Download 2010 생명의약연구원 월례정기세미나

2010 생명의약연구원 월례정기세미나
 세미나 주제
“이온통로와 질환”
 세미나 일정
2010년 12월 15일 17:00~ 19:30 (수요일)
 세미나 장소
중앙대학교 약대 교수 세미나실
 연자; (20분 발표, 10분 질문)
1. 강원대학교 의과대학 생리학교실, 박원선 교수(17:10~17:40)
2. 중앙대학교 의과대학 생리학교실, 고재홍 교수(17:40~18:10)
3. 성균관대학교 의과대학 생리학교실, 강동묵 교수(18:10~18:40)
4. 서울대학교 의과대학 생리학교실, 김성준 교수(18:40~19:10)
박원선교수;
Patho-, Physiological role of inward rectifer K+ channels in small diameter coronary
arteries
K+ channels play indispensable roles in establishing the membrane potential and
in regulating the contractile tone of arterial smooth muscle cells. There are four types of
K+ channels in arterial smooth muscle: voltage-dependent K+ (KV), Ca2+-dependent K+
(BKCa), ATP-dependent K+ (KATP), and inward rectifier K+ (Kir2) channels. Comparatively few
physiological studies have focused on Kir2 channels, because they are present only in
certain small-diameter cerebral and submucosal arterioles, as well as in coronary arterial
smooth muscle. Here, we review the characteristics and regulation of Kir2 channels in
vascular arterial smooth muscle. Current knowledge of the predominant Kir2 channel
subtype is Kir2.1, not Kir2.2 and 2.3. Electrophysiological measurements to determine the
current-voltage relationship in arterial smooth muscle revealed inward rectification with a
single-channel conductance of 21 pS. Kir2 channels were found to influence the resting
tone of cerebral and coronary arteries based on the fact that barium (Ba 2+) induces the
constriction of these arteries at resting tone. Kir2 channels are also highly responsive to
vasoconstrictors and vasodilators. For example, the vasoconstrictors endothelin-1 and
angiotensin II inhibit Kir2 channel function by activating protein kinase C (PKC), and the
vasodilator adenosine stimulates Kir2 channel function by increasing the level of cAMP,
which subsequently activates protein kinase A (PKA). Certain pathological conditions such
as left ventricular hypertrophy are associated with a decrease in Kir2 channels expression.
Although our understanding of the physiological role and regulation of Kir2 channels is
incomplete, it is believed that Kir2 channels contribute to the control of vascular tone in
small-diameter vessels via various intracellular signalling pathways that regulate cell
membrane potential.
Key Words: inward rectifier K+ channel, protein kinase C, protein kinase A, vasoconstrictor,
vasodilator, hypertrophy
고재홍 교수
Cloning of large-conductance Ca2+-activated K+ channel alpha-subunits in mouse
cardiomyocytes
Large-conductance Ca2+-activated K+ (BKCa) channels are widely distributed in
cellular membranes of various tissues, but have not previously been found in
cardiomyocytes. In this study, we cloned a gene encoding the mouse cardiac BKCa
channel α-subunit (mCardBKa). Sequence analysis of the cDNA revealed an open reading
frame encoding 1154 amino acids. Another cDNA variant, identical in amino acid
sequence, was also identified by sequence analysis. The nucleotide sequences of the two
mCardBKa cDNAs, type 1 (mCardBKa1) and type 2 (mCardBKa2), differed by three
nucleotide insertions and one nucleotide substitution in the N-terminal sequence. The
amino acid sequence demonstrated that mCardBKa was a unique BKCa channel α-subunit
in mouse cardiomyocytes, with amino acids 41-1153 being identical to mouse Slo1 and
amino acids 1-40 corresponding to Kcnma1. These findings suggest that a unique BKCa
channel α-subunit is expressed in mouse cardiomyocytes.
강동묵 교수
Regulation of skeletal muscle differentiation by store-operated Ca2+ channels
Store-operated Ca2+ entry (SOC) channels are known to activate by the depletion of
calcium inside of endoplasmic reticulum (ER) of the cells. By the activation of SOC
channels, entry of extracellular calcium into the cytoplasm replenishes ER Ca2+ stores.
Recently, stromal interaction molecule (STIM1, STIM2) and the Orai family of plasma
membrane channels (Orai1, Orai2, Orai3) have been discovered as the molecular identity
of SOC channels. It is now well established that STIM is the Ca2+ sensor protein on ER
membrane and is required to activate SOC channels. Upon depletion of ER calcium store,
STIM1 redistribute to plasma membrane and binds with the Orai1 Ca2+ channel to form
SOC channels. It has been recognized that STIM1 and Orai1 are highly expressed in
skeletal muscle cells, and genetic ablation of STIM1 or Orai1 produces a severe growth
defect of mice. In the present study, we used genetic ablation or over-expression of
STIM1 to investigate the role of STIM1 during the differentiation process of C2C12
skeletal muscle cell line. In addition, the functional interaction of STIM1 with a Ca 2+dependent phosphatase (calcineurin) and a transcriptional factor (NFATc) was investigated.
STIM1, STIM2 and Orai1 gene expression is markedly increased by the induction of
C2C12 skeletal muscle differentiation. As a consequence, the activity of SOC was higher
in differentiated myotubes than proliferating myoblasts. A commonly used SOC inhibitor,
2-APB, markedly inhibited the muscle differentiation. Over-expression of STIM1 enhanced
the SOC activity and the myoblast differentiation, whereas knock-down of STIM1 using
siRNA technique produced apposite effects. When the myoblasts were treated with
calcineurin inhibitors (cyclosporine A or FK506), expression of STIM1, STIM2, the SOC
activity, and the degree of myoblast differentiation were all decreased. Luciferase assay
revealed that the ablation of STIM1 decreased the activity of NFATc, which is a
transcription factor dictated by activated calcineurin, whereas over-expression of STIM1
exert opposite effect on NFATc activity. As expected, calcineurin inhibitors markedly
decreased NFATc activity. Taken together, we suggest that STIM1-calcineurin-NFATc
signaling pathway is important for regulating skeletal muscle differentiation processes.
김성준 교수
Exercise training increases K+ channel currents and augments K+-mediated
vasodilation in deep femoral artery of rats
Aims: A moderate increase in extracellular [K+] ([K+]e) induces relaxation of small arteries
via activating inwardly rectifying K+ current (IKir). The K+-vasodilation is an important
mechanism for exercise-induced hyperemia in skeletal muscle. We investigated whether
IKir and K+-vasodilation are enhanced in deep femoral arteries (DFA) from exercise-trained
rats (ET-rats, treadmill-running (20 m/min, 20 min, six days for two week). The effects of
ET on K+-vasodilations and IKir were also compared with cerebral arteries and mesenteric
arteries.
Methods and Results: The K+-vasodilation of DFA and the density of IKir and voltagegated K+ current (IKv) were increased in ET-rats. The myogenic tone of DFA was
unchanged in ET-rats. Although the functional up-regulations of IKir and IKv were also
observed in cerebral arteries, the K+-vasodilation was not increased in ET-rats.
Interestingly, background Na+ conductance was also increased in the cerebral arterial
myocytes while not in DFA myocytes from ET-rats. Neither IKir nor K+-vasodilation was
observed in the mesenteric arteries of ET-rats.
Conclusion: We firstly report that regular exercise up-regulates IKir in the myocytes of
DFA and cerebral artery. Albeit the common increase of IKir, augmentation of K+relaxation was observed in DFA only, which might be due to the increased Na+
conductance in cerebral artery of ET-rats. The increases of IKir and K+-vasodilation of
skeletal arteries suggest novel mechanisms of improved exercise hyperemia by physical
training.
Keywords: exercise training, skeletal artery, smooth muscle, inward rectifying K+ channel