c-mip impairs podocyte proximal signaling and induces heavy proteinuria.
Idiopathic nephrotic syndrome comprises several podocyte diseases of unknown origin that affect the glomerular podocyte, which controls the permeability of the filtration barrier in the kidney to proteins. It is characterized by the daily loss of more than 3 g of protein in urine and the lack of inflammatory lesions or cell infiltration. We found that the abundance of c-mip (c-maf inducing protein) was increased in the podocytes of patients with various acquired idiopathic nephrotic syndromes in which the podocyte is the main target of injury. Mice engineered to have excessive c-mip in podocytes developed proteinuria without morphological alterations, inflammatory lesions, or cell infiltration. Excessive c-mip blocked podocyte signaling by preventing the interaction of the slit diaphragm transmembrane protein nephrin with the tyrosine kinase Fyn, thereby decreasing phosphorylation of nephrin in vitro and in vivo. Moreover, c-mip inhibited interactions between Fyn and the cytoskeletal regulator N-WASP (neural Wiskott-Aldrich syndrome protein) and between the adaptor protein Nck and nephrin, potentially accounting for cytoskeletal disorganization and the effacement of foot processes seen in idiopathic nephrotic syndromes. The intravenous injection of small interfering RNA targeting c-mip prevented lipopolysaccharide-induced proteinuria in mice. Together, these results identify c-mip as a key component in the molecular pathogenesis of acquired podocyte diseases.
Zhang
Shao-Yu
SY
INSERM, UMR 955, Equipe 21, F-94010 Créteil, France.
Kamal
Maud
M
Dahan
Karine
K
Pawlak
André
A
Ory
Virginie
V
Desvaux
Dominique
D
Audard
Vincent
V
Candelier
Marina
M
BenMohamed
Fatima
F
Mohamed
Fatima Ben
FB
Matignon
Marie
M
Christov
Christo
C
Decrouy
Xavier
X
Bernard
Veronique
V
Mangiapan
Gilles
G
Lang
Philippe
P
Guellaën
Georges
G
Ronco
Pierre
P
Sahali
Djillali
D
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D010766:Phosphorylation; D050199:Podocytes / Q000378:metabolism / Q000502:physiology*; D011485:Protein Binding; D011507:Proteinuria / Q000503:physiopathology*; D051076:Proto-Oncogene Proteins c-fyn / Q000378:metabolism; D034622:RNA Interference; D015398:Signal Transduction / Q000502:physiology*; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; C540426:CMIP protein, human; D002352:Carrier Proteins; C551587:Cmip protein, mouse; D008565:Membrane Proteins; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; C113267:nephrin; C494957:FYN protein, human; D051076:Proto-Oncogene Proteins c-fyn