Involvement of Niemann-Pick type C2 protein in hematopoiesis regulation.
Niemann-Pick type C2 (NPC2) protein has been characterized as a cholesterol-binding protein. Its loss leads to NPC2 disease, an inherited neurodegenerative disorder. When analyzing gene expression profile, we noticed high expression of both NPC2 and its receptor, mannose 6-phosphate receptor (MPR), in murine hematopoietic stem cells. NPC2 protein, in the presence of thrombopoietin (TPO), causes an increase in CFU-GEMM (colony-forming unit-granulocyte-erythroid-macrophage-megakaryocyte) and a decrease in CFU-GM (colony-forming unit-granulocyte-macrophage) colony number in colony-forming cell (CFC) assays. This effect is independent of cholesterol binding but does require the presence of MPR. With M07e cells, a TPO-dependent hematopoietic leukemia cell line, NPC2 can inhibit TPO-induced differentiation and enhance TPO-mediated anti-apoptosis effects. Strikingly, these results are not observed under the standard 20% O(2) level of the standard incubator, but rather at 7% O(2), the physiological oxygen level of bone marrow. Furthermore, NPC2 protein upregulates hypoxia inducible factor 1-alpha protein level at 7% O(2), but not at 20% O(2). Our results demonstrate that NPC2 protein plays a role in hematopoiesis at the physiologic bone marrow level of O(2).
Heo
Kyu
K
Department of Biochemistry and Molecular Biology, University of Southern California, Keck School of Medicine, Los Angeles, 90033, USA.
Jariwala
Unnati
U
Woo
Jeongim
J
Zhan
Yuxia
Y
Burke
Kathleen A
KA
Zhu
Lunjian
L
Anderson
W French
WF
Zhao
Yi
Y
D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation; D002460:Cell Line; D002470:Cell Survival; D002784:Cholesterol / Q000378:metabolism; D003114:Colony-Forming Units Assay; D018076:DNA, Complementary / Q000235:genetics; D015870:Gene Expression; D006410:Hematopoiesis / Q000235:genetics / Q000502:physiology*; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009154:Mutation; D010100:Oxygen / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017527:Receptor, IGF Type 2 / Q000235:genetics / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism*
D018076:DNA, Complementary; C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C497045:Npc2 protein, mouse; D012333:RNA, Messenger; D017527:Receptor, IGF Type 2; D033921:Vesicular Transport Proteins; D002784:Cholesterol; D010100:Oxygen