title: Chaperone stress 70 protein (STCH) binds and regulates two acid/base transporters NBCe1-B and NHE1.
abstract: 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.
authors.affiliation: Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Seoul 110-749, Republic of Korea.
authors.forename: Jun-Seok
authors.initials: JS
authors.lastname: Bae
authors.forename: Na-Youn
authors.initials: NY
authors.lastname: Koo
authors.forename: Eun
authors.initials: E
authors.lastname: Namkoong
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Davies
authors.forename: Seul-Ki
authors.initials: SK
authors.lastname: Choi
authors.forename: Yonghwan
authors.initials: Y
authors.lastname: Shin
authors.forename: Meihong
authors.initials: M
authors.lastname: Jin
authors.forename: Sung-Min
authors.initials: SM
authors.lastname: Hwang
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Mikoshiba
authors.forename: Kyungpyo
authors.initials: K
authors.lastname: Park
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D017136:Ion Transport / Q000502:physiology; D011485:Protein Binding; D027982:Sodium-Bicarbonate Symporters / Q000235:genetics / Q000378:metabolism*; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D013312:Stress, Physiological / Q000502:physiology*; D014981:Xenopus
chemical_list: D027682:Cation Transport Proteins; D018840:HSP70 Heat-Shock Proteins; C086345:HSPA13 protein, human; C498898:SLC4A4 protein, human; C490998:SLC9A1 protein, human; D027982:Sodium-Bicarbonate Symporters; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers