The physical environment of the skeleton is known to play an important role in the establishment and maintenance of structurally competent bone. However, the mechanisms by which physical signals exert such biological effects are unclear. While biophysical signals elicit a variety of cellular responses in bone cells, the mechanism by which these responses are initiated is unknown. In this study we propose that annexin V (AnxV), a CA2+-dependent phospholipid binding protein, is a critical protein required for initiating mechanotransduction. AnxV has a number of attributes, which suggest that it is ideally suited for a role as a mechanoreceptor, possibly a mechanosensitive ion channel. These include the ability to function as a Ca2+ selective membrane ion channel, and the ability to interact with both extracellular matrix proteins such as collagen, and cytoskeletal elements such as actin. ? ? Hypothesis: our central hypothesis is that bone cells detect and transduce physical signals into biological responses via a mechanism requiring AnxV. ? ? Aims: Our goal is test this hypothesis by determining the role of AnxV in the response of bone cells to oscillating fluid flow, a physiologically relevant physical signal in bone. We will determine whether AnxV, in a role as a Ca2+ selective, mechanosensitive ion channel, is required for flow-induced Ca2+ influx, global increases in Ca2+i and ultimately gene expression in human osteoblast-like MG63 cells and murine osteocytic MLO-Y4 cells (Aims 1, 2 and 3). We will also determine whether expression and cellular location of AnxV are regulated by fluid flow (Aim 4). ? ? Significance: The long-term goal of these studies is to increase our understanding of how biophysical signals are selected and converted into an appropriate biological response by bone cells. Identification of critical """"""""mechanotransducer"""""""" proteins may also provide novel targets for future therapeutic interventions in the fight against bone diseases such as osteoporosis.

Agency
National Institute of Health (NIH)
Institute
National Institute on Aging (NIA)
Type
Research Project (R01)
Project #
5R01AG022305-05
Application #
6943485
Study Section
Special Emphasis Panel (ZRG1-OBM-2 (06))
Program Officer
Kohanski, Ronald A
Project Start
2002-09-30
Project End
2007-08-31
Budget Start
2005-09-01
Budget End
2006-08-31
Support Year
5
Fiscal Year
2005
Total Cost
$265,125
Indirect Cost
Name
University of California Davis
Department
Veterinary Sciences
Type
Schools of Veterinary Medicine
DUNS #
047120084
City
Davis
State
CA
Country
United States
Zip Code
95618
Morgan, Jessica M; Wong, Alice; Yellowley, Clare E et al. (2011) Regulation of tenascin expression in bone. J Cell Biochem 112:3354-63
Morgan, Jessica M; Wong, Alice; Genetos, Damian C et al. (2011) Src is sufficient, but not necessary, for osteopontin induction in osteoblasts. Biorheology 48:65-74
Genetos, Damian C; Yellowley, Clare E; Loots, Gabriela G (2011) Prostaglandin E2 signals through PTGER2 to regulate sclerostin expression. PLoS One 6:e17772
Genetos, Damian C; Wong, Alice; Watari, Shinya et al. (2010) Hypoxia increases Annexin A2 expression in osteoblastic cells via VEGF and ERK. Bone 47:1013-9
Genetos, Damian C; Toupadakis, Chrisoula A; Raheja, Leah F et al. (2010) Hypoxia decreases sclerostin expression and increases Wnt signaling in osteoblasts. J Cell Biochem 110:457-67
Genetos, Damian C; Lee, Christina M; Wong, Alice et al. (2009) HIF-1alpha regulates hypoxia-induced EP1 expression in osteoblastic cells. J Cell Biochem 107:233-9
Genetos, Damian C; Kephart, Curtis J; Zhang, Yue et al. (2007) Oscillating fluid flow activation of gap junction hemichannels induces ATP release from MLO-Y4 osteocytes. J Cell Physiol 212:207-14
Lee, Christina M; Genetos, Damian C; You, Zongbing et al. (2007) Hypoxia regulates PGE(2) release and EP1 receptor expression in osteoblastic cells. J Cell Physiol 212:182-8
Haut Donahue, T L; Genetos, D C; Jacobs, C R et al. (2004) Annexin V disruption impairs mechanically induced calcium signaling in osteoblastic cells. Bone 35:656-63