Ezrin-radixin-moesin-binding sequence of PSGL-1 glycoprotein regulates leukocyte rolling on selectins and activation of extracellular signal-regulated kinases.
P-selectin glycoprotein ligand-1 (PSGL-1) mediates the capture (tethering) of free-flowing leukocytes and subsequent rolling on selectins. PSGL-1 interactions with endothelial selectins activate Src kinases and spleen tyrosine kinase (Syk), leading to α(L)β(2) integrin-dependent leukocyte slow rolling, which promotes leukocyte recruitment into tissues. In addition, but through a distinct pathway, PSGL-1 engagement activates ERK. Because ezrin, radixin and moesin proteins (ERMs) link PSGL-1 to actin cytoskeleton and because they serve as adaptor molecules between PSGL-1 and Syk, we examined the role of PSGL-1 ERM-binding sequence (EBS) on cell capture, rolling, and signaling through Syk and MAPK pathways. We carried out mutational analysis and observed that deletion of EBS severely reduced 32D leukocyte tethering and rolling on L-, P-, and E-selectin and slightly increased rolling velocity. Alanine substitution of Arg-337 and Lys-338 showed that these residues play a key role in supporting leukocyte tethering and rolling on selectins. Importantly, EBS deletion or Arg-337 and Lys-338 mutations abrogated PSGL-1-induced ERK activation, whereas they did not prevent Syk phosphorylation or E-selectin-induced leukocyte slow rolling. These studies demonstrate that PSGL-1 EBS plays a critical role in recruiting leukocytes on selectins and in activating the MAPK pathway, whereas it is dispensable to phosphorylate Syk and to lead to α(L)β(2)-dependent leukocyte slow rolling.
Service and Central Laboratory of Hematology, Lausanne University Hospital, Rue du Bugnon 46, 1011 Lausanne, Switzerland.
Caroline
C
Spertini
Service and Central Laboratory of Hematology, Lausanne University Hospital, Rue du Bugnon 46, 1011 Lausanne, Switzerland.
Bénédicte
B
Baïsse
Service and Central Laboratory of Hematology, Lausanne University Hospital, Rue du Bugnon 46, 1011 Lausanne, Switzerland. Electronic address: Olivier.Spertini@chuv.ch.
Olivier
O
Spertini
D000818:Animals; D016466:CHO Cells; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D036904:Leukocyte Rolling / Q000502:physiology*; D007962:Leukocytes / Q000166:cytology / Q000378:metabolism*; D016169:Lymphocyte Function-Associated Antigen-1 / Q000235:genetics / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000502:physiology; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D019087:Selectins / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D000072377:Syk Kinase; D019061:src-Family Kinases / Q000235:genetics / Q000378:metabolism; D000099149:Ezrin
D003598:Cytoskeletal Proteins; D048049:Extracellular Signal-Regulated MAP Kinases; D047908:Intracellular Signaling Peptides and Proteins; D016169:Lymphocyte Function-Associated Antigen-1; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D008840:Microfilament Proteins; D011505:Protein-Tyrosine Kinases; D019087:Selectins; D000072377:Syk Kinase; D019061:src-Family Kinases; D000099149:Ezrin; C084882:P-selectin ligand protein; C071058:moesin; C071776:radixin; C000606896:SYK protein, human