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XB-ART-46518
J Biol Chem 2013 Mar 01;2889:6295-305. doi: 10.1074/jbc.M112.392001.
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Chaperone stress 70 protein (STCH) binds and regulates two acid/base transporters NBCe1-B and NHE1.

Bae JS, Koo NY, Namkoong E, Davies AJ, Choi SK, Shin Y, Jin M, Hwang SM, Mikoshiba K, Park K.


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Regulation of intracellular pH is critical for the maintenance of cell homeostasis in response to stress. We used yeast two-hybrid screening to identify novel interacting partners of the pH-regulating transporter NBCe1-B. We identified Hsp70-like stress 70 protein chaperone (STCH) as interacting with NBCe1-B at the N-terminal (amino acids 96-440) region. Co-injection of STCH and NBCe1-B cRNA into Xenopus oocytes significantly increased surface expression of NBCe1-B and enhanced bicarbonate conductance compared with NBCe1-B cRNA alone. STCH siRNA decreased the rate of Na(+)-dependent pHi recovery from NH4(+) pulse-induced acidification in an HSG (human submandibular gland ductal) cell line. We observed that in addition to NBCe1-B, Na(+)/H(+) exchanger (NHE)-dependent pHi recovery was also impaired by STCH siRNA and further confirmed the interaction of STCH with NHE1 but not plasma membrane Ca(2+) ATPase. Both NBCe1-B and NHE1 interactions were dependent on a specific 45-amino acid region of STCH. In conclusion, we identify a novel role of STCH in the regulation of pHi through site-specific interactions with NBCe1-B and NHE1 and subsequent modulation of membrane transporter expression. We propose STCH may play a role in pHi regulation at times of cellular stress by enhancing the recovery from intracellular acidification.

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Species referenced: Xenopus
Genes referenced: hsp70 hspa1l slc4a4

References [+] :
Aoki, A genetic variant in the gene encoding the stress70 protein chaperone family member STCH is associated with gastric cancer in the Japanese population. 2005, Pubmed