Septin 7 forms a complex with CD2AP and nephrin and regulates glucose transporter trafficking.
Podocytes are insulin-sensitive and take up glucose in response to insulin. This requires nephrin, which interacts with vesicle-associated membrane protein 2 (VAMP2) on GLUT4 storage vesicles (GSVs) and facilitates their fusion with the plasma membrane. In this paper, we show that the filament-forming GTPase septin 7 is expressed in podocytes and associates with CD2-associated protein (CD2AP) and nephrin, both essential for glomerular ultrafiltration. In addition, septin 7 coimmunoprecipitates with VAMP2. Subcellular fractionation of cultured podocytes revealed that septin 7 is found in both cytoplasmic and membrane fractions, and immunofluorescence microscopy showed that septin 7 is expressed in a filamentous pattern and is also found on vesicles and the plasma membrane. The filamentous localization of septin 7 depends on CD2AP and intact actin organization. A 2-deoxy-d-glucose uptake assay indicates that depletion of septin 7 by small interfering RNA or alteration of septin assembly by forchlorfenuron facilitates glucose uptake into cells and further, knockdown of septin 7 increased the interaction of VAMP2 with nephrin and syntaxin 4. The data indicate that septin 7 hinders GSV trafficking and further, the interaction of septin 7 with nephrin in glomeruli suggests that septin 7 may participate in the regulation of glucose transport in podocytes.
Department of Pathology, Haartman Institute, 00014 University of Helsinki, Finland.
Anita A
AA
Wasik
Zydrune
Z
Polianskyte-Prause
Meng-Qiu
MQ
Dong
Andrey S
AS
Shaw
John R
JR
Yates
Marilyn G
MG
Farquhar
Sanna
S
Lehtonen
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D051275:Glucose Transporter Type 4 / Q000378:metabolism*; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D010671:Phenylurea Compounds / Q000494:pharmacology; D050199:Podocytes / Q000378:metabolism; D021381:Protein Transport; D011725:Pyridines / Q000494:pharmacology; D050765:Qa-SNARE Proteins / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering; D051381:Rats; D017207:Rats, Sprague-Dawley; D058112:Septins / Q000235:genetics / Q000378:metabolism*; D050988:Vesicle-Associated Membrane Protein 2 / Q000378:metabolism*
D048868:Adaptor Proteins, Signal Transducing; C114545:CD2-associated protein; D003598:Cytoskeletal Proteins; D051275:Glucose Transporter Type 4; D007328:Insulin; D008565:Membrane Proteins; D010671:Phenylurea Compounds; D011725:Pyridines; D050765:Qa-SNARE Proteins; D034741:RNA, Small Interfering; C494706:Vamp2 protein, rat; D050988:Vesicle-Associated Membrane Protein 2; C113267:nephrin; C512894:Septin7 protein, rat; D058112:Septins; C116093:N-(2-chloro-4-pyridyl)-N'-phenylurea