Hyaluronan promotes signaling interaction between CD44 and the transforming growth factor beta receptor I in metastatic breast tumor cells.

Abstract

In this study we have examined the interaction between CD44 (a hyaluronan (HA) receptor) and the transforming growth factor beta (TGF-beta) receptors (a family of serine/threonine kinase membrane receptors) in human metastatic breast tumor cells (MDA-MB-231 cell line). Immunological data indicate that both CD44 and TGF-beta receptors are expressed in MDA-MB-231 cells and that CD44 is physically linked to the TGF-beta receptor I (TGF-betaRI) (and to a lesser extent to the TGF-beta receptor II (TGF-betaRII)) as a complex in vivo. Scatchard plot analyses and in vitro binding experiments show that the cytoplasmic domain of CD44 binds to TGF-betaRI at a single site with high affinity (an apparent dissociation constant (K(d)) of approximately 1.78 nm). These findings indicate that TGF-betaRI contains a CD44-binding site. Furthermore, we have found that the binding of HA to CD44 in MDA-MB-231 cells stimulates TGF-betaRI serine/threonine kinase activity which, in turn, increases Smad2/Smad3 phosphorylation and parathyroid hormone-related protein (PTH-rP) production (well known downstream effector functions of TGF-beta signaling). Most importantly, TGF-betaRI kinase activated by HA phosphorylates CD44, which enhances its binding interaction with the cytoskeletal protein, ankyrin, leading to HA-mediated breast tumor cell migration. Overexpression of TGF-betaRI by transfection of MDA-MB-231 cells with TGF-betaRIcDNA stimulates formation of the CD44.TGF-betaRI complex, the association of ankyrin with membranes, and HA-dependent/CD44-specific breast tumor migration. Taken together, these findings strongly suggest that CD44 interaction with the TGF-betaRI kinase promotes activation of multiple signaling pathways required for ankyrin-membrane interaction, tumor cell migration, and important oncogenic events (e.g. Smad2/Smad3 phosphorylation and PTH-rP production) during HA and TGF-beta-mediated metastatic breast tumor progression.

• Authors: Lilly Y W Bourguignon, Patrick A Singleton, Hongbo Zhu, Bo Zhou
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 277 Issue 42 Pg. 39703-12 (Oct 18 2002) ISSN: 0021-9258 [Print] United States
• PMID: 12145287 (Publication Type: Journal Article, Research Support, U.S. Gov't, Non-P.H.S., Research Support, U.S. Gov't, P.H.S.)

Chemical References

• DNA, Complementary
• Hyaluronan Receptors
• Receptors, Transforming Growth Factor beta
• Hyaluronic Acid
• Protein Serine-Threonine Kinases
• Activin Receptors, Type I
• Receptor, Transforming Growth Factor-beta Type I

Topics

• Activin Receptors, Type I (metabolism)
• Animals
• Breast Neoplasms (metabolism)
• COS Cells
• Cell Line
• Cell Movement
• Cytoplasm (metabolism)
• DNA, Complementary (metabolism)
• Escherichia coli (metabolism)
• Humans
• Hyaluronan Receptors (metabolism)
• Hyaluronic Acid (chemistry, metabolism)
• Kinetics
• Neoplasm Metastasis
• Phosphorylation
• Precipitin Tests
• Protein Binding
• Protein Serine-Threonine Kinases
• Protein Structure, Tertiary
• Receptor, Transforming Growth Factor-beta Type I
• Receptors, Transforming Growth Factor beta (metabolism)
• Signal Transduction
• Transfection
• Tumor Cells, Cultured