Oxidative stress induces CHIP-mediated ubiquitination and roteasomal degradation of soluble guanylyl cyclase

Abstract

Oxidative stress attenuates the NO-cGMP pathway, e.g. in the vascular system, through scavenging of free NO radicals by superoxide O 2•-, by inactivation of soluble guanylyl cyclase (sGC) via oxidation of its central Fe 2+ ion, and by down-regulation of sGC protein levels. While the former pathways are well established, the molecular mechanisms underlying the latter are still obscure. Using oxidative sGC inhibitor ODQ we demonstrate rapid down-regulation of sGC protein in mammalian cells. Coincubation with proteasomal inhibitor MG132 results in accumulation of ubiquitinated sGC whereas sGC activator BAY 58-2667 prevents ubiquitination. ODQ-induced down-regulation of sGC is mediated through selective ubiquitination of its b subunit, and BAY 58-2667 abrogates this effect. Ubiquitination of sGC-b is dramatically enhanced by E3 ligase CHIP. Our data indicate that oxidative stress promotes ubiquitination of sGC b subunit through E3 ligase CHIP, and that sGC activator 58-2667 reverts this effect, most likely through stabilization of the heme-free b subunit. Thus the deleterious effects of oxidative stress can be counter-balanced by an activator of a key enzyme of vascular homeostasis.

Distinct molecular requirements for activation or stabilization of soluble guanylyl cyclase upon haem oxidation‐induced degradation

“…Recent findings suggest that increased levels of oxidative stress as observed under pathophysiological conditions can lead to oxidation or even loss of the sGC haem group, rendering the enzyme insensitive to NO and prone to ubiquitin‐mediated degradation (Stasch et al. , 2006; Meurer et al. , 2007; Xia et al.…”

“…Occupation of the sGC haem pocket with high affinity metallo‐porphyrins or compounds resembling the spatial structure and charge distribution of haem such as BAY 58‐2667 is able to prevent the oxidation‐induced degradation of sGC (Stasch et al. , 2006; Meurer et al. , 2007).…”

“…In addition to this acute inactivation of sGC, oxidation of the haem group facilitates the degradation of the enzyme (Stasch et al. , 2006; Meurer et al. , 2007).…”

“…In addition to its activating effect, BAY 58‐2667 is able to rescue the oxidation‐impaired sGC from enhanced ubiquitin‐mediated degradation, thus accumulating its receptor in a positive feedback loop (Stasch et al. , 2006; Meurer et al. , 2007).…”