Objectives and Study: The glomerular filtration barrier is a unique structure characterized by a specialized
three-dimensional framework of podocytes. Mutations in genes encoding for slitdiaphragm
proteins Nephrin (NPHS1) and Podocin (NPHS2) cause a hereditary nephrotic syndrome
in humans and genetic deletion of Neph1, a slit diaphragm protein closely related
toNephrin, leads to congenital nephrotic syndrome in mice. An apico-basal polarity
axis allows for podocyte orientation between the urinary space and the glomerular
basement membrane. Our recent studies document that conserved polarity protein complexes
such as the Par3, Par6 and aPKC (PAR) complex co-localize with the Nephrin complex
and are essential regulators of podocyte morphology. Glomerular development, slit
diaphragm targeting and apico-basolateral distribution of molecules seems to be tightly
regulated by these polarity signaling pathways.
Methods: Immunoprecipitation,Immunofluorescence, shRNA knockdown, knock-out mouse.
Results: We identified the polarity molecule Scribble as novel Neph1- associated protein.
The fourth PDZ domain of Scribble mediates the interaction with the conserved carboxy
terminal residues in Neph1. Scribble co-localizes with Neph1 in podocyte foot processes
during glomerular development. Strikingly, Scribble translocates together with apical
junctionproteins like ZO–1 to the basolateral side of maturing podocytes. A scribble
knockdwon via shRNA in cultured podocytes surprisingly did not affect podocyte survival
or cell migratory abilities. To further investigate what role Scribble plays for glomerular
development, maintenance and podocyte integrity a conditional scribble knock-out mouse
is currently under investigation.
Conclusions: Our data provide an important link between cell recognition mediated through the
Neph1-Nephrin complex and Scribble-dependant polarity signaling.
Neph1 - Scribble - glomerular development - nephrotic syndrome - podocyte
