Squalamine, a novel cationic steroid, specifically inhibits the brush- border NA+/H+ exchanger isoform NHE3

S. Akhter, S. K. Nath, G. M. Tse, J. Williams, M. Zasloff, M. Donowitz

Research output: Contribution to journalArticle

Abstract

Squalamine, an endogenous molecule found in the liver and other tissues of Squalus acanthias, has antibiotic properties and causes changes in endothelial cell shape. The latter suggested that its potential targets might include transport proteins that control cell volume or cell shape. The effect of purified squalamine was examined on cloned Na+/H+ exchanger isoforms NHE1, NHE2, and NHE3 stably transfected in PS120 fibroblasts. Squalamine (1- h pretreatment) decreased the maximal velocity of rabbit NHE3 in a concentration-dependent manner (13, 47, and 57% inhibition with 3, 5, and 7 μg/ml, respectively) and also increased K'[H+](i). Squalamine did not affect rabbit NHE1 or NHE2 function. The inhibitory effect of squalamine was 1) time dependent, with no effect of immediate addition and maximum effect with 1 h of exposure, and 2) fully reversible. Squalamine pretreatment of the ileum for 60 min inhibited brush-border membrane vesicle Na+/H+ activity by 51%. Further investigation into the mechanism of squalamine's effects showed that squalamine required the COOH-terminal 76 amino acids of NHE3. Squalamine had no cytotoxic effect at the concentrations studied, as indicated by monitoring lactate dehydrogenase release. These results indicate that squalamine 1) is a specific inhibitor of the brush-border NHE isoform NHE3 and not NHE1 or NHE2, 2) acts in a nontoxic and fully reversible manner, and 3) has a delayed effect, indicating that it may influence brush-border Na+/H+ exchanger function indirectly, through an intracellular signaling pathway or by acting as an intracellular modulator.

Original languageEnglish (US)
Pages (from-to)C136-C144
JournalAmerican Journal of Physiology - Cell Physiology
Volume276
Issue number1 45-1
DOIs
StatePublished - 1999

Keywords

  • Intestinal brush border
  • Sodium absorption

ASJC Scopus subject areas

  • Physiology
  • Cell Biology

Fingerprint Dive into the research topics of 'Squalamine, a novel cationic steroid, specifically inhibits the brush- border NA<sup>+</sup>/H<sup>+</sup> exchanger isoform NHE3'. Together they form a unique fingerprint.

Cite this