Cellular distribution and regulation of NHE-1 isoform of the Na-H exchanger in the avian osteoclast

A. Gupta, J. C. Edwards, Keith A. Hruska

Research output: Contribution to journalArticle

32 Scopus citations

Abstract

The sodium-hydrogen exchanger (NHE) has been implicated in bone resorption by osteoclasts. We have studied expression of NHE-1, an isoform of the NHE, in chicken bone marrow mononuclear phagocyte precursors during differentiation into the osteoclast phenotype in culture. A monoclonal antibody raised against the carboxy-terminus of NHE-1 detected the presence of a ~100 kDa protein (similar to the mammalian form of NHE-1) in the osteoclasts. Laser scanning confocal microscopy revealed association with the α(v)β3 integrin and focal adhesion kinase (pp125FAK) at the basolateral membrane (BLM) of the osteoclast in addition to a more generalized cellular distribution. A fragment of avian NHE-1 cDNA was obtained by polymerase chain reaction cloning, and it was used to characterize expression of NHE-1 transcripts in cultured chicken osteoclast precursors. The avian NHE-1 message was a 3.9 kB band on Northern analysis, which differed from the mammalian message. Retinoic acid (RA) elicited an increase in the steady-state intracellular pH (pH(i)) from 6.87 to 7.10 in the absence of bicarbonate and was inhibited by ethylisopropylamiloride, an inhibitor of Na-H exchange. Using ribonuclease protection assays, we found that NHE-1 transcripts are induced as cells differentiate in vitro and in response to 13-cis-RA. Western blot analysis indicated that protein levels also increased in response to 13-cis-RA. Our results demonstrate expression of NHE-1 in avian osteoclasts with a complex cellular distribution in culture, and NHE-1 expression is induced as cells differentiate into mature osteoclasts in response to 13-cis-RA.

Original languageEnglish
Pages (from-to)87-95
Number of pages9
JournalBone
Volume18
Issue number2
DOIs
StatePublished - Feb 1996

Keywords

  • Confocal microscopy
  • Focal adhesion
  • Integrin
  • Na-H exchanger
  • Osteoclast
  • Vitronectin receptor

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