Molecular cloning, sequencing, tissue distribution, and functional expression of a Na+/H+ exchanger (NHE-2).

Abstract

The present studies demonstrate cloning, sequencing, tissue distribution, and functional expression of a Na+/H+ exchanger which was isolated from a rat intestinal cDNA library. The cloned cDNA recognizes two transcripts in poly(A)+ RNA from the stomach, jejunum, ileum, liver, large intestine, and uterus. Based on deduced amino acid sequences, this clone shares sequence homology with the other known Na+/H+ exchanger isoforms (NHE-1, NHE-3, and NHE-4) except for its 5' end. Overall, the protein exhibits 47.8%, 41.2%, and 56.2% amino acid sequence identity to NHE-1, NHE-3, and NHE-4, respectively. The hydropathy profi'le of the predicted protein shows 10 transmembrane domains, suggesting a protein with transport characteristics. The tissue distribution differs from that of the other Na+/H+ exchanger isoforms. The cDNA hybridizes to two closely related transcripts in the mRNA of these tissues, which suggests that the predominant transcript of this clone is alternatively spliced. Transfection of this cDNA into Na+/H+ exchanger-deficient mutant fibroblasts (PS120 cells) results in functional Na+/H+ exchange activity. These data suggest that we have cloned a member of the Na+/H+ exchanger family with tissue-specific expression. We suggest the designation of NHE-2 for this

Subcloning, localization, and expression of the rat intestinal sodium-hydrogen exchanger isoform 8

“…The full-length rat NHE-8 cDNA was radiolabeled as the probe for NHE-8 mRNA detection. Northern blot analyses were performed under high-stringency washing conditions as described previously (8). 1B15 (encoding rat cyclophilin) cDNA (13) specific probes were used as internal standards for quantitating NHE-8 gene expression.…”

Regulation of intestinal NaPi-IIb cotransporter gene expression by estrogen

“…mRNA was isolated from rat jejunal mucosa using the Fast-Track mRNA purification kit (Invitrogen, Carlsbad, CA). mRNA (10 g) was used for Northern blot analyses with rat NaPi-IIb cDNA probes (31) under high-stringency washing conditions, as described previously (9). 1B15 (encoding rat cyclophilin; see Ref.…”

Na+/H+ Exchangers of Mammalian Cells

“…9). A variant rat NHE2 cDNA lacking the coding sequences for the N-terminal 116 amino acids was isolated and postulated to be derived from an alternatively spliced transcript (10). However, the possibility remains that this cDNA represents a partially processed RNA transcript retaining an intron sequence at its 5Ј end.…”