In response to protein load podocytes reorganize cytoskeleton and modulate endothelin-1 gene: implication for permselective dysfunction of chronic nephropathies.
Effacement of podocyte foot processes occurs in many proteinuric nephropathies and is accompanied by rearrangement of the actin cytoskeleton. Here, we studied whether protein overload affects intracellular pathways, leading to cytoskeletal architecture changes and ultimately to podocyte dysfunction. Mouse podocytes bound and endocytosed both albumin and IgG via receptor-specific mechanisms. Protein overload caused redistribution of F-actin fibers instrumental to up-regulation of the prepro-endothelin (ET)-1 gene and production of the corresponding peptide. Increased DNA-binding activity for nuclear factor (NF)-kappaB and Ap-1 nuclear proteins was measured in nuclear extracts of podocytes exposed to excess proteins. Both Y27632, which inhibits Rho kinase-dependent stress fiber formation, and jasplakinolide, an F-actin stabilizer, decreased NF-kappaB and Ap-1 activity and reduced ET-1 expression. This suggested a role for the cytoskeleton, through activated Rho, in the regulation of the ET-1 peptide. Focal adhesion kinase (FAK), an integrin-associated nonreceptor tyrosine kinase, was phosphorylated by albumin treatment via Rho kinase-triggered actin reorganization. FAK activation led to NF-kappaB- and Ap-1-dependent ET-1 expression. These data suggest that reorganization of the actin cytoskeletal network in response to protein load is implicated in modulation of the ET-1 gene via Rho kinase-dependent FAK activation of NF-kappaB and Ap-1 in differentiated podocytes. Increased ET-1 generation might alter glomerular permselectivity and amplify the noxious effect of protein overload on dysfunctional podocytes.
Morigi
Marina
M
Mario Negri Institute for Pharmacological Research, Via Gavazzeni 11, 24125 Bergamo, Italy. morigi@marionegri.it
Buelli
Simona
S
Angioletti
Stefania
S
Zanchi
Cristina
C
Longaretti
Lorena
L
Zoja
Carla
C
Galbusera
Miriam
M
Gastoldi
Sara
S
Mundel
Peter
P
Remuzzi
Giuseppe
G
Benigni
Ariela
A
D000199:Actins / Q000502:physiology; D000818:Animals; D002454:Cell Differentiation; D002461:Cell Line, Transformed; D002908:Chronic Disease; D003599:Cytoskeleton / Q000187:drug effects / Q000502:physiology*; D019332:Endothelin-1 / Q000235:genetics* / Q000494:pharmacology; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000378:metabolism; D007668:Kidney / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D007674:Kidney Diseases / Q000378:metabolism; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D010539:Permeability; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D012709:Serum Albumin / Q000378:metabolism / Q000494:pharmacology*; D015398:Signal Transduction / Q000502:physiology; D014018:Tissue Distribution; D018808:Transcription Factor AP-1 / Q000378:metabolism
D000199:Actins; D019332:Endothelin-1; D007074:Immunoglobulin G; D008840:Microfilament Proteins; D016328:NF-kappa B; C503967:SYNPO protein, human; D012709:Serum Albumin; C503968:Synpo protein, mouse; D018808:Transcription Factor AP-1; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; C496051:Ptk2 protein, mouse