Please use this identifier to cite or link to this item: https://hdl.handle.net/2440/6792
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Type: Journal article
Title: Casein kinase 2 phosphorylation of recombinant rat osteopontin enhances adhesion of osteoclasts but not osteoblasts
Author: Katayama, Y.
House, C.
Udagawa, N.
Kazama, J.
McFarland, R.
Martin, T.
Findlay, D.
Citation: Journal of Cellular Physiology, 1998; 176(1):179-187
Issue Date: 1998
ISSN: 0021-9541
1097-4652
Abstract: Osteopontin (OP) is a highly phosphorylated bone matrix protein and contains the RGD cell-binding motif, which mediates cell adhesion through integrin receptors that include alpha(v)beta3. Casein kinase 2 (CK2) is a factor-independent serine/threonine kinase, which may be the predominant physiologically relevant kinase for OP phosphorylation. This study was designed to examine the effects of unphosphorylated recombinant rat OP, and CK2-phosphorylated OP (P-OP), on the adhesion and function of mouse osteoclasts (OC) and osteoblast-like cells (UMR 201-10B and UMR 106-06) in vitro. OP significantly increased OC adhesion compared to plastic alone, and cell attachment was further increased at least twofold on OP phosphorylated with CK2. Attachment was dependent on the integrity of the RGD domain and was completely abolished in the presence of 1 mM RGD peptide. Neither CK2 phosphorylation of mutant OP, in which the RGD was converted to RGE or RAD, nor protein kinase C (PKC) phosphorylation of wild-type OP enhanced OC attachment. An antibody to the beta3 integrin subunit, but not anti-mouse CD44 antibody, specifically blocked the proportion of attachment due to phosphorylation of OP. Actin ring formation in OC was increased by plating cells onto OP, with no further increase by phosphorylation. Both OP and CK2-phosphorylated OP enhanced attachment of the two osteoblastic cell lines, compared to plastic, but in contrast to OCs, there was no significant difference with phosphorylation. Osteoblast attachment was totally blocked by 1 mM RGD peptide, but was not influenced by the beta3 integrin antibody. Plating of UMR 201-10B cells onto OP further increased retinoic acid-induced alkaline phosphatase expression. The results suggest that specific phosphorylation of OP is important for interaction with OCs, compared with osteoblastic cells, and that alternative integrins may be important in the interaction between osteoblastic cells and OP compared with OCs.
Keywords: Cell Line
Osteoclasts
Osteoblasts
Animals
Rats
Tretinoin
Actins
Alkaline Phosphatase
Protein Kinases
Casein Kinases
Protein Kinase C
Sialoglycoproteins
Oligopeptides
Integrins
Recombinant Proteins
Adenosine Triphosphate
Cell Adhesion
Phosphorylation
Mutation
Osteopontin
DOI: 10.1002/(SICI)1097-4652(199807)176:1<179::AID-JCP19>3.0.CO;2-2
Appears in Collections:Aurora harvest 5
Orthopaedics and Trauma publications

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