Nephrotic plasma alters slit diaphragm-dependent signaling and translocates nephrin, Podocin, and CD2 associated protein in cultured human podocytes.
Podocytes are critical in maintaining the filtration barrier of the glomerulus and are dependent on the slit diaphragm (SD) proteins nephrin, podocin, and CD2-associated protein (CD2AP) to function optimally. The effects of normal human plasma and nephrotic plasma on podocytes were tested, focusing particularly on the SD complex. With the use of a conditionally immortalized human podocyte cell line, it first was shown that exposure to normal and non-nephrotic human plasma leads to a concentration of nephrin, podocin, CD2AP, and actin at the cell surface. Next, the effects of plasma from patients with nephrotic conditions to non-nephrotic conditions were compared. When exposed to all nephrotic plasma samples (and a non-human serum control), nephrin podocin and CD2AP assumed a cytoplasmic distribution; nephrin and synaptopodin were selectively downregulated, and the relocation of nephrin induced by nephrotic plasma could be rescued back to the plasma membrane by co-incubation with non-nephrotic plasma. Furthermore, intracellular calcium signaling was altered by nephrotic plasma, which was mediated by tyrosine kinase phosphorylation. With the use of nephrin mutant human cell lines, it was shown that this signaling and translocation response to normal plasma is nephrin dependent. This work demonstrates that nephrotic plasma seems to be deficient in factors that act via the podocyte SD complex, which are essential in maintaining its physiologic function.
Coward
Richard J M
RJ
Academic and Children's Renal Unit, Southmead Hospital, University of Bristol, Bristol, UK.
Foster
Rebecca R
RR
Patton
David
D
Ni
Lan
L
Lennon
Rachel
R
Bates
David O
DO
Harper
Steven J
SJ
Mathieson
Peter W
PW
Saleem
Moin A
MA
D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing; D000293:Adolescent; D001798:Blood Proteins / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D002461:Cell Line, Transformed; D002648:Child; D003598:Cytoskeletal Proteins; D005260:Female; D006801:Humans; D007223:Infant; D047908:Intracellular Signaling Peptides and Proteins; D007678:Kidney Glomerulus / Q000166:cytology / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D008875:Middle Aged; D009154:Mutation; D009401:Nephrosis / Q000097:blood*; D011506:Proteins / Q000235:genetics / Q000378:metabolism
D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D001798:Blood Proteins; C114545:CD2-associated protein; D003598:Cytoskeletal Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C407223:NPHS2 protein; D011506:Proteins; C113267:nephrin; D002118:Calcium