PDF《differentiation》

Apoptosis (2006) 11:2103C2113 DOI 10.

1007/s10495-006-0196-4 Signaling through the TRAIL receptor DR5/FADD pathway plays a role in the apoptosis associated with skeletal myoblast differentiation J. O'

Flaherty ・ Y. Mei ・ M. Freer ・ C. M. Weyman Published online:

12 October

2006 C Springer Science + Business Media, LLC

2006 Abstract Apoptosis rather than differentiation is a physio- logical process during myogenesis and muscle regeneration. When cultured myoblasts were induced to differentiate, we detected an increase in caspase

8 activity. Pharmacological inhibition of caspase

8 activity decreased apoptosis. Expres- sion of a dominant-negative mutant of the adapter protein FADD also abrogated apoptosis, implicating a death lig- and pathway. Treatment with TRAIL, but not Fas, induced apoptosis in these myoblasts. Accordingly, treatment with a soluble TRAIL decoy receptor or expression of a dominant- negative mutant of the TRAIL receptor DR5 abrogated apop- tosis. While TRAIL expression levels remained unaltered in apoptotic myoblasts, DR5 expression levels increased. Finally, we also detected a reduction in FLIP, a death- receptor effector protein and caspase

8 competitive in- hibitor, to undetectable levels in apoptotic myoblasts. Thus, our data demonstrate an important role for the TRAIL/DR5/FADD/caspase

8 pathway in the apoptosis as- sociated with skeletal myoblast differentiation. Identifying the functional apoptotic pathways in skeletal myoblasts may prove useful in minimizing the myoblast apoptosis that con- tributes pathologically to a variety of diseases and in mini- mizing the apoptosis of transplanted myoblasts to treat these and other disease states. Keywords Myoblast . Apoptosis . FADD . DR5 . FLIP Abbreviations FADD Fas-associated death domain J. O'

Flaherty ・ Y. Mei ・ M. Freer ・ C. M. Weyman ( ) Department of Biological, Geological, and Environmental Sciences, Cleveland State University, Cleveland, OH

44115 e-mail: c.weyman@csuohio.edu TRAIL Tumor necrosis factor related apoptosis-inducing ligand FLIP FADD-like IL-1-converting enzyme-inhibitory protein Introduction Apoptosis is a common physiological process that occurs in all tissues and is critical to proper development and home- ostasis [1]. In fact, apoptosis and differentiation are often coordinately regulated with apoptosis serving the critical function of removing excess or physiologically ineffective cells [1C3]. Skeletal myoblast apoptosis occurs during myo- genesis [2] and muscle regeneration [3] and has been care- fully documented in cultures of primary myoblasts [4, 5], in established myoblast cell lines [6, 7], and in an estab- lished muscle satellite cell line [8]. While the coordinate regulation of differentiation and apoptosis is clearly impor- tant under normal physiological conditions, it is likely detri- mental to the use of myoblast transfer as a treatment for a variety of diseases [9, 10]. Further, inappropriate myoblast apoptosis contributes pathologically to a variety of diseases [11C13]. Thus, an understanding of the apoptotic process within skeletal myoblasts may identify targets for therapeu- tic manipulation relevant to disease states with associated muscle degeneration and to the use of myoblast transfer as a therapeutic approach. Further, such information may prove relevant to the use of apoptotic modi?ers to treat a variety of other pathological conditions [14C18]. While analysis of the apoptotic process that occurs during the differentiation of skeletal myoblasts is only beginning [7, 19, 20], the apoptotic process in other systems has been extensively studied. Mitochondrial permeabilization, resulting in the release of several pro-apoptotic proteins Springer