Acute inducible ablation of GRP78 reveals its role in hematopoietic stem cell survival, lymphogenesis and regulation of stress signaling.
GRP78, a master regulator of the unfolded protein response (UPR) and cell signaling, is required for inner cell mass survival during early embryonic development. However, little is known about its role in adult hematopoietic stem cells (HSCs) and hematopoiesis. Here we generated a conditional knockout mouse model that acutely deletes Grp78 in the adult hematopoietic system. Acute GRP78 ablation resulted in a significant reduction of HSCs, common lymphoid and myeloid progenitors, and lymphoid cell populations in the mutant mice. The GRP78-null induced reduction of the HSC pool could be attributed to increased apoptosis. Chimeric mice with Grp78 deletion only in the hematopoietic cells also showed a loss of HSCs and lymphopenia, suggesting a cell intrinsic effect. Analysis of GRP78 deficient bone marrow (BM) cells showed constitutive activation of all the major UPR signaling pathways, including activation of eIF2α, ATF6, xbp-1 splicing, as well as caspase activation. A multiplex cytokine assay further revealed alteration in select cytokine and chemokine serum levels in the mutant mice. Collectively, these studies demonstrate that GRP78 plays a pleiotropic role in BM cells and contributes to HSC survival and the maintenance of the lymphoid lineage.
Department of Biochemistry and Molecular Biology, University of Southern California Keck School of Medicine, University of Southern California Norris Comprehensive Cancer Center, Los Angeles, California, USA.
Shiuan
S
Wey
Biquan
B
Luo
Amy S
AS
Lee
D000818:Animals; D017209:Apoptosis / Q000235:genetics; D001854:Bone Marrow Cells / Q000378:metabolism; D002470:Cell Survival / Q000235:genetics; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D017353:Gene Deletion; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins / Q000172:deficiency / Q000235:genetics*; D006410:Hematopoiesis / Q000235:genetics*; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D054503:Lymphoid Progenitor Cells / Q000378:metabolism*; D008231:Lymphopenia / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D008954:Models, Biological; D015398:Signal Transduction; D013312:Stress, Physiological; D056811:Unfolded Protein Response / Q000235:genetics
D016207:Cytokines; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse