15, 16 Differentiating muscle cells15, 17 and transfected HeLa,16 HEK293,17-20 Cos-7,21 Hep3B,21, 22 and HepG216, 23, 24 cells release soluble ≈50 and ≈40 kDa isoforms (sHjv) in extracellular media; sHjv has also been detected in human,22, 25 rat,17 and mouse21 serum. Hjv interacts with neogenin, which may modulate the secretion of sHjv in a positive24 or a negative20 manner. sHjv can be generated by proteolytic cleavage with either furin and other pro-protein convertases,19, 21, 26 or matriptase-2.27 The latter, a protease encoded by

the TMPRSS6 gene,28 see more inactivates cellular Hjv27 and inhibits hepcidin expression by attenuating BMP signaling.29 Furin cleaves cellular Hjv at R332 and matriptase-2 at R288.30 Cleavage of the GPI anchor, possibly by phospholipase A, may yield full-length Selleckchem Stem Cell Compound Library sHjv, consisting of the entire ectodomain.19 In vitro experiments with purified recombinant sHjv and with conditioned media from Hjv-transfected cells suggested that this protein functions as a decoy receptor and inhibits BMP

signaling to hepcidin.19, 20, 22 Moreover, a sHjv.Fc fusion construct was shown to directly interact with BMP610 and to decrease hepcidin expression in vivo.31 Nevertheless, sHjv generated by matriptase cleavage did not compete BMP signaling to hepcidin.30 To elucidate the tissue-specific function of Hjv in the control of body iron homeostasis, we generated mice with targeted disruption of the Hfe2 gene in liver hepatocytes or in muscles. We show that only hepatic Hjv is essential for an appropriate hepcidin 上海皓元医药股份有限公司 response, whereas muscle Hjv does not exert any apparent iron-regulatory function. BMP, bone morphogenetic protein; GPI, glycosylphosphatidylinositol; Hjv, hemojuvelin; RGM, repulsive guidance molecule; sHjv, soluble hemojuvelin; TfR2, transferrin receptor 2; TIBC, total iron binding capacity. For conditional disruption of Hfe2, a targeting vector32 (kindly provided by Dr. Stephane Richard, McGill University) was employed to “flox” a 3.4 kb region spanning exons

2-4, with loxP sites. A neo-PGK cassette was also introduced for antibiotic selection of homologous recombination events. The targeting construct was transfected into 129S6/SvEvTac embryonic stem cells and two (out of 500) positive clones were identified. The clones were expanded and microinjected into C57BL/6J blastocysts; this procedure was performed at the McIntyre Cancer Centre Transgenic Core Facility of McGill University. The resulting chimeras were crossed with female C57/BL6 mice to produce agouti mice, which were polymerase chain reaction (PCR)-genotyped for germline transmission of the floxed Hfe2 allele. Heterozygotes (Hfe2wt/f) were crossed to obtain Hfe2f/f mice. PCR genotyping from tail genomic DNA was performed by using the RedExtract kit (Sigma) with primers shown in Table 1A. Alb-Cre mice (B6.Cg-Tg(Alb-cre)21Mgn/J strain) were purchased from the Charles River Laboratories (Cambridge, MA).