Abstract-The (pro)renin receptor [(P)RR] is a 35-kDa transmembrane protein that plays a pivotal role in angiotensin tissue generation and in nonproteolytic prorenin activation. We detected a soluble form of (P)RR [s(P)RR; 28 kDa] in the conditioned medium of cultured cells. The aims of our study were to identify the protease responsible for the generation of s(P)RR, the site of shedding, and to establish the existence of circulating s(P)RR in plasma. We identified furin as the protease responsible for the shedding of endogenous (P)RR based on the following: LoVo colon carcinoma cells devoid of active furin synthesize full-length (P)RR but do not secrete s(P)RR; transfection of Chinese hamster ovary cells with a plasmid coding for ␣1-antitrypsin Portland variant, an inhibitor of furin, completely inhibited the generation of s(P)RR, whereas addition of GM6001, an inhibitor of metalloproteases or of tumor necrosis factor-␣ protease inhibitor-1, an inhibitor of ADAM17, in the culture medium has no effect; when the cDNA coding for (P)RR was translated in vitro and incubated with recombinant furin or ADAM17, only furin was able to generate the 28 kDa-s(P)RR, and mutagenesis in the potential furin cleavage R275A/KT/R278A site abolished s(P)RR generation.Immunofluorescence study in glomerular epithelial cells showed that (P)RR was cleaved in the trans-Golgi, and coprecipitation experiments with renin showed that s(P)RR was present in plasma. In conclusion, our results show that s(P)RR is generated intracellularly by furin cleavage, and that s(P)RR detected in plasma is able to bind renin. Key Words: (pro)renin receptor Ⅲ soluble (pro)renin receptor Ⅲ plasma Ⅲ furin Ⅲ renin-angiotensin system A receptor specific for renin and prorenin, named (P)RR for (pro)renin receptor, was first identified in human mesangial cells 1 and cloned in 2002. 2 Studies so far have focused on the functions of the full-length transmembrane protein because of the potential role of (P)RR in cardiovascular and renal diseases. 3 However, 2 studies reported that the majority of (P)RR was found in the cytosol of cardiomyocytes 4 and in the endoplasmic reticulum in cells transfected and overexpressing tagged (P)RR. 5 Shortly before (P)RR was described as an integral membrane protein of 39 kDa, a truncated form of 8.9 kDa called M8.9 was reported to coprecipitate with the membrane sector of the vacuolar H ϩ -ATPase (V-ATPase) from bovine chromaffin granules. 6 The V-ATPase is a complex molecule made of the assembly of 13 subunits that plays an essential role in the cellular pH homeostasis and acidification of intracellular vesicles, 7 and the gene coding for the M8.9 was then called ATP6ap2, for ATPase accessory protein 2. Because there is only one gene coding for (P)RR and M8.9, 8 we reasoned that M8.9 must derive from the full-length (P)RR by an intracellular cleavage suggested to take place at a furin-like cleavage site 9,10 predicted by the search for a conserved pattern in the linear amino-acid sequence analysis of (P)RR amino-acid sequence.Weste...

SummaryIn skeletal muscle, new functions for vessels have recently emerged beyond oxygen and nutrient supply, through the interactions that vascular cells establish with muscle stem cells. Here, we demonstrate in human and mouse that endothelial cells (ECs) and myogenic progenitor cells (MPCs) interacted together to couple myogenesis and angiogenesis in vitro and in vivo during skeletal muscle regeneration. Kinetics of gene expression of ECs and MPCs sorted at different time points of regeneration identified three effectors secreted by both ECs and MPCs. Apelin, Oncostatin M, and Periostin were shown to control myogenesis/angiogenesis coupling in vitro and to be required for myogenesis and vessel formation during muscle regeneration in vivo. Furthermore, restorative macrophages, which have been previously shown to support myogenesis in vivo, were shown in a 3D triculture model to stimulate myogenesis/angiogenesis coupling, notably through Oncostatin M production. Our data demonstrate that restorative macrophages orchestrate muscle regeneration by controlling myogenesis/angiogenesis coupling.