ABSTRACT
Execution Phase of Ca2þ-Induced Apoptosis .............................. 440 16.4 Methods to Detect Alterations in Ca2þ Homeostasis
Associated with Apoptosis ........................................................................ 442
16.4.1 Measuring Cytoplasmic Ca2þ Elevation Induced by an Apoptotic Signal................................................................. 442
16.4.2 Determining Whether Cytoplasmic Ca2þ
Elevation Mediates Apoptosis...................................................... 444
16.4.3 Detecting Alterations in Intracellular Ca2þ
Distribution ................................................................................... 445
16.5 Methods to Investigate the Involvement of IP3 Receptors in Apoptosis.............................................................................. 448
16.6 Concluding Remarks ................................................................................. 448
Acknowledgments ................................................................................................ 449
References............................................................................................................. 449
The aim of this chapter is to summarize how established methods of Ca2þ signaling research are used to elucidate the involvement of Ca2þ in apoptosis. Selected examples of apoptosis are used to illustrate methodological principles and applica-
tions. For a comprehensive review of the role of Ca2þ in a wide range of apoptotic processes, the reader is referred to a number of excellent in-depth reviews [1-5]
This chapter is directed at two major audiences. First are those who have
considerable experience in Ca2þ signaling but want to know more about apoptosis
and how it is triggered by Ca2þ signals. Second are those who work in the area of apoptosis research and are interested in learning more about Ca2þ and its measurement because of the increasing number of reports implicating Ca2þ in apoptosis. The author formally belongs to neither of the camps and therefore has the unique
perspective of one who was drawn into apoptosis research by the desire to under-
stand a physiological process of great clinical relevance (i.e., the killing of lympho-
cytes by glucocorticosteroid hormones) and was lured to the realm of Ca2þ
signaling by unexpected findings implicating Ca2þ release from the endoplasmic reticulum (ER) in this process [6, 7] and the regulation of ER Ca2þ release by the apoptosis regulatory protein Bcl-2 [8]. This avenue of research has led to recent
evidence that the anti-apoptotic protein Bcl-2 interacts functionally with inositol
1,4,5-trisphospate receptors and thereby regulates Ca2þ release from the ER in lymphocytes [9]. But applying the techniques of Ca2þ measurement in the context of apoptosis has been sobering and therefore one goal of this chapter is to alert
newcomers to some of the pitfalls unique to this area of research.
