Rat glomerular epithelial cells produce and bear factor H on their surface that is up-regulated under complement attack.
BACKGROUND
Factor H is a potent complement inhibitory molecule that is primarily produced by the liver and appears in plasma as a soluble protein. Yet there is evidence that other cells, including those in the kidney, can produce factor H, and that it can be cell-associated as well as present as a plasma protein. Here we studied factor H in rat glomerular epithelial cells (GEC).


METHODS
A polyclonal antibody to factor H was used to identify factor H protein. A polymerase chain reaction (PCR)-based strategy was utilized to clone the full-length cDNA of GEC factor H. The relative quantity of factor H mRNA was measured by quantitative reverse transcription (RT)-PCR in cultured GEC exposed to complement activation and in the passive Heymann nephritis (PHN) model of membranous nephropathy.


RESULTS
By immunofluorescence microscopy, factor H protein was present on the plasma membranes of cultured GEC. Based upon Western blot studies, this appeared to be the full-length 150 kD factor H protein. Factor H cDNA cloned from GEC was identical to the newly deposited sequence for rat liver factor H cDNA. In cultured GEC in which complement was activated, factor H mRNA increased over time. Similarly, in the PHN model in which complement was activated on GEC in vivo, factor H mRNA and protein also increased over time.


CONCLUSIONS
Cultured GEC and glomeruli express factor H mRNA and protein. As modeled both in vitro and in vivo in the rat, factor H is up-regulated in membranous nephropathy. This is likely to be a direct response of GEC to complement attack and may represent a protective response of this cell.
Ren
Guohui
G
Section of Nephrology, The University of Chicago, Chicago, Illinois, USA.
Doshi
Mona
M
Hack
Bradley K
BK
Alexander
Jessy J
JJ
Quigg
Richard J
RJ
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003001:Cloning, Molecular; D003167:Complement Activation / Q000502:physiology*; D017242:Complement Factor H / Q000235:genetics / Q000378:metabolism*; D018076:DNA, Complementary / Q000235:genetics; D004847:Epithelial Cells / Q000378:metabolism; D007678:Kidney Glomerulus / Q000166:cytology / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D015854:Up-Regulation
D018076:DNA, Complementary; D012333:RNA, Messenger; D017242:Complement Factor H