Glucokinase regulatory protein is essential for the proper subcellular localisation of liver glucokinase

Iglesia, Núria de la; Veiga‐da‐Cunha, Maria; Schaftingen, Emile Van; Guinovart, Joan J.; Ferrer, Juan C.

doi:10.1016/s0014-5793(99)00971-0

Cited by 86 publications

(91 citation statements)

References 26 publications

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“…It was reported that the allosteric effectors of GKRP such as F1P and F6P bind GKRP and alter the interaction between GK and GKRP and eventually the GK activity (11,14,16). As xGKRP has been shown to be insensitive to the binding of F6P and F1P (24), we used hGKRP to investigate the molecular mechanism by which effectors of GKRP modulate the GK activity.…”

Section: Resultsmentioning

confidence: 99%

“…GKRP is known to be located mainly in hepatocytes with an excess ratio to GK, regulating the allosteric GK in response to glucose concentration (12,14,15). To get some insight into the physiological implications for the role of GKRP, we attempted to investigate the regulatory features of GKRP.…”

Section: Resultsmentioning

confidence: 99%

“…In hepatocytes, GK is regulated by GK regulatory protein (GKRP) that is located mainly in hepatocytes with an excess ratio to GK (11,12). GKRP allosterically regulates the activity and subcellular localization of GK (13,14). GKRP inhibits and sequesters GK into the nucleus of hepatocytes and releases GK into the cytoplasm in response to glucose concentration (13)(14)(15).…”

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confidence: 99%

“…GKRP allosterically regulates the activity and subcellular localization of GK (13,14). GKRP inhibits and sequesters GK into the nucleus of hepatocytes and releases GK into the cytoplasm in response to glucose concentration (13)(14)(15). GK is also indirectly regulated by allosteric effectors of GKRP, such as fructose-1-phosphate (F1P) and fructose-6-phosphate (F6P) (11,16).…”

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confidence: 99%

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Molecular basis for the role of glucokinase regulatory protein as the allosteric switch for glucokinase

Choi¹,

Seo²,

Kyeong³

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Glucokinase (GK) is a monomeric allosteric enzyme and plays a pivotal role in blood glucose homeostasis. GK is regulated by GK regulatory protein (GKRP), and indirectly by allosteric effectors of GKRP. Despite the critical roles of GK and GKRP, the molecular basis for the allosteric regulation mechanism of GK by GKRP remains unclear. We determined the crystal structure of Xenopus GK and GKRP complex in the presence of fructose-6-phosphate at 2.9 Å. GKRP binds to a super-open conformation of GK mainly through hydrophobic interaction, inhibiting the GK activity by locking a small domain of GK. We demonstrate the molecular mechanism for the modulation of GK activity by allosteric effectors of GKRP. Importantly, GKRP releases GK in a sigmoidal manner in response to glucose concentration by restricting a structural rearrangement of the GK small domain via a single ion pair. We find that GKRP acts as an allosteric switch for GK in blood glucose control by the liver.hexokinase | sigmoidicity I conformational restriction | type 2 diabetes

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Molecular basis for the role of glucokinase regulatory protein as the allosteric switch for glucokinase

Choi¹,

Seo²,

Kyeong³

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…Immunostaining-Cells cultured on 13-mm coverslips were washed in PBS, fixed in 4% paraformaldehyde in PBS (30 min), and washed in PBS (11). They were incubated with NaBH 4 (1 mg/ml, 10 min) and then permeabilized in 0.2% (v/v) Triton X-100 in PBS and blocked with 1% bovine serum albumin/0.02% Triton X-100/PBS.…”

Section: Methodsmentioning

confidence: 99%

The Role of the Regulatory Protein of Glucokinase in the Glucose Sensory Mechanism of the Hepatocyte

Iglesia¹,

Mukhtar²,

Seoane³

et al. 2000

Journal of Biological Chemistry

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112

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Glucokinase has a very high flux control coefficient (greater than unity) on glycogen synthesis from glucose in hepatocytes (Agius et al., J. Biol. Chem. 271, 30479 -30486, 1996). Hepatic glucokinase is inhibited by a 68-kDa glucokinase regulatory protein (GKRP) that is expressed in molar excess. To establish the relative control exerted by glucokinase and GKRP, we applied metabolic control analysis to determine the flux control coefficient of GKRP on glucose metabolism in hepatocytes. Adenovirus-mediated overexpression of GKRP (by up to 2-fold above endogenous levels) increased glucokinase binding and inhibited glucose phosphorylation, glycolysis, and glycogen synthesis over a wide range of concentrations of glucose and sorbitol. It decreased the affinity of glucokinase translocation for glucose and increased the control coefficient of glucokinase on glycogen synthesis. GKRP had a negative control coefficient of glycogen synthesis that is slightly greater than unity (؊1.2) and a control coefficient on glycolysis of ؊0.5. The control coefficient of GKRP on glycogen synthesis decreased with increasing glucokinase overexpression (4-fold) at elevated glucose concentration (35 mM), which favors dissociation of glucokinase from GKRP, but not at 7.5 mM glucose. Under the latter conditions, glucokinase and GKRP have large and inverse control coefficients on glycogen synthesis, suggesting that a large component of the positive control coefficient of glucokinase is counterbalanced by the negative coefficient of GKRP. It is concluded that glucokinase and GKRP exert reciprocal control; therefore, mutations in GKRP affecting the expression or function of the protein may impact the phenotype even in the heterozygote state, similar to glucokinase mutations in maturity onset diabetes of the young type 2. Our results show that the mechanism comprising glucokinase and GKRP confers a markedly extended responsiveness and sensitivity to changes in glucose concentration on the hepatocyte.Glucokinase (hexokinase IV) is the predominant glucose phosphorylating enzyme in hepatocytes and insulin-secreting and glucagon-secreting cells of the pancreas and has a major role in the control of blood glucose homeostasis (1, 2). Its importance has been confirmed by the finding that mutations in its gene cause a form of diabetes known as maturity onset diabetes of the young type 2 (MODY-2), 1 which is characterized by mild hyperglycemia, decreased glucose-induced insulin secretion, impaired hepatic glycogen storage, and dominant inheritance (3), and by studies on hepatic glucokinase knockout mice (4). Hepatic glucokinase is Regulated by a 68-kDa regulatory protein (GKRP) (5, 6). Expression of GKRP during development precedes expression of glucokinase (7), and no physiological situations are known in which hepatic glucokinase is expressed in the absence of its regulatory protein. GKRP is located mainly in the nucleus of hepatocytes, whereas glucokinase translocates between the nucleus and the cytoplasm (8). Glucokinase binds GKRP in the nucleus at...

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Subcellular localization of aldolase B

S�ez

Slebe

2000

J. Cell. Biochem.

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The localization of the aldolase B isozyme was determined immunohistochemically in rat kidney and liver using a polyclonal antibody. Aldolase B was preferentially localized in a nuclear region of hepatocytes from the periportal region and was absent in those from the perivenous region. Aldolase B was also preferentially localized in the proximal tubules and was absent in other structures of the renal cortex as well as in the renal medulla. Using reflection confocal microscopy, the enzyme was preferentially localized in a nuclear position in liver and renal cells, which was similar to the cellular and intracellular location found for the gluconeogenic enzyme fructose‐1,6‐bisphosphatase (Sáez et al. [1996] J. Cell. Biochem. 63:453–462). Subcellular fractionation studies followed by enzyme activity assays revealed that aldolase activity was associated with subcellular particulate structures. Overall, the data suggest that different aldolase isoenzymes are needed in the glycolytic and gluconeogenic pathways. J. Cell. Biochem. 78:62–72, 2000. © 2000 Wiley‐Liss, Inc.

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Glucokinase regulatory protein is essential for the proper subcellular localisation of liver glucokinase

Cited by 86 publications

References 26 publications

Molecular basis for the role of glucokinase regulatory protein as the allosteric switch for glucokinase

Molecular basis for the role of glucokinase regulatory protein as the allosteric switch for glucokinase

The Role of the Regulatory Protein of Glucokinase in the Glucose Sensory Mechanism of the Hepatocyte

Subcellular localization of aldolase B

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