P292
NEPHRIN REGULATED NF-B ACTIVATION MEDIATES GLOMERULAR INJURY IN
VIVO.
Koziell, A1, Hussain, S1, Romio, L1, Mathieson, P2, Moscat, J3, Diaz-Meco, M3, Saleem, M2,
Scambler, P 1
1
Institute of Child Health, London, 2 Southmead Hospital, Bristol, 3University of Cincinnati, USA.
SUMMARY: NF-kappaB (NF-B) activation plays an important role in cellular stress, inflammation,
immunity and the control of cell growth and differentiation. Increasing evidence implicates NF-B
activation in renal glomerular injury, although the mechanisms or nature of any modifiers are unknown.
To identify the cellular processes involved and to what extent dysregulation of key podocyte genes may
contribute, we examined in vitro cell culture models and the renal phenotype of a transgenic mouse in
which hyperactivation of NF-B is a key feature.
METHODS: Signal transduction assays were performed in transfected MDCK cells using a pNF-B
luciferase reporter end point (Mercury Pathway Profiling System, Clontech) and results confirmed in
human cultured podocytes. Analysis of aPKC and NF-B expression was conducted using nonstimulated wild type human podocytes1 and compared with that in podocytes carrying a constitutive
121delCT frameshift mutation without functional nephrin2. Mice genetically deficient for Par4, a
natural inhibitor of the aPKC/NF-B axis were generated by homologous recombination3.
RESULTS: Data from signal transduction assays supports a direct functional relationship between the
key podocyte protein nephrin and NF-B. The mechanism here appeared to be that nephrin specifically
repressed NF-B activation in vitro, with further analysis corroborating atypical protein kinase C
(aPKC) as a pathway intermediary. Moreover, loss of nephrin resulted in NF-B and aPKCζ/ activation
in human glomerular podocytes. Subsequent generation of transgenic mice with hyperactivation of
RelA/NF-B by genetic disruption of the aPKC/NF-B axis led to glomerulosclerosis and urinary
protein loss within the first month of life.
CONCLUSIONS: We propose that NF-B meets slit diaphragm signalling and that this is regulated by
nephrin. Loss of nephrin results in inappropriate induction of NF-B and glomerular damage mediated
by NF-B dependent pathways.
REFERENCES:
1. Saleem, M.A. et al. J. Am. Soc. Nephrol. 13, 630-638 (2002).
2. Coward, R.J. et al. J. Am. Soc. Nephrol 16, 629-37 (2005).
3. Garcia-Cao, I. et al. EMBO Rep. 4, 307-312 (2003).