The type 1 ryanodine receptor (RyR1) on the sarcoplasmic reticulum (SR) is the major calcium (Ca2+) release channel required for skeletal muscle excitation–contraction (EC) coupling. RyR1 function is modulated by proteins that bind to its large cytoplasmic scaffold domain, including the FK506 binding protein (FKBP12) and PKA. PKA is activated during sympathetic nervous system (SNS) stimulation. We show that PKA phosphorylation of RyR1 at Ser2843 activates the channel by releasing FKBP12. When FKB12 is bound to RyR1, it inhibits the channel by stabilizing its closed state. RyR1 in skeletal muscle from animals with heart failure (HF), a chronic hyperadrenergic state, were PKA hyperphosphorylated, depleted of FKBP12, and exhibited increased activity, suggesting that the channels are “leaky.” RyR1 PKA hyperphosphorylation correlated with impaired SR Ca2+ release and early fatigue in HF skeletal muscle. These findings identify a novel mechanism that regulates RyR1 function via PKA phosphorylation in response to SNS stimulation. PKA hyperphosphorylation of RyR1 may contribute to impaired skeletal muscle function in HF, suggesting that a generalized EC coupling myopathy may play a role in HF.

Background-␤-Adrenergic receptor blockade is one of the most effective treatments for heart failure, a leading cause of mortality worldwide. The use of ␤-adrenergic receptor blockers in patients with heart failure is counterintuitive, however, because they are known to decrease contractility in normal hearts. The ryanodine receptor (RyR2) on cardiac sarcoplasmic reticulum is the key calcium release channel required for excitation-contraction coupling. In failing hearts, the stoichiometry and function of the RyR2 macromolecular complex is altered. Decreased levels of phosphatases (PP1 and PP2A) and hyperphosphorylation by protein kinase A result in dissociation of the regulatory protein FKBP12.6 and channels with increased open probability. Methods and Results-Here, we show that systemic oral administration of a ␤-adrenergic receptor blocker reverses protein kinase A hyperphosphorylation of RyR2, restores the stoichiometry of the RyR2 macromolecular complex, and normalizes single-channel function in a canine model of heart failure. Conclusions-These results may, in part, explain the improved cardiac function observed in heart failure patients treated with ␤-adrenergic receptor blockers. Key Words: heart failure Ⅲ calcium Ⅲ sarcoplasmic reticulum Ⅲ ion channels Ⅲ receptors, adrenergic, beta C linical trials have shown that ␤-adrenergic receptor blocker therapy results in a 20% to 66% reduction in mortality at 12 months in patients with heart failure (HF). [1][2][3] It is not intuitively obvious, however, how ␤-adrenergic receptor blockers can improve cardiac function in failing hearts, because they are known to decrease contractility in normal hearts. 4 -6 HF is a complex disease 7 that is characterized by a hyperadrenergic state. 8 However, ␤ 1 -adrenergic receptors are downregulated and uncoupled from G proteins in failing hearts. 9,10 Nevertheless, we recently showed that ryanodine receptor (RyR2) is protein kinase A (PKA)-hyperphosphorylated in HF, 11 indicating that the net effect of ␤-adrenergic signaling is upregulated in HF with respect to RyR2 as a substrate for PKA phosphorylation. It is likely that the PKA hyperphosphorylation of RyR2 is a maladaptive response, 12 because it results in the depletion of the regulatory subunit FKBP12.6, 11,13 yielding channels that are pathologically sensitive to Ca 2ϩ -induced Ca 2ϩ release from the sarcoplasmic reticulum (SR). 11 RyR2 is a macromolecular complex that includes FKBP12.6 as well as PKA and 2 phosphatases (PP1 and PP2A) that are bound to the cytoplasmic domain of the channel via targeting proteins. 11,14 In failing hearts, the RyR2 macromolecular complex undergoes remodeling characterized by a reduction in the amounts of PP1, PP2A, and FKBP12.6 that are bound to the cytoplasmic domain of the channel. 11 In the present study, we used a well-characterized canine model of pacing-induced HF to show that ␤-adrenergic receptor blockade both restores the normal stoichiometry of the RyR2 macromolecular complex and normalizes the function of the channel. Methods H...

Fusobacterium nucleatum (F. nucleatum) plays key roles in the initiation and progression of periodontitis. However, the pathogenic effect of F. nucleatum on human oral tissues and cells has not been fully evaluated. In this study, we aimed to analyze the pathogenic effects of F. nucleatum on human gingival fibroblasts (GFs) and clarify the potential mechanisms. RNA-sequencing analysis confirmed that F. nucleatum significantly altered the gene expression of GF as the stimulation time increased. Cell counting and EdU-labeling assays indicated that F. nucleatum inhibited GF proliferation and promoted cell apoptosis in a time- and dose-dependent manner. In addition, cell apoptosis, intracellular reactive oxygen species (ROS) generation, and proinflammatory cytokine production were dramatically elevated after F. nucleatum stimulation. Furthermore, we found that the AKT/MAPK and NF-κB signaling pathways were significantly activated by F. nucleatum infection and that a large number of genes related to cellular proliferation, apoptosis, ROS, and inflammatory cytokine production downstream of AKT/MAPK and NF-κB signaling pathways were significantly altered in F. nucleatum-stimulated GFs. These findings suggest that F. nucleatum inhibits GF proliferation and promotes cell apoptosis, ROS generation, and inflammatory cytokine production partly by activating the AKT/MAPK and NF-κB signaling pathways. Our study opens a new window for understanding the pathogenic effects of periodontal pathogens on the host oral system.

Carnitine palmitoyl transferase 1A (CPT1A) protein catalyzes the rate-limiting step of Fatty-acid oxidation (FAO) pathway, which can promote cell proliferation and suppress apoptosis. Targeting CPT1A has shown remarkable anti-leukemia activity. But, its prognostic value remains unclear in Acute Myeloid Leukemia (AML). In two independent cohorts of cytogenetically normal AML (CN-AML) patients, compared to low expression of CPT1A (CPT1Alow), high expression of CPT1A (CPT1Ahigh) was significantly associated with adverse outcomes, which was also shown in European Leukemia Network (ELN) Intermediate-I category. Multivariable analyses adjusting for known factors confirmed CPT1Ahigh as a high risk factor. Significant associations between CPT1Ahigh and adverse outcomes were further validated whether for all AML patients (OS: P = 0.008; EFS: P = 0.002, n = 334, no M3) or for National Comprehensive Cancer Network (NCCN) Intermediate-Risk subgroup (OS: P = 0.021, EFS: P = 0.024, n = 173). Multiple omics analysis revealed aberrant alterations of genomics and epigenetics were significantly associated with CPT1A expression, including up- and down-regulation of oncogenes and tumor suppressor, activation and inhibition of leukemic (AML, CML) and immune activation pathways, hypermethylation enrichments on CpG island and gene promoter regions. Combined with the previously reported anti-leukemia activity of CPT1A's inhibitor, our results proved CPT1A as a potential prognosticator and therapeutic target for AML.