Functional analysis of the glucose transporters-1α, -6, and -13.1 expressed by zebrafish epithelial cells
Journal
American Journal of Physiology - Regulatory Integrative and Comparative Physiology
Journal Volume
300
Journal Issue
2
Date Issued
2011
Author(s)
Abstract
The hexose supply and subsequent metabolism are crucial for the operations of the iono- and osmoregulatory mechanisms in fish, but how hexose is transported and supplied to cells of the ionoregulatory epithelia is unknown. Three zebrafish glucose transporters (zGLUTs), zGLUT1a, -13.1, and -6, were previously found to respectively be expressed by ionocytes (Na +-K+-ATPase-rich, Na+-Cl- cotransporter-expressing, and H+-ATPase-rich cells) and adjacent energy-depositing cells [glycogen-rich (GR) cells] in zebrafish skin and gills (32). The present study aimed to test if the transport kinetics of these three zGLUTs differ, and if the transport functional differences are of physiological relevance to the respective functions of epithelial cells. The three zGLUTs expressed by Xenopus laevis oocytes revealed different D-glucose transport kinetics; zGLUT13.1 showed the lowest Michaelis constant (Km), whereas zGLUT6 had the highest Km and maximal velocity. In morpholino injection experiments, translational knockdown of zGLUT1a and -13.1, respectively, impaired Cl-/Ca2+ and Na+/Ca 2+ uptake, but loss-of-function of zGLUT6 did not cause a significant effect on ion uptake functions in zebrafish. Based on these results, zGLUT1a and -13.1 appear to be superior to zGLUT6 in competing for glucose under a situation of low blood glucose due to extensive energy consumption, whereas, in a high blood glucose situation, zGLUT6 is able to absorb the excess glucose for energy deposition. The timely and sufficient supply of energy to ionocytes so that they can carry out ion regulation is definitely a more important event than storing energy in GR cells, particularly when acute environmental change disturbs the ion balance in zebrafish. Copyright © 2011 the American Physiological Society.
Subjects
Energy; Glycogen-rich cell; Ion regulation; Ionocyte; Transport kinetics
SDGs
Other Subjects
calcium; chlorine; cytochalasin B; deoxyglucose; glucose transporter; glucose transporter 13.1; glucose transporter 1alpha; glucose transporter 6; sodium; unclassified drug; animal cell; animal experiment; article; calcium transport; concentration (parameters); controlled study; embryo; energy consumption; epithelium cell; female; glucose blood level; glucose transport; Michaelis constant; nonhuman; oocyte; priority journal; protein analysis; protein function; RNA translation; sodium transport; staining; Xenopus laevis; zebra fish; Animals; Biological Transport; Calcium; Chlorides; Cytochalasin B; Embryo, Nonmammalian; Epithelial Cells; Glucose; Glucose Transport Proteins, Facilitative; Kinetics; Oligonucleotides, Antisense; Oocytes; Recombinant Fusion Proteins; Sodium; Xenopus laevis; Zebrafish; Zebrafish Proteins
Type
journal article