Cumulated Ca2+ spike duration underlies Ca2+ oscillation frequency-regulated NFκB transcriptional activity
Liping Zhu
1
2
Shanshan Song
1
2
Yubo Pi
1
2
Yang Yu
1
2
Weibin She
1
2
Hong Ye
1
2
Yuan Su
0
1
Qinghua Hu
()
1
2
3
0
Department of Respiratory Medicine, Union Hospital, Tongji Medical College, Huazhong Science and Technology University
, Wuhan 430030,
People's Republic of China
1
Key Laboratory of Pulmonary Diseases of Ministry of Health of China, Tongji Medical College, Huazhong Science and Technology University
, Wuhan 430030,
People's Republic of China
2
Department of Pathophysiology, Tongji Medical College, Huazhong Science and Technology University
, Wuhan 430030,
People's Republic of China
3
The MOE Key Laboratory of Environment and Health, School of Public Health, Tongji Medical College, Huazhong Science and Technology University
, Wuhan 430030,
People's Republic of China
-
Summary
ce [Ca2+]i oscillations drive downstream events, like transcription, in a frequency-dependent manner. Why [Ca2+]i oscillation frequency
n regulates transcription has not been clearly revealed. A variation in [Ca2+]i oscillation frequency apparently leads to a variation in the
ic time duration of cumulated [Ca2+]i elevations or cumulated [Ca2+]i spike duration. By manipulating [Ca2+]i spike duration, we
e
S generated a series of [Ca2+]i oscillations with the same frequency but different cumulated [Ca2+]i spike durations, as well as [Ca2+]i
lle oscillations with the different frequencies but the same cumulated [Ca2+]i spike duration. Molecular assays demonstrated that, when
C generated in artificial models alone, under physiologically simulated conditions or repetitive pulses of agonist exposure, [Ca2+]i
fo oscillation regulates NFkB transcriptional activity, phosphorylation of IkBa and Ca2+-dependent gene expression all in a way actually
la dependent on cumulated [Ca2+]i spike duration whether or not frequency varies. This study underlines that [Ca2+]i oscillation frequency
rn regulates NFkB transcriptional activity through cumulated [Ca2+]i spike-duration-mediated IkBa phosphorylation.
u
o
J
Introduction
[Ca2+]i oscillations, a series of repetitive [Ca2+]i spikes, were first
demonstrated in hepatocytes (Woods et al., 1986) and have been
observed in almost all non-excitable cells ever studied. Investigation
over the past two decades has established (Berridge et al., 2003;
Jacob et al., 1988) that [Ca2+]i oscillation regulates cellular
downstream events, including transcription, through its frequency
(Colella et al., 2008; De Koninck and Schulman, 1998; Dolmetsch
et al., 1998; Hajnoczky et al., 1995; Hu et al., 1999; Li et al., 1998;
Tomida et al., 2003; Zhu et al., 2008). Frequency-dependent
regulation of downstream events is generally important because it
provides advantages over amplitude-dependent regulation (Berridge
et al., 2003; Jacob et al., 1988), it regulates transcription more
efficiently and specifically than sustained [Ca2+]i elevations
(Dolmetsch et al., 1998; Tomida et al., 2003) and also efficiently
cooperates with intracellular reactive oxygen species (ROS) in
regulating nuclear factor kB (NFkB) transcriptional activity and
subsequent gene expression (Zhu et al., 2008). Dynamic differences
between dephosphorylation of cytoplasmic nuclear factor of
activated T-cells (NFAT) and rephosphorylation of nucleoplasmic
NFAT has been suggested as an explanation for how [Ca2+]i
oscillation regulates NFAT activation (Tomida et al., 2003). To the
best of our knowledge, however, there has never been an
experimental attempt to address why [Ca2+]i oscillation frequency
by itself regulates downstream events, such as transcription, leaving
a fundamental issue unsolved. Apparently, when [Ca2+]i oscillates
for a period of time, a long cumulated time duration of [Ca2+]i
elevation accompanies a high frequency of oscillation and vice
versa. Here, we hypothesized that [Ca2+]i oscillation frequency
regulates transcription through a mechanism associated with the
cumulated time duration of [Ca2+]i elevations.
The cumulated time duration of [Ca2+]i elevations is controlled
by frequency, but another determinant is [Ca2+]i spike duration
(SD) or [Ca2+]i spike width, which is profoundly modulated by a
variety of extracellular and intracellular conditions or physiological
and pathophysiological circumstances, such as agonist species and
their concentration (Cobbold et al., 1991; Moccia et al., 2003;
Morgan and Jacob, 1998; Shuttleworth and Thompson, 1996),
extracellular Ca2+ concentration (Igarashi et al., 1997; Zhao et al.,
1990), extracellular pH (Jackson and Thayer, 2006; Zhao et al.,
1990), the endoplasmic reticulum Ca2+-ATPase (Morgan and Jacob,
1998; Petersen et al., 1993), protein kinase C (PKC) (Young et al.,
2002), mitochondria (Jackson and Thayer, 2006) and even
temperature (Lee et al., 2005; Schipke et al., 2008; Szekely et al.,
2009). When [Ca2+]i SD varies, the same frequency of [Ca2+]i
oscillations have a different cumulated time duration of [Ca2+]i
elevation or cumulated [Ca2+]i spike duration (CSD). Related to
our hypo (...truncated)