Neutrophil stress and apoptosis underlie myeloid dysfunction in glycogen storage disease type Ib.
Glycogen storage disease type Ib (GSD-Ib) is caused by a deficiency in the glucose-6-phosphate (G6P) transporter (G6PT) that works with a liver/kidney/intestine-restricted glucose-6-phosphatase-alpha (G6Pase-alpha) to maintain glucose homeostasis between meals. Clinically, GSD-Ib patients manifest disturbed glucose homeostasis and neutrophil dysfunctions but the cause of the latter is unclear. Neutrophils express the ubiquitously expressed G6PT and G6Pase-beta that together transport G6P into the endoplasmic reticulum (ER) lumen and hydrolyze it to glucose. Because we expected G6PT-deficient neutrophils to be unable to produce endogenous glucose, we hypothesized this would lead to ER stress and increased apoptosis. Using GSD-Ib mice, we showed that GSD-Ib neutrophils exhibited increased production of ER chaperones and oxidative stress, consistent with ER stress, increased annexin V binding and caspase-3 activation, consistent with an increased rate of apoptosis. Bax activation, mitochondrial release of proapoptotic effectors, and caspase-9 activation demonstrated the involvement of the intrinsic mitochondrial pathway in these processes. The results demonstrate that G6P translocation and hydrolysis are required for normal neutrophil functions and support the hypothesis that neutrophil dysfunction in GSD-Ib is due, at least in part, to ER stress and increased apoptosis.
Kim
So Youn
SY
Section on Cellular Differentiation, Heritable Disorders Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892-1830, USA.
Jun
Hyun Sik
HS
Mead
Paul A
PA
Mansfield
Brian C
BC
Chou
Janice Y
JY
D000818:Animals; D017920:Antiporters / Q000235:genetics / Q000378:metabolism; D017209:Apoptosis / Q000502:physiology*; D053453:Caspase 9 / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000473:pathology; D005947:Glucose / Q000378:metabolism; D019298:Glucose-6-Phosphate / Q000378:metabolism; D005953:Glycogen Storage Disease Type I / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D008817:Mice, Mutant Strains; D008928:Mitochondria / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000235:genetics / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism* / Q000473:pathology*; D018384:Oxidative Stress / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism
D017920:Antiporters; C494827:Bax protein, mouse; D009004:Monosaccharide Transport Proteins; D017382:Reactive Oxygen Species; D051028:bcl-2-Associated X Protein; C111261:glucose 6-phosphate(transporter); D019298:Glucose-6-Phosphate; D053453:Caspase 9; D005947:Glucose