Osteopontin stimulates gelsolin-associated phosphoinositide levels and phosphatidylinositol triphosphate-hydroxyl kinase.
Based on previous studies demonstrating activation of phosphatidylinositol 3-hydroxyl kinase (PI3-kinase) and stimulation of a change in cell shape, we examined the effect of osteopontin on the association of phospholipids with gelsolin, an actin-capping/severing protein. Osteopontin stimulated a rapid increase in phosphatidylinositol bisphosphate and phosphatidylinositol triphosphate levels associated with gelsolin in Triton-soluble fractions of cell lysates. The increased levels of phosphatidylinositol triphosphate associated with gelsolin were due to stimulation of PI3-kinase activity associated with gelsolin in the Triton-soluble fractions, and they were blocked by the PI3-kinase inhibitor wortmannin. Osteopontin stimulated translocation of PI3-kinase from the Triton-insoluble to Triton-soluble gelsolin. Osteopontin also decreased Triton-soluble gelsolin/actin complexes consistent with actin uncapping, and increased F-actin levels, which were also blocked by wortmannin. The osteopontin effects were mediated through binding to the alpha(v)beta 3 integrin. Taken together, our studies indicate that osteopontin/alpha(v)beta 3-mediated changes in gelsolin-associated phosphoinositide levels and PI3-kinase activity are related to stimulation of F-actin formation in osteoclasts.
Chellaiah
M
M
Renal Division, Jewish Hospital of St. Louis, Missouri 63110, USA.
Hruska
K
K
D000199:Actins / Q000378:metabolism; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002855:Chromatography, Thin Layer; D004533:Egtazic Acid / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D018260:Gelsolin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010010:Osteoclasts / Q000201:enzymology*; D053495:Osteopontin; D019869:Phosphatidylinositol 3-Kinases; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010743:Phospholipids / Q000032:analysis; D010750:Phosphoproteins / Q000494:pharmacology; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011233:Precipitin Tests; D012795:Sialoglycoproteins / Q000494:pharmacology*; D013997:Time Factors; D000077191:Wortmannin
D000199:Actins; D000730:Androstadienes; D004791:Enzyme Inhibitors; D018260:Gelsolin; D018129:Phosphatidylinositol Phosphates; D010743:Phospholipids; D010750:Phosphoproteins; D012795:Sialoglycoproteins; D053495:Osteopontin; D004533:Egtazic Acid; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D000077191:Wortmannin