Xuan, C. | bioRxiv Science

bioRxiv2024

Apelin-13 in the paraventricular nucleus protects myocardium from ischemia via V1a receptor of the paraventricular nucleus and GABAA receptor γ2 of the nucleus tractus solitarii in rats

BackgroundApelin system plays a significant role in central blood pressure regulation, but its role in neural control of myocardial injury protection is poorly understood. Thus, this study was undertaken to evaluate the effects of apelin-13 in the paraventricular nucleus (PVN) on myocardial infarction (MI) and ischemia/reperfusion (I/R). MethodsThe cardiac functions were assessed after microinjecting or transferring the apelin-13 gene into the paraventricular nucleus (PVN) of rat models with myocardial infarction (MI) or ischemia/reperfusion (I/R). ResultsIn MI rats, we showed that apelin-13 expression decreased in PVN, V1a receptor expression increased in PVN and nucleus tractus solitarii (NTS), and GABAA receptor (GAR) {gamma}2 expression increased in NTS. In primary cultured hypothalamus and medulla oblongata neurons, V1a receptor expression was downregulated by APJ receptor antagonist or GAR agonist, indicating that there are interactions between these receptors in neurons. Apelin-13 overexpression in PVN significantly improved cardiac function of MI and I/R rats, including left-ventricular end-diastolic diameter, left-ventricular end-systolic diameter, left-ventricular ejection fraction, and left-ventricular fractions shortening, accompanied by decreased noradrenaline and increased vasopressin plasma levels. Myocardial ischemia-related apoptotic and inflammatory pathway markers (Bcl-1, Bax, TGF-{beta}1, CCR5, Smad2) were downregulated and four neuropeptides of the parasympathetic endocrine system (somatostatin, cholecystokinin, glucagon-like peptide 1, vasoactive intestinal peptide) were increased in serum correspondingly with cardiac function improving. V1a receptor antagonist in PVN or NTS and GAR agonist in NTS decreased the effects of apelin-13 overexpression on cardiac function of MI and I/R rats. ConclusionsOverexpression of apelin-13 in PVN leads to cardiac function improvement via V1a receptor in PVN and NTS, and GAR{gamma}2 in NTS. Parasympathetic endocrine system and myocardial ischemia-related apoptotic and inflammation signaling pathways are involved in apelin-13 in PVN-mediated cardiac function regulation, which provides evidence for neural regulation of cardiovascular diseases.

neuroscience↗

bioRxiv2022

Structural insights into the viral proteins binding by TRIM7 reveal a general C-terminal glutamine recognition mechanism

The E3 ligase TRIM7 has emerged as a critical player in viral infection and pathogenesis. A recent study found that TRIM7 inhibits human enteroviruses through ubiquitination and proteasomal degradation of viral 2BC protein by targeting the 2C moiety of 2BC protein. Here, we report the crystal structures of TRIM7 in complex with 2C, where the C-terminal region of 2C is inserted into a positively charged groove of the TRIM7 PRY-SPRY domain. Structure-guided biochemical studies revealed the C-terminus glutamine residue of 2C as the primary determinant for TRIM7 binding. Such a glutamine-end motif binding mechanism can be successfully extended to other substrates of TRIM7. More importantly, leveraged by this finding, we were able to identify norovirus and SARS-CoV-2 proteins, and physiological proteins, as new TRIM7 substrates. We further show that TRIM7 may function as a restriction factor to promote the degradation of the viral proteins of norovirus and SARS-CoV-2, thereby restoring the Type I interferon immune response and inhibiting viral infection. Several crystal structures of TRIM7 in complex with SARS-CoV-2 proteins are also determined, and a conserved C-terminus glutamine-specific interaction is observed. These findings unveil a common recognition mode by TRIM7, providing the foundation for further mechanistic characterization of antiviral and cellular functions of TRIM7.

biochemistry↗