Archives

  • 2018-07
  • 2019-04
  • 2019-05
  • 2019-06
  • 2019-07
  • 2019-08
  • 2019-09
  • 2019-10
  • 2019-11
  • 2019-12
  • 2020-01
  • 2020-02
  • 2020-03
  • 2020-04
  • 2020-05
  • 2020-06
  • 2020-07
  • 2020-08
  • 2020-09
  • 2020-10
  • 2020-11
  • 2020-12
  • 2021-01
  • 2021-02
  • 2021-03
  • 2021-04
  • 2021-05
  • 2021-06
  • 2021-07
  • 2021-08
  • 2021-09
  • 2021-10
  • 2021-11
  • 2021-12
  • 2022-01
  • 2022-02
  • 2022-03
  • 2022-04
  • 2022-05
  • 2022-06
  • 2022-07
  • 2022-08
  • 2022-09
  • 2022-10
  • 2022-11
  • 2022-12
  • 2023-01
  • 2023-02
  • 2023-03
  • 2023-04
  • 2023-05
  • 2023-06
  • 2023-07
  • 2023-08
  • 2023-09
  • 2023-10
  • 2023-11
  • 2023-12
  • 2024-01
  • 2024-02
  • 2024-03
  • br Introduction The signaling molecule nitric oxide NO plays

    2022-05-13


    Introduction The signaling molecule nitric oxide (NO) plays an essential role in vessel homeostasis by initiating vasodilation [1], [2], [3]. After biosynthesis in endothelial cells, NO diffuses into the subjacent smooth muscle layer to reach its target enzyme, soluble guanylyl cyclase (sGC, EC 4.6.1.2). Upon binding of NO to the prosthetic heme group of sGC, the enzyme gets activated and catalyzes the formation of the second messenger cGMP. Elevated levels of cGMP eventually lead to relaxation of vascular smooth muscle [4]. As sGC plays a crucial role in vasodilation, there is great interest in the pharmacological modulation of this enzyme in a variety of cardiovascular diseases [5]. Low molecular weight compounds that increase sGC activity in tissues have been described as stimulators and activators of the enzyme. While stimulators sensitize holo-sGC towards NO, activators mimic formation of the active nitrosyl-heme complex by binding to the heme-free enzyme [6]. The first described stimulator of sGC was YC-1 [7], [8], which stabilizes the NO-heme complex. High throughput screening and pharmacokinetic optimization resulted in the development of the orally usable drug riociguat (BAY 63-2521) [9]. The two most frequently studied activators of sGC are cinaciguat (BAY 58-2667) and ML385 BAY 60-2770. Activators are of great interest in the therapy of cardiovascular diseases associated with oxidative stress in the vasculature [6], [10], [11], [12]. Besides these low molecular weight compounds some proteins are known to regulate sGC activity by direct protein-protein interaction. Members of the heat shock protein (Hsp) family are of particular interest. Hsp70 was claimed to act as endogenous activator of sGC, but addition of exogenous Hsp70 to purified sGC had no effect [13], so the role of Hsp70 is still unclear. In contrast, there is a large body of evidence indicating that Hsp90 functions as chaperone in the maturation of the NO-responsive active sGC heterodimer (for review, see Ref. [14]). Recently, we reported that heme-free cytosolic preparations of porcine coronary arteries (PCA) increase the maximal activity of NO-stimulated sGC [15]. Preliminary experiments suggested that this effect is mediated by a protein which will be further referred to as sGC-activating factor (sGC-AF). In the present study we describe the partial purification and identification of this protein.
    Materials & methods
    Results
    Discussion
    Acknowledgement This work was supported by the Austrian Science Fund [P24946].
    Introduction Guanylyl cyclases (GCs) are a family of enzymes that catalyze the conversion of guanosine triphosphate (GTP) to the intracellular second messenger 3′,5′-cyclic guanosine monophosphate (cGMP). The enzyme family comprises both soluble and particulate isoforms (sGC and pGC). In contrast to sGC, which is activated by the gaseous messenger nitric oxide (NO), membrane-bound receptor guanylyl cyclases are regulated by diverse extracellular agonists, including peptide hormones and bacterial toxins (Lucas et al., 2000, Tamura et al., 2001, Potter, 2005, Garbers et al., 2006). Seven different mammalian receptor guanylyl cyclases, named GC-A through GC-G, have been identified up to now. GC-A, also known as natriuretic peptide receptor-A or -1 (NPR-A or NPR-1), is the receptor for atrial and brain natriuretic peptides (ANP and BNP). GC-B or natriuretic peptide receptor-B or -2 (NPR-B or NPR-2) is mainly activated by C-type natriuretic peptide (CNP). GC-C was first characterized as a receptor for heat-stable bacterial enterotoxins (STa). Later on guanylin and uroguanylin, small peptides with homology to STa, were suggested as the natural endogenous ligands for GC-C (Vandraager, 2002, Forte, 2004, Potter et al., 2006, Potter et al., 2009). Recently, different ligands have been proposed as GC-D agonists, namely guanylin, uroguanylin and the gaseous messenger CO2 (Hu et al., 2007, Leinders-Zufall et al., 2007, Duda and Sharma, 2008, Cockerham et al., 2009, Sun et al., 2009). Up to now, no ligands have been identified for the orphan receptors GC-E, GC-F and GC-G (Tamura et al., 2001, Garbers et al., 2006).