Improved nutrition and healthcare are just two of a plethora of factors contributing to the increased longevity of the American people. Coincident with the increased life expectancy is a steady decline in ambulatory function, a product of age-associated atrophy of muscle tissue. The loss in mobility with age is a consequence of both fewer muscle cells and a reduction in cell size. With a trend toward increasing the average lifespan of an individual, a concomitant rise in muscle disuse and atrophy will follow leading to quality of life concerns and rising healthcare costs for the immobile elderly. Thus, it is imperative that our understanding of the basic processes of muscle formation be significantly advanced such that novel therapeutic approaches can be developed to alleviate muscle atrophy. We have identified an essential signaling pathway that negatively impacts myofiber development. Chronic activation of Raf kinase initiated phosphorylation events suppresses myofiber formation and muscle gene expression. The molecular means by which Raf disrupts skeletal muscle formation may involve synthesis and secretion of a TGF-beta-like protein as well as stimulation of alternate signaling pathways. By further characterization of the Raf kinase intracellular signaling modules present in skeletal myoblasts, we can pinpoint critical downstream effectors that participate in the block to optimal muscle formation and thereby, provide targets for intervention therapy. Therefore, the Specific Aims of this grant are: 1. To establish that activated Raf signaling induces expression of members of the TGF-beta superfamily of genes that leads to the creation of an autocrine myogenic inhibitory loop. 2. To identify novel Raf-interacting proteins that participate in the atypical MEK-independent block to muscle formation. 3. To delineate the molecular basis for Raf-induced positive and negative regulation of myogenic gene transcription.

Agency
National Institute of Health (NIH)
Institute
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
Type
Research Project (R01)
Project #
5R01AR048830-03
Application #
6952336
Study Section
Special Emphasis Panel (ZRG1-SMB (01))
Program Officer
Nuckolls, Glen H
Project Start
2003-09-26
Project End
2007-06-30
Budget Start
2005-07-01
Budget End
2006-06-30
Support Year
3
Fiscal Year
2005
Total Cost
$268,377
Indirect Cost
Name
University of Florida
Department
Veterinary Sciences
Type
Schools of Earth Sciences/Natur
DUNS #
969663814
City
Gainesville
State
FL
Country
United States
Zip Code
32611
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Reed, Sarah A; Ouellette, Sara E; Liu, Xiaosong et al. (2007) E2F5 and LEK1 translocation to the nucleus is an early event demarcating myoblast quiescence. J Cell Biochem 101:1394-408
Li, Ju; Johnson, Sally E (2006) ERK2 is required for efficient terminal differentiation of skeletal myoblasts. Biochem Biophys Res Commun 345:1425-33
Johnson, Sally E; Winner Jr, Dane G; Wang, Xu (2006) Ran binding protein 9 interacts with Raf kinase but does not contribute to downstream ERK1/2 activation in skeletal myoblasts. Biochem Biophys Res Commun 340:409-16
Page, Jeanine L; Wang, Xu; Sordillo, Lorraine M et al. (2004) MEKK1 signaling through p38 leads to transcriptional inactivation of E47 and repression of skeletal myogenesis. J Biol Chem 279:30966-72