title: G-CSF improves murine G6PC3-deficient neutrophil function by modulating apoptosis and energy homeostasis.
abstract: G6PC3 (or glucose-6-phosphatase-β) deficiency underlies a congenital neutropenia syndrome in which neutrophils exhibit enhanced endoplasmic reticulum (ER) stress, increased apoptosis, impaired energy homeostasis, and impaired functionality. Here we show that murine G6pc3(-/-) neutrophils undergoing ER stress activate protein kinase-like ER kinase and phosphatidylinositol 3,4,5-trisphosphate/Akt signaling pathways, and that neutrophil apoptosis is mediated in part by the intrinsic mitochondrial pathway. In G6PC3-deficient patients, granulocyte colony-stimulating factor (G-CSF) improves neutropenia, but its impact on neutrophil apoptosis and dysfunction is unknown. We now show that G-CSF delays neutrophil apoptosis in vitro by modulating apoptotic mediators. However, G6pc3(-/-) neutrophils in culture exhibit accelerated apoptosis compared with wild-type neutrophils both in the presence or absence of G-CSF. Limiting glucose (0.6mM) accelerates apoptosis but is more pronounced for wild-type neutrophils, leading to similar survival profiles for both neutrophil populations. In vivo G-CSF therapy completely corrects neutropenia and normalizes levels of p-Akt, phosphatidylinositol 3,4,5-trisphosphate, and active caspase-3. Neutrophils from in vivo G-CSF-treated G6pc3(-/-) mice exhibit increased glucose uptake and elevated intracellular levels of G6P, lactate, and adenosine-5'-triphosphate, leading to improved functionality. Together, the results strongly suggest that G-CSF improves G6pc3(-/-) neutrophil survival by modulating apoptotic mediators and rectifies function by enhancing energy homeostasis.
authors.affiliation: Section on Cellular Differentiation, Program in Developmental Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 10 Center Drive, Bethesda, MD 20892, USA.
authors.forename: Hyun Sik
authors.initials: HS
authors.lastname: Jun
authors.forename: Young Mok
authors.initials: YM
authors.lastname: Lee
authors.forename: Ki Duk
authors.initials: KD
authors.lastname: Song
authors.forename: Brian C
authors.initials: BC
authors.lastname: Mansfield
authors.forename: Janice Y
authors.initials: JY
authors.lastname: Chou
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D002478:Cells, Cultured; D004353:Drug Evaluation, Preclinical; D004734:Energy Metabolism / Q000187:drug effects* / Q000235:genetics; D005952:Glucose-6-Phosphatase / Q000235:genetics* / Q000502:physiology; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology*; D006706:Homeostasis / Q000187:drug effects / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009504:Neutrophils / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D021122:Protein Subunits; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D019892:eIF-2 Kinase / Q000378:metabolism / Q000502:physiology
chemical_list: D005952:Glucose-6-Phosphatase; D016179:Granulocyte Colony-Stimulating Factor; D018129:Phosphatidylinositol Phosphates; D021122:Protein Subunits; D051057:Proto-Oncogene Proteins c-akt; D019892:eIF-2 Kinase; C060974:phosphatidylinositol 3,4,5-triphosphate; C519262:glucose-6-phosphatase-beta, mouse