Tyro 3 receptor tyrosine kinase and its ligand, Gas6, stimulate the function of osteoclasts.
Bone is continuously being formed and resorbed. This process is accomplished by the precise coordination of two cell types: osteoblasts and osteoclasts. Osteoclasts are large, multinucleated cells that are derived from the same hematopoietic precursors as macrophages. However, these bone-resorbing cells are difficult to study directly because of their relative inaccessibility. The purification of primary osteoclasts from rabbit bones by their adherent nature provides an opportunity for investigating the molecules in osteoclasts. We have examined the expression of receptor tyrosine kinase by polymerase chain reaction (PCR) and found that Tyro 3 was frequently identified from primary osteoclasts in PCR cloning. Immunohistochemistry revealed that Tyro 3 was expressed on the multinucleated osteoclasts which were positive for tartrate-resistant acid phosphatase (TRAP), but not on mononuclear TRAP-positive cells. The Tyro 3 ligand, Gas6, induced the phosphorylation of Tyro 3 receptors in osteoclasts in two to five min. Gas6 and protein S directly enhanced the bone resorbing activity of mature osteoclasts. This effect of Gas6 was inhibited by the addition of a tyrosine kinase inhibitor, herbimycin A. However, Gas6 did not affect the differentiation of osteoclasts from bone marrow cells. Gas6 and protein S are dependent on vitamin K, a cofactor for the enzyme responsible for carboxylation of glutamic acid residues. The findings in this study are the first to indicate a new biological activity of Gas6 and protein S as a direct regulator of osteoclastic function; they give an insight into the role of these vitamin K-dependent ligands in bone resorption in vivo.
Nakamura
Y S
YS
Department of Cell Differentiation, Institute of Molecular Embryology and Genetics, Kumamoto University School of Medicine, Honjo, Japan.
Hakeda
Y
Y
Takakura
N
N
Kameda
T
T
Hamaguchi
I
I
Miyamoto
T
T
Kakudo
S
S
Nakano
T
T
Kumegawa
M
M
Suda
T
T
D000135:Acid Phosphatase / Q000096:biosynthesis; D000818:Animals; D015415:Biomarkers; D001854:Bone Marrow Cells / Q000166:cytology*; D001862:Bone Resorption; D002117:Calcitriol / Q000494:pharmacology; D002454:Cell Differentiation; D002478:Cells, Cultured; D003001:Cloning, Molecular; D003094:Collagen; D017931:DNA Primers; D006412:Hematopoietic Stem Cells / Q000166:cytology; D036341:Intercellular Signaling Peptides and Proteins; D007527:Isoenzymes / Q000096:biosynthesis; D051379:Mice; D008810:Mice, Inbred C57BL; D010010:Osteoclasts / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D010766:Phosphorylation; D016133:Polymerase Chain Reaction; D011506:Proteins / Q000494:pharmacology*; D011817:Rabbits; D020794:Receptor Protein-Tyrosine Kinases / Q000096:biosynthesis / Q000502:physiology*; D011994:Recombinant Proteins / Q000096:biosynthesis; D000071681:Tartrate-Resistant Acid Phosphatase; D000099255:Growth Arrest-Specific Protein 6
D000135:Acid Phosphatase; D015415:Biomarkers; D002117:Calcitriol; D003094:Collagen; D017931:DNA Primers; D036341:Intercellular Signaling Peptides and Proteins; D007527:Isoenzymes; D011506:Proteins; D020794:Receptor Protein-Tyrosine Kinases; D011994:Recombinant Proteins; D000071681:Tartrate-Resistant Acid Phosphatase; D000099255:Growth Arrest-Specific Protein 6; C084944:TYRO3 protein, human; C000605511:Acp5 protein, mouse