Na + /H + exchanger isoform 1-induced osteopontin expression facilitates cardiac hypertrophy through p90 ribosomal S6 kinase

Cardiovascular diseases are the leading cause of death worldwide. One in three cases of heart failure is due to dilated cardiomyopathy. The Na+/H+ exchanger isoform 1 (NHE1), a multifunctional protein and the key pH regulator in the heart, has been demonstrated to be increased in this condition. We have previously demonstrated that elevated NHE1 activity induced cardiac hypertrophy in vivo. Furthermore, the overexpression of active NHE1 elicited modulation of gene expression in cardiomyocytes including an upregulation of myocardial osteopontin (OPN) expression. To determine the role of OPN in inducing NHE1-mediated cardiomyocyte hypertrophy, double transgenic mice expressing active NHE1 and OPN knockout were generated and assessed by echocardiography and the cardiac phenotype. Our studies showed that hearts expressing active NHE1 exhibited cardiac remodeling indicated by increased systolic and diastolic left ventricular internal diameter and increased ventricular volume. Moreover, these hearts demonstrated impaired function with decreased fractional shortening and ejection fraction. Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) mRNA was upregulated, and there was an increase in heart cell cross-sectional area confirming the cardiac hypertrophic effect. Moreover, NHE1 transgenic mice also showed increased collagen deposition, upregulation of CD44 and phosphorylation of p90 ribosomal s6 kinase (RSK), effects that were regressed in OPN knockout mice. In conclusion, we developed an interesting comparative model of active NHE1 transgenic mouse lines which express a dilated hypertrophic phenotype expressing CD44 and phosphorylated RSK, effects which were regressed in absence of OPN.Scopu

Sci signal

Endothelial cells serve as a barrier between blood and tissues. Maintenance of the endothelial cell barrier depends on the integrity of intercellular junctions, which is regulated by a polarity complex that includes the ζ isoform of atypical protein kinase C (PKCζ) and partitioning defective 3 (PAR3). We revealed that the E3 ubiquitin ligase PDZ domain-containing ring finger 3 (PDZRN3) regulated endothelial intercellular junction integrity. Endothelial cell-specific overexpression of Pdzrn3 led to early embryonic lethality with severe hemorrhaging and altered organization of endothelial intercellular junctions. Conversely, endothelial-specific loss of Pdzrn3 prevented vascular leakage in a mouse model of transient ischemic stroke, an effect that was mimicked by pharmacological inhibition of PKCζ. PDZRN3 regulated Wnt signaling and associated with a complex containing PAR3, PKCζ, and the multi-PDZ domain protein MUPP1 (Discs Lost-multi-PDZ domain protein 1) and targeted MUPP1 for proteasomal degradation in transfected cells. Transient ischemic stroke increased the ubiquitination of MUPP1, and deficiency of MUPP1 in endothelial cells was associated with decreased localization of PKCζ and PAR3 at intercellular junctions. In endothelial cells, Pdzrn3 overexpression increased permeability through a PKCζ-dependent pathway. In contrast, Pdzrn3 depletion enhanced PKCζ accumulation at cell-cell contacts and reinforced the cortical actin cytoskeleton under stress conditions. These findings reveal how PDZRN3 regulates vascular permeability through a PKCζ-containing complex

Clin Sci (Lond)

Autosomal dominant inherited Protein S deficiency (PSD) (MIM 612336) is a rare disorder caused by rare mutations, mainly located in the coding sequence of the structural PROS1 gene, and associated with an increased risk of venous thromboembolism. To identify the molecular defect underlying PSD observed in an extended French pedigree with seven PSD affected members in whom no candidate deleterious PROS1 mutation was detected by Sanger sequencing of PROS1 exons and their flanking intronic regions or via an multiplex ligation-dependent probe amplification (MLPA) approach, a whole genome sequencing strategy was adopted. This led to the identification of a never reported C to T substitution at c.-39 from the natural ATG codon of the PROS1 gene that completely segregates with PSD in the whole family. This substitution ACG→ATG creates a new start codon upstream of the main ATG. We experimentally demonstrated in HeLa cells that the variant generates a novel overlapping upstream open reading frame (uORF) and inhibits the translation of the wild-type PS. This work describes the first example of 5′UTR PROS1 mutation causing PSD through the creation of an uORF, a mutation that is not predicted to be deleterious by standard annotation softwares, and emphasizes the need for better exploration of such type of non-coding variations in clinical genomics

Desert Hedgehog Promotes Ischemia-Induced Angiogenesis by Ensuring Peripheral Nerve Survival

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