BCL-xL-dependent light scattering by apoptotic cells.
We measured the intensity ratio of wide-to-narrow angle scatter, optical scatter image ratio (OSIR), in single cells during apoptosis and after overexpression of the mitochondria-bound antiapoptotic protein BCL-xL. OSIR is sensitive to particle size/shape for objects with wavelength-scale dimensions, and was used as a morphometric measure of cellular response. Three cell variants were treated with staurosporine (STS): nontransfected parental CSM14.1, CSM14.1 stably expressing yellow fluorescent protein (YFP) with diffuse YFP fluorescence, and apoptosis-resistant CSM14.1 stably expressing the fusion protein construct YFP-BCL-xL with YFP fluorescence localized on the mitochondria. After treatment with 1 or 2 muM STS, the measured OSIR decreased monotonically by approximately 25% in the nontransfected and YFP variants, and reached a steady-state value 40-60 min after STS treatment. The decrease in OSIR at the onset of apoptosis preceded phosphatidyl serine exposure by 5 h. In the YFP-BCL-xL cell variant, the initial OSIR was already approximately 24% lower than the initial OSIR in YFP and nontransfected cells, and only decreased by <10% after STS treatment. Alterations in light scattering by cells overexpressing BCL-xL even before apoptosis induction raise interesting questions as to the role of BCL-xL in conferring apoptosis resistance by preconditioning the cells and possibly altering mitochondrial morphology.
Boustany
Nada N
NN
Department of Biomedical Engineering, Rutgers University, Piscataway, New Jersey 08854, USA. nboustan@rci.rutgers.edu
Tsai
Yien-Che
YC
Pfister
Bryan
B
Joiner
Wilsaan M
WM
Oyler
George A
GA
Thakor
Nitish V
NV
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002460:Cell Line; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008027:Light; D008636:Mesencephalon / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D008859:Microscopy, Polarization / Q000379:methods*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D012542:Scattering, Radiation; D013050:Spectrometry, Fluorescence / Q000379:methods*; D051020:bcl-X Protein
C494813:Bcl2l1 protein, rat; D019253:Proto-Oncogene Proteins c-bcl-2; D011994:Recombinant Proteins; D051020:bcl-X Protein