title: Neph1 is reduced in primary focal segmental glomerulosclerosis, minimal change nephrotic syndrome, and corresponding experimental animal models of adriamycin-induced nephropathy and puromycin aminonucleoside nephrosis.
abstract: OBJECTIVE
  The transmembrane proteins Neph1 and nephrin form a complex in the slit diaphragm (SD) of podocytes. As recent studies indicate an involvement of this complex in the polymerization of the actin cytoskeleton and proteinuria, we wanted to study the subcellular localization of Neph1 in the normal human kidney and its expression in focal segmental glomerulosclerosis (FSGS), minimal change nephrotic syndrome (MCNS), and the corresponding experimental models of Adriamycin-induced nephropathy (ADR) and puromycin aminonucleoside nephrosis (PAN). All these disorders are characterized by substantial foot process effacement (FPE) and proteinuria.
  
  
  METHODS
  Kidney biopsies from patients with primary FSGS (perihilar type) and MCNS were compared to normal renal tissue. Mouse and rat kidney cortices from days 7 and 14 after Adriamycin injection and days 2 and 4 after puromycin aminonucleoside injection, respectively, were compared to control mouse and rat kidney. Polyclonal antibodies against Neph1 and nephrin were used for immunoelectron microscopy, and semiquantification was performed.
  
  
  RESULTS
  We localized Neph1 mainly to, and in close proximity to, the SD. Double staining of Neph1 and nephrin showed the proteins to be in close connection in the SD. The total amount of Neph1 in the podocytes was significantly reduced in FSGS, MCNS, ADR, and PAN. The reduction of Neph1 was also seen in areas with and without FPE. Nephrin was reduced in MCNS and PAN but unchanged in FSGS.
  
  
  CONCLUSIONS
  With nephrin (but not Neph1) unchanged in FSGS, there might be a disruption of the complex and an involvement of Neph1 in its pathogenesis.
authors.affiliation: Department of Clinical Science, Intervention and Technology, Stockholm, Sweden.
authors.forename: Jenny
authors.initials: J
authors.lastname: Hulkko
authors.affiliation: Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Jaakko
authors.initials: J
authors.lastname: Patrakka
authors.affiliation: Department of Medical Biochemistry and Biophysics, Stockholm, Sweden.
authors.forename: Mark
authors.initials: M
authors.lastname: Lal
authors.affiliation: Department of Medical Biochemistry and Biophysics, Stockholm, Sweden.
authors.forename: Karl
authors.initials: K
authors.lastname: Tryggvason
authors.affiliation: Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Kjell
authors.initials: K
authors.lastname: Hultenby
authors.affiliation: Department of Clinical Science, Intervention and Technology, Stockholm, Sweden.
authors.forename: Annika
authors.initials: A
authors.lastname: Wernerson
keywords: Adriamycin-induced nephropathy; Focal segmental glomerulosclerosis; Minimal change nephrotic syndrome; Neph1; Puromycin aminonucleoside nephrosis