Incorporation of CXCR4 into membrane lipid rafts primes homing-related responses of hematopoietic stem/progenitor cells to an SDF-1 gradient.
We found that supernatants of leukapheresis products (SLPs) of patients mobilized with granulocyte-colony-stimulating factor (G-CSF) or the various components of SLPs (fibrinogen, fibronectin, soluble vascular cell adhesion molecule-1 [VCAM-1], intercellular adhesion molecule-1 [ICAM-1], and urokinase plasminogen activator receptor [uPAR]) increase the chemotactic responses of hematopoietic stem/progenitor cells (HSPCs) to stromal-derived factor-1 (SDF-1). However, alone they do not chemoattract HSPCs, but they do increase or prime the cells' chemotactic responses to a low or threshold dose of SDF-1. We observed that SLPs increased calcium flux, phosphorylation of mitogen-activated protein kinase (MAPK) p42/44 and AKT, secretion of matrix metalloproteinases, and adhesion to endothelium in CD34+ cells. Furthermore, SLPs increased SDF-dependent actin polymerization and significantly enhanced the homing of human cord blood (CB)- and bone marrow (BM)-derived CD34+ cells in a NOD/SCID mouse transplantation model. Moreover, the sensitization or priming of cell chemotaxis to an SDF-1 gradient was dependent on cholesterol content in the cell membrane and on the incorporation of the SDF-1 binding receptor CXCR4 and the small GTPase Rac-1 into membrane lipid rafts. This colocalization of CXCR4 and Rac-1 in lipid rafts facilitated guanosine triphosphate (GTP) binding/activation of Rac-1. Hence, we postulate that CXCR4 could be primed by various factors related to leukapheresis and mobilization that increase its association with membrane lipid rafts, allowing the HSPCs to better sense the SDF-1 gradient. This may partially explain why HSPCs from mobilized peripheral blood leukapheresis products engraft more quickly in patients than do those from BM or CB. Based on our findings, we suggest that the homing of HSPCs is optimal when CXCR4 is incorporated in membrane lipid rafts and that ex vivo priming of HSPCs with some of the SLP-related molecules before transplantation could increase their engraftment.
Stem Cell Biology Program, James Graham Brown Cancer Center, University of Louisville, KY 40202, USA.
Marcin
M
Wysoczynski
Ryan
R
Reca
Janina
J
Ratajczak
Magda
M
Kucia
Neeta
N
Shirvaikar
Marek
M
Honczarenko
Michael
M
Mills
Jens
J
Wanzeck
Anna
A
Janowska-Wieczorek
Mariusz Z
MZ
Ratajczak
D000199:Actins / Q000378:metabolism; D000818:Animals; D018952:Antigens, CD34 / Q000378:metabolism; D001853:Bone Marrow / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002448:Cell Adhesion; D002478:Cells, Cultured; D054377:Chemokine CXCL12; D019743:Chemokines, CXC / Q000494:pharmacology*; D002633:Chemotaxis / Q000187:drug effects*; D003094:Collagen; D004338:Drug Combinations; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007797:Laminin; D007937:Leukapheresis; D020782:Matrix Metalloproteinases / Q000378:metabolism; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011509:Proteoglycans; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D019718:Receptors, CXCR4 / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
D000199:Actins; D018952:Antigens, CD34; C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D019743:Chemokines, CXC; C515256:Cxcl12 protein, mouse; D004338:Drug Combinations; D007797:Laminin; D011509:Proteoglycans; D011518:Proto-Oncogene Proteins; D019718:Receptors, CXCR4; C059485:matrigel; D003094:Collagen; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020782:Matrix Metalloproteinases; D020830:rac1 GTP-Binding Protein; D002118:Calcium