cyclic-gmp and Protein-Aggregation--Pathological

Maintaining a redox balance by means of precisely controlled systems that regulate production, and elimination, and metabolism of electrophilic substances (electrophiles) is essential for normal cardiovascular function. Electrophilic signaling is mainly regulated by endogenous electrophiles that are generated from reactive oxygen species, nitric oxide, and the derivative reactive species of nitric oxide during stress responses, as well as by exogenous electrophiles including compounds in foods and environmental pollutants. Among electrophiles formed endogenously, 8-nitroguanosine 3',5'-cyclic monophosphate (8-nitro-cGMP) has unique cell signaling functions, and pathways for its biosynthesis, signaling mechanism, and metabolism in cells have been clarified. Reactive persulfide species such as cysteine persulfides and polysulfides that are endogenously produced in cells are likely to be involved in 8-nitro-cGMP metabolism. These new aspects of redox biology may stimulate innovative and multidisciplinary research in cardiovascular physiology and pathophysiology. In our review, we focus on the redox-dependent regulation of electrophilic signaling via reduction and metabolism of electrophiles by reactive persulfides in cardiac cells, and we include suggestions for a new therapeutic strategy for cardiovascular disease.

Topics: Animals; Cardiomyopathies; Cyclic GMP; Cysteine; Disulfides; Gene Expression Regulation; GTP-Binding Proteins; Humans; Myocardium; Myocytes, Cardiac; Nitric Oxide; Oxidation-Reduction; Oxidative Stress; Protein Aggregation, Pathological; Reactive Oxygen Species; Signal Transduction; Sulfides

Guanylate Cyclase-Activating Protein 1 (GCAP1) regulates the enzymatic activity of the photoreceptor guanylate cyclases (GC), leading to inhibition or activation of the cyclic guanosine monophosphate (cGMP) synthesis depending on its Ca2+- or Mg2+-loaded state. By genetically screening a family of patients diagnosed with cone-rod dystrophy, we identified a novel missense mutation with autosomal dominant inheritance pattern (c.332A>T; p.(Glu111Val); E111V from now on) in the GUCA1A gene coding for GCAP1. We performed a thorough biochemical and biophysical investigation of wild type (WT) and E111V human GCAP1 by heterologous expression and purification of the recombinant proteins. The E111V substitution disrupts the coordination of the Ca2+ ion in the high-affinity site (EF-hand 3, EF3), thus significantly decreasing the ability of GCAP1 to sense Ca2+ (∼80-fold higher Kdapp compared to WT). Both WT and E111V GCAP1 form dimers independently on the presence of cations, but the E111V Mg2+-bound form is prone to severe aggregation over time. Molecular dynamics simulations suggest a significantly increased flexibility of both the EF3 and EF4 cation binding loops for the Ca2+-bound form of E111V GCAP1, in line with the decreased affinity for Ca2+. In contrast, a more rigid backbone conformation is observed in the Mg2+-bound state compared to the WT, which results in higher thermal stability. Functional assays confirm that E111V GCAP1 interacts with the target GC with a similar apparent affinity (EC50); however, the mutant shifts the GC inhibition out of the physiological [Ca2+] (IC50E111V ∼10 μM), thereby leading to the aberrant constitutive synthesis of cGMP under conditions of dark-adapted photoreceptors.

Topics: Biophysical Phenomena; Calcium; Cone-Rod Dystrophies; Cyclic GMP; Gene Expression Regulation; Guanylate Cyclase-Activating Proteins; Humans; Magnesium; Molecular Dynamics Simulation; Mutation, Missense; Pedigree; Protein Aggregation, Pathological; Protein Binding; Retinal Cone Photoreceptor Cells; Retinal Degeneration