A syndecan-4/CXCR4 complex expressed on human primary lymphocytes and macrophages and HeLa cell line binds the CXC chemokine stromal cell-derived factor-1 (SDF-1).
The stromal cell-derived factor-1 (SDF-1) is a CXC chemokine, which plays critical roles in migration, proliferation, and differentiation of leukocytes. SDF-1 is the only known ligand of CXCR4, the coreceptor of X4 HIV strains. We show that SDF-1 binds to high- and low-affinity sites on HeLa cells. Coimmunoprecipitation studies demonstrate that glycanated and oligomerized syndecan-4 but neither syndecan-1, syndecan-2, betaglycan, nor CD44 forms complexes with SDF-1 and CXCR4 on these cells as well as on primary lymphocytes or macrophages. Moreover, biotinylated SDF-1 directly binds in a glycosaminoglycans (GAGs)-dependent manner to electroblotted syndecan-4, and colocalization of SDF-1 with syndecan-4 was visualized by confocal microscopy. Glycosaminidases pretreatment of the HeLa cells or the macrophages decreases the binding of syndecan-4 to the complex formed by it and SDF-1. In addition, this treatment also decreases the binding of the chemokine to CXCR4 on the primary macrophages but not on the HeLa cells. Therefore GAGs-dependent binding of SDF-1 to the cells facilitates SDF-1 binding to CXCR4 on primary macrophages but not on HeLa cell line. Finally, an SDF-1-independent heteromeric complex between syndecan-4 and CXCR4 was visualized on HeLa cells by confocal microscopy as well as by electron microscopy. Moreover, syndecan-4 from lymphocytes, monocyte derived-macrophages, and HeLa cells coimmunoprecipitated with CXCR4. This syndecan-4/CXCR4 complex is likely a functional unit involved in SDF-1 binding. The role of these interactions in the pathophysiology of SDF-1 deserves further study.
Hamon
Morgan
M
Laboratoire de Biologie Cellulaire, Biothérapies Bénéfices et Risques, UPRES 3410, and Hôpital Jean Verdier, 93, Bondy, France.
Mbemba
Elisabeth
E
Charnaux
Nathalie
N
Slimani
Hocine
H
Brule
Séverine
S
Saffar
Line
L
Vassy
Roger
R
Prost
Catherine
C
Lievre
Nicole
N
Starzec
Anna
A
Gattegno
Liliane
L
D054377:Chemokine CXCL12; D019743:Chemokines, CXC / Q000378:metabolism*; D005453:Fluorescence; D015870:Gene Expression; D006367:HeLa Cells; D006801:Humans; D008214:Lymphocytes / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000378:metabolism; D011485:Protein Binding; D011509:Proteoglycans / Q000096:biosynthesis / Q000378:metabolism*; D019718:Receptors, CXCR4 / Q000378:metabolism*; D053671:Syndecan-4
C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D019743:Chemokines, CXC; D008562:Membrane Glycoproteins; D046912:Multiprotein Complexes; D011509:Proteoglycans; D019718:Receptors, CXCR4; C508304:SDC4 protein, human; D053671:Syndecan-4