Bone morphogenetic protein-2 (BMP-2) and transforming growth factor-beta1 (TGF-beta1) alter connexin 43 phosphorylation in MC3T3-E1 Cells.
BACKGROUND
Bone morphogenetic proteins (BMPs) and transforming growth factor-betas (TGF-betas) are important regulators of bone repair and regeneration. BMP-2 and TGF-beta1 have been shown to inhibit gap junctional intercellular communication (GJIC) in MC3T3-E1 cells. Connexin 43 (Cx43) has been shown to mediate GJIC in osteoblasts and it is the predominant gap junctional protein expressed in these murine osteoblast-like cells. We examined the expression, phosphorylation, and subcellular localization of Cx43 after treatment with BMP-2 or TGF-beta1 to investigate a possible mechanism for the inhibition of GJIC.


RESULTS
Northern blot analysis revealed no detectable change in the expression of Cx43 mRNA. Western blot analysis demonstrated no significant change in the expression of total Cx43 protein. However, significantly higher ratios of unphosphorylated vs. phosphorylated forms of Cx43 were detected after BMP-2 or TGF-beta1 treatment. Immunofluorescence and cell protein fractionation revealed no detectable change in the localization of Cx43 between the cytosol and plasma membrane.


CONCLUSIONS
BMP-2 and TGF-beta1 do not alter expression of Cx43 at the mRNA or protein level. BMP-2 and TGF-beta1 may inhibit GJIC by decreasing the phosphorylated form of Cx43 in MC3T3-E1 cells.
Wyatt
L E
LE
Plastic Surgery Section, VA Greater Los Angeles Healthcare System, Los Angeles, CA 90073, USA. lance_wyatt@hotmail.com
Chung
C Y
CY
Carlsen
B
B
Iida-Klein
A
A
Rudkin
G H
GH
Ishida
K
K
Yamaguchi
D T
DT
Miller
T A
TA
D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology*; D002460:Cell Line; D018031:Connexin 43 / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D012333:RNA, Messenger / Q000096:biosynthesis; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D053773:Transforming Growth Factor beta1
C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D018031:Connexin 43; D012333:RNA, Messenger; C508961:Tgfb1 protein, mouse; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1