Novel functional interaction between Na⁺/H⁺exchanger 1 and tyrosine phosphatase SHP-2

Abstract

Besides being a intracellular pH (pHi) regulator, Na+/H+ exchanger (NHE)1 has recently been postulated as a membrane scaffold that assembles protein complexes and coordinates various signaling pathways. The aim of the present study was to uncover NHE1 interactive partners and study their functional implications. NHE1 interactive partners were screened in the mouse brain with a signal transduction AntibodyArray. Ten of 400 tested proteins appeared to be potentially associated with NHE1. These partners have been shown to be involved in either cell proliferative or apoptotic pathways. The interactions between NHE1 and Src homology 2 domain-containing protein tyrosine phosphatase (SHP-2), Bin1, and heat shock protein (HSP)70 were reciprocally confirmed by coimmunoprecipitation. Moreover, in vitro binding data have shown that NHE1 COOH terminus interacts directly with SHP-2. The functional significance of the association between NHE1 and SHP-2 was further investigated by measuring pHi, cell proliferation, and cell death with the fluorescent dye BCECF, [3H]thymidine incorporation, and medium lactate dehydrogenase activity, respectively. Our results revealed that cells with SHP-2 overexpression exhibited a higher steady-state pHi and a faster, NHE1-dependent pHi recovery rate from acid load in HEPES buffer. In addition, SHP-2 overexpression diminished the HOE-642-induced inhibition of cell proliferation and protected cells from hypoxic injury, especially in the presence of HOE-642. Together, our findings demonstrate that SHP-2 not only is physically associated with NHE1 but also modulates NHE1 functions such as pHi regulation, cell proliferation, and cell death under hypoxia.

Chaperone Stress 70 Protein (STCH) Binds and Regulates Two Acid/Base Transporters NBCe1-B and NHE1 *

“…There are two previous reports of NHE1 interacting with heat shock protein 70 (27,28). Although Hsp70 does not include the same region of STCH (aa 314 -359), it does possess several partner proteins with which it functions in the cell.…”

An Inhibitor of Na+/H+Exchanger (NHE), Ethyl-Isopropyl Amiloride (EIPA), Diminishes Proliferation of MKN28 Human Gastric Cancer Cells by Decreasing the Cytosolic Cl-Concentration via DIDS-Sensitive Pathways

“…NHE family, which is ubiquitously expressed in most cells, is a major regulator of pH c , and 10 isoforms of NHEs have been identified [10,11]. NHE1 is the most ubiquitously expressed one among 10 isoforms, and its activity is regulated by numerous growth factors, mitogens, integlins, tyrosine phosphatases and cytokines [12][13][14][15][16][17][18]. NHE in tumor cells is a key transporter to maintain pH c at a normal level [19], and regulation of NHE activity is one of the most important factors for proliferation and migration of many tumor cells [20][21][22].…”

Insulin inhibits Na+/H+exchange in vascular smooth muscle and endothelial cells in situ: involvement of H2O2and tyrosine phosphatase SHP-2

“…The actions of H 2 O 2 are widespread, but one important action appears to be the inhibition of protein tyrosine phosphatases (PTPs) through stepwise oxidation of a critical cysteine residue at the catalytic site (18). PTPs make up a large family of enzymes involved in many cellular signaling pathways, and a recent study suggests that PTPs also affect the regulation of pH i (37). The Src homology 2 domain containing tyrosine phosphatase 2 (SHP-2) was shown to interact physically with NHE1, and overexpression of SHP-2 in BAF3 cells resulted in increased NHE activity (37).…”

“…PTPs make up a large family of enzymes involved in many cellular signaling pathways, and a recent study suggests that PTPs also affect the regulation of pH i (37). The Src homology 2 domain containing tyrosine phosphatase 2 (SHP-2) was shown to interact physically with NHE1, and overexpression of SHP-2 in BAF3 cells resulted in increased NHE activity (37). SHP-2 expression has previously been found to be abundant in VSMCs (3) and ECs (23).…”