Tyrosine Hydroxylase Is Short-Term Regulated by the Ubiquitin-Proteasome System in PC12 Cells and Hypothalamic and Brainstem Neurons from Spontaneously Hypertensive Rats: Possible Implications in Hypertension

LONGO CARBAJOSA N; CORRADI G; LOPEZ VERRILLI MA; GUIL MJ; VATTA MS; GIRONACCI M

PLOS ONE

PUBLIC LIBRARY SCIENCE

Lugar: San Francisco; Año: 2015

1932-6203

Aberrations in the ubiquitin-proteasome system (UPS) are implicated in the pathogenesis ofvarious diseases. Tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholaminesbiosynthesis, is involved in hypertension development. In this study we investigated whetherUPS regulated TH turnover in PC12 cells and hypothalamic and brainstem neurons fromspontaneously hypertensive rats (SHR) and whether this system was impaired in hypertension.PC12 cells were exposed to proteasome or lysosome inhibitors and TH protein levelevaluated by Western blot. Lactacystin, a proteasome inhibitor, induced an increase of86±15% in TH levels after 30 min of incubation, then it started to decrease up to 6 h to reachcontrol levels and finally it rose up to 35.2±8.5% after 24 h. Bafilomycin, a lysosome inhibitor,did not alter TH protein levels during short times, but it increased TH by 92±22% abovebasal after 6 h treatment. Before degradation proteasome substrates are labeled by conjugationwith ubiquitin. Efficacy of proteasome inhibition on TH turnover was evidenced byaccumulation of ubiquitinylated TH after 30 min. Further, the inhibition of proteasome increasedthe quantity of TH phosphorylated at Ser40, which is essential for TH activity, by2.7±0.3 fold above basal. TH protein level was upregulated in neurons from hypothalamiand brainstem of SHR when the proteasome was inhibited during 30 min, supporting thatneuronal TH is also short-term regulated by the proteasome. Since the increased TH levelsreported in hypertension may result from proteasome dysfunction, we evaluate proteasmeactivity. Proteasome activity was significantly reduced by 67±4% in hypothalamic and brainstemneurons from SHR while its protein levels did not change. Present findings show thatTH is regulated by the UPS. The impairment in proteasome activity observed in SHR neuronsmay be one of the causes of the increased TH protein levels reported in hypertension.