Interaction of Osteopontin with Osteoclast Integrins

Mammalian osteoclasts express three integrin receptors--alpha v beta 3 (vitronectin receptor), alpha 2 beta 1 and alpha v beta 1. The vitronectin receptor recognizes bone matrix proteins, including bone sialoproteins, in an RGD-dependent manner, whereas adhesion to collagen involves beta 1 integrins...

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Bibliographic Details
Published in:Annals of the New York Academy of Sciences 1995-08, Vol.760 (1), p.190-200
Main Authors: HORTON, MICHAEL A., NESBIT, M. ANDREW, HELFRICH, MIEP H.
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
Cell Adhesion
Gene Expression
Humans
Integrin-Binding Sialoprotein
Integrins - physiology
Mice
Molecular Sequence Data
Osteoclasts - physiology
Osteopontin
Rats
Receptors, Cytoadhesin - physiology
Receptors, Vitronectin
RNA, Messenger - genetics
Sialoglycoproteins - metabolism
Sialoglycoproteins - physiology
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Summary:Mammalian osteoclasts express three integrin receptors--alpha v beta 3 (vitronectin receptor), alpha 2 beta 1 and alpha v beta 1. The vitronectin receptor recognizes bone matrix proteins, including bone sialoproteins, in an RGD-dependent manner, whereas adhesion to collagen involves beta 1 integrins. Interference with integrin function, by anti-receptor antibodies or RGD-peptides, blocks bone resorption. Data on the mechanism of osteoclast adhesion to sialoproteins and the differential synthesis of osteopontin and bone sialoprotein by osteoclasts is presented. Thus, osteoclasts adhere to both osteopontin and bone sialoprotein with a characteristic irregular morphology with numerous, peripherally placed, actin-rich podosomes. Adhesion is predominantly RGD and beta 3 dependent, though alpha v beta 1 may also be involved in adhesion to bone sialoprotein. KQAGD and AGDV, but not H12, fibrinogen peptides induce osteoclast 'rounding' on osteopontin suggesting there is an alternative anti-adhesive signal to 'RGD.' However, adhesion is not completely inhibited and is not specific for osteopontin as equivalent effects are seen with adhesion to serum. The role of sialoproteins in osteoclast adhesion in situ in the skeleton is complicated by the finding of endogenous synthesis of osteopontin, but not bone sialoprotein, by osteoclasts. The disposition of osteoclast integrins during resorption and the role of integrins and sialoprotein-derived peptides in osteoclast adhesion and function is also reviewed.
ISSN:0077-8923
1749-6632
DOI:10.1111/j.1749-6632.1995.tb44630.x