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Updated: Aug 21, 2026

Detection of Signaling Effector-Complexes Downstream of BMP4 Using in situ PLA, a Proximity Ligation Assay
Published on: March 3, 2011
CD44 modulates Smad1 activation in the BMP-7 signaling pathway
Richard S Peterson1, Roma A Andhare, Kathleen T Rousche
1Dept. of Biochemistry, Rush Medical College, Rush University Medical Center, 1653 West Congress Parkway, Chicago, IL 60612, USA.
Abstract:
Bone morphogenetic protein 7 (BMP-7) regulates cellular metabolism in embryonic and adult tissues. Signal transduction occurs through the activation of intracellular Smad proteins. In this paper, using a yeast two-hybrid screen, Smad1 was found to interact with the cytoplasmic domain of CD44, a receptor for the extracellular matrix macromolecule hyaluronan. Coimmunoprecipitation experiments confirmed the interaction of Smad1 with full-length CD44-interactions that did not occur when CD44 receptors truncated within the cytoplasmic domain were tested. Chondrocytes overexpressing a truncated CD44 on a background of endogenous full-length CD44 no longer exhibited Smad1 nuclear translocation upon BMP-7 stimulation. Further, pretreatment of chondrocytes with Streptomyces hyaluronidase to disrupt extracellular hyaluronan-cell interactions inhibited BMP-7-mediated Smad1 phosphorylation, nuclear translocation of Smad1 or Smad4, and SBE4-luciferase reporter activation. These results support a functional link between the BMP signaling cascade and CD44. Thus, changes in hyaluronan-cell interactions may serve as a means to modulate cellular responsiveness to BMP.
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