IQGAP1 interacts with components of the slit diaphragm complex in podocytes and is involved in podocyte migration and permeability in vitro.
IQGAP1 is a scaffold protein that interacts with proteins of the cytoskeleton and the intercellular adhesion complex. In podocytes, IQGAP1 is associated with nephrin in the glomerular slit diaphragm (SD) complex, but its role remains ill-defined. In this work, we investigated the interaction of IQGAP1 with the cytoskeleton and SD proteins in podocytes in culture, and its role in podocyte migration and permeability. Expression, localization, and interactions between IQGAP1 and SD or cytoskeletal proteins were determined in cultured human podocytes by Western blot (WB), immunocytolocalization (IC), immunoprecipitation (IP), and In situ Proximity Ligation assay (IsPL). Involvement of IQGAP1 in migration and permeability was also assessed. IQGAP1 expression in normal kidney biopsies was studied by immunohistochemistry. IQGAP1 expression by podocytes increased during their in vitro differentiation. IC, IP, and IsPL experiments showed colocalizations and/or interactions between IQGAP1 and SD proteins (nephrin, MAGI-1, CD2AP, NCK 1/2, podocin), podocalyxin, and cytoskeletal proteins (α-actinin-4). IQGAP1 silencing decreased podocyte migration and increased the permeability of a podocyte layer. Immunohistochemistry on normal human kidney confirmed IQGAP1 expression in podocytes and distal tubular epithelial cells and also showed an expression in glomerular parietal epithelial cells. In summary, our results suggest that IQGAP1, through its interaction with components of SD and cytoskeletal proteins, is involved in podocyte barrier properties.
INSERM U1026, Université Bordeaux Segalen, Bordeaux, France. claire.rigothier@etud.u-bordeaux2.fr
Claire
C
Rigothier
Patrick
P
Auguste
Gavin I
GI
Welsh
Sébastien
S
Lepreux
Colette
C
Deminière
Peter W
PW
Mathieson
Moin A
MA
Saleem
Jean
J
Ripoche
Christian
C
Combe
D000185:Actinin / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D015815:Cell Adhesion Molecules; D015816:Cell Adhesion Molecules, Neuronal / Q000378:metabolism; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology*; D003598:Cytoskeletal Proteins / Q000378:metabolism; D051528:Guanylate Kinases; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D007678:Kidney Glomerulus / Q000166:cytology / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D015513:Oncogene Proteins / Q000378:metabolism; D010539:Permeability; D050199:Podocytes / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D012795:Sialoglycoproteins / Q000378:metabolism; D051176:beta Catenin / Q000378:metabolism; D020703:ras GTPase-Activating Proteins / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; C114545:CD2-associated protein; D015815:Cell Adhesion Molecules; D015816:Cell Adhesion Molecules, Neuronal; D003598:Cytoskeletal Proteins; C101203:IQ motif containing GTPase activating protein 1; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C407223:NPHS2 protein; C078332:Nck protein; D015513:Oncogene Proteins; D012795:Sialoglycoproteins; D051176:beta Catenin; C113267:nephrin; C001643:podocalyxin; D020703:ras GTPase-Activating Proteins; D000185:Actinin; D051528:Guanylate Kinases; C113338:MAGI1 protein, human