title: Role of the atypical chemoattractant receptor CRAM in regulating CCL19 induced CCR7 responses in B-cell chronic lymphocytic leukemia.
abstract: BACKGROUND
  The non-signalling chemokine receptors, including receptors DARC, D6 and CCX-CKR, have recently been shown to be involved in chemokine clearance and activity regulation. The human chemokine receptor CRAM (also known as HCR or CCRL2) is the most recently identified member of this atypical group. CRAM is expressed on B cells in a maturation-stage dependent manner and absent on T cells. We have recently shown that it competitively binds CCL19. CCL19 and its signalling receptor CCR7 are critical components involved in cell recruitment to secondary lymphoid organs and in maturation. B cell Chronic Lymphocytic Leukemia (B-CLL) is a low-grade lymphoma characterized by proliferative centres (or pseudofollicles). Proliferative centres develop due to abnormal cellular localisation and they are involved in the development of malignant cells. CCR7 is highly expressed on B cells from CLL patients and mediates migration towards its ligands CCL19 and CCL21, while CRAM expression and potential interferences with CCR7 are yet to be characterized.
  
  
  RESULTS
  In this study, we show that B cells from patients with B-CLL present highly variable degrees of CRAM expression in contrast to more consistently high levels of CCR7. We investigated the hypothesis that, similar to the atypical receptor DARC, CRAM can modulate chemokine availability and/or efficacy, resulting in the regulation of cellular activation. We found that a high level of CRAM expression was detrimental to efficient chemotaxis with CCL19. MAP-kinase phosphorylation and intracellular calcium release induced by CCL19 were also altered by CRAM expression. In addition, we demonstrate that CRAM-induced regulation of CCL19 signalling is maintained over time.
  
  
  CONCLUSIONS
  We postulate that CRAM is a factor involved in the fine tuning/control of CCR7/CCL19 mediated responses. This regulation could be critical to the pivotal role of CCL19 induced formation of proliferation centres supporting the T/B cells encounter as well as disease progression in B-CLL.
authors.affiliation: University Clinic of Freiburg, Department of Hematology and Oncology, Hugstetterstr, 55, 79106, Freiburg, Germany.
authors.forename: Julie
authors.initials: J
authors.lastname: Catusse
authors.forename: Marion
authors.initials: M
authors.lastname: Leick
authors.forename: Mareike
authors.initials: M
authors.lastname: Groch
authors.forename: David J
authors.initials: DJ
authors.lastname: Clark
authors.forename: Maike V
authors.initials: MV
authors.lastname: Buchner
authors.forename: Katja
authors.initials: K
authors.lastname: Zirlik
authors.forename: Meike
authors.initials: M
authors.lastname: Burger
mesh_terms: D000906:Antibodies / Q000494:pharmacology; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D054415:Chemokine CCL19 / Q000494:pharmacology*; D054421:Chemokine CCL21 / Q000494:pharmacology; D002633:Chemotaxis / Q000187:drug effects; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D054388:Receptors, CCR / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054400:Receptors, CCR7 / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D000906:Antibodies; C487531:CCRL2 protein, human; D054415:Chemokine CCL19; D054421:Chemokine CCL21; D054388:Receptors, CCR; D054400:Receptors, CCR7