CNK and HYP form a discrete dimer by their SAM domains to mediate RAF kinase signaling

RAF kinase functions in the mitogen-activated protein kinase (MAPK) pathway to transmit growth signals to the downstream kinases MEK and ERK. Activation of RAF catalytic activity is facilitated by a regulatory complex comprising the proteins CNK (Connector enhancer of KSR), HYP (Hyphen), and KSR (Kinase Suppressor of Ras). The sterile alpha-motif (SAM) domain found in both CNK and HYP plays an essential role in complex formation. Here, we have determined the x-ray crystal structure of the SAM domain of CNK in complex with the SAM domain of HYP. The structure reveals a single-junction SAM domain dimer of 1:1 stoichiometry in which the binding mode is a variation of polymeric SAM domain interactions. Through in vitro and in vivo mutational analyses, we show that the specific mode of dimerization revealed by the crystal structure is essential for RAF signaling and facilitates the recruitment of KSR to form the CNK/HYP/KSR regulatory complex. We present two docking-site models to account for how SAM domain dimerization might influence the formation of a higher-order CNK/HYP/KSR complex.     

Estimated blood pressure trajectories and hypertension patterns among pregnant women living with HIV,Haiti, 2007–2017

Hypertension in pregnancy is a key driver of mortality and morbidity among Haitian women. HIV infection and treatment may worsen hypertension and increase cardiovascular disease risk. The authors examined blood pressure and hypertension patterns among 1965 women (2306 pregnancies ending in live births) in a prevention of maternal‐to‐child transmission (PMTCT) program in Port‐au‐Prince, Haiti, between 2007 and 2017. Hypertension was defined as blood pressure ≥140/90 mm Hg on two consecutive visits. Latent class analysis assessed trajectories of mean arterial pressure (MAP) and multinomial ordinal logistic regression examined factors associated with higher trajectories. Between 2007–2009 and 2013–2016, hypertension at PMTCT entry increased from 1.3% to 3.8% (p = .005), while incidence at any time during PMTCT follow‐up increased from 5.0 to 16.1 per 100 person‐years (p < .001). Hypertension detected ≤20 weeks and > 20 weeks of gestation (possible gestational hypertension) increased from 1.1% to 3.5% (p = .003) and from 2.3% to 6.9% (p < .001), respectively. Five MAP trajectories ranged from low‐stable to high‐increasing. In multivariable analysis controlling for history of antiretroviral therapy, age, parity, and weight, program entry in more recent years was associated with greater odds of higher MAP trajectory (adjusted odds ratio for 2013–2016 vs. 2007–2009 = 3.1, 95% confidence interval: 1.7–5.6). The increasing prevalence and incidence of hypertension highlight a need for screening and management prior to PMTCT entry and during follow‐up. In a population with limited access to chronic disease care, and where many deliveries occur outside of a clinical setting, the period of PMTCT follow‐up represents an opportunity to diagnose and initiate management of preexisting and pregnancy‐related hypertension.     

Association of Major Histocompatibility Complex Class 1 Chain-Related Gene A Dimorphism with Type 1 Diabetes and Latent Autoimmune Diabetes in Adults in the Algerian Population

Major histocompatibility complex class I chain-related gene A (MICA-129) dimorphism was investigated in 73 autoimmune diabetes patients (type 1 diabetes and latent autoimmune diabetes in adults) and 75 controls from Algeria. Only MICA-129 Val allele and MICA-129 Val/Val genotype frequencies were higher among patients than in the control group. Statistical analysis of the estimated extended HLA-DR-DQ-MICA haplotypes shown that individual effects of MICA alleles on HLA-DQ2-DR3-MICA-129 Val/Val and HLA-DQ8-DR4-MICA-129 Val/Val haplotypes were significantly higher in patients than in the control groups. These preliminary data might suggest a relevant role of MICA-129 Val/Val single nucleotide polymorphism (weak/weak binders of NKG2D receptor) in the pathogenesis of T1D and LADA.     

A KSR/CNK complex mediated by HYP, a novel SAM domain-containing protein, regulates RAS-dependent RAF activation in Drosophila

RAF is a critical effector of the small GTPase RAS in normal and malignant cells. Despite intense scrutiny, the mechanism regulating RAF activation remains partially understood. Here, we show that the scaffold KSR (kinase suppressor of RAS), a RAF homolog known to assemble RAF/MEK/ERK complexes, induces RAF activation in Drosophila by a mechanism mediated by its kinase-like domain, but which is independent of its scaffolding property or putative kinase activity. Interestingly, we found that KSR is recruited to RAF prior to signal activation by the RAF-binding protein CNK (connector enhancer of KSR) in association with a novel SAM (sterile alpha motif) domain-containing protein, named Hyphen (HYP). Moreover, our data suggest that the interaction of KSR to CNK/HYP stimulates the RAS-dependent RAF-activating property of KSR. Together, these findings identify a novel protein complex that controls RAF activation and suggest that KSR does not only act as a scaffold for the MAPK (mitogen-activated protein kinase) module, but may also function as a RAF activator. By analogy to catalytically impaired, but conformationally active B-RAF oncogenic mutants, we discuss the possibility that KSR represents a natural allosteric inducer of RAF catalytic function.     

Acutely decompensated heart failure with preserved and reduced ejection fraction present with comparable haemodynamic congestion

Aims

Congestion is a central feature of acute heart failure (HF) and its assessment is important for clinical decisions (e.g. tailoring decongestive treatments). It remains uncertain whether patients with acute HF with preserved ejection fraction (HFpEF) are comparably congested as in acute HF with reduced EF (HFrEF). This study assessed congestion, right ventricular (RV) and renal dysfunction in acute HFpEF, HFrEF and non‐cardiac dyspnoea.

Methods and results

We compared echocardiographic and circulating biomarkers of congestion in 146 patients from the MEDIA‐DHF study: 101 with acute HF (38 HFpEF, 41 HFrEF, 22 HF with mid‐range ejection fraction) and 45 with non‐cardiac dyspnoea. Compared with non‐cardiac dyspnoea, patients with acute HF had larger left and right atria, higher E/e', pulmonary artery systolic pressure and inferior vena cava (IVC) diameter at rest, and lower IVC variability (all P < 0.05). Mid‐regional pro‐atrial natriuretic peptide (MR‐proANP) and soluble CD146 (sCD146), but not B‐type natriuretic peptide (BNP), correlated with echocardiographic markers of venous congestion. Despite a lower BNP level, patients with HFpEF had similar evidence of venous congestion (enlarged IVC, left and right atria), RV dysfunction (tricuspid annular plane systolic excursion), elevated MR‐proANP and sCD146, and renal impairment (estimated glomerular filtration rate; all P > 0.05) compared with HFrEF.

Conclusion

In acute conditions, HFpEF and HFrEF presented in a comparable state of venous congestion, with similarly altered RV and kidney function, despite higher BNP in HFrEF.

     

Loop Diuretics in the Treatment of Hypertension

Loop diuretics are not recommended in current hypertension guidelines largely due to the lack of outcome data. Nevertheless, they have been shown to lower blood pressure and to offer potential advantages over thiazide-type diuretics. Torsemide offers advantages of longer duration of action and once daily dosing (vs. furosemide and bumetanide) and more reliable bioavailability (vs. furosemide). Studies show that the previously employed high doses of thiazide-type diuretics lower BP more than furosemide. Loop diuretics appear to have a preferable side effect profile (less hyponatremia, hypokalemia, and possibly less glucose intolerance). Studies comparing efficacy and side effect profiles of loop diuretics with the lower, currently widely prescribed, thiazide doses are needed. Research is needed to fill gaps in knowledge and common misconceptions about loop diuretic use in hypertension and to determine their rightful place in the antihypertensive arsenal.