Oxalate-inducible AMBP gene and its regulatory mechanism in renal tubular epithelial cells

Jasjit S. Grewal, Jeng Y. Tsai, Saeed R. Khan

Research output: Contribution to journalArticle

Abstract

The AMBP [A1M (γ1-microglobulin)/bikunin precursor] gene encodes two plasma glycoproteins: A1M, an immunosuppressive lipocalin, and bikunin, a member of plasma serine proteinase inhibitor family with prototypical Kunitz-type domain. Although previously believed to be constitutively expressed exclusively in liver, the present study demonstrates the induction of this gene by oxalate in porcine proximal tubular LLC-PK1 cells and rat kidney. In liver, the precursor protein is cleaved in the Golgi network by a furin-like enzyme to release constituent proteins, which undergo glycosylation before their export from the cell. In the renal tubular cells, A1M and bikunin co-precipitate, indicating lack of cleavage of the precursor protein. As the expression of the AMBP gene is regulated by A1M-specific cis elements and transcription factors, A1M protein was studied as a representative of AMBP gene expression in renal cells. Oxalate treatment (500 μM) resulted in a time- and dose-dependent induction of A1M protein in LLC-PK1 cells. Of the four transcription factors, HNF-4 (hepatocyte nuclear factor-4) has been reported previously to be a major regulator of AMBP gene expression in liver. Electrophoretic mobility-shift assay, supershift assay, immunoreactivity assay and transfection-based studies showed the presence of an HNF-4 or an HNF-4-like protein in the kidney, which can affect the expression of the AMBP gene. In situ hybridization and immunocytochemical studies showed that the expression of this gene in kidney was mainly restricted to cells lining the renal tubular system.

Original languageEnglish (US)
Pages (from-to)609-616
Number of pages8
JournalBiochemical Journal
Volume387
Issue number3
DOIs
StatePublished - May 1 2005
Externally publishedYes

Fingerprint

Oxalates
Regulator Genes
Hepatocyte Nuclear Factor 4
Genes
Epithelial Cells
Kidney
Liver
Gene Expression
Assays
Protein Precursors
LLC-PK1 Cells
Gene expression
Proteins
Transcription Factors
Furin
Glycosylation
Lipocalins
Plasmas
Electrophoretic mobility
Serine Proteinase Inhibitors

Keywords

  • α-microglobulin/bikunin precursor gene
  • Immunocytochemistry
  • LLC-PK cells
  • Oxalate
  • Renal tubular epithelial cells
  • Transcription factor hepatocyte nuclear factor-4 (HNF-4)

ASJC Scopus subject areas

  • Biochemistry

Cite this

Oxalate-inducible AMBP gene and its regulatory mechanism in renal tubular epithelial cells. / Grewal, Jasjit S.; Tsai, Jeng Y.; Khan, Saeed R.

In: Biochemical Journal, Vol. 387, No. 3, 01.05.2005, p. 609-616.

Research output: Contribution to journalArticle

Grewal, Jasjit S. ; Tsai, Jeng Y. ; Khan, Saeed R. / Oxalate-inducible AMBP gene and its regulatory mechanism in renal tubular epithelial cells. In: Biochemical Journal. 2005 ; Vol. 387, No. 3. pp. 609-616.
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