Positive feedback regulation of PLCgamma1/Ca(2+) signaling by PKCtheta in restimulated T cells via a Tec kinase-dependent pathway.
PKCtheta plays an essential role in activation of mature T cells. Here, we report that the TCR/CD28-induced tyrosine phosphorylation and activation of PLCgamma1 was significantly impaired in PKCtheta (-/-) primary, restimulated T cells. Consistent with this finding, receptor-induced Ca(2+) mobilization, NF-AT DNA-binding activity and the membrane translocation of PKCalpha, a PLCgamma1-dependent conventional PKC, were also markedly reduced in the same cells. Moreover, a dominant-negative PLCgamma1 mutant blocked the PKCtheta-induced activation of an AP-1 reporter gene in Jurkat and primary cells. Regulation of PLCgamma1 signaling by PKCtheta required the tyrosine kinase Tec since a dominant-negative Tec mutant blocked PKCtheta-induced AP-1 (but not NF-kappaB) activation. In addition, wild-type Tec, but not Itk or Rlk, potently activated AP-1. Furthermore, Tec was found to constitutively associate with PKCtheta, an interaction that like AP-1 activation required the pleckstrin-homology domain of Tec. These findings define a novel PKCtheta-initiated pathway that regulates Ca(2+) signaling and AP-1 activation via Tec and PLCgamma1. Moreover, they identify Tec as a key point downstream of PKCtheta, where TCR- and PKCtheta-induced signaling pathways, leading to AP-1 versus NF-kappaB activation, diverge in T cells.
Altman
Amnon
A
Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121, USA. amnon@liai.org
Kaminski
Sandra
S
Busuttil
Valere
V
Droin
Nathalie
N
Hu
Junru
J
Tadevosyan
Yuri
Y
Hipskind
Robert A
RA
Villalba
Martin
M
D000818:Animals; D020013:Calcium Signaling; D002478:Cells, Cultured; D005799:Genes, Dominant / Q000235:genetics; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D019169:Jurkat Cells; D008213:Lymphocyte Activation; D051379:Mice; D009154:Mutation / Q000235:genetics; D016328:NF-kappa B / Q000378:metabolism; D051966:Phospholipase C gamma; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D000074121:Protein Kinase C-theta; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000378:metabolism*; D013601:T-Lymphocytes / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D010738:Type C Phospholipases / Q000378:metabolism*
D007527:Isoenzymes; D016328:NF-kappa B; D018808:Transcription Factor AP-1; C089848:Tec protein-tyrosine kinase; D011505:Protein-Tyrosine Kinases; C076233:PRKCQ protein, human; C489593:Prkcq protein, mouse; D011493:Protein Kinase C; D000074121:Protein Kinase C-theta; D010738:Type C Phospholipases; D051966:Phospholipase C gamma