A724A polymorphism of sarco(endo)plasmic reticulum Ca2+-ATPase 2 (SERCA2) in hypertensive patients

Inactivation of Cys674 in SERCA2 increases BP by inducing endoplasmic reticulum stress and soluble epoxide hydrolase

BACKGROUND AND PURPOSE

The kidney is essential in regulating sodium homeostasis and BP. The irreversible oxidation of Cys⁶⁷⁴ (C674) in the sarcoplasmic/endoplasmic reticulum calcium ATPase 2 (SERCA2) is increased in the renal cortex of hypertensive mice. Whether inactivation of C674 promotes hypertension is unclear. Here we have investigated the effects on BP of the inactivation of C674, and its role in the kidney.

EXPERIMENTAL APPROACH

We used heterozygous SERCA2 C674S knock-in (SKI) mice, where half of C674 was substituted by serine, to represent partial irreversible oxidation of C674. The BP, urine volume, and urine composition of SKI mice and their littermate wild-type (WT) mice were measured. The kidneys were collected for cell culture, Na⁺ /K⁺ -ATPase activity, protein expression, and immunohistological analysis.

KEY RESULTS

Compared with WT mice, SKI mice had higher BP, lower urine volume and sodium excretion, up-regulated endoplasmic reticulum (ER) stress markers and soluble epoxide hydrolase (sEH), and down-regulated dopamine D₁ receptors in renal cortex and cells from renal proximal tubule. ER stress and sEH were mutually regulated, and both upstream of D₁ receptors. Inhibition of ER stress or sEH up-regulated expression of D₁ receptors, decreased the activity of Na⁺ /K⁺ -ATPase, increased sodium excretion, and lowered BP in SKI mice.

CONCLUSIONS AND IMPLICATIONS

The inactivation of SERCA2 C674 promotes the development of hypertension by inducing ER stress and sEH. Our study highlights the importance of C674 redox status in BP control and the contribution of SERCA2 to sodium homeostasis and BP in the kidney.

Novel mutations in Darier disease and association to self-reported disease severity

Darier disease is a rare and severe autosomal dominant skin disease characterised by malodorous keratotic papules in seborrheic areas of the skin. Darier disease affects up to 1 in 30 000 people and is caused by mutations in the ATP2A2 gene, which encodes to the sarco/endoplasmic reticulum calcium-ATPase isoform 2 that pumps calcium into the endoplasmic reticulum. Although many ATP2A2 variants have been described, it is not known if genotype correlates with phenotype, which could be important for prognosis and treatment. This is the first study to use whole exome sequencing to screen the ATP2A2 gene in a cohort of 28 clinically diagnosed Darier disease patients. Twenty-one different disease causing variants were identified and 15 of these were novel. Sixteen of the 21 variants were predicted to be pathogenic using in silico prediction programs. There were seven missense, four intronic/splice-sites, three frameshifts, two in-frame deletions, four nonsense and one synonymous mutations. This study also found ten patients who harbour more than one ATP2A2 variant. The phenotype of the patient cohort was assessed by photography and by patient questionnaires. The genotype-phenotype association was examined for all variants in relation to the patient's disease severity score, and no correlation could be established.