Phosphorylation of histone deacetylase 7 by protein kinase D mediates T cell receptor–induced Nur77 expression and apoptosis

Abstract

The molecular basis of thymocyte negative selection, a crucial mechanism in establishing central tolerance, is not yet resolved. Histone deacetylases (HDACs) have emerged as key transcriptional regulators in several major developmental programs. Recently, we showed that the class IIa member, HDAC7, regulates negative selection by repressing expression of Nur77, an orphan nuclear receptor involved in antigen-induced apoptosis of thymocytes. Engagement of the T cell receptor (TCR) alleviates this repression through phosphorylation-dependent nuclear exclusion of HDAC7. However, the identity of the TCR-activated kinase that phosphorylates and inactivates HDAC7 was still unknown. Here, we demonstrate that TCR-induced nuclear export of HDAC7 and Nur77 expression is mediated by activation of protein kinase D (PKD). Indeed, active PKD stimulates HDAC7 nuclear export and Nur77 expression. In contrast, inhibition of PKD prevents TCR-mediated nuclear exclusion of HDAC7 and associated Nur77 activation. Furthermore, we show that HDAC7 is an interaction partner and a substrate for PKD. We identify four serine residues in the NH2 terminus of HDAC7 as targets for PKD. More importantly, a mutant of HDAC7 specifically deficient in phosphorylation by PKD, inhibits TCR-mediated apoptosis of T cell hybridomas. These findings indicate that PKD is likely to play a key role in the signaling pathways controlling negative selection.

CRM1 mediates nuclear export of HDAC7 independently of HDAC7 phosphorylation and association with 14‐3‐3s

“…2B and 5). Taken together, these data suggest that the kinases including CaMKs and PKD [21,22,25] phosphorylate class IIa HDACs and sequester them in the cytoplasm, blocking their nuclear import. One possible mechanism is that Ser 178 (14-3-3 binding site) is closely adjacent to the NLS (amino acids 183-191) and association of phosphorylated HDAC7 with 14-3-3s may mask recognition of the NLS by importin a [30].…”

“…In addition to CaMKs, protein kinase D family kinases and Mirk/dyrk1B also play a role in subcellular distribution of class IIa HDACs [21][22][23][24][25]. Nonetheless, it is not clear whether phosphorylation of these conserved residues is essential for nuclear export of HDAC7.…”

Kidins220/ARMS Associates with B-Raf and the TCR, Promoting Sustained Erk Signaling in T Cells

“…Our finding that Kidins220 plays a role in TCR signaling might also shed light on the function of PKD in T cells, because Kidins220 is the only PKD substrate known (24), other than histone deacetylase 7 (63). PKD is recruited to the plasma membrane upon TCR activation (64), where it could phosphorylate Kidins220 and modulate signaling.…”

Class IIa histone deacetylases: regulating the regulators

“…Surprisingly, the corresponding motif is also conserved in HDAC5 and -9 ( Figure 1b). In addition, we recently identified a cryptic 14-3-3 binding site (Ser 181 ) in HDAC7 (Dequiedt et al, 2005(Dequiedt et al, , 2006. This site was overlooked in previous mutational analyses because its phosphorylation seems dependent on prior phosphorylation of the most N-terminal serine residue, Ser 155 .…”

“…This is the case for the PKC activator phorbol 13-myristate 12-acetate, for the B-and T-cell receptors and for several other cell surface receptors, such as the serotonin receptor and the G protein-coupled receptors (GPCR) endothelin receptor, a 1 -AR and PGF2a. Signaling via Rho-guanosine triphosphates, mediators of GPCR signaling, and via phospholipase C, a mediator that lies downstream of a 1 -AR, also activates PKD and triggers phosphorylationdependent nuclear export of HDAC5 (Chang et al, 2005;Dequiedt et al, 2005;Harrison et al, 2006). Some of these cell surface receptors also activate calcium fluxes and thus part of their effects could be mediated through activation of CaMKs .…”