Alternative splicing of ryanodine receptors modulates cardiomyocyte Ca2+ signaling and susceptibility to apoptosis
Alternative splicing of ryanodine receptors modulates cardiomyocyte Ca2+ signaling and susceptibility to apoptosis
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DOI：
10.1161/01.res.0000260804.77807.cf
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发表时间：
2007-03-30
影响因子：
20.1
通讯作者：
Lai, F. Anthony
中科院分区：
文献类型：
--
作者：
George, Christopher H.;Rogers, Sarah A.;Lai, F. Anthony
Ca（2+）通过2型兰尼碱受体（RyR 2）释放调节心脏功能。人类RyR 2的分子克隆鉴定出2种可变剪接变体，包括30-和24-bp序列插入;但它们在塑造心肌细胞Ca（2+）信号传导和细胞表型中的作用尚不清楚。我们分析了这些变异体的发育调节和组织及物种特异性，并表明它们在HL-1心肌细胞中的重组表达深刻地调节了细胞核和细胞质Ca（2+）的释放。所有的剪接变体定位于肌浆网，核周高尔基体，和指状内陷的核膜（核浆网）。引人注目的是，在胚胎和成人心脏中以低水平存在的24-bp剪接插入对于将RyR 2靶向核内高尔基体是必不可少的，并促进了该变体的细胞内分离。在表达30-和24-bp剪接变异体的非刺激心肌细胞中，细胞核和细胞质Ca（2+）通量的幅度变异性降低，并与较低的细胞凋亡基础水平相关。含有24 bp插入的RyR 2的表达也抑制了长时间暴露于咖啡因（1 mmol/L，16小时）后的细胞内Ca（2+）通量，从而保护细胞免于凋亡。这种变体的抗凋亡作用与Bcl-2磷酸化水平的增加有关。与此相反，RyR 2含有30 bp的插入，这是丰富的人胚胎心脏，但在心脏发育过程中减少，并没有保护心肌细胞从咖啡因诱发的细胞凋亡。因此，我们提供的第一个证据表明，RyR 2剪接变异体精细地调节细胞内Ca（2+）信号传导，是心肌细胞凋亡易感性的关键决定因素。
Ca(2+) release via type 2 ryanodine receptors ( RyR2) regulates cardiac function. Molecular cloning of human RyR2 identified 2 alternatively spliced variants, comprising 30- and 24-bp sequence insertions; yet their role in shaping cardiomyocyte Ca(2+) signaling and cell phenotype is unknown. We profiled the developmental regulation and the tissue and species specificity of these variants and showed that their recombinant expression in HL-1 cardiomyocytes profoundly modulated nuclear and cytoplasmic Ca(2+) release. All splice variants localized to the sarcoplasmic reticulum, perinuclear Golgi apparatus, and to finger-like invaginations of the nuclear envelope ( nucleoplasmic reticulum). Strikingly, the 24-bp splice insertion that was present at low levels in embryonic and adult hearts was essential for targeting RyR2 to an intranuclear Golgi apparatus and promoted the intracellular segregation of this variant. The amplitude variability of nuclear and cytoplasmic Ca(2+) fluxes were reduced in nonstimulated cardiomyocytes expressing both 30- and 24-bp splice variants and were associated with lower basal levels of apoptosis. Expression of RyR2 containing the 24-bp insertion also suppressed intracellular Ca(2+) fluxes following prolonged caffeine exposure ( 1 mmol/L, 16 hours) that protected cells from apoptosis. The antiapoptotic effects of this variant were linked to increased levels of Bcl-2 phosphorylation. In contrast, RyR2 containing the 30- bp insertion, which was abundant in human embryonic heart but was decreased during cardiac development, did not protect cardiomyocytes from caffeine-evoked apoptosis. Thus, we provide the first evidence that RyR2 splice variants exquisitely modulate intracellular Ca(2+) signaling and are key determinants of cardiomyocyte apoptotic susceptibility.