytoplasmic tail of CD28. Mutation of the proximal tyrosine motif interrupted PI3-kinase binding and prevented CD28-dependent phosphorylation of protein kinase B (PKB)/ Akt; however, there was no detectable effect on interleukin-2 (IL-2) secretion, expression of Bcl-XL, or on T-cell function in vivo. Furthermore, we demonstrate that signaling initiated by the C-terminal proline motif is directly responsible for tyrosine phosphorylation of phosphoinosotide-dependent kinase 1, protein kinase Cβ, and glycogen synthase kinase 3β, as well as contributing to threonine phosphorylation of PKB. T cells mutated in this domain were profoundly impaired in IL-2 secretion, and the mice had marked impairment of humoral responses as well as less severe disease manifestations in experimental allergic encephalomyelitis. These data demonstrate that the distal proline motif initiates a critical nonredundant signaling pathway, whereas direct activation of PI3-kinase by the proximal tyrosine motif of CD28 is not required for normal T-cell function.
UR - http://www.scopus.com/inward/record.url?scp=67650072922&partnerID=8YFLogxK
U2 - 10.1128/MCB.01869-08
DO - 10.1128/MCB.01869-08
M3 - Article
C2 - 19398586
AN - SCOPUS:67650072922
SN - 0270-7306
VL - 29
SP - 3710
EP - 3721
JO - Molecular and cellular biology
JF - Molecular and cellular biology
IS - 13
ER -