title: PKC alpha mediates beta-arrestin2-dependent nephrin endocytosis in hyperglycemia.
abstract: Nephrin, the key molecule of the glomerular slit diaphragm, is expressed on the surface of podocytes and is critical in preventing albuminuria. In diabetes, hyperglycemia leads to the loss of surface expression of nephrin and causes albuminuria. Here, we report a mechanism that can explain this phenomenon: hyperglycemia directly enhances the rate of nephrin endocytosis via regulation of the β-arrestin2-nephrin interaction by PKCα. We identified PKCα and protein interacting with c kinase-1 (PICK1) as nephrin-binding proteins. Hyperglycemia induced up-regulation of PKCα and led to the formation of a complex of nephrin, PKCα, PICK1, and β-arrestin2 in vitro and in vivo. Binding of β-arrestin2 to the nephrin intracellular domain depended on phosphorylation of nephrin threonine residues 1120 and 1125 by PKCα. Further, cellular knockdown of PKCα and/or PICK1 attenuated the nephrin-β-arrestin2 interaction and abrogated the amplifying effect of high blood glucose on nephrin endocytosis. In C57BL/6 mice, hyperglycemia over 24 h caused a significant increase in urinary albumin excretion, supporting the concept of the rapid impact of hyperglycemia on glomerular permselectivity. In summary, we have provided a molecular model of hyperglycemia-induced nephrin endocytosis and subsequent proteinuria and highlighted PKCα and PICK1 as promising therapeutic targets for diabetic nephropathy.
authors.affiliation: Department of Nephrology, Heinrich Heine University, 40225 Duesseldorf, Germany. ivo.quack@med.uni-duesseldorf.de
authors.forename: Ivo
authors.initials: I
authors.lastname: Quack
authors.forename: Magdalena
authors.initials: M
authors.lastname: Woznowski
authors.forename: Sebastian A
authors.initials: SA
authors.lastname: Potthoff
authors.forename: Romy
authors.initials: R
authors.lastname: Palmer
authors.forename: Eva
authors.initials: E
authors.lastname: Königshausen
authors.forename: Sema
authors.initials: S
authors.lastname: Sivritas
authors.forename: Mario
authors.initials: M
authors.lastname: Schiffer
authors.forename: Johannes
authors.initials: J
authors.lastname: Stegbauer
authors.forename: Oliver
authors.initials: O
authors.lastname: Vonend
authors.forename: Lars Christian
authors.initials: LC
authors.lastname: Rump
authors.forename: Lorenz
authors.initials: L
authors.lastname: Sellin
mesh_terms: D000419:Albuminuria / Q000235:genetics / Q000378:metabolism; D000818:Animals; D019390:Arrestins / Q000235:genetics / Q000378:metabolism*; D001786:Blood Glucose / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins; D003928:Diabetic Nephropathies / Q000235:genetics / Q000378:metabolism; D004705:Endocytosis; D006801:Humans; D006943:Hyperglycemia / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000235:genetics; D051571:Protein Kinase C-alpha / Q000235:genetics / Q000378:metabolism*; D000071557:beta-Arrestins
chemical_list: D019390:Arrestins; D001786:Blood Glucose; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D008565:Membrane Proteins; D009687:Nuclear Proteins; C498297:PICk1 protein, human; C091822:Prkcabp protein, mouse; D000071557:beta-Arrestins; C113267:nephrin; C496628:PRKCA protein, human; C496630:Prkca protein, mouse; D051571:Protein Kinase C-alpha