title: Induction of Phosphoenolpyruvate Carboxykinase (PEPCK) during Acute Acidosis and Its Role in Acid Secretion by V-ATPase-Expressing Ionocytes.
abstract: Vacuolar-Type H(+)-ATPase (V-ATPase) takes the central role in pumping H(+) through cell membranes of diverse organisms, which is essential for surviving acid-base fluctuating lifestyles or environments. In mammals, although glucose is believed to be an important energy source to drive V-ATPase, and phosphoenolpyruvate carboxykinase (PEPCK), a key enzyme for gluconeogenesis, is known to be activated in response to acidosis, the link between acid secretion and PEPCK activation remains unclear. In the present study, we used zebrafish larva as an in vivo model to show the role of acid-inducible PEPCK activity in glucose production to support higher rate of H(+) secretion via V-ATPase, by utilizing gene knockdown, glucose supplementation, and non-invasive scanning ion-selective electrode technique (SIET). Zebrafish larvae increased V-ATPase-mediated acid secretion and transiently expression of Pck1, a zebrafish homolog of PEPCK, in response to acid stress. When pck1 gene was knocked down by specific morpholino, the H(+) secretion via V-ATPase decreased, but this effect was rescued by supplementation of glucose into the yolk. By assessing changes in amino acid content and gene expression of respective enzymes, glutamine and glutamate appeared to be the major source for replenishment of Krebs cycle intermediates, which are subtracted by Pck1 activity. Unexpectedly, pck1 knockdown did not affect glutamine/glutamate catalysis, which implies that Pck1 does not necessarily drive this process. The present study provides the first in vivo evidence that acid-induced PEPCK provides glucose for acid-base homeostasis at an individual level, which is supported by rapid pumping of H(+) via V-ATPase at the cellular level.
authors.affiliation: 1. Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, Taiwan ; 2. Department of Marine Biology and Environmental Sciences, Faculty of Agriculture, University of Miyazaki, Miyazaki, Japan.
authors.forename: Fumiya
authors.initials: F
authors.lastname: Furukawa
authors.affiliation: 3. Department of Life Science, National Taiwan Normal University, Taipei, Taiwan.
authors.forename: Yung-Che
authors.initials: YC
authors.lastname: Tseng
authors.affiliation: 3. Department of Life Science, National Taiwan Normal University, Taipei, Taiwan.
authors.forename: Sian-Tai
authors.initials: ST
authors.lastname: Liu
authors.affiliation: 1. Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, Taiwan.
authors.forename: Yi-Ling
authors.initials: YL
authors.lastname: Chou
authors.affiliation: 1. Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, Taiwan.
authors.forename: Ching-Chun
authors.initials: CC
authors.lastname: Lin
authors.affiliation: 4. Department of Life Science, National Taiwan University, Taipei, Taiwan.
authors.forename: Po-Hsuan
authors.initials: PH
authors.lastname: Sung
authors.affiliation: 2. Department of Marine Biology and Environmental Sciences, Faculty of Agriculture, University of Miyazaki, Miyazaki, Japan.
authors.forename: Katsuhisa
authors.initials: K
authors.lastname: Uchida
authors.affiliation: 3. Department of Life Science, National Taiwan Normal University, Taipei, Taiwan.
authors.forename: Li-Yih
authors.initials: LY
authors.lastname: Lin
authors.affiliation: 1. Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, Taiwan.
authors.forename: Pung-Pung
authors.initials: PP
authors.lastname: Hwang
mesh_terms: D000138:Acidosis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism; D064751:Ammonium Compounds / Q000378:metabolism; D000818:Animals; D002952:Citric Acid Cycle; D055785:Gene Knockdown Techniques; D005947:Glucose / Q000378:metabolism; D005969:Glutamate Dehydrogenase / Q000378:metabolism; D005972:Glutaminase / Q000378:metabolism; D008293:Malates / Q000378:metabolism; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011522:Protons; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D013312:Stress, Physiological; D025262:Vacuolar Proton-Translocating ATPases / Q000378:metabolism* / Q000502:physiology; D015027:Zebrafish / Q000235:genetics / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000378:metabolism* / Q000502:physiology
chemical_list: D000596:Amino Acids; D064751:Ammonium Compounds; D008293:Malates; D011522:Protons; D012333:RNA, Messenger; D029961:Zebrafish Proteins; C030298:malic acid; D005969:Glutamate Dehydrogenase; D005972:Glutaminase; D025262:Vacuolar Proton-Translocating ATPases; D019764:Phosphoenolpyruvate Carboxykinase (ATP); D005947:Glucose
keywords: Gluconeogenesis; PEPCK; V-ATPase; acid-base regulation; glutamine