Ayumu Yoshikawa

The (pro)renin receptor is cleaved by ADAM19 in the Golgi leading to its secretion into extracellular space

The (pro)renin receptor ((P)RR), which is a recently discovered molecule of the renin–angiotensin system, plays an important role in the development of cardiovascular diseases. However, the molecular properties and the subcellular distribution of (P)RR remain controversial. In this study, (P)RR-Venus in Chinese hamster ovary (CHO) cells ((P)RR-Venus-CHO) or endogenous (P)RR in human vascular smooth muscle cells (VSMC) were constitutively cleaved without any stimulation, and secretion of the amino-terminal fragment (NTF-(P)RR) into the media was determined using western blot analysis. Immunofluorescent analysis showed robust expression of (P)RR in the endoplasmic reticulum (ER) or the Golgi but not in the plasma membrane. Moreover, we identified ADAM19, which is expressed in the Golgi, as one of cleaving proteases of (P)RR. Transfected ADAM19 evoked the shedding of (P)RR, whereas transfected dominant negative ADAM19 suppressed it. Although (P)RR contains a furin cleavage site, neither the furin-deficient LoVo cells nor furin inhibitor-treated VSMC lost NTF-(P)RR in the media. The secreted NTF-(P)RR induced the renin activity of prorenin in the extracellular space. We describe that (P)RR is mainly localized in the subcellular organelles, such as the ER and Golgi, and (P)RR is cleaved by ADAM19 in the Golgi resulting in two fragments, NTF-(P)RR and CTF-(P)RR. These results may suggest that (P)RR is predominantly secreted into the extracellular space.

Non-activated APJ suppresses the angiotensin II type 1 receptor, whereas apelin-activated APJ acts conversely

Apelin and its G-protein-coupled receptor APJ are potent regulators of the cardiovascular system. Recent studies have suggested that apelin–APJ reverses the function of angiotensin II (Ang II)–the Ang II type 1 receptor (AT1). However, the mechanism remains unclear because of the accumulating evidences that apelin–APJ may contribute to both cardioprotection and pathological progression. In human embryonic kidney 293 cells, we found that coexpression with APJ significantly suppressed the phosphorylation of extracellular signal-regulated kinases 1/2 (ERK1/2) induced by Ang II–AT1, whereas apelin abolished this attenuation through activated APJ independently of its heterodimerization. Pretreatment with the Gi/o-specific inhibitor pertussis toxin (PTX) restituted the ERK1/2 phosphorylation level similar to that found with AT1 and APJ coexpression without apelin stimulation. In contrast, coexpression of the beta-2-adrenergic receptor or the pharmacologically non-activated Ang II type 2 receptor (AT2) pretreated with the AT2-specific antagonist, PD123319, did not affect ERK1/2 phosphorylation through AT1. Pretreatment with 30 nM of the AT1 blocker (ARB) TA-606A suppressed 50% of the AT1-mediated ERK1/2 phosphorylation, whereas 30 nM of TA-606A achieved 75% suppression when the non-activated APJ was coexpressed without ligand or PTX. However, 120 nM of TA-606A failed to reach the target phosphorylation when it was coexpressed with activated APJ with apelin. Based on these results, we demonstrated that non-activated APJ may suppress Ang II–AT1 signaling, whereas this ligand-independent function was diminished with apelin activation. These results may be relevant to the potential contribution of apelin–APJ to ARB treatment in the clinical realm.

Hesr1 knockout mice exhibit behavioral alterations through the dopaminergic nervous system.

The basic helix‐loop‐helix (bHLH) transcriptional factor Hesr1 gene (hairy and enhancer of split‐related 1, also called Hey1/HRT1/CHF2/HERP2) has been identified and characterized as a member of the subfamily of hairy/Enhancer of split, and shown to be involved in cardiovascular and neural development. We report that HESR1 binds directly to a part of the 3′ non‐coding region of the human dopamine transporter (DAT1) gene and represses the endogenous DAT1 gene in HEK293 cells. To investigate functions of the HESR1 gene in the dopaminergic nervous system in vivo, we analyzed the expressions of dopamine‐related genes in the postnatal day 0 whole brains of Hesr1 knockout mice by real‐time RT‐PCR analysis. Several dopamine‐related genes, such as DAT, dopamine receptors D1, D2, D4, and D5, were significantly upregulated. Moreover, young adults of Hesr1 knockout mice showed a decrease in spontaneous locomotor activity and a reduction in exploratory behavior or behavioral responses to novelty in the open‐field, and elevated plus‐maze tests. These results indicate that the HESR1 gene is related to neuropsychiatric disorders and behavioral traits through the dopaminergic nervous system.