Lipid-independent activation of a muscle-specific PKCα splicing variant.
Lipid-independent activation of a muscle-specific PKCα splicing variant.
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肌肉特异性 PKCα 剪接变体的脂质独立激活。
DOI：
10.1152/ajpheart.00304.2022
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发表时间：
2022
期刊：
影响因子：
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通讯作者：
Steinberg,SusanF
中科院分区：
文献类型：
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作者：
Gao,Chen;Gong,Jianli;Cao,Nancy;Wang,Yibin;Steinberg,SusanF
蛋白激酶C-α（PKC α）在多种细胞过程中发挥重要作用。迄今为止的研究已经完全基于先前注释的普遍表达的原型同种型来定义PKC α的调节控制和功能。从小鼠心脏中基于RNA-seq的转录组分析中，我们鉴定了一种先前未注释的由选择性RNA剪接产生的PKC α变体。这种PKC α转录变体，我们将其命名为PKC α-novel exon（PKC α-NE），在外显子16和外显子17之间含有一个额外的外显子，并且在成年小鼠心肌和骨骼肌中特异性检测到，但在其他组织中检测不到;它也在人类心脏中检测到。该转录变体产生在其COOH末端可变区插入额外16个氨基酸的PKC α同种型。虽然经典的PKC α酶是一种脂质依赖性激酶，但体外激酶测定显示PKC α-NE显示出高水平的基础脂质非依赖性催化活性。我们的无偏蛋白质组学分析确定了PKC α-NE和真核细胞延伸因子-1 α（eEF1A1）之间的特异性相互作用。在心肌细胞中的研究将PKC α-NE表达与eEF1A1磷酸化增加和蛋白质合成升高联系起来。综上所述，我们发现了一种以前未被鉴定的肌肉特异性PKC α剪接变体，PKC α-NE，它具有独特的生物化学特性，在心肌细胞蛋白质合成机制的控制中起着独特的作用。然而，除了一种原型亚型外，还没有报道PKC α的亚型。首次在啮齿动物和人类心脏组织中检测到Prkcagene的可变mRNA剪接，其可产生先前未知的PKC α-新外显子（NE）异构体。PKC α-NE的生物化学和分子生物学效应与PKC α野生型有显著差异，提示PKC α信号通路在肌肉中可能存在功能多样性。
Protein kinase C-α (PKCα) plays a major role in a diverse range of cellular processes. Studies to date have defined the regulatory controls and function of PKCα entirely based upon the previously annotated ubiquitously expressed prototypical isoform. From RNA-seq-based transcriptome analysis in murine heart, we identified a previously unannotated PKCα variant produced by alternative RNA splicing. This PKCα transcript variant, which we named PKCα-novel exon (PKCα-NE), contains an extra exon between exon 16 and exon 17, and is specifically detected in adult mouse cardiac and skeletal muscle, but not other tissues; it is also detected in human hearts. This transcript variant yields a PKCα isoform with additional 16 amino acids inserted in its COOH-terminal variable region. Although the canonical PKCα enzyme is a lipid-dependent kinase, in vitro kinase assays show that PKCα-NE displays a high level of basal lipid-independent catalytic activity. Our unbiased proteomic analysis identified a specific interaction between PKCα-NE and eukaryotic elongation factor-1α (eEF1A1). Studies in cardiomyocytes link PKCα-NE expression to an increase in eEF1A1 phosphorylation and elevated protein synthesis. In summary, we have identified a previously uncharacterized muscle-specific PKCα splicing variant, PKCα-NE, with distinct biochemical properties that plays a unique role in the control of the protein synthesis machinery in cardiomyocytes.NEW & NOTEWORTHYPKCα is an important signaling molecule extensively studied in many cellular processes. However, no isoforms have been reported for PKCα except one prototypic isoform. Alternative mRNA splicing ofPrkcagene was detected for the first time in rodent and human cardiac tissue, which can produce a previously unknown PKCα-novel exon (NE) isoform. The biochemistry and molecular effects of PKCα-NE are markedly different from PKCα wild type, suggesting potential functional diversity of PKCα signaling in muscle.