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

Abstract

Aberrations in the ubiquitin-proteasome system (UPS) are implicated in the pathogenesis of various diseases. Tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamines biosynthesis, is involved in hypertension development. In this study we investigated whether UPS regulated TH turnover in PC12 cells and hypothalamic and brainstem neurons from spontaneously hypertensive rats (SHR) and whether this system was impaired in hypertension. PC12 cells were exposed to proteasome or lysosome inhibitors and TH protein level evaluated by Western blot. Lactacystin, a proteasome inhibitor, induced an increase of 86±15% in TH levels after 30 min of incubation, then it started to decrease up to 6 h to reach control 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% above basal after 6 h treatment. Before degradation proteasome substrates are labeled by conjugation with ubiquitin. Efficacy of proteasome inhibition on TH turnover was evidenced by accumulation of ubiquitinylated TH after 30 min. Further, the inhibition of proteasome increased the quantity of TH phosphorylated at Ser40, which is essential for TH activity, by 2.7±0.3 fold above basal. TH protein level was upregulated in neurons from hypothalami and brainstem of SHR when the proteasome was inhibited during 30 min, supporting that neuronal TH is also short-term regulated by the proteasome. Since the increased TH levels reported in hypertension may result from proteasome dysfunction, we evaluate proteasme activity. Proteasome activity was significantly reduced by 67±4% in hypothalamic and brainstem neurons from SHR while its protein levels did not change. Present findings show that TH is regulated by the UPS. The impairment in proteasome activity observed in SHR neurons may be one of the causes of the increased TH protein levels reported in hypertension.

Tyrosine hydroxylase phosphorylation in vivo

“…The first is hierarchical phosphorylation of TH (Bevilaqua et al 2001;Toska et al 2002;Bobrovskaya et al 2004;Kansy et al 2004;Lehmann et al 2006;Royo & Colette Daubner 2006;Gordon et al 2009a;Salvatore & Pruett 2012). The second is TH stability and turnover (Doskeland & Flatmark 2002;Toska et al 2002;Moy & Tsai 2004;Royo et al 2005;Obsilova et al 2008;Posser et al 2009;Franco et al 2010;Nakashima et al 2011;Kawahata et al 2015;Nakashima et al 2016;Nakashima et al 2018;Congo Carbajosa et al 2015).…”

Lactacystin-Induced Model of Hypertension in Rats: Effects of Melatonin and Captopril

“…The ubiquitin-proteasome system degrades many cytosolic, nuclear and myofibrillar proteins [ 12 ]. Lactacystin is a proteasome inhibitor that interferes with the synthesis and degradation of several proteins involved in cardiovascular organ remodelling such as nuclear factor-kappa B (NF-κB), a nuclear transcriptional factor [ 13 ], tyrosine hydroxylase, the rate limiting enzyme in catecholamine biosynthesis [ 14 ], cyclooxygenase-2, a marker of inflammation [ 15 ], and the sarcomeric myosin heavy chain [ 16 ].…”

Effects of Tianshu Capsule on Spontaneously Hypertensive Rats as Revealed by 1H-NMR-Based Metabolic Profiling

“…With the exploitation of metabolite-related proteins and researching the literature (Schroeder and Adams, 1941; Masserano and Weiner, 1983; Yoshimura et al, 1987; Ito et al, 2000; Burkhard et al, 2001; Kwok et al, 2002; Whitfield et al, 2002; Nakanishi et al, 2004; Han et al, 2010; Kimura, 2011; Caplin et al, 2012; Congo Carbajosa et al, 2015), finally 10 proteins (TH, CBS, DDC, CTH, TYR, HDC, PLD2, AGXT2, KAT, ALT) considered as potential markers of TSC on SHR rats were preliminarily confirmed. Metabolite-protein correlations are listed in Figure 5 .…”