Bone morphogenetic protein-2 modulates Wnt and frizzled expression and enhances the canonical pathway of Wnt signaling in normal keratinocytes.
BACKGROUND
Bone morphogenetic protein-2 (BMP-2) and Wnt are involved in the normal development and tumorigenesis of several organs, and in the development of skin and skin appendages as a morphogen. However, the crosstalk between BMP-2 and the Wnt/beta-catenin signaling pathway is not clear.


OBJECTIVE
We examined BMP-2-dependent expression of Wnt and its receptor frizzled in normal human keratinocytes.


METHODS
The mRNA expression of the Wnt and frizzled families was analyzed by reverse transcription-polymerase chain reaction (RT-PCR) or ribonuclease protection assay. beta-Catenin expression was measured using RT-PCR and Western blotting. T-cell factor/lymphoid enhancing factor activity was analyzed using the luciferase reporter assay.


RESULTS
We detected the expression of Wnt-2b/13, -4, -5a, -5b, -7a, -7b, and -10a, frizzled-1, -4, -5, -6, -8, -9, and -10, MFRP, and SFRP-1/SARP-2 in keratinocytes. BMP-2 increased Wnt-2b/13, -5b, and -7b, and frizzled-6, -8, and -10. Conversely, BMP-2 suppressed Wnt-10a and SFRP-1/SARP-2. Although Wnt-4 expression was not affected by BMP-2 in confluent conditioned keratinocytes, BMP-2 suppressed cell density-dependent Wnt-4 induction. The transcriptional activity of TCF/LEF, which is a target of the canonical Wnt pathway, was upregulated by BMP-2 in both time- and dose-dependent manners. However, BMP-2-dependent differentiation of keratinocytes suppressed TCF/LEF transcriptional activity.


CONCLUSIONS
These results suggest that BMP-2 modulates the expression of molecules involved in Wnt signaling, and activates the canonical Wnt pathway in normal human keratinocytes. Moreover, Wnt signaling may be influenced by the fate of keratinocytes, such as proliferation, migration, and differentiation.
Yang
Lujun
L
Department of Dermatology, Ehime University School of Medicine, Shitsukawa, Toon, Ehime 791-0295, Japan.
Yamasaki
Kenshi
K
Shirakata
Yuji
Y
Dai
Xiuju
X
Tokumaru
Sho
S
Yahata
Yoko
Y
Tohyama
Mikiko
M
Hanakawa
Yasushi
Y
Sayama
Koji
K
Hashimoto
Koji
K
D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000502:physiology*; D002478:Cells, Cultured; D051157:Frizzled Receptors; D005786:Gene Expression Regulation; D006801:Humans; D007223:Infant; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism*; D008297:Male; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis*; D017981:Receptors, Neurotransmitter / Q000096:biosynthesis*; D015398:Signal Transduction; D016212:Transforming Growth Factor beta / Q000502:physiology*; D051153:Wnt Proteins / Q000096:biosynthesis*; D060528:Wnt4 Protein
C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; C489740:FZD1 protein, human; D051157:Frizzled Receptors; D011518:Proto-Oncogene Proteins; D017981:Receptors, Neurotransmitter; D016212:Transforming Growth Factor beta; C555581:WNT4 protein, human; D051153:Wnt Proteins; D060528:Wnt4 Protein