Abstract
The glucose-6-phosphatase (G6Pase) system participates in the regulation of glucose
homeostasis by converting glucose-6-phosphate (G6P) into glucose and inorganic phosphates.
We have used an RT-PCR-based cloning and sequencing approach to study the expression
of components of the G6Pase system in the hypothalamus and cortex tissues of the ob/ob
mouse. We observed the expression of hepatic G6Pase catalytic subunit, G6PC, in both
tissues, although increased template inputs were required for its detection. Conversely,
expression of both the mouse homologue of the previously-described brain-specific
G6P translocase T1 (G6PT1) variant and of the hepatic G6PT1 isoform was easily detectable
in hypothalamus and cortex tissues. Of the proposed G6Pase catalytic subunit homologues,
the expression of murine ubiquitous G6Pase catalytic subunit-related protein (UGRP,
G6PC3) was also easily detectable in both tissues. However, islet-specific G6Pase
catalytic subunit-related protein (IGRP, G6PC2) was expressed in a tissue-specific
manner, and was detectable only in hypothalamus tissue at increased template inputs.
We conclude that cells within ob/ob mouse hypothalamus and cortex tissues express
genes with either established or proposed roles in G6P hydrolysis.
Key words
Cortex - G6PC - G6PC2 - G6PC3 - G6PT1 - glucose-6-phosphate - ob/ob
References
- 1 Nordlie R C.
Glucose-6-Phosphatase-Phosphotransferase: Roles and Regulation in Relation to Gluconeogenesis. In: Hanson RW, Mehlman MA (eds) Gluconeogenesis: its regulation in mammalian species. New
York; John Wiley & Sons Inc 1976: 93-152
- 2
van de Werve G, Lange A, Newgard C, Méchin M-C, Li Y, Berteloot A.
New lessons in the regulation of glucose metabolism taught by the glucose-6-phosphatase
system.
Eur J Biochem.
2000;
267
1533-1549
- 3
Shelly L L, Lei K-J, Pan C-J, Sakata S F, Ruppert S, Schultz G, Chou J Y.
Isolation of the gene for murine glucose-6-phosphatase, the enzyme deficient in glycogen
storage disease type 1a.
J Biol Chem.
1993;
268
21 482-21 485
- 4
Gerin I, Veiga-da-Cunha M, Achouri Y, Collet J F, van Schaftingen E.
Sequence of a putative glucose-6-phosphate translocase, mutated in glycogen storage
disease type 1b.
FEBS Lett.
1997;
419
235-238
- 5
Ashmore J, Hastings A B, Nesbett F B.
The effect of diabetes and fasting on liver glucose-6-phosphatase.
Proc Natl Acad Sci USA.
1954;
40
673-678
- 6
Segal H L, Washko M E.
Studies of liver glucose-6-phosphatase. III. Solubilization and properties of the
enzyme from normal and diabetic rats.
J Biol Chem.
1959;
234
1937-1941
- 7
Liu Z Q, Barrett E J, Dalkin A C, Zwart A D, Chou J Y.
Effect of acute diabetes on rat hepatic glucose-6-phosphatase activity and its messenger
RNA level.
Biochem Biophys Res Commun.
1994;
205
680-686
- 8
Massillon D, Barzilai N, Chen W, Hu M, Rossetti L.
Glucose regulates in vivo glucose-6-phosphatase gene expression in the liver of diabetic rats.
J Biol Chem.
1996;
271
9871-9874
- 9
Li Y, Méchin M-C, van de Werve G.
Diabetes affects similarly the catalytic subunit and putative glucose-6-phosphate
translocase of glucose-6-phosphatase.
J Biol Chem.
1999;
274
33 866-33 868
- 10
Arden S D, Zahn T, Steegers S, Webb S, Bergman B, O’Brien R M, Hutton J C.
Molecular cloning of a pancreatic islet-specific glucose-6-phosphatase catalytic subunit-related
protein.
Diabetes.
1999;
48
531-542
- 11
Martin C C, Oeser J K, Svitek C A, Hunter S I, Hutton J C, O’Brien R M.
Identification and characterization of a human cDNA and gene encoding a ubiquitously
expressed glucose-6-phosphatase catalytic subunit-related protein.
J Mol Endocrinol.
2002;
29
205-222
- 12
Petrolonis A J, Yang Q, Tummino P J, Fish S M, Prack A E, Jain S, Parsons T F, Li P,
Dales N A, Ge L, Langston S P, Schuller A G, An W F, Tartaglia L A, Chen H, Hong S B.
Enzymatic characterization of the pancreatic islet-specific glucose-6-phosphatase-related
protein (IGRP).
J Biol Chem.
2004;
279
13 976-13 983
- 13
Guionie O, Clottes E, Stafford K, Burchell A.
Identification and characterization of a new human glucose-6-phosphatase isoform.
FEBS Lett.
2003;
551
159-164
- 14
Boustead J N, Martin C C, Oeser J K, Svitek C A, Hunter S I, Hutton J C, O’Brien R M.
Identification and characterization of a cDNA and the gene encoding the mouse ubiquitously
expressed glucose-6-phosphatase catalytic subunit-related protein.
J Mol Endocrinol.
2004;
32
33-53
- 15
Shieh J J, Pan C J, Mansfield B C, Chou J Y.
A glucose-6-phosphate hydrolase, widely expressed outside the liver, can explain age-dependent
resolution of hypoglycemia in glycogen storage disease type Ia.
J Biol Chem.
2003;
278
47 098-47 103
- 16
Lin B, Annabi B, Hiraiwa H, Pan C-J, Chou J Y.
Cloning and characterization of cDNAs encoding a candidate glycogen storage disease
type 1b protein in rodents.
J Biol Chem.
1998;
273
31 656-31 660
- 17
Lin B, Pan C-J, Chou J-Y.
Human variant glucose-6-phosphate transporter is active in microsomal transport.
Hum Genet.
2000;
107
526-529
- 18
Martin C C, Bischof L J, Bergman B, Hornbuckle L A, Hilliker C, Frigeri C, Wahl D,
Svitek C A, Wong R, Goldman J K, Oeser J K, Lepetre F, Froguel P, O’Brien R M, Hutton J C.
Cloning and characterization of the human and rat islet-specific glucose-6-phosphatase
catalytic subunit-related protein (IGRP) genes.
J Biol Chem.
2001;
276
25 197-25 207
- 19
Rajas F, Bruni N, Montano S, Zitoun A, Mithieux G.
The glucose-6 Phosphatase Gene Is Expressed in Human and Rat Small Intestine: Regulation
of Expression in Fasted and Diabetic Rats.
Gastroenterology.
1999;
117
132-139
- 20
Goh B-H, Efendić S, Khan A, Portwood N.
Evidence for the expression of both the hydrolase and translocase components of hepatic
glucose-6-phosphatase in murine pancreatic islets.
Biochem Biophys Res Comm.
2003;
307
935-941
- 21
Colilla W, Jorgenson R A, Nordlie R C.
Mammalian Carbamyl Phosphate: Glucose Phosphotransferase and Glucose-6-phosphate Phosphohydrolase:
Extended Tissue Distribution.
Biochim Biophys Acta.
1975;
377
117-125
- 22
Huang M-T, Veech R L.
The Quantitative Determination of the in vivo Dephosphorylation of Glucose 6-Phosphate
in Rat Brain.
J Biol Chem.
1982;
257
11 358-11 363
- 23
Khan A, Zong-Chao L, Efendić S, Landau B R.
Glucose-6-Phosphatase Activity in the Hypothalamus of the ob/ob Mouse.
Metab Clin Exp.
1998;
47
627-629
- 24
Zhang Y, Proenca R, Maffei M, Barone M, Leopold L, Friedman J M.
Positional cloning of the mouse obese gene and its human homologue.
Nature.
1994;
372
425-432
- 25
Schwartz M W, Seeley R J, Campfield L A, Burn P, Baskin D G.
Identification of Targets of Leptin Action in Rat Hypothalamus.
J Clin Invest.
1996;
98
1101-1106
- 26
Wynne K, Stanley S, McGowan B, Bloom S.
Appetite control.
J Endocrinol.
2005;
184
291-318
- 27 Slotnick B M, Leonard C M. A Stereotaxic Atlas of the Albino Mouse Forebrain. Rockville,
MD; US Department of Health, Education, and Welfare, Alcohol, Drug Abuse and Mental
Health Administration 1975
- 28
Tadros H, Chrétien M, Mbikay M.
The testicular germ-cell protease PC4 is also expressed in macrophage-like cells of
the ovary.
J Reprod Immunol.
2001;
49
133-152
- 29
Middleditch C, Clottes E, Burchell A.
A different isoform of the transport protein mutated in glycogen storage disease 1b
is expressed in brain.
FEBS Lett.
1998;
433
33-36
- 30
Forsyth R J, Bartlett K, Burchell A, Scott H M, Eyre J A.
Astrocytic glucose-6-phosphatase and the permeability of brain microsomes to glucose
6-phosphate.
Biochem J.
1993;
294
145-151
- 31
Anuradha B, Varalakshmi P.
Activities of Glucose-metabolizing Enzymes in Experimental Neurotoxic Models with
Lipoate as an Alleviator.
J Appl Toxicol.
1999;
19
405-409
- 32
Ghosh A, Cheung Y Y, Mansfield B C, Chou J Y.
Brain Contains a Functional Glucose-6-Phosphatase Complex Capable of Endogenous Glucose
Production.
J Biol Chem.
2005;
280
11 114-11 119
- 33 Palkovits M.
Micro- and Macroscopic Structure, Innervation, and Vasculature of the Hypothalamus. In: Conn PM, Freeman ME (eds) Neuroendocrinology in Physiology and Medicine. New
Jersey; Humana Press Inc 2000: 23-40
Neil Portwood
The Rolf Luft Center for Diabetes Research · Department of Molecular Medicine and
Surgery · Karolinska Institute
SE-171 76 · Stockholm · Sweden ·
Telefon: +46 (8) 517 73398/+46 (8) 517 79459
Fax: +46 (8) 517 73658
eMail: Neil.Portwood@molmed.ki.se