Control Of DAPK Protein Expression By Sumo Signalling Pathway

SUMO is a ubiquitin-like polypeptide. the molecular weight of which is about 11 kDa. In eukaryotic cells, sumo is involved in a variety of important physiological and biochemical reactions including transcriptional regulation, nuclear/cytoplasmic transport, cell cycle, DNA replication and repair and signal transduction. SUMO specific proteases (SENPs) not only catalize SUMO precursors to mature, but also catalize substrate desumoylation.Death Associated Protein Kinase 1 (DAPK) is a serine/threonine kinase involved in the regulation of multiple cellular events such as apoptosis, autophagy and proliferation. Deregulation of DAPK is closely related to diseases such as cancer, stroke, inflammation. Alzheimer's disease and atherosclerosis. DAPK expression is mainly reguated by DNA methylation and protein degradation. The degradation of DAPK is mediated by both ubiquitin proteasome system (UPS) and lysosomal systems. But at present, the study of DAPK degradation regulation is limited to the E3s in the proteasome pathway.In this study, when the expression of the 24 E2 genes were knocked down, we found that sumo E2, UBC9/UBC21. can regulate TSC2-medicated DAPK downregulation. DAPK protein expression was downregulated when SUMO signaling pathway was activated. Overexpression of SENPs led to increased DAPK expression and inhibiton of TSC2-mediated degradation of DAPK, indicating that SENPs can inhibit sumo pathway to antagonizes TSC2-mediated DAPK downregulation. Then we found that SENPs can significantly increase DAPK mRNA expression (?26.82%, P<0.05). But at protein level, Overexpression of SENPs. DAPK protein upregulated about 2-4 times. Therefore, the regulation of SUMO signaling pathway on the expression of DAPK protein is not entirely determined by the transcription of DAPK. Using point mutations, we found that SENPs regulated DAPK via the 1-364 domain, which was dependent on the 141st and 167st lysine residues of DAPK. Different SENPs have different preferrential lysine residues. We also found the peoteasome pathway can regulate the expression of HA-1-364 protein, and chloroquine can antagonize SENP1-mediated HA-1-364 regulation.This work explored the regulation of sumo signaling pathway on the expression of DAPK. DAPK is a potential drug target. But most DAPK studies focused on its kinase activity. Of note, specific molecules that prolong protein half-life can also play a role similar to the kinase activator. Therefore, better understanding of DAPK degradation regulation may shed light on alternative approaches for targeting DAPK in related diseases.