Cathepsin B increases ENaC activity leading to hypertension early in nephrotic syndrome.
The NPHS2 gene, encoding the slit diaphragm protein podocin, accounts for genetic and sporadic forms of nephrotic syndrome (NS). Patients with NS often present symptoms of volume retention, such as oedema formation or hypertension. The primary dysregulation in sodium handling involves an inappropriate activation of the epithelial sodium channel, ENaC. Plasma proteases in a proteinuria-dependent fashion have been made responsible; however, referring to the timeline of symptoms occurring and underlying mechanisms, contradictory results have been published. Characterizing the mouse model of podocyte inactivation of NPHS2 (Nphs2∆pod ) with respect to volume handling and proteinuria revealed that sodium retention, hypertension and gross proteinuria appeared sequentially in a chronological order. Detailed analysis of Nphs2∆pod during early sodium retention, revealed increased expression of full-length ENaC subunits and αENaC cleavage product with concomitant increase in ENaC activity as tested by amiloride application, and augmented collecting duct Na+ /K+ -ATPase expression. Urinary proteolytic activity was increased and several proteases were identified by mass spectrometry including cathepsin B, which was found to process αENaC. Renal expression levels of precursor and active cathepsin B were increased and could be localized to glomeruli and intercalated cells. Inhibition of cathepsin B prevented hypertension. With the appearance of gross proteinuria, plasmin occurs in the urine and additional cleavage of γENaC is encountered. In conclusion, characterizing the volume handling of Nphs2∆pod revealed early sodium retention occurring independent to aberrantly filtered plasma proteases. As an underlying mechanism cathepsin B induced αENaC processing leading to augmented channel activity and hypertension was identified.
['Larionov|Alexey|A|', 'Dahlke|Eileen|E|', 'Kunke|Madlen|M|', 'Zanon Rodriguez|Luis|L|', 'Schiessl|Ina M|IM|', 'Magnin|Jean-Luc|JL|', 'Kern|Ursula|U|', 'Alli|Abdel A|AA|', 'Mollet|Geraldine|G|', 'Schilling|Oliver|O|', 'Castrop|Hayo|H|', 'Theilig|Franziska|F|0000-0001-8810-4717']
D000584:Amiloride D000818:Animals D002401:Cathepsin B D062686:Epithelial Sodium Channel Blockers D053503:Epithelial Sodium Channels D005923:Glomerulosclerosis, Focal Segmental D006973:Hypertension D047908:Intracellular Signaling Peptides and Proteins D007684:Kidney Tubules D008247:Lysosomes D008565:Membrane Proteins D051379:Mice D008822:Mice, Transgenic D009404:Nephrotic Syndrome D011507:Proteinuria D059748:Proteolysis D012964:Sodium
hypertension nephrotic syndrome epithelial sodium channel focal segmental glomerulosclerosis