CXCR4-mediated bone marrow progenitor cell maintenance and mobilization are modulated by c-kit activity.
BACKGROUND
The mobilization of bone marrow (BM) progenitor cells (PCs) is largely governed by interactions between stromal cell-derived factor (SDF)-1 and CXC chemokine receptor (CXCR)4. Ischemic injury disrupts the SDF-1-CXCR4 interaction and releases BM PCs into the peripheral circulation, where the mobilized cells are recruited to the injured tissue and contribute to vessel growth. BM PCs can also be mobilized by the pharmacological CXCR4 antagonist AMD3100, but the other components of the SDF-1-CXCR4 signaling pathway are largely unknown. c-kit, a membrane-bound tyrosine kinase and the receptor for stem cell factor, has also been shown to play a critical role in BM PC mobilization and ischemic tissue repair.


OBJECTIVE
To investigate the functional interaction between SDF-1-CXCR4 signaling and c-kit activity in BM PC mobilization.


RESULTS
AMD3100 administration failed to mobilize BM PCs in mice defective in c-kit kinase activity or in mice transplanted with BM cells that expressed a constitutively active c-kit mutant. Furthermore, BM levels of phosphorylated (phospho)-c-kit declined after AMD3100 administration and after CXCR4 deletion. In cells adhering to culture plates coated with vascular cell adhesion molecule 1, SDF-1 and stem cell factor increased phospho-c-kit levels, and AMD3100 treatment suppressed SDF-1-induced, but not SCF-induced, c-kit phosphorylation. SDF-1-induced c-kit phosphorylation also required the activation of Src nonreceptor tyrosine kinase: pretreatment of cells with a selective Src inhibitor blocked both c-kit phosphorylation and the interaction between c-kit and phospho-Src.


CONCLUSIONS
These findings indicate that the regulation of BM PC trafficking by SDF-1 and CXCR4 is dependent on Src-mediated c-kit phosphorylation.
Cheng
Min
M
Feinberg Cardiovascular Research Institute, Northwestern University Feinberg School of Medicine, 303 E Chicago Avenue, Chicago, IL 60611, USA.
Zhou
Junlan
J
Wu
Min
M
Boriboun
Chan
C
Thorne
Tina
T
Liu
Ting
T
Xiang
Zhifu
Z
Zeng
Qiutang
Q
Tanaka
Toshikazu
T
Tang
Yao Liang
YL
Kishore
Raj
R
Tomasson
Michael H
MH
Miller
Richard J
RJ
Losordo
Douglas W
DW
Qin
Gangjian
G
D000818:Animals; D001596:Benzylamines; D001854:Bone Marrow Cells / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D002460:Cell Line; D002465:Cell Movement / Q000235:genetics / Q000502:physiology*; D054377:Chemokine CXCL12 / Q000502:physiology; D000080027:Cyclams; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D006571:Heterocyclic Compounds / Q000494:pharmacology; D006801:Humans; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D019009:Proto-Oncogene Proteins c-kit / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D019718:Receptors, CXCR4 / Q000172:deficiency / Q000235:genetics / Q000502:physiology*; D013234:Stem Cells / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D019061:src-Family Kinases / Q000502:physiology
D001596:Benzylamines; C514936:CXCR4 protein, mouse; D054377:Chemokine CXCL12; C515256:Cxcl12 protein, mouse; D000080027:Cyclams; D006571:Heterocyclic Compounds; D019718:Receptors, CXCR4; D019009:Proto-Oncogene Proteins c-kit; D019061:src-Family Kinases; C088327:plerixafor