214 A histone deacetylase 7-derived 7-amino acid peptide acts as a phosphorylation carrier

Abstract

compounds such as endothelin-1 (ET-1) and NO are required to maintain vascular tine. An imbalance, resulting in increased ET-1 and reduced NO levels promotes vascular stiffening and consequently diseases such as diabetic retinopathy, nephropathy and atherosclerosis. Diseases caused by an increased atherosclerosis burden including coronary heart disease and stroke are major causes of death in obese and diabetic populations. Aims Determine (1) whether enhanced Ab levels are sufficient to induce vascular dysfunction and (2) if reducing Ab production can reverse diet-induced vascular dysfunction. Methods Measurements of vascular function was determined in vivo by the vascular response to Acetylcholine (endothelial dependent or Sodium Nitroprusside (endothelial independent) using laser Doppler imaging in two studies; (i) Wild-type (C57BL/6) mice fed a regular chow diet were infused with murine ab42 or scrambled peptide (ScP; 3.36mg/kg) in aCSF for 6 weeks or (ii) a BACE1 inhibitor (M-3; 10mg/kg) or vehicle (DMSO/PBS) into diet-induced obese (DIO) C57BL/6 mice. Western blotting and ELISAs were used to measure vascular NO signalling and Ab production. Results Circulating levels of Ab42, not the more prevalent Ab40 isoform, are increased in both high fat fed mice and obese/diabetic human patients. Infusion of M-3 into DIO mice rescued endothelial dependent reactivity (M-3 27.1 ± 5.9, vehicle 1.3 ± 2.9; P<0.01). In contrast, infusion of Ab42 promoted impaired vascular responses Ab 14.1±3.7, ScP 38.3±3.2; P<0.001) on regular chow with no change in body weight. In line with our hypothesis infusion of Ab42 increases the ET-1/NO ratio (ScP 1.12b± 0.05, Ab42 5.35 ± 0.89; P<0.001), while DIO mice treated with a BACE1 inhibitor, thus with reduced plasma Ab42 levels, have a low ET-1/NO ratio (M-3 1.29 ± 0.9, DIO 4.6 ± 1.3; P<0.05). Conclusions We suggest that amyloid processing has a role in normal vascular function with aberrant processing leading to endothelial dysfunction and hypertension. Here we show that pharmacological inhibition of BACE1 can reverse diet-induced endothelial dysfunction, via modulation of plasma Ab42 levels, as infusion of Ab42 can promote the dysfunction independent of a high fat diet. Histone deacetylase 7 (HDAC7) belongs to the class II HDAC family and plays a pivotal role in the maintenance of endothelium integrity. There are 8 splicing variants in mouse HDAC7 mRNAs. Within the 5' terminal non-coding area of some variants, there exist some short open reading frames (sORFs). Whether these sORFs can be translated and whether the resulting peptides play roles in cellular physiology remain unclear. In this study, we demonstrated that one sORF encoding a 7-amino-acid (7-aa) peptide could be translated in vascular progenitor cells (VPCs). Importantly, this 7-aa peptide (7A) could transfer the phosphate group from the phosphorylated Ser393 site of MEKK1 to the Thr145 site of 14-3-3g protein.The phosphorylated 7A (7Ap) could then directly phosphorylate 14-3-3g protein in a cell-free, in-gel buffer system. The...