Rat Glomerular Epithelial Cells Produce and Bear Factor H on Their Surface That Is Up-Regulated Under Complement Attack

Kidney Int. 2003 Sep;64(3):914-22. doi: 10.1046/j.1523-1755.2003.00188.x.

Abstract

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.

Conclusion: 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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cell Membrane / metabolism
  • Cells, Cultured
  • Cloning, Molecular
  • Complement Activation / physiology*
  • Complement Factor H / genetics
  • Complement Factor H / metabolism*
  • DNA, Complementary / genetics
  • Epithelial Cells / metabolism
  • Kidney Glomerulus / cytology
  • Kidney Glomerulus / metabolism*
  • RNA, Messenger / metabolism
  • Rats
  • Up-Regulation

Substances

  • DNA, Complementary
  • RNA, Messenger
  • Complement Factor H