ROLE OF INTRACELLULAR
CALCIUM IN
GLUCOCORTICOID-EVOKED
LYMPHOID CELL APOPTOSIS
Devin Morris
California State University, Northridge
Apoptosis
Stimuli/
Death signals
Release of
cyctochrome c
Apaf-1
Activation of
caspase cascade
Apoptosis
Caspase 9
Apoptosome
formation
Effector
Caspases
Physiological roles of apoptosis
Proliferation
Cell Population
• Development
• Homeostasis
• Disease
Cell Death
Glucocorticoid Pathway
ABC
IPC
R R
4
2
R R
R IPC
3
R
1
R
ligand
receptor
IPC
interacting
proteins
coactivator
complex
basal trans.
factors
Susceptibility of CEM Cell Clones to GC-Evoked
Apoptosis
GC-induced Increase in Intracellular Calcium in
GC-Susceptible CEM cells
Time- & GC-Dose-Dependent Increase in [Ca+2]i in
CEM-C7-14 Cells
24 hours
EtOH
100 nM Dex
A
1mM Dex
B
4.4%
6%
E
14.1%
F
48 hours
D
C
5%
24.8%
62.1%
Modulators of [Ca+2]i Levels Influence GC-Evoked Death
of CEM Cells
Cells/ml x 10-5
100
EtOH
Dex (100nM)
10
BAPTA 1 uM
Dex/BAPTA1
1
EGTA 20 uM
Dex/EGTA20
0.1
0
1
2
Days
3
4
Cells/ml x 10
-5
10.00
1.00
Control
Dex
A23187
Dex+A23187
0.10
0
1
2
Days
3
EGTA Suppresses GC-Evoked Increase in [Ca+2]i
Levels in CEM-C7-14 Cells
EtOH
100 nM Dex
B
C
Ethanol
A
1mM Dex
20 mM EGTA
4.4%
D
16.4%
E
2%
35%
F
12.4%
23.1%
Glucocorticoid Signaling Pathway
Pathway Inhibitors
TMB-8
GC
W7 or
calmidazolium
chloride
[Ca+2]i
Ca+2-CaM
(Release from
Intracellular
Stores)
Binding and
Activation
Normal Pathway
KN-62 or
KN-93
Activation of
CAMK II
Activation of
Calcineurin
FK-506 or
Cyclosporine A
Inhibition of Calmodulin Protects CEM-C7-14 Cells
from GC-evoked Death
Cells/ml x 10-5
100
EtOH
Dex (100nM)
10
CC 100 nM
CC 1 uM
1
Dex/CC100nM
Dex/CC 1uM
0.1
0
1
2
Days
3
4
Inhibition of Calmodulin Kinase II Protects CEMC7-14 Cells from GC-evoked Death
100
Cells/ml x 10
-5
EtOH
Dex (100nM)
10
KN-93 100 nM
KN-93 1 uM
1
Dex/KN-93 100nM
Dex/KN-93 1uM
0.1
0
1
2
3
Days
4
Inhibition of Calcineurin Protects CEM-C7-14 Cells
from GC-evoked Death
Cells/ml x 10-5
100
EtOH
Dex (100nM)
10
CsA 100 nM
CsA 1 uM
1
Dex/CsA 100nM
Dex/CsA 1uM
0.1
0
1
2
3
Days
4
Conclusions
• GCs increase [Ca+2]i levels only in the GC-susceptible CEM-C7-14
cell line in a dose dependent manner; not in the GC-resistant sister cell
line, CEM-C1-15.
• Calcium chelation by either BAPTA or EGTA protected CEM-C7-14
cells from GC-evoked apoptosis, in conjunction with a reduction in the
amount of free [Ca+2]i.
• The calcium ionophore A23187 causes sensitization of CEM-C1-15
cells to GC-evoked apoptosis.
• Inhibition of calmodulin, calmodulin kinase II or calcineurin, all
intermediates in the calcium signaling pathway, impart varying degrees
of protection to CEM-C7-14 cells from GC-evoked apoptosis.
• Our data demonstrate a clear correlation between calcium signaling
and GC-evoked apoptosis
Future Goals
• Further studies will aim to understand Ca+2-dependent
changes in gene regulation that contribute to apoptosis.
Candidate genes such as the transcriptional repressor
E4BP4, and its downstream targets are being studied.
• Our ultimate goal is to understand the molecular pathway
for apoptosis in T-lymphoid cells as well as in other
physiologically relevant models for apoptosis, such as
osteoblasts, keratinocytes and macrophages.
Acknowledgements
Funded by grants from the NIH MBRS-SCORE Program, the
CSUN Office of Graduate Studies, Research and
International Programs, and the CSUN College of Science
& Mathematics.
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Dr. Rheem Medh
Saul Priceman
Dr. Carol Shubin
NASA CSUN/JPL Pair Program