Alternative titles; symbols
HGNC Approved Gene Symbol: NHERF2
Cytogenetic location: 16p13.3 Genomic coordinates (GRCh38) : 16:2,026,902-2,039,026 (from NCBI)
NHE3 (SLC9A3; 182307) is a sodium/hydrogen exchanger in the brush border membrane of the proximal tubule, small intestine, and colon that plays a major role in transepithelial sodium absorption. SLC9A3R2, as well as SLC9A3R1 (604990) and protein kinase A phosphorylation, may play a role in NHE3 regulation.
Using a yeast 2-hybrid screen of a HeLa cell cDNA library with SRY (480000) as bait, Poulat et al. (1997) obtained a cDNA encoding SLC9A3R2, which they termed SIP1. The deduced 326-amino acid protein contains 2 highly conserved PDZ domains. Northern blot analysis revealed wide expression of SLC9A3R2, suggesting a function not restricted to the sex-determination process. Western blot analysis showed expression of a 34-kD protein. Binding and mutational analyses confirmed the interaction of the PDZ domains of SLC9A3R2 with the C terminus of SRY. Immunofluorescence microscopy demonstrated nuclear expression of SLC9A3R2.
By means of a yeast 2-hybrid screen of a lung fibroblast cDNA library with the cytoplasmic tail of NHE3 as bait, Yun et al. (1997) isolated a cDNA encoding SLC9A3R2, which they designated E3KARP. Sequence analysis predicted that the 337-amino acid protein is 55% identical to SLC9A3R1 (Reczek et al., 1997). Yun et al. (1997) concluded that either E3KARP or EBP50 (SLC9A3R1) is necessary for the cAMP-dependent inhibition of NHE3.
Hall et al. (1998) determined that the DS/TxL motif at the cytoplasmic tail of the beta-2 adrenergic receptor (ADRB2; 109690), P2Y1 (601167), and CFTR (602421) is necessary for interaction with the first PDZ domain of NHERF (SLC9A3R1) and NHERF2. They suggested that the presence of this motif at the C terminus of a variety of proteins is a useful indicator of potential NHERF binding to intracellular proteins.
Yun et al. (1998) showed that a central domain of NHE3, not a C-terminal domain, interacts with NHERF2 through its second PDZ domain plus its C terminus. Confocal microscopy demonstrated predominantly cytosolic expression of NHERF2 in the absence of NHE3, with more plasma membrane expression in the presence of NHE3. Gel overlay analysis showed that, as seen with NHERF, the N terminus of ezrin (VIL2; 123900) interacts with the C-terminal residues of NHERF2.
Mahon et al. (2002) demonstrated that parathyroid hormone receptor-1 (PTHR1; 168468) binds to the sodium/hydrogen exchanger regulatory factors NHERF1 (604990) and NHERF2 through a PDZ-domain interaction in vitro and in PTH target cells. NHERF2 simultaneously binds phospholipase C-beta-1 and an atypical, carboxyl-terminal PDZ consensus motif, ETVM, of the PTHR1 through PDZ1 and PDZ2, respectively. PTH treatment of cells that express the NHERF2-PTH1R complex markedly activated phospholipase C-beta and inhibits adenylylcyclase through stimulation of inhibitory G proteins (see 139310). NHERF-mediated assembly of PTHR1 and phospholipase C-beta is a unique mechanism to regulate PTH signaling in cells and membranes of polarized cells that express NHERF, which may account for many tissue- and cell-specific actions of PTH/PTH-related protein (168470) and may also be relevant to signaling by many G protein-coupled receptors.
By yeast 2-hybrid analysis of a human brain cDNA expression library, DeMarco et al. (2002) found that PCMA2b (108733) interacted with NHERF2. Coimmunoprecipitation analysis indicated that the interaction was specific and selective, in that PCMA4b (108732) did not interact with either NHERF2 or NHERF1, and PCMA2b preferred NHERF2 over NHERF1. Fluorescence-tagged PCMA2b was expressed at the apical membrane of canine kidney epithelial cells, where it colocalized with apically targeted NHERF2. DeMarco et al. (2002) hypothesized that the PCMA2b-NHERF2 interaction may allow the assembly of PMCA2b in a multiprotein Ca(2+) signaling complex.
Using yeast 2-hybrid analysis of a rat glomerular cDNA library, Takeda et al. (2001) found that the PDZ-binding motif in the cytoplasmic C-terminal tail of rat podocalyxin (PODXL; 602632) bound the second PDZ domain of Nherf2. Immunocytochemical analysis colocalized Nherf2 with podocalyxin and ezrin along the apical domain of the glomerular epithelial cell membrane. Coimmunoprecipitation analysis showed that Nherf2 and ezrin formed a multimeric complex with podocalyxin. The complex interacted with the actin cytoskeleton, and this interaction was disrupted in glomerular epithelial cells from rats treated with agents that cause loss of foot processes. Takeda et al. (2001) concluded that NHERF2 functions as a scaffold protein linking podocalyxin to ezrin and the actin cytoskeleton.
By sequence analysis of the 3-prime-flanking sequence of the NTHL1 gene (602656), Imai et al. (1998) mapped the SLC9A3R2 gene to an adjacent region on chromosome 16p13.3.
DeMarco, S. J., Chicka, M. C., Strehler, E. E. Plasma membrane Ca(2+) ATPase isoform 2b interacts preferentially with Na+/H+ exchanger regulatory factor 2 in apical plasma membranes. J. Biol. Chem. 277: 10506-10511, 2002. [PubMed: 11786550] [Full Text: https://doi.org/10.1074/jbc.M111616200]
Hall, R. A., Ostedgaard, L. S., Premont, R. T., Blitzer, J. T., Rahman, N., Welsh, M. J., Lefkowitz, R. J. A C-terminal motif found in the beta-2-adrenergic receptor, P2Y1 receptor and cystic fibrosis transmembrane conductance regulator determines binding to the Na(+)/H(+) exchanger regulatory factor family of PDZ proteins. Proc. Nat. Acad. Sci. 95: 8496-8501, 1998. [PubMed: 9671706] [Full Text: https://doi.org/10.1073/pnas.95.15.8496]
Imai, K., Sarker, A. H., Akiyama, K., Ikeda, S., Yao, M., Tsutsui, K., Shohmori, T., Seki, S. Genomic structure and sequence of a human homologue (NTHL1/NTH1) of Escherichia coli endonuclease III with those of the adjacent parts of TSC2 and SLC9A3R2 genes. Gene 222: 287-295, 1998. [PubMed: 9831664] [Full Text: https://doi.org/10.1016/s0378-1119(98)00485-5]
Mahon, M. J., Donowitz, M., Yun, C. C., Segre, G. V. Na+/H+ exchanger regulatory factor 2 directs parathyroid hormone 1 receptor signalling. Nature 417: 858-861, 2002. [PubMed: 12075354] [Full Text: https://doi.org/10.1038/nature00816]
Poulat, F., de Santa Barbara, P., Desclozeaux, M., Soullier, S., Moniot, B., Bonneaud, N., Boizet, B., Berta, P. The human testis determining factor SRY binds a nuclear factor containing PDZ protein interaction domains. J. Biol. Chem. 272: 7167-7172, 1997. [PubMed: 9054412] [Full Text: https://doi.org/10.1074/jbc.272.11.7167]
Reczek, D., Berryman, M., Bretscher, A. Identification of EBP50: a PDZ-containing phosphoprotein that associates with members of the ezrin-radixin-moesin family. J. Cell Biol. 139: 169-179, 1997. [PubMed: 9314537] [Full Text: https://doi.org/10.1083/jcb.139.1.169]
Takeda, T., McQuistan, T., Orlando, R. A., Farquhar, M. G. Loss of glomerular foot processes is associated with uncoupling of podocalyxin from the actin cytoskeleton. J. Clin. Invest. 108: 289-301, 2001. [PubMed: 11457882] [Full Text: https://doi.org/10.1172/JCI12539]
Yun, C.-H. C., Lamprecht, G., Forster, D. V., Sidor, A. NHE3 kinase A regulatory protein E3KARP binds the epithelial brush border Na(+)/H(+) exchanger NHE3 and the cytoskeletal protein ezrin. J. Biol. Chem. 273: 25856-25863, 1998. [PubMed: 9748260] [Full Text: https://doi.org/10.1074/jbc.273.40.25856]
Yun, C. H. C., Oh, S., Zizak, M., Steplock, D., Tsao, S., Tse, C.-M., Weinman, E. J., Donowitz, M. cAMP-mediated inhibition of the epithelial brush border Na(+)/H(+) exchanger, NHE3, requires an associated regulatory protein. Proc. Nat. Acad. Sci. 94: 3010-3015, 1997. Note: Erratum: Proc. Nat. Acad. Sci. 94: 10006 only, 1997. [PubMed: 9096337] [Full Text: https://doi.org/10.1073/pnas.94.7.3010]