title: Role of Sodium Bicarbonate Cotransporters in Intracellular pH Regulation and Their Regulatory Mechanisms in Human Submandibular Glands.
abstract: Sodium bicarbonate cotransporters (NBCs) are involved in the pH regulation of salivary glands. However, the roles and regulatory mechanisms among different NBC isotypes have not been rigorously evaluated. We investigated the roles of two different types of NBCs, electroneutral (NBCn1) and electrogenic NBC (NBCe1), with respect to pH regulation and regulatory mechanisms using human submandibular glands (hSMGs) and HSG cells. Intracellular pH (pHi) was measured and the pHi recovery rate from cell acidification induced by an NH4Cl pulse was recorded. Subcellular localization and protein phosphorylation were determined using immunohistochemistry and co-immunoprecipitation techniques. We determined that NBCn1 is expressed on the basolateral side of acinar cells and the apical side of duct cells, while NBCe1 is exclusively expressed on the apical membrane of duct cells. The pHi recovery rate in hSMG acinar cells, which only express NBCn1, was not affected by pre-incubation with 5 μM PP2, an Src tyrosine kinase inhibitor. However, in HSG cells, which express both NBCe1 and NBCn1, the pHi recovery rate was inhibited by PP2. The apparent difference in regulatory mechanisms for NBCn1 and NBCe1 was evaluated by artificial overexpression of NBCn1 or NBCe1 in HSG cells, which revealed that the pHi recovery rate was only inhibited by PP2 in cells overexpressing NBCe1. Furthermore, only NBCe1 was significantly phosphorylated and translocated by NH4Cl, which was inhibited by PP2. Our results suggest that both NBCn1 and NBCe1 play a role in pHi regulation in hSMG acinar cells, and also that Src kinase does not regulate the activity of NBCn1.
authors.affiliation: Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Seoul, 110-749, Korea.
authors.forename: Eun
authors.initials: E
authors.lastname: Namkoong
authors.affiliation: Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Seoul, 110-749, Korea.
authors.forename: Yong-Hwan
authors.initials: YH
authors.lastname: Shin
authors.affiliation: Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Seoul, 110-749, Korea.
authors.forename: Jun-Seok
authors.initials: JS
authors.lastname: Bae
authors.affiliation: Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Seoul, 110-749, Korea.
authors.forename: Seulki
authors.initials: S
authors.lastname: Choi
authors.affiliation: Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Seoul, 110-749, Korea.
authors.forename: Minkyoung
authors.initials: M
authors.lastname: Kim
authors.affiliation: Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Seoul, 110-749, Korea.
authors.forename: Nahyun
authors.initials: N
authors.lastname: Kim
authors.affiliation: Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Seoul, 110-749, Korea.
authors.forename: Sung-Min
authors.initials: SM
authors.lastname: Hwang
authors.affiliation: Department of Physiology, School of Dentistry, Seoul National University and Dental Research Institute, Seoul, 110-749, Korea.
authors.forename: Kyungpyo
authors.initials: K
authors.lastname: Park
mesh_terms: D001639:Bicarbonates / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D009062:Mouth Neoplasms / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D027982:Sodium-Bicarbonate Symporters / Q000235:genetics / Q000378:metabolism*; D013363:Submandibular Gland / Q000378:metabolism* / Q000473:pathology; D014443:Tyrosine / Q000378:metabolism
chemical_list: D001639:Bicarbonates; D012333:RNA, Messenger; C498898:SLC4A4 protein, human; C422022:SLC4A7 protein, human; D027982:Sodium-Bicarbonate Symporters; D014443:Tyrosine