Differentiation-induced cultured podocytes express endocytically active megalin, a heymann nephritis antigen.
OBJECTIVE
Megalin is a multiligand endocytic receptor expressed in a number of epithelia. In the Lewis rat kidney, podocytes, as well as proximal tubule cells, express megalin that acts as a pathogenic antigen for Heymann nephritis (HN), an experimental model of membranous nephropathy. To obtain a tool to investigate the molecular mechanisms of megalin-mediated endocytosis and the pathogenesis of HN, we examined whether a differentiation-inducible mouse podocyte cell line expressed endocytically active megalin.


METHODS
Immunofluorescence and immunoprecipitation analyses with an anti-rat megalin antibody were carried out to investigate whether megalin was expressed in the differentiated and undifferentiated podocytes. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis was performed to elucidate whether the cells synthesize megalin mRNA. 125I-labeled receptor-associated protein (RAP), an endocytic ligand for megalin, was used for cellular internalization and degradation assays.


RESULTS
Immunofluorescence, immunoprecipitation and RT-PCR analyses revealed that megalin was synthesized in both differentiated and undifferentiated cells and localized to the cell surfaces. Effective endocytosis of RAP via megalin was shown under the differentiated condition.


CONCLUSIONS
Endocytically active megalin is expressed in differentiation-induced cultured podocytes. This cell line could be a useful tool for studies on megalin-mediated endocytosis and the pathogenesis of HN.
Yamazaki
Hajime
H
Division of Clinical Nephrology and Rheumatology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
Saito
Akihiko
A
Ooi
Hidemi
H
Kobayashi
Naoto
N
Mundel
Peter
P
Gejyo
Fumitake
F
D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D004705:Endocytosis; D015870:Gene Expression; D007678:Kidney Glomerulus / Q000166:cytology* / Q000378:metabolism; D008024:Ligands; D026561:Low Density Lipoprotein Receptor-Related Protein-2 / Q000235:genetics / Q000378:metabolism*; D051379:Mice
D008024:Ligands; D026561:Low Density Lipoprotein Receptor-Related Protein-2