: Extracellular superoxide dismutase (ecSOD), a major form of SOD expressed in the vasculature, is a """"""""secretory"""""""" copper-containing enzyme and plays an important role in regulating blood pressure and endothelial function by modulating the levels of O2 in the extracellular space. Particularly, in angiotensin H-induced hypertension model, the excessive 02 is observed in the vessel wall and the hypertension is ameliorated by treatment with membrane-targeted forms of SOD. Moreover, we have found that blood pressure and 02 production in the vessel were highly elevated in ecSOD-deficient mice infused with angiotensin II. Thus, ecS0D is a potentially important modulator of oxidative phenomena in the pathogenesis of hypertension. Recently, it has been shown that copper chaperones (CCS) are critical for copper transport and delivery to copper containing enzymes. Our preliminary data strongly suggests that CCS with signal peptide (CCS-SP) which targets to Golgi plays an important role in the transport of copper to ecSOD, which is required for full activity of the ecSOD. We will propose the following specific aim to address how ecSOD activity is controlled by copper transport system such as CCS and copper transporter in the yeast system, vascular cells and in vivo model of hypertension.
In aim 1, we will characterize a role of copper transport system for full expression of ecSOD activity using the yeast system. First, by generating several CCS-SP cDNA constructs including the truncated form, we will determine which region is critical for copper loading-to ecSOD. Second, we will determine if copper loading to ecSOD requires MNK, a copper transporter in the trans-Golgi network, using the yeast strain deficient in MNK.
In aim 2, we will identify endogenous copper chaperone for ecSOD in human aortic smooth muscle cells (HASM) that highly expresses ecSOD, by using the highly conserved region of CCS as a probe that have detected novel CCS-like transcript and protein in HASM. Next, we will determine if copper delivery to ecSOD requires MTNK in mammalian cells, by using the murine MNK-mutant fibroblast and aorta from MNK-mutant mice.
In aim 3, we will examine the role of copper transport system for ecSOD in blood pressure, vascular O2 production and endothelial function in angiotensin II induced hypertension by using MNK-mutant mice. These studies will provide new insight into a copper transport system for ecSOD as a novel modulator of oxidative stress linked to the pathogenesis of hypertension and as essential to anti-oxidant therapy.
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