7 research outputs found
New Modularity of DAP-Kinases: Alternative Splicing of the DRP-1 Gene Produces a ZIPk-Like Isoform
DRP-1 and ZIPk are two members of the Death Associated Protein Ser/Thr Kinase
(DAP-kinase) family, which function in different settings of cell death
including autophagy. DAP kinases are very similar in their catalytic domains but
differ substantially in their extra-catalytic domains. This difference is
crucial for the significantly different modes of regulation and function among
DAP kinases. Here we report the identification of a novel alternatively spliced
kinase isoform of the DRP-1 gene, termed DRP-1Ξ². The
alternative splicing event replaces the whole extra catalytic domain of DRP-1
with a single coding exon that is closely related to the sequence of the extra
catalytic domain of ZIPk. As a consequence, DRP-1Ξ² lacks the calmodulin
regulatory domain of DRP-1, and instead contains a leucine zipper-like motif
similar to the protein binding region of ZIPk. Several functional assays proved
that this new isoform retained the biochemical and cellular properties that are
common to DRP-1 and ZIPk, including myosin light chain phosphorylation, and
activation of membrane blebbing and autophagy. In addition, DRP-1Ξ² also
acquired binding to the ATF4 transcription factor, a feature characteristic of
ZIPk but not DRP-1. Thus, a splicing event of the DRP-1 produces a ZIPk like
isoform. DRP-1Ξ² is highly conserved in evolution, present in all known
vertebrate DRP-1 loci. We detected the corresponding mRNA and
protein in embryonic mouse brains and in human embryonic stem cells thus
confirming the in vivo utilization of this isoform. The
discovery of module conservation within the DAPk family members illustrates a
parsimonious way to increase the functional complexity within protein families.
It also provides crucial data for modeling the expansion and evolution of DAP
kinase proteins within vertebrates, suggesting that DRP-1 and ZIPk most likely
evolved from their ancient ancestor gene DAPk by two gene duplication events
that occurred close to the emergence of vertebrates
A High Throughput Proteomics Screen Identifies Novel Substrates of Death-associated Protein Kinase
DAP-kinase-mediated phosphorylation on the BH3 domain of beclin 1 promotes dissociation of beclin 1 from Bcl-XL and induction of autophagy
Autophagy, an evolutionarily conserved process, has functions both in cytoprotective and programmed cell death mechanisms. Beclin 1, an essential autophagic protein, was recently identified as a BH3-domain-only protein that binds to Bcl-2 anti-apoptotic family members. The dissociation of beclin 1 from its Bcl-2 inhibitors is essential for its autophagic activity, and therefore should be tightly controlled. Here, we show that death-associated protein kinase (DAPK) regulates this process. The activated form of DAPK triggers autophagy in a beclin-1-dependent manner. DAPK phosphorylates beclin 1 on Thr 119 located at a crucial position within its BH3 domain, and thus promotes the dissociation of beclin 1 from Bcl-XL and the induction of autophagy. These results reveal a substrate for DAPK that acts as one of the core proteins of the autophagic machinery, and they provide a new phosphorylation-based mechanism that reduces the interaction of beclin 1 with its inhibitors to activate the autophagic machinery