Skeletal strength is achieved through a stringently controlled balance of bone formation and bone degradation. The cells responsible for this regulated degradation are osteoclasts, large multinucleated cells of the monocytic lineage. Osteoclasts undergo a cycle of activity that includes migration, polarization, bone resorption, and depolarization. These events require engagement of integrins and extensive rearrangements of the actin cytoskelton. Failure of osteoclasts to undergo these processes results in diminished cell function and potentially severe consequences to skeletal health such as osteopetrosis. The goal of this proposal is to examine the dynamics of the actin cytoskeleton in osteoclasts during events such as migration and polarization, and to understand the cellular elements required for this aspect of normal osteoclast function.
The first aim of this proposal is directed toward the molecular motor myosin IIA, which is closely associated with dynamic actin structures involved in osteoclast migration and polarization. The potential functions of this motor will be assessed both by suppressing its activity and by following its trafficking in living cells. The goal of the second aim is directed toward understanding roles of other myosin isoforms in osteoclasts, particularly as they might pertain to cell signaling pathways. Finally, we have identified isoforms of tropomyosins with defined distributions in osteoclasts. Tropomyosins are filamentous proteins that can regulate the stability of actin, as well as its accessibility to other actin-binding proteins. We will examine the functions of these tropomyosins by alternately suppressing or enhancing their expression, and determining the effects on actin rearrangements in osteoclasts. These studies will provide new understanding of crucial processes mediated by the actin cytoskeleton in this dynamic cell type. Relevance: The ongoing process of bone formation and degradation must be kept in balance to maintain skeletal health. Bone degradation is performed by cells called osteoclasts, which depend on changes in their internal shape and structure for activity. The objective of this work is to understand some of the proteins that regulate the shape of osteoclasts, as part of a greater effort to comprehend how the activity of these cells is regulated. ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR051515-02
Application #
7211414
Study Section
Skeletal Biology Development and Disease Study Section (SBDD)
Program Officer
Sharrock, William J
Project Start
2006-04-01
Project End
2010-03-31
Budget Start
2007-04-01
Budget End
2008-03-31
Support Year
2
Fiscal Year
2007
Total Cost
$255,490
Indirect Cost
Name
Ohio State University
Department
Physiology
Type
Schools of Medicine
DUNS #
832127323
City
Columbus
State
OH
Country
United States
Zip Code
43210
McMichael, Brooke K; Scherer, Katharine F; Franklin, Nicole C et al. (2014) The RhoGAP activity of myosin IXB is critical for osteoclast podosome patterning, motility, and resorptive capacity. PLoS One 9:e87402
Jeyaraj, Selvi C; Singh, Mamata; Ayupova, Dina A et al. (2010) Transcriptional control of human antigen R by bone morphogenetic protein. J Biol Chem 285:4432-40
McMichael, Brooke K; Cheney, Richard E; Lee, Beth S (2010) Myosin X regulates sealing zone patterning in osteoclasts through linkage of podosomes and microtubules. J Biol Chem 285:9506-15
McMichael, Brooke K; Wysolmerski, Robert B; Lee, Beth S (2009) Regulated proteolysis of nonmuscle myosin IIA stimulates osteoclast fusion. J Biol Chem 284:12266-75
Ayupova, Dina A; Singh, Mamata; Leonard, Ellen C et al. (2009) Expression of the RNA-stabilizing protein HuR in ischemia-reperfusion injury of rat kidney. Am J Physiol Renal Physiol 297:F95-F105
McMichael, Brooke K; Lee, Beth S (2008) Tropomyosin 4 regulates adhesion structures and resorptive capacity in osteoclasts. Exp Cell Res 314:564-73
Kotadiya, Preeyal; McMichael, Brooke K; Lee, Beth S (2008) High molecular weight tropomyosins regulate osteoclast cytoskeletal morphology. Bone 43:951-60
McMichael, Brooke K; Kotadiya, Preeyal; Singh, Tejdeep et al. (2006) Tropomyosin isoforms localize to distinct microfilament populations in osteoclasts. Bone 39:694-705