RNF128 acts as a suppressor of pathological cardiac dysfunction by catalyzing K63-linked polyubiquitination of SERCA2a at K476, thereby inhibiting autophagy-lysosome-mediated degradation of SERCA2a and protecting cardiac function.
Key Findings
Results
RNF128 expression is reduced in pathological cardiac hypertrophy in both human and murine samples.
Expression of RNF128 was characterized via public database analysis, single-cell RNA sequencing (scRNA-seq), and validated in clinical myocardial samples and mouse disease models.
Reduced RNF128 expression was confirmed across human clinical samples and mouse disease models of pathological cardiac hypertrophy.
The downregulation was consistent across multiple independent data sources and experimental systems.
Results
Cardiomyocyte-specific RNF128 knockout aggravated cardiac dysfunction and pathological remodeling.
Cardiomyocyte-specific RNF128 knockout mice were generated to assess loss-of-function effects in vivo.
RNF128 deficiency worsened both cardiac dysfunction and pathological cardiac remodeling compared to controls.
These findings were validated using in vivo mouse models with cardiomyocyte-specific gene deletion.
Results
Overexpression of RNF128 via cTnT-AAV9-mediated delivery protected cardiac function in mouse models.
Cardiac troponin T promoter-driven AAV9 (cTnT-AAV9) was used to achieve cardiomyocyte-specific overexpression of RNF128 in vivo.
RNF128 overexpression protected cardiac function against pathological hypertrophy.
In vitro validation was performed in Angiotensin II (Ang II)-stimulated neonatal mouse cardiomyocytes (NMCMs).
Results
RNF128 directly interacts with SERCA2a and catalyzes K63-linked polyubiquitination of SERCA2a at lysine residue K476.
The downstream target of RNF128 was identified through integrated analysis of scRNA-seq, interactome profiling, and quantitative proteomics, followed by molecular assays.
RNF128 was found to directly interact with SERCA2a (sarcoplasmic/endoplasmic reticulum Ca2+-ATPase 2a), a key calcium handling protein in cardiomyocytes.
RNF128 catalyzed Lys63 (K63)-linked polyubiquitination specifically at lysine 476 (K476) of SERCA2a.
K63-linked polyubiquitination is a non-degradative ubiquitin linkage type, distinct from the degradative K48-linked chains.
Results
K63-linked polyubiquitination of SERCA2a by RNF128 impairs SERCA2a recognition by the autophagy receptor SQSTM1/p62, thereby inhibiting autophagy-lysosome-mediated degradation of SERCA2a.
RNF128-mediated K63-linked polyubiquitination at K476 of SERCA2a reduced recognition of SERCA2a by the selective autophagy receptor SQSTM1/p62 (sequestosome 1).
By impairing SQSTM1/p62 recognition, RNF128 blocked autophagy-lysosome-mediated degradation of SERCA2a, thereby stabilizing SERCA2a protein levels.
This mechanism links ubiquitination-dependent protein regulation to calcium handling in cardiomyocytes.
The stabilization of SERCA2a is cardioprotective, as SERCA2a is critical for calcium reuptake into the sarcoplasmic reticulum during cardiac relaxation.
Conclusions
RNF128 is identified as a novel E3 ubiquitin ligase with therapeutic value as a target for heart failure treatment.
RNF128 (Ring Finger Protein 128) functions as an E3 ubiquitin ligase in cardiomyocytes.
The study highlights RNF128 as a novel therapeutic target for heart failure.
The mechanism connects ubiquitination-dependent protein regulation to calcium handling, a key pathophysiological pathway in heart failure.
What This Means
This research investigates a protein called RNF128 and its role in a condition known as pathological cardiac hypertrophy — an abnormal enlargement of the heart in response to chronic stress, such as high blood pressure, which can lead to heart failure. The researchers found that levels of RNF128 are reduced in diseased hearts from both human patients and mouse models. When they experimentally eliminated RNF128 specifically from heart muscle cells in mice, heart function worsened. Conversely, when they boosted RNF128 levels using a gene therapy approach (injecting a virus that delivers the RNF128 gene specifically to heart cells), heart function was protected against disease progression.
The study also uncovered how RNF128 protects the heart at a molecular level. RNF128 is an enzyme that attaches small protein tags (called ubiquitin) to other proteins in a process called ubiquitination. The researchers found that RNF128 attaches a specific type of ubiquitin chain (called K63-linked) to a critical calcium-handling protein called SERCA2a at a precise location (lysine 476). This modification acts like a 'do not destroy' signal: it prevents another protein (SQSTM1/p62) from flagging SERCA2a for destruction through a cellular recycling process called autophagy. By protecting SERCA2a from degradation, RNF128 helps maintain normal calcium cycling in heart muscle cells, which is essential for proper heart contraction and relaxation.
This research suggests that RNF128 represents a new potential therapeutic target for heart failure. The findings connect two important areas of heart biology — how proteins are tagged and degraded, and how calcium is managed inside heart cells — and open potential avenues for developing treatments that preserve SERCA2a function by targeting the RNF128 pathway.
Zhang Y, Liu X, Yu L, Liu C, Li J, Han Q, et al.. (2026). Cardiomyocyte-Specific RNF128 Attenuates Pathological Cardiac Hypertrophy Progression by Stabilizing SERCA2a through Lys63-Linked Polyubiquitination.. Theranostics. https://doi.org/10.7150/thno.133221