N-glycosylation is a critical post-translational modification of proteins, which is involved in distinct molecular processes including protein folding, stability and signal transduction (Esmail and Manolson, 2021). The disruption of N-glycosylation impacts on protein expression and cellular function in cardiomyocyte, which is associated with cardiac disease such as dilated cardiomyopathy and heart failure (Ednie et al., 2019, Gladysheva et al., 2008, Wang et al., 2015). DNA damage is considered as a molecular signature of heart disease (Dai et al., 2023, de Boer et al., 2023, Henpita et al., 2023). Studies indicate that DNA damage and defective DNA repair contribute to a gradual loss of heart function and cardiac hypertrophy, eventually transitioning to heart failure (Higo et al., 2017, Shukla et al., 2010). However, the studies of glycosylation machinery responding to DNA damage and repair are mainly focused on O-glycosylation (Cui et al., 2021, Li et al., 2023, Ping and Stark, 2022). For example, protein O-GlcNAcylation of the ATM (ATM serine/threonine kinase)-mediated DNA damage response pathway is regulated through ATM and its downstream targets H2AX and Chk2, which participates in governing DNA damage and repair (Peixoto et al., 2019). Up to now, very few studies have addressed the relationship between N-glycosylation and DNA damage.
Cell adhesion associated, oncogene regulated (CDON) is a type I transmembrane receptor with five immunoglobulin (Ig) domains, three fibronectin type III (FNIII) repeats, transmembrane (TM) and a long cytoplasmic (CD) domain (Kang et al., 1997). CDON plays an essential role in cell adhesion, differentiation, vascular calcification, proliferation and apoptosis in various cell types (Ahn et al., 2023, Bae et al., 2009, Bae et al., 2010, Kang et al., 2008, Kim et al., 2023, Wang and Almazan, 2016). In cardiomyocyte, Cdon deficiency causes systolic dysfunction and cardiac remodeling (Jeong et al., 2017). As a glycosylation protein, the different N-glycosylation sites were predicted in the extracellular region of CDON (Kang et al., 1997). Cdon mutation in the Ig domain may alter the glycosylation of mutated protein (Chitsazan et al., 2016). Although protein glycosylation is a contributor to the DNA damage response, CDON glycosylation on DNA damage and repair pathways remains largely unknown.
In the current study, we aimed to determine the effect of N-glycosylation of CDON on DNA damage. We created 9 predicted N-glycosylation site mutants of rat CDON and expressed them in H9c2 cardiomyocytes. Our findings provide evidence that reduced CDON expression induces DNA damage and altered N-glycosylation has impact on DNA damage and DNA repair gene expression.