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Na+/H+ exchangers (NHEs) of mammalian cells are plasma membrane intrinsic proteins mediating exchange of N+ and H+ ions in various tissues. The NHE catalyzes the electroneural transport of extracellular Na+ for intracellular H+. They play a major role in regulation of intracellular pH (pHi) in addition to trans-cellular absorption of Na+, cell volume regulation and possibly in cell proliferation. These primary functions of the Na+/H+ exchanger have been related to many pathophysiological states, include hypertension, organ growth and hypertrophy, regression of cancer and renal intestinal disorders.

At least seven NHE isoforms have been cloned to date and functionally expressed with a length ranging from 669-898 amino acids with 10-12 putative transmembrane domains. They are all similar in their primary structure and the predicted secondary structure. They are predicted to have two structurally and functionally distinct domains: an NT-domain, consisting of 10-12 putative transmembrane alpha helix, and a long cytoplasmic COOH-terminal domain. There are no known homologies with other exchanger or coo-transporters. Antibody studies have suggested that the COOH-terminals of NHE1, NHE2 and NHE3 are intracellular. The N-terminus and the first TM domain are predicted to be signal peptides cleaved off in the intact proteins. The cytoplasmic domains show 20-30% homology.

NHE1 (rat/mouse; 820 aa) is 'House Keeper' and is expressed ubiquitously in all tissues. It is implicated in pH homeostasis, volume regulation, and probably cell proliferation. It is expressed on basolateral surface of several epithelia. NHE2 (rat 813 aa) has been implicated in volume regulation in renal inner medullary collecting duct cells. Its mRNA is found in kidney medulla, cortex, colon, jejunum, ileum, human jejunum, ileum, duodenum, stomach and adrenal glands. NHE3 (rat, 831aa) is involved in trans-epithelial Na+ absorption. The NHE3 mRNA is found in kidney cortex, medulla, jejunum, ileum, colon and stomach.

NHE4 (rat, 717aa) expression is most abundant in rat stomach followed by colon and intestine, and in low levels in rat kidney, uterus, and brain. Its expression correlates with regions of high tissue osmolarity. NHE5 is expressed in human brain, testis, spleen and skeletal muscle. Its involved in pH regulation to eliminate acids generated by active metabolism. It's a major proton extruding system driven by the inward sodium ion chemical gradient. ADI has produced rabbit-anti NHEs using specific peptide sequences. These antigenic peptides have no significant homology between each other or with other proteins. The appropriate control immunogenic peptides are also available to confirm specificity of antibodies.

Mammalian homolog of yeast NHA2 has been identified and classified as NHE6 (KIAA0267). NHE6 is 669 aa (mol wt ~75 kDa), and predicted to contain 12 TM domains within the cytoplasmic N-terminus; the C-terminus may reside in the matrix. NHE6 is ubiquitously expressed but it is most abundant in mitochondrial-rich tissues such as brain, skeletal muscle, and heart.

NHE7 (human 725 aa, chromosome Xp11.4) is ubiquitously expressed, and predominantly localizes to the trans-golgi network. NHE7 mediates the influx of Na+ or K+ in exchange for H+. It is ~70% related to NHE6 but relatively less (~25%) homolohgous with other NHEs.

ADI has produced rabbit-anti NHEs using specific peptide sequences. These antigenic peptides have no significant homology between each other or with other proteins. The appropriate control immunogenic peptides are also available to confirm specificity of antibodies.

m=mouse; r=rat; h=human; b=bovine; d=dog; ~CT or ~NT=near C or N-terminus. EC=Extracellular; CP=Cytoplasmic domain; Control peptides (unconjugated, free, antigenic peptides), because of their small size, are not recommended for Western. They should be used in ELISA/antibody blocking studies.

* Expected antibody crossreactivity information is mostly based upon high (>70%) sequence conservation of antigenic/control peptides in various species. When antibody crossreactivity has actually been experimentally confirmed in various species, it will be mentioned in the appropriate data sheets.

"Neat Antisera or antisera" are the unpurified antiserum and it is suitable for ELISA and Western.
"Affinity pure" IgG may be more suitable for immunohistochemical (IHC) applications and to reduce background in most immunological applications including ELISA and Western.
"Control peptides" can not be used for Western as they are very short peptides. They are intended for ELISA or antibody blocking studies to establish antibody specificity.
Western blot +ve protein controls, where available, are semi-pure, pure or recombinant proteins that are formulated in SDS-PAGE sample buffer. They are recommended to be used for Western (load 10 ul/lane) for visulaization with antibodies.

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