title: CXCR4 and CXCR7 Mediate TFF3-Induced Cell Migration Independently From the ERK1/2 Signaling Pathway.
abstract: OBJECTIVE
  Trefoil factor family (TFF) peptides, and in particular TFF3, are characteristic secretory products of mucous epithelia that promote antiapoptosis, epithelial migration, restitution, and wound healing. For a long time, a receptor for TFF3 had not yet been identified. However, the chemokine receptor CXCR4 has been described as a low affinity receptor for TFF2. Additionally, CXCR7, which is able to heterodimerize with CXCR4, has also been discussed as a potential TFF2 receptor. Since there are distinct structural similarities between the three known TFF peptides, this study evaluated whether CXCR4 and CXCR7 may also act as putative TFF3 receptors.
  
  
  METHODS
  We evaluated the expression of both CXCR4 and CXCR7 in samples of human ocular surface tissues and cell lines, using RT-PCR, immunohistochemistry, and Western blot analysis. Furthermore, we studied possible binding interactions between TFF3 and the receptor proteins in an x-ray structure-based modeling system. Functional studies of TFF3-CXCR4/CXCR7 interaction were accomplished by cell culture-based migration assays, flow cytometry, and evaluation of activation of the mitogen-activated protein (MAP) kinase signaling cascade.
  
  
  RESULTS
  We detected both receptors at mRNA and protein level in all analyzed ocular surface tissues, and in lesser amount in ocular surface cell lines. X-ray structure-based modeling revealed CXCR4 and CXCR7 dimers as possible binding partners to TFF3. Cell culture-based assays revealed enhanced cell migration under TFF3 stimulation in a conjunctival epithelial cell line, which was completely suppressed by blocking CXCR4 and/or CXCR7. Flow cytometry showed increased proliferation rates after TFF3 treatment, while blocking both receptors had no effect on this increase. Trefoil factor family 3 also activated the MAP kinase signaling cascade independently from receptor activity.
  
  
  CONCLUSIONS
  Dimers CXCR4 and CXCR7 are involved in TFF3-dependent activation of cell migration, but not cell proliferation. The ERK1/2 pathway is activated in the process, but not influenced by CXCR4 or CXCR7. These results implicate a dependence of TFF3 activity as to cell migration on the chemokine receptors CXCR4 and CXCR7 at the ocular surface.
authors.affiliation: Department of Ophthalmology University of Leipzig, Leipzig, Germany 2Department of Anatomy II, Friedrich Alexander University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Dieckow
authors.affiliation: Department of Bioorganic Chemistry, Leibniz Institute of Plant Biochemistry, Halle, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Brandt
authors.affiliation: Institute of Anatomy, Christian Albrecht University of Kiel, Kiel, Germany.
authors.forename: Kirsten
authors.initials: K
authors.lastname: Hattermann
authors.affiliation: Department of Anatomy II, Friedrich Alexander University Erlangen-Nürnberg, Erlangen, Germany 5Department of Neuroradiology, University of Leipzig, Leipzig, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schob
authors.affiliation: Department of Anatomy and Cell Biology, Martin Luther University Halle-Wittenberg, Halle, Germany.
authors.forename: Ute
authors.initials: U
authors.lastname: Schulze
authors.affiliation: Institute of Anatomy, Christian Albrecht University of Kiel, Kiel, Germany.
authors.forename: Rolf
authors.initials: R
authors.lastname: Mentlein
authors.affiliation: Department of Ophthalmology, Heinrich Heine University Düsseldorf, Düsseldorf, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Ackermann
authors.affiliation: Department of Ophthalmology, Ruprecht Karl University Heidelberg, Heidelberg, Germany.
authors.forename: Saadettin
authors.initials: S
authors.lastname: Sel
authors.affiliation: Department of Anatomy II, Friedrich Alexander University Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: Friedrich P
authors.initials: FP
authors.lastname: Paulsen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017209:Apoptosis; D015153:Blotting, Western; D002102:Cadaver; D002460:Cell Line; D002465:Cell Movement; D049109:Cell Proliferation; D019573:Epithelium, Corneal / Q000166:cytology / Q000378:metabolism*; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D007150:Immunohistochemistry; D020935:MAP Kinase Signaling System / Q000502:physiology*; D008297:Male; D010455:Peptides / Q000235:genetics* / Q000378:metabolism; D012313:RNA / Q000235:genetics*; D054387:Receptors, CXCR / Q000096:biosynthesis / Q000235:genetics*; D019718:Receptors, CXCR4 / Q000096:biosynthesis / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D000071164:Trefoil Factor-2; D000071165:Trefoil Factor-3
chemical_list: C501896:ACKR3 protein, human; C527276:CXCR4 protein, human; D010455:Peptides; D054387:Receptors, CXCR; D019718:Receptors, CXCR4; C000604007:TFF2 protein, human; C082495:TFF3 protein, human; D000071164:Trefoil Factor-2; D000071165:Trefoil Factor-3; D012313:RNA