Search bioRxiv⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2023.10.26.564170

GCN5L1-mediated acetylation prevents Rictor degradation in cardiac cells after hypoxic stress

Bugga, P.·Manning, J. R.·Mushala, B. A.·Stoner, M. W.·Sembrat, J.·Scott, I.
View original source ↗Export metadata ↓

Abstract

Cardiomyocyte apoptosis and cardiac fibrosis are the leading causes of mortality in patients with ischemic heart disease. As such, these processes represent potential therapeutic targets to treat heart failure resulting from ischemic insult. We previously demonstrated that the mitochondrial acetyltransferase protein GCN5L1 regulates cardiomyocyte cytoprotective signaling in ischemia- reperfusion injury in vivo and hypoxia-reoxygenation injury in vitro. The current study investigated the mechanism underlying GCN5L1-mediated regulation of the Akt/mTORC2 cardioprotective signaling pathway. Rictor protein levels in cardiac tissues from human ischemic heart disease patients were significantly decreased relative to non-ischemic controls. Rictor protein levels were similarly decreased in cardiac AC16 cells following hypoxic stress, while mRNA levels remained unchanged. The reduction in Rictor protein levels after hypoxia was enhanced by the knockdown of GCN5L1, and was blocked by GCN5L1 overexpression. These findings correlated with changes in Rictor lysine acetylation, which were mediated by GCN5L1 acetyltransferase activity. Rictor degradation was regulated by proteasomal activity, which was antagonized by increased Rictor acetylation. Finally, we found that GCN5L1 knockdown restricted cytoprotective Akt signaling, in conjunction with decreased mTOR abundance and activity. In summary, these studies suggest that GCN5L1 promotes cardioprotective Akt/mTORC2 signaling by maintaining Rictor protein levels through enhanced lysine acetylation.

Source connections

Explore related subjects

cell biologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Bugga, P., Manning, J. R., Mushala, B. A., Stoner, M. W., Sembrat, J., Scott, I.. 2023-10-26. GCN5L1-mediated acetylation prevents Rictor degradation in cardiac cells after hypoxic stress. https://doi.org/10.1101/2023.10.26.564170

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

The nuclear membrane protein Samp1 links peripheral genome organization to the myogenic transcriptional program

Samp1 is an inner nuclear membrane protein required for myogenic differentiation and involved in chromatin organization at the nuclear periphery. Here, we investigated whether these functions are connected by studying the effects of Samp1 depletion during C2C12 myogenic differentiation using immunofluorescence microscopy, RNA sequencing, FRIC, and chromosome-positioning analysis. Samp1-depleted cells showed strongly reduced MyHC expression and virtually abrogated multinucleated fiber formation. Although cell-cycle withdrawal was not prevented, the transcriptional program driving differentiation was drastically perturbed, with reduced muscle-associated transcripts and incomplete repression of genes normally downregulated during myogenesis. Samp1 depletion also disrupted peripheral chromatin organization and prevented the accumulation of peripheral heterochromatin typically seen during differentiation. In addition, radial chromosome distribution was disrupted, evidenced by the failure of chromosome 8 to reposition to the nuclear periphery during differentiation. Together, these findings link the requirement for Samp1 in myogenic differentiation to its role in genome organization at the nuclear periphery.

cell biology↗
bioRxiv2026

Unraveling the metabolic landscape of alkaptonuria through a human-relevant in vitro liver disease model

Alkaptonuria (AKU) is a rare inherited metabolic disorder of tyrosine catabolism caused by a deficient homogentisate 1,2-dioxygenase (HGD) enzyme. This results in the accumulation of homogentisic acid (HGA), driving a progressive multisystem pathology characterized by debilitating early-onset osteoarthritis due to connective tissue degeneration. While previous in vitro studies have primarily relied on exogenous HGA exposure in osteoarticular cell models, the direct metabolic consequences of endogenous HGD deficiency within its native hepatic context remain poorly understood. Here, we established the first human-relevant HGD knockout hepatic in vitro model using a universal in-house-developed homology-directed repair approach. Integrative multi-omic analysis revealed that HGD deficiency induces widespread metabolic rewiring extending beyond disrupted tyrosine catabolism. HGD-deficient hepatocytes exhibited elevated oxidative stress accompanied by impaired mitochondrial respiration and a pseudohypoxic metabolic adaptation toward increased glycolytic dependency. Despite this glycolytic shift, the cells displayed reduced anabolic and translational activity alongside attenuated proliferation, consistent with a chronic stress-adaptive survival state rather than a proliferative metabolic phenotype. This study provides systems-level insights into the pathophysiology of AKU and establishes a versatile platform for mechanistic and therapeutic investigation.

cell biology↗
bioRxiv2026

The circadian clock regulates KCNH2 (hERG) promoter activity through daily temperature rhythms.

Background: KCNH2 encodes Kv11.1 channel proteins that conduct the rapidly activating delayed-rectifier K+ current (IKr), which is critical for cardiac repolarization. KCNH2 encodes two functional isoforms, Kv11.1a and Kv11.1b, via alternative transcription start sites. Kv11.1a is the principal determinant of cardiac IKr and ventricular repolarization. The circadian clock, a transcriptional-translational feedback loop that cycles with a period of ~24 hours and drives the circadian expression of many genes, including Kcnh2 in the mouse heart. Because daily body temperature rhythms provide a systemic signal that synchronizes cardiac circadian clocks, we tested whether physiological temperature cycles drive the circadian promoter activity of the cloned human KCNH2 (hKCNH2) promoter. Hypothesis: hKCNH2 is a direct transcriptional target of the circadian clock, with temperature driving its promoter activity through BMAL1:CLOCK acting at a conserved tandem E-box. Methods: We cloned the conserved proximal promoter of KCNH2 (-1631 bp upstream of Kv11.1a exon 1) to generate hKCNH2 promoter luciferase reporter constructs. Constructs were transfected into C2C12 myotubes and synchronized by serum shock (static 37{degrees}C) or temperature cycling (36.5-38.5{degrees}C). Bioluminescence was recorded and assessed for period, phase, and amplitude. BMAL1:CLOCK dependence was tested via dominant-negative CLOCK{Delta}19 co-expression. Results: Temperature cycling did not exhibit the rapid damping characteristic of serum-shock-synchronized oscillations, consistent with continuous entrainment by an external zeitgeber rather than a free-running oscillator. Deletion analysis identified a conserved tandem E-box required for oscillation under both serum shock and temperature cycling, and for BMAL1:CLOCK-dependent transactivation (1.75 {+/-} 0.21 vs. 0.86 {+/-} 0.06 RLU, p = 0.0038). CLOCK{Delta}19 reduced hKCNH2 promoter amplitude under temperature cycling without altering period. Conclusion: The circadian clock regulates KCNH2 promoter activity through daily temperature rhythms.

cell biology↗