Uterine Smooth MuscleS-Nitrosylproteome in Pregnancy

Abstract

The molecular mechanisms involved in uterine quiescence during gestation and those responsible for induction of labor are not completely known. Nitric oxide relaxes uterine smooth muscle in a manner disparate from that for other smooth muscles because global elevation of cGMP after activation of soluble guanylyl cyclase does not relax the muscle. S-Nitrosylation, the covalent addition of an nitric oxide (NO) group to a cysteine thiol is a likely mechanism to explain the ability of NO to relax myometrium. This work is the first to describe the myometrial S-nitrosylproteome in both pregnant and nonpregnant tissue states. Using the guinea pig model, we show that specific sets of proteins involved in contraction and relaxation are S-nitrosylated in laboring and nonlaboring muscle and that many of these proteins are uniquely S-nitrosylated in only one state of the tissue. In particular, we show that S-nitrosylation of the intermediate filament protein desmin is significantly increased (5.7-fold, p Ͻ 0.005) in pregnancy and that this increase cannot be attributed solely to the increase in protein expression (1.8-fold, p Ͻ 0.005) that accompanies pregnancy. Elucidation of the myometrial S-nitrosylproteome provides a list of mechanistically important proteins that can constitute the basis of hypotheses formed to explain the regulation of uterine contraction/relaxation.

S‐nitrosylation of cytoskeletal proteins

“…Among the microtubule motors, only kinesin has been found to be S-nitrosylated (Abat et al, 2008;Ulrich et al, 2012). The functional effects of that S-nitrosylation are unknown.…”

“…S-nitrosylation of myosin heavy and light chains in intact cardiac myofibrils correlates with a decrease in ATPase activity (Figueiredo-Freitas et al, 2015); the authors of that study suggested Cys191 on myosin light chain 3 as the potential causative factor. The heavy chains of some unconventional myosin isoforms have also been found to be nitrosylated, but the functional impacts of S-nitrosylation of these isoforms are unknown (Abat et al, 2008;Batool et al, 2017;Greco et al, 2006;Kohr et al, 2011;Shi et al, 2008;Ulrich et al, 2012). The heavy chains of some unconventional myosin isoforms have also been found to be nitrosylated, but the functional impacts of S-nitrosylation of these isoforms are unknown (Abat et al, 2008;Batool et al, 2017;Greco et al, 2006;Kohr et al, 2011;Shi et al, 2008;Ulrich et al, 2012).…”

The role of S-nitrosoglutathione reductase (GSNOR) in human disease and therapy

“…The pathway through which NO relaxes the myometrium independent of cGMP is unknown, but it is likely that the S-nitrosation of contractile proteins plays a role. It has been determined that the state of labor (full term vs. preterm) can vastly alter the S-nitrosated protein landscape in uterine smooth muscle after exposure to GSNO (Ulrich et al, 2012). It is also well known that S-nitrosation can vary significantly based upon the cytoplasmic availability GSNOR (Broniowska and Hogg, 2012; Hess et al, 2005; Thomas and Jourd’heuil, 2012).…”

Pathophysiology of Hypertension in the Absence of Nitric Oxide/Cyclic GMP Signaling

“…Combined with the observation that GSNOR inhibition causes relaxation of murine aortic rings[91], these results suggest that increased levels of protein S-nitrosylation are associated with improved vasodilation and lower blood pressure. Multiple possible targets of S-nitrosylation have been identified in smooth muscle, including structural and contractile proteins[92, 93]. For example, the direct activation of VSMC Ca 2+ -dependent K + channels by S-nitrosylation[94] was proposed as a potential mechanism of cGMP-independent vasorelaxation[95].…”