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GROWTH, DIFFERENTIATION, AND APOPTOSIS
1Laboratory of Neuroendocrinology-Molecular Cell Physiology, Institute of Pathophysiology, Medical Faculty, University of Ljubljana, Ljubljana; and 2Celica Biomedical Sciences Center, Ljubljana, Slovenia
Submitted 5 July 2005 ; accepted in final form 30 September 2005
A key step in the intrinsic apoptotic pathway is the assembly of the apoptosome complex. The apoptosome components are well known; however, the physiology of the assembly of the apoptosome complex at the cellular level is still poorly defined. The aim of this work was to study the subcellular distribution of the apoptosome scaffold protein apoptotic protease-activating factor 1 (Apaf-1) before and after triggering apoptosis in single somatotrophs. Somatotrophs are the subject of extensive pituitary tissue remodeling in different physiological situations in which the quality and the number of pituitary cells are determined by cell proliferation and apoptosis. We show herein that 2 h after triggering apoptosis with rotenone, Apaf-1 redistributed to the proximity of mitochondria. In addition, the degree of colocalization between Apaf-1 and fluorescently labeled caspase-9 significantly increased during the same period. Furthermore, we show herein for the first time in single cells that the colocalization between Apaf-1 and cytochrome c increases only transiently, indicating a transient interaction between cytochrome c and Apaf-1 during the activation of apoptosis in these cells.
cytochrome c; caspase-9; apoptosis; apoptosome complex
ka 4, SI-1000 Ljubljana, Slovenia (e-mail: Robert.Zorec{at}mf.uni-lj.si)
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