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Inhibiting O-GlcNAcylation impacts p38 and Erk1/2 signaling and perturbs cardiomyocyte hypertrophy
Kyriakos N Papanicolaou1, Jessica Jung1, Deepthi Ashok1
1Division of Cardiology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Abstract:
The dynamic cycling of O-linked GlcNAc (O-GlcNAc) on and off Ser/Thr residues of intracellular proteins, termed O-GlcNAcylation, is mediated by the conserved enzymes O-GlcNAc transferase (OGT) and O-GlcNAcase. O-GlcNAc cycling is important in homeostatic and stress responses, and its perturbation sensitizes the heart to ischemic and other injuries. Despite considerable progress, many molecular pathways impacted by O-GlcNAcylation in the heart remain unclear. The mitogen-activated protein kinase (MAPK) pathway is a central signaling cascade that coordinates developmental, physiological, and pathological responses in the heart. The developmental or adaptive arm of MAPK signaling is primarily mediated by Erk kinases, while the pathophysiologic arm is mediated by p38 and Jnk kinases. Here, we examine whether O-GlcNAcylation affects MAPK signaling in cardiac myocytes, focusing on Erk1/2 and p38 in basal and hypertrophic conditions induced by phenylephrine. Using metabolic labeling of glycans coupled with alkyne-azide "click" chemistry, we found that Erk1/2 and p38 are O-GlcNAcylated. Supporting the regulation of p38 by O-GlcNAcylation, the OGT inhibitor, OSMI-1, triggers the phosphorylation of p38, an event that involves the NOX2-Ask1-MKK3/6 signaling axis and also the noncanonical activator Tab1. Additionally, OGT inhibition blocks the phenylephrine-induced phosphorylation of Erk1/2. Consistent with perturbed MAPK signaling, OSMI-1-treated cardiomyocytes have a blunted hypertrophic response to phenylephrine, decreased expression of cTnT (key component of the contractile apparatus), and increased expression of maladaptive natriuretic factors Anp and Bnp. Collectively, these studies highlight new roles for O-GlcNAcylation in maintaining a balanced activity of Erk1/2 and p38 MAPKs during hypertrophic growth responses in cardiomyocytes.
Insights
O-GlcNAcylation dynamically regulates key heart signaling pathways. This study reveals how O-GlcNAc modification impacts MAPK signaling, influencing cardiac hypertrophy and function.
Area of Science:
- Cellular biology
- Biochemistry
- Cardiovascular research
Background:
- O-linked GlcNAc (O-GlcNAc) cycling is a dynamic post-translational modification crucial for cellular homeostasis and stress responses.
- Perturbations in O-GlcNAcylation are linked to cardiac injury, yet its specific roles in cardiac signaling pathways remain incompletely understood.
- The mitogen-activated protein kinase (MAPK) pathway, involving Erk1/2, p38, and Jnk, is central to cardiac development, physiology, and pathology.
Purpose of the Study:
- To investigate the impact of O-GlcNAcylation on MAPK signaling (Erk1/2 and p38) in cardiac myocytes.
- To elucidate the molecular mechanisms by which O-GlcNAcylation regulates MAPK activity under basal and hypertrophic conditions.
- To determine the functional consequences of altered MAPK signaling due to O-GlcNAcylation on cardiomyocyte hypertrophic responses.
Main Methods:
- Metabolic labeling of glycans combined with alkyne-azide "click" chemistry to detect O-GlcNAcylation on specific proteins.
- Pharmacological inhibition of O-GlcNAc transferase (OGT) using OSMI-1 to assess effects on MAPK phosphorylation.
- Analysis of cardiomyocyte hypertrophy markers (cTnT, Anp, Bnp) and signaling pathway components (NOX2, Ask1, MKK3/6, Tab1).
Main Results:
- Erk1/2 and p38 MAPKs were identified as O-GlcNAcylated proteins in cardiac myocytes.
- OGT inhibition (OSMI-1) induced p38 phosphorylation via the NOX2-Ask1-MKK3/6-Tab1 axis and blocked Erk1/2 phosphorylation.
- OSMI-1 treatment resulted in blunted phenylephrine-induced cardiac hypertrophy, decreased cTnT, and increased Anp/Bnp expression.
Conclusions:
- O-GlcNAcylation plays a critical role in modulating Erk1/2 and p38 MAPK signaling in cardiomyocytes.
- This modification is essential for maintaining balanced MAPK activity during hypertrophic growth.
- Dysregulation of O-GlcNAcylation significantly impairs adaptive hypertrophic responses and promotes maladaptive signaling in the heart.
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