The primary goal of the studies in the current proposal is to determine the functions of the Galpha12/13- RhoA/Rhq kinase-phospholipase D signaling pathway in the actions of parathyroid hormone (PTH) in osteoblasts. Our studies during the previous funding period have characterized the PTH regulation of this pathway in UMR-106 osteoblastic cells, and have established that it mediates PTH-stimulated translocation of protein kinase C alpha and contributes to activation of interleukin-6. In other tissues, the pathway plays a prominent role in survival signaling and in cell adhesion, spreading, and cell-cell interactions. Effects of PTH to promote cell survival are likely to be critical for the anabolic effects of PTH on bone, and cell-matrix and cell-cell. interactions are likely to be important in bone remodeling. Therefore, the first specific aim is to examine the role of the pathway in PTH actions on cell survival and survival signaling, including effects on MAP kinase, Akt, Runx-2 and insulin-like growth factor -1, on anabolic effects in bone organ culture, and on cytoskeleton changes in osteoblasts including stimulation of the formation of actin stress fibers and focal adhesions, antagonism of the rapid cAMP-mediated contraction and stimulation of expression of proteins critical to cytoskeletal events, i.e. focal adhesion kinase, paxillin, ICAM-1 and connexin-43. A second specific aim derives from the fact that statins and aminobisphosphonates, important bone regulating drugs, could affect the pathway through their effects to inhibit the generation of isoprenyl groups. This proposed mechanism will be tested, as will the possibility that these drugs affect osteoblast activity through their actions on the pathway. A third specific aim is to define the mechanisms of interactions within the signaling pathway, including the interactions between G12/G13 alpha subunits of heterotrimeric G proteins and RhoA and the regulation of the pathway by calcium. We will be determined whether the regulation of the pathway is similar in primary osteoblasts to what was observed in UMR-106 cells. We will determine the role of phosphatidic acid, the immediate downstream product of PLD activity, in PTH actions. The findings from the research will provide a more comprehensive understanding of the role of this newly recognized signaling pathway in osteoblasts and will test the hypothesis that it is involved in effects that are critical for the anabolic actions of PTH and that mediate PTH interactions with statins and bisphosphonates on bone. ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
2R01AR011262-35A2
Application #
7100698
Study Section
Skeletal Biology Development and Disease Study Section (SBDD)
Program Officer
Sharrock, William J
Project Start
1978-07-01
Project End
2010-03-31
Budget Start
2006-04-01
Budget End
2007-03-31
Support Year
35
Fiscal Year
2006
Total Cost
$263,120
Indirect Cost
Name
Northwestern University at Chicago
Department
Pharmacology
Type
Schools of Medicine
DUNS #
005436803
City
Chicago
State
IL
Country
United States
Zip Code
60611
Wang, J; Stern, P H (2011) Dose-dependent differential effects of risedronate on gene expression in osteoblasts. Biochem Pharmacol 81:1036-42
Wang, J; Gilchrist, A; Stern, P H (2011) Antagonist minigenes identify genes regulated by parathyroid hormone through G protein-selective and G protein co-regulated mechanisms in osteoblastic cells. Cell Signal 23:380-8
Wang, Jun; Stern, Paula H (2010) Osteoclastogenic activity and RANKL expression are inhibited in osteoblastic cells expressing constitutively active G?(12) or constitutively active RhoA. J Cell Biochem 111:1531-6
Yoshida, Tomohiko; Clark, Mary F; Stern, Paula H (2009) The small GTPase RhoA is crucial for MC3T3-E1 osteoblastic cell survival. J Cell Biochem 106:896-902
Kazmers, Nikolas H; Ma, Sophia A; Yoshida, Tomohiko et al. (2009) Rho GTPase signaling and PTH 3-34, but not PTH 1-34, maintain the actin cytoskeleton and antagonize bisphosphonate effects in mouse osteoblastic MC3T3-E1 cells. Bone 45:52-60
Singh, A T K; Gilchrist, A; Voyno-Yasenetskaya, T et al. (2005) G alpha12/G alpha13 subunits of heterotrimeric G proteins mediate parathyroid hormone activation of phospholipase D in UMR-106 osteoblastic cells. Endocrinology 146:2171-5
Dossing, Debra A; Stern, Paula H (2005) Receptor activator of NF-kappaB ligand protein expression in UMR-106 cells is differentially regulated by parathyroid hormone and calcitriol. J Cell Biochem 95:1029-41
Singh, Amareshwar T K; Frohman, Michael A; Stern, Paula H (2005) Parathyroid hormone stimulates phosphatidylethanolamine hydrolysis by phospholipase D in osteoblastic cells. Lipids 40:1135-40
Radeff, Julie M; Nagy, Zsolt; Stern, Paula H (2004) Rho and Rho kinase are involved in parathyroid hormone-stimulated protein kinase C alpha translocation and IL-6 promoter activity in osteoblastic cells. J Bone Miner Res 19:1882-91
Radeff, Julie M; Singh, Amareshwar T K; Stern, Paula H (2004) Role of protein kinase A, phospholipase C and phospholipase D in parathyroid hormone receptor regulation of protein kinase Calpha and interleukin-6 in UMR-106 osteoblastic cells. Cell Signal 16:105-14

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