INVESTIGADORES
GIRONACCI Mariela Mercedes
congresos y reuniones científicas
Título:
Tyrosine Hydroxylase, An Enzyme Implicated In Hypertension Development, Is Regulated By The Ubiquitin-proteasome System
Autor/es:
NADIA LONGO-CARBAJOSA, ALEJANDRA LOPEZ VERRILLI, MARIELA GIRONACCI,
Reunión:
Congreso; High Blood Pressure Research 2011; 2011
Resumen:
Cellular protein degradation is temporally controlled and tightly regulated, which plays a fundamental role in many processes during cell life and death. Aberrations in this process are implicated in the pathogenesis of many diseases. The ubiquitin-proteasome system (UPS) is the major pathway for intracellular protein degradation in eukaryotic cells. Tyrosine hydroxylase (TH) is a key enzyme in catecholamines biosynthesis and is involved in hypertension development. The aim of our study is to investigate whether TH turnover is regulated by the UPS. PC12 cells were incubated in the absence and presence of proteasome and lysosomes inhibitors during different times and TH expression was evaluated by Western blot. Time dependent experiments with 1 µmol/L lactacystin, a proteasome inhibitor, showed an increase of 86+15% in TH protein expression after 30 min of incubation, then began to decrease up to 6 h to reach equal levels to control group, and finally it rose up to 35.2+8.5% after 24 h treatment. In contrast, 5 nmol/L bafilomycin, an inhibitor of H+-ATPase, the enzyme that maintains the acidic pH within lysosomes, did not alter TH expression during short times, while it induced an increase of 92+22% above basal after 6 h treatment. 1 µmol/L napsul, a cathepsin G inhibitor, did not modify TH expression. Before degradation, proteasome substrates are labeled by conjugation with multiubiquitin chains. Efficacy of proteasome inhibition on TH turnover was evidenced by accumulation of poly-ubiquitinylated TH after 30 min treatment. Phosphorylation of TH at Ser40, which is essential for TH activity, was increased by 155±45% above basal when cells were treated with the proteasome inhibitor. Our results demonstrate that TH expression and activity are short-term regulated by the UPS and long-term by lysosomes. Alterations in the UPS activity may explain the increased expression of TH observed in hypertension.