CXCL4L1 and CXCL4 signaling in human lymphatic and microvascular endothelial cells and activated lymphocytes: involvement of mitogen-activated protein (MAP) kinases, Src and p70S6 kinase.
CXC chemokines influence a variety of biological processes, such as angiogenesis, both in a physiological and pathological context. Platelet factor-4 (PF-4)/CXCL4 and its variant PF-4var/CXCL4L1 are known to favor angiostasis by inhibiting endothelial cell proliferation and chemotaxis. CXCL4L1 in particular is a potent inhibitor of angiogenesis with anti-tumoral characteristics, both through regulation of neovascularization and through attraction of activated lymphocytes. However, its underlying signaling pathways remain to be elucidated. Here, we have identified various intracellular pathways activated by CXCL4L1 in comparison with other CXCR3 ligands, including CXCL4 and interferon-γ-induced protein 10/CXCL10. Signaling experiments show involvement of the mitogen-activated protein kinase (MAPK) family in CXCR3A-transfected cells, activated lymphocytes and human microvascular endothelial cells (HMVEC). In CXCR3A transfectants, CXCL4 and CXCL4L1 activated p38 MAPK, as well as Src kinase within 30 and 5 min, respectively. Extracellular signal-regulated kinase (ERK) phosphorylation occurred in activated lymphocytes, yet was inhibited in microvascular and lymphatic endothelial cells. CXCL4L1 and CXCL4 counterbalanced the angiogenic chemokine stromal cell-derived factor-1/CXCL12 in both endothelial cell types. Notably, inhibition of ERK signaling by CXCL4L1 and CXCL4 in lymphatic endothelial cells implies that these chemokines might also regulate lymphangiogenesis. Furthermore, CXCL4, CXCL4L1 and CXCL10 slightly enhanced forskolin-stimulated cAMP production in HMVEC. Finally, CXCL4, but not CXCL4L1, induced activation of p70S6 kinase within 5 min in HMVEC. Our findings confirm that the angiostatic chemokines CXCL4L1 and CXCL4 activate both CXCR3A and CXCR3B and bring new insights into the complexity of their signaling cascades.
Laboratory of Molecular Immunology, KU Leuven - University of Leuven, Department of Microbiology and Immunology, Rega Institute for Medical Research, Minderbroedersstraat 10, 3000, Leuven, Belgium.
Katrien
K
Van Raemdonck
Mieke
M
Gouwy
Stefanie Antoinette
SA
Lepers
Jo
J
Van Damme
Sofie
S
Struyf
D000262:Adenylyl Cyclases / Q000378:metabolism; D002460:Cell Line; D054377:Chemokine CXCL12; D042783:Endothelial Cells / Q000201:enzymology / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D042601:Lymphatic Vessels / Q000166:cytology*; D008213:Lymphocyte Activation; D008214:Lymphocytes / Q000166:cytology / Q000201:enzymology*; D055806:Microvessels / Q000166:cytology*; D010766:Phosphorylation; D010978:Platelet Factor 4 / Q000378:metabolism*; D054367:Receptors, CXCR3 / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D015398:Signal Transduction; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism
D054377:Chemokine CXCL12; C064936:PF4V1 protein, human; D054367:Receptors, CXCR3; D010978:Platelet Factor 4; D019061:src-Family Kinases; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D048049:Extracellular Signal-Regulated MAP Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D000262:Adenylyl Cyclases