The Journal of Clinical Investigation http://www.jci.org Volume 123 Number 1 January 2013
S-nitrosylation: integrator of cardiovascular
performance and oxygen delivery
Saptarsi M. Haldar1 and Jonathan S. Stamler1,2,3
1Department of Medicine and Cardiovascular Division, 2Harrington Discovery Institute, and 3Institute for Transformative Molecular Medicine,
Case Western Reserve University School of Medicine and University Hospitals Case Medical Center, Cleveland, Ohio, USA.
Delivery of oxygen to tissues is the primary function of the cardiovascular system. NO, a gasotransmitter that signals
predominantly through protein S-nitrosylation to form S-nitrosothiols (SNOs) in target proteins, operates coordi-
nately with oxygen in mammalian cellular systems. From this perspective, SNO-based signaling may have evolved
as a major transducer of the cellular oxygen-sensing machinery that underlies global cardiovascular function. Here
we review mechanisms that regulate S-nitrosylation in the context of its essential role in “systems-level” control
of oxygen sensing, delivery, and utilization in the cardiovascular system, and we highlight examples of aberrant
S-nitrosylation that may lead to altered oxygen homeostasis in cardiovascular diseases. Thus, through a bird’s-eye
view of S-nitrosylation in the cardiovascular system, we provide a conceptual framework that may be broadly appli-
cable to the functioning of other cellular systems and physiological processes and that illuminates new therapeutic
promise in cardiovascular medicine.
Oxygen and NO: co-evolution for common function
From the appearance of the simplest metazoans to the most com-
plex multicellular life forms, the ability to efficiently handle oxygen
has remained essential for survival and has therefore been subject
to intense evolutionary pressure. A single-cell organism must rap-
idly adapt its core homeostatic processes to fluctuations in oxy-
gen tension, functions retained in specialized cells of higher verte-
brates (1, 2). In addition to cell-autonomous pathways for oxygen
homeostasis, complex multicellular organisms have also developed
sophisticated mechanisms to efficiently coordinate oxygen delivery
and utilization across diverse organ systems (3–5). From this per-
spective, the human cardiovascular system in all its complexity has
evolved for the principal purpose of oxygen delivery.
Although oxygen itself can function as a signaling molecule (2,
6), its signaling repertoire is dependent largely on heme binding
and is therefore limited, as hemes do not generally convey cellular
signals. Thus, organisms have necessarily evolved parallel mecha-
nisms to precisely control oxygen flux and function. Utilization
of the ancient gasotransmitter NO, highly abundant in the pri-
mordial atmosphere and linked to anaerobic respiration, likely
co-evolved with oxygen to serve a common function — regulation
of aerobic respiration (i.e., oxygen delivery and utilization). While
NO, like O2, binds transition metal centers to elicit cellular signals,
the majority of its cellular influence is achieved through posttrans-
lational modification (PTM) of cysteine thiols, a process termed
S-nitrosylation (7). The universal presence of cysteine thiols in all
major classes of proteins greatly expands signaling possibilities,
and regulation of protein function via S-nitrosylation may be
viewed as the prototypical system for redox-based and gasotrans-
mitter-mediated signal transduction (8).
Recent reviews of S-nitrosylation have detailed the redox biochem-
istry of reactive nitrogen species (8–10) and cataloged the myriad
proteins and cellular processes known to be regulated by this mod-
ification across systems, including the cardiovascular system (11,
12). Nearly 1,000 S-nitrosylated proteins have been identified in the
heart alone (13, 14), and cross-talk with a plethora of other PTMs
has been described (15). Principles underlying reversibility, specific-
ity, and enzymatic control of S-nitrosylation have received particular
attention. Here, we take a thematic perspective that highlights the
essential role of protein S-nitrosylation in the systems-level control
of oxygen delivery and utilization, which is arguably the essential
function of the cardiovascular system. Using these physiological
insights, we highlight examples of how S-nitrosylation is dysregu-
lated in cardiovascular disease and how modulation of this signal-
ing mechanism holds therapeutic promise. Through this bird’s-eye
view of S-nitrosylation in the cardiovascular system, we provide a
conceptual framework that may be broadly applicable to cellular
systems, physiological processes, and diseases.
S-nitrosylation as a prototypical system of protein PTM
Systems governing PTM of proteins generally fall into two broad
categories, those with a ubiquitous sphere of influence (e.g., phos-
phorylation) and those with a more limited cellular purview (e.g.,
methylation). S-nitrosylation, like phosphorylation, is clearly
evolutionarily conserved and ubiquitous, affecting most, if not
all classes of proteins across all cellular compartments (8, 9, 16).
By contrast, other oxygen/redox-based modifications, including
hydroxylation and sulfenylation, have been identified to date with
specific classes of proteins and functions (2, 17). Here, we draw
parallels between S-nitrosylation and other important PTMs (e.g.,
phosphorylation, ubiquitinylation, acetylation) to provide a con-
ceptual framework for understanding the molecular machinery
that governs this fundamental biologic process (Figure 1).
In mammals, the principal sources of newly synthesized NO
are the three NOS isoforms (NOS1–3). Nitrate and nitrite may
also contribute to the NO reservoir (18, 19), particularly under
duress. The transfer of the NO moiety to cysteine thiols in target
proteins is carried out by peptide or protein nitrosylases, which
mediate either metal-to-Cys or Cys-to-Cys transfer. Metal-to-Cys
nitrosylases are proteins that transfer NO groups from transition
metals (e.g., Fe2+, Cu2+) to cysteine thiol. For example, mammalian
hemoglobin (Hb) undergoes auto-nitrosylation via intramolecu-
lar transfer of NO from heme iron (iron nitrosyl; HbFeNO) to a
Conflict of interest: The authors have declared that no conflict of interest exists.
Citation for this article: J Clin Invest. 2013;123(1):101–110. doi:10.1172/JCI62854.
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