Protein kinase D2 contributes to either IL-2 promoter regulation or induction of cell death upon TCR stimulation depending on its activity in Jurkat cells

Abstract

Members of protein kinase D (PKD) family serine/threonine kinases (PKD1, PKD2 and PKD3) are expressed in wide range of cells and regulate various cellular responses including immune responses. We have previously shown that PKD is involved in the signaling pathways of a human CD4(+) T cell clone stimulated with its cognate antigen. Contrary to foregoing publications, PKD1 mRNA was not detected in human T cells, Jurkat cells and mouse thymocytes and splenocytes. Instead, mass-spectrometric and reverse transcription-PCR analyses revealed that PKD2 was predominant in T cells. To investigate the roles of PKD2, wild-type (WT) and constitutively active (CA) PKD2 were expressed in Jurkat cells together with IL-2 promoter-driven reporter gene. Expression of WT-PKD2 enhanced IL-2 promoter activity upon stimulation with anti-CD3 mAb, while expression of CA-PKD2 inhibited IL-2 promoter activity and induced cell death. Although the cell death was suppressed by the treatment with caspase inhibitor, the IL-2 promoter activity was rarely recovered in CA-PKD2-expressing cells upon TCR stimulation. WT-PKD2 localized mainly in the cytoplasm translocated into the nucleus after TCR stimulation, while CA-PKD2 was present in both the cytoplasm and the nuclei before and after stimulation. Proteomic analyses revealed that CA-PKD2 enhanced the amount of phosphorylated SET protein, a histone chaperon that regulates histone acetylation, in Jurkat cells and the recombinant SET protein was phosphorylated by CA-PKD2 in vitro. The data provide a renewing insight into the subset of PKD family kinases expressed in T cells and suggest that PKD2 is involved in IL-2 promoter regulation and cell death depending on its activity upon TCR stimulation.

Protein kinase D1/2 is involved in the maturation of multivesicular bodies and secretion of exosomes in T and B lymphocytes

“…PKD2 is the main PKD isotype in human and mouse T lymphocytes. 25,26 We therefore analyzed T lymphoblasts from mice that lacked PKD2 (ref. 26 ) to determine its contribution to MVB traffic and exosome secretion.…”

“…PKD2 is the major PKD isotype expressed in human and mouse T lymphocytes. 25,26 In Jurkat T cells, GFP-tagged PKD1 and endogenous PKD2 have identical regulatory mechanisms, as well as similar activation kinetics and subcellular localization in response to TCR. 62 The effects observed for exogenously expressed PKD1 constructs may thus be the result of inhibition of endogenous PKD2 and activation of PKD2 downstream effectors.…”

“…64 Our data characterize a role for PKD2 in primary T-cell AICD and coincide with studies showing that expression of a constitutively active PKD2 mutant in Jurkat cells enhances AICD. 25 Although loss of PKD2 enhances thymic output during T lymphocyte development, it does not affect T-cell selection or inhibit expression of Vβ8 TCR, 63 the major murine TCR repertoire recognized by SEB. 50 PKD2 − / − T lymphoblasts show no changes in TCR-triggered, transcriptional induction of genes that encode proteins involved in CTL activity and AICD, such as FasL and perforin.…”

“…21) are expressed in a wide range of cells, with PKD2 the most abundant isotype in T lymphocytes. 25,26 PKD have two DAG-binding domains (C1a and C1b) at the N terminus, 21 which mediate PKD recruitment to cell membranes. Protein kinase C (PKC) phosphorylation at the PKD activation loop further promotes PKD autophosphorylation and activation.…”

Regulation and Function of Protein Kinase D Signaling

“…Upon T-cell receptor engagement, PKD stimulated hematopoietic progenitor kinase 1 (HPK1) activity in Jurkat T cells and enhanced HPK1-driven SAPK/JNK and NF-kB activation (Arnold et al 2005). However, other investigators found that PKD2 is the predominant PKD isoform in T cells (Irie et al 2006). Expression of PKD2 enhanced interleukin (IL)-2 promoter activity upon stimulation with anti-CD3 mAb in Jurkat T cells, suggesting that PKD2 is involved in IL-2 promoter regulation in response to TCR stimulation (Irie et al 2006).…”