Identification of a mechanism by which lens epithelial cells limit accumulation of overexpressed ferritin H-chain.

Abstract

The primary cultures of canine lens epithelial cells were transiently transfected with cDNAs for dog ferritin H- or L-chains in order to study differential expression of these chains. By using chain-specific antibodies, we determined that at 48 h after transfection overexpression of L-chain was much higher (9-fold over control) than that of H-chain (1.7-fold). We discovered that differentially transfected cells secrete overexpressed chains as homopolymeric ferritin into the media. Forty-eight hours after transfection accumulation of H-ferritin in the media was much higher (3-fold) than that of L-ferritin. This resulted in lowering of the concentration of H-chain in the cytosol. Co-transfection of cells with both H- and L-chain cDNAs increased the intracellular levels of H-chain and eliminated secretion of H-ferritin to the media. We concluded that lens epithelial cells differentially regulate concentration of both ferritin chains in the cytosol. The overexpressed L-chain accumulated in the cytosol as predominantly homopolymeric L-ferritin. This is in contrast to H-chain, which is removed to the media unless there is an L-chain available to form heteropolymeric ferritin. These data indicate that the inability of cells to more strictly control cytosolic levels of L-chain may augment its accumulation in lenses of humans with hereditary hyperferritinemia cataract syndrome, which is caused by overexpression of L-chain due to mutation in the regulatory element in the untranslated region of the mRNA of the chain.

• Authors: Malgorzata Goralska, Benjamin L Holley, M Christine McGahan
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 278 Issue 44 Pg. 42920-6 (Oct 31 2003) ISSN: 0021-9258 [Print] United States
• PMID: 12920121 (Publication Type: Journal Article)

Chemical References

• DNA, Complementary
• Peptides
• RNA, Messenger
• Recombinant Proteins
• Ferritins
• Apoferritins

Topics

• Animals
• Apoferritins
• Blotting, Western
• Cataract (metabolism)
• Cytosol (metabolism)
• DNA, Complementary (metabolism)
• Dogs
• Electrophoresis, Polyacrylamide Gel
• Epithelial Cells (metabolism)
• Eye Diseases, Hereditary (metabolism)
• Ferritins (biosynthesis, chemistry, metabolism)
• Humans
• Iron Metabolism Disorders
• Lens, Crystalline (metabolism)
• Mutation
• Peptides (chemistry)
• Plasmids (metabolism)
• Precipitin Tests
• RNA, Messenger (metabolism)
• Recombinant Proteins (metabolism)
• Time Factors
• Transfection