Diacylglycerol kinase alpha enhances protein kinase Czeta-dependent phosphorylation at Ser311 of p65/RelA subunit of nuclear factor-kappaB.

We recently reported that diacylglycerol kinase (DGK) alpha enhanced tumor necrosis factor-alpha (TNF-alpha)-induced activation of nuclear factor-kappaB (NF-kappaB). However, the signaling pathway between DGKalpha and NF-kappaB remains unclear. Here, we found that small interfering RNA-mediated knockdown of DGKalpha strongly attenuated protein kinase C (PKC) zeta-dependent phosphorylation of a large subunit of NF-kappaB, p65/RelA, at Ser311 but not PKCzeta-independent phosphorylation at Ser468 or Ser536. Moreover, knockdown and overexpression of PKCzeta suppressed and synergistically enhanced DGKalpha-mediated NF-kappaB activation, respectively. These results strongly suggest that DGKalpha positively regulates TNF-alpha-dependent NF-kappaB activation via the PKCzeta-mediated Ser311 phosphorylation of p65/RelA.