Quantitative plasma proteomic analysis in children after superior cavopulmonary anastomosis with pulmonary arteriovenous malformations.

Approximately 1000 children are born every year in the United States with one effective cardiac pumping chamber, or single ventricle heart disease. One of the early causes of mortality in this population is pulmonary arteriovenous malformations (PAVMs), which allow blood to bypass gas exchange in the lungs. PAVMs most frequently occur in children after superior cavopulmonary anastomosis (SCPA), a procedure that redirects venous blood from the upper body to the lungs. Because plasma proteins are in part responsible for directing angiogenesis, we hypothesized that differential protein concentrations would be observed in superior caval blood among children after SCPA according to PAVM status. We performed quantitative plasma proteomics from 11 children with PAVMs and in seven children without PAVMs; an additional 11 children with Fontan circulation were included as a reference. Among children with SCPA, there were no significant differences in the plasma proteomes for those with and without PAVMs. When comparing children with Fontan circulation to those with SCPA and PAVMs, 18 proteins exhibited differential expression (10 downregulated and eight upregulated) in superior caval plasma. These results suggest that factors other than, or in addition to, plasma proteins may be responsible for single ventricle patients' susceptibility to PAVMs after SCPA. IMPACT: What is the key message of your article? We did not identify significant differences in plasma proteins when comparing those children with and without pulmonary arteriovenous malformations (PAVMs) after superior cavopulmonary anastomosis (SCPA). What does it add to the existing literature? The etiology of PAVMs in this population is likely due to factors other than, or in addition to, differences in plasma proteins. What is the impact? Further studies are needed to identify causes of PAVMs among children after SCPA.

Klotho enhances diastolic function in aged hearts through Sirt1-mediated pathways.

Aging leads to a progressive decline in cardiac function, increasing the risk of heart failure with preserved ejection fraction (HFpEF). This study elucidates the impact of α-Klotho, an anti-aging hormone, on cardiac diastolic dysfunction and explore its downstream mechanisms. Aged wild-type and heterozygous Klotho-deficient mice received daily injection of soluble α-Klotho (sKL) for 10 weeks, followed by a comprehensive assessment of heart function by echocardiography, intracardiac pressure catheter, exercise tolerance, and cardiac pathology. Our findings show that klotho deficiency accentuated cardiac hypertrophy, diastolic dysfunction, and exercise intolerance, while sKL treatment ameliorates these abnormalities and improves cardiac capillary densities. Downstream of klotho, we focused on the Sirtuin1 (Sirt1) signaling pathway to elucidate the potential underlying mechanism by which Klotho improves diastolic function. We found that decreased Klotho levels were linked with Sirt1 deficiency, whereas sKL treatment restored Sirt1 expression in aged hearts and mitigated the DNA damage response pathway activation. Through tandem mass tag proteomics and unbiased acetylomics analysis, we identified 220 significantly hyperacetylated lysine sites in critical cardiac proteins of aged hearts. We found that sKL supplementation attenuated age-dependent DNA damage and cardiac diastolic dysfunction. In contrast, Klotho deficiency significantly increased hyperacetylation of several crucial cardiac contractile proteins, potentially impairing ventricular relaxation and diastolic function, thus predisposing to HFpEF. These results suggest the potential benefit of sKL supplementation as a promising therapeutic strategy for combating HFpEF in aging.

Chromatin targeting of the RNF12/RLIM E3 ubiquitin ligase controls transcriptional responses.

Protein ubiquitylation regulates key biological processes including transcription. This is exemplified by the E3 ubiquitin ligase RNF12/RLIM, which controls developmental gene expression by ubiquitylating the REX1 transcription factor and is mutated in an X-linked intellectual disability disorder. However, the precise mechanisms by which ubiquitylation drives specific transcriptional responses are not known. Here, we show that RNF12 is recruited to specific genomic locations via a consensus sequence motif, which enables co-localisation with REX1 substrate at gene promoters. Surprisingly, RNF12 chromatin recruitment is achieved via a non-catalytic basic region and comprises a previously unappreciated N-terminal autoinhibitory mechanism. Furthermore, RNF12 chromatin targeting is critical for REX1 ubiquitylation and downstream RNF12-dependent gene regulation. Our results demonstrate a key role for chromatin in regulation of the RNF12-REX1 axis and provide insight into mechanisms by which protein ubiquitylation enables programming of gene expression.