Hepcidin is a key regulator of iron homeostasis, while hemojuvelin is an important component of the hepcidin regulation pathway. It has been recently proposed that soluble hemojuvelin, produced from hemojuvelin by the protease furin, decreases hepcidin expression. The aim of the presented study was to examine the downregulation of hepcidin by chronic bleeding in hemojuvelin-mutant mice. Male mice with targeted disruption of the hemojuvelin gene (Hjv-/- mice) and wild-type littermates were maintained on an iron-deficient diet and subjected to weekly phlebotomies for 7 weeks. Gene expression was examined by real-time PCR. In wild type mice, repeated bleeding decreased hepcidin mRNA by two orders of magnitude. In Hjv-/- mice, basal hepcidin expression was low; however, repeated bleeding also decreased hepcidin mRNA content by an order of magnitude. Phlebotomies reduced hepatic iron overload in Hjv-/- mice by 80 %. Liver and muscle furin mRNA content was not significantly changed. No effect on hepatic Tmprss6 mRNA content was observed. Results from the study indicate that soluble hemojuvelin is not the sole factor responsible for hepcidin downregulation. In addition, the presented data suggest that, under in vivo conditions, tissue hypoxia does not transcriptionally regulate the activity of furin or TMPRSS6 proteases.

• MeSH
• časové faktory MeSH
• deficit železa MeSH
• dietní železo aplikace a dávkování   MeSH
• down regulace MeSH
• erytropoéza * MeSH
• flebotomie MeSH
• furin metabolismus   MeSH
• GPI-vázané proteiny MeSH
• hepcidiny MeSH
• hypoxie buňky MeSH
• játra metabolismus   MeSH
• kationické antimikrobiální peptidy genetika   metabolismus   MeSH
• kosterní svaly metabolismus   MeSH
• krvácení etiologie   genetika   metabolismus   MeSH
• membránové proteiny nedostatek   genetika   metabolismus   MeSH
• messenger RNA metabolismus   MeSH
• modely nemocí na zvířatech MeSH
• myši knockoutované MeSH
• myši MeSH
• přetížení železem metabolismus   prevence a kontrola   MeSH
• protein hemochromatózy MeSH
• serinové endopeptidasy metabolismus   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• dietní železo MeSH
• furin MeSH
• GPI-vázané proteiny MeSH
• Hamp protein, mouse MeSH Prohlížeč
• hepcidiny MeSH
• HJV protein, mouse MeSH Prohlížeč
• kationické antimikrobiální peptidy MeSH
• matriptase 2 MeSH Prohlížeč
• membránové proteiny MeSH
• messenger RNA MeSH
• protein hemochromatózy MeSH
• serinové endopeptidasy MeSH

Filamentous fungi produce and secrete beta-N-acetylhexosaminidases, Hex, as important components of the binary chitinolytic systems involved in the formation of septa and hyphenation. Enzyme reconstitution experiments published previously indicate that Hex can occur in the form of two molecular species containing either one or two molecules of the propeptide noncovalently associated with the enzyme dimer. Here, we describe a novel mechanism for the regulation of the activity of Hex based on the association of their catalytic subunits with the large N-terminal propeptides in vivo. We show that the enzyme precursor is processed early in the biosynthesis, shortly after the addition of N-glycans through the action of a dibasic peptidase, cleaving both before and after the dibasic sequence. The processing site for this unique dibasic peptidase, different from that of kexins, is conserved among the beta-N-acetylhexosaminidases from filamentous fungi, and inhibition of the dibasic peptidase abrogates enzyme folding and activation. Binding of the released propeptide to the catalytic subunit of Hex is essential for its activation. An examination of the kinetics of Hex activation and dimerization in vitro allowed us to understand the unusually high efficiency of the assembly of this enzyme. We also report that the fungus is able to actively regulate the concentration of the processed propeptide in endoplasmic reticulum and thus the specific activity of the produced Hex. This novel regulatory mechanism enables the control of the catalytic activity and architecture of the secreted enzyme according to the needs of the producing cell at various stages of its growth cycle.

• MeSH
• acetylglukosamin analogy a deriváty   farmakologie   MeSH
• aktivace enzymů MeSH
• beta-N-acetylhexosaminidasy metabolismus   MeSH
• biologický transport MeSH
• dimerizace MeSH
• endoplazmatické retikulum metabolismus   MeSH
• furin metabolismus   MeSH
• genetická transkripce MeSH
• houby enzymologie   MeSH
• katalýza MeSH
• molekulární sekvence - údaje MeSH
• prekurzory enzymů metabolismus   MeSH
• sekvence aminokyselin MeSH
• sekvenční homologie aminokyselin MeSH
• stabilita enzymů MeSH
• thiazoly farmakologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• acetylglukosamin MeSH
• beta-N-acetylhexosaminidasy MeSH
• furin MeSH
• N-acetylglucosamine thiazoline MeSH Prohlížeč
• prekurzory enzymů MeSH
• thiazoly MeSH