Activated protein kinase C isoforms target to cardiomyocyte caveolae - Stimulation of local protein phosphorylation
Activated protein kinase C isoforms target to cardiomyocyte caveolae - Stimulation of local protein phosphorylation
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DOI：
10.1161/01.res.84.9.980
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发表时间：
1999-05-14
影响因子：
20.1
通讯作者：
Steinberg, SF
中科院分区：
文献类型：
--
作者：
Rybin, VO;Xu, XH;Steinberg, SF
蛋白激酶C（PKC）亚型是心肌细胞对各种细胞外刺激反应的信号转导途径的重要组成部分。转运到不同的细胞内位点是PKC亚型激活的重要步骤，可能是稳定获得底物的先决条件。小窝是质膜的专门亚结构域，据报道其浓缩关键信号传导蛋白，并且可能代表PKC作用的位点，因为已经报道PKC激活剂显著改变小窝形态。因此，本研究探讨PKC亚型是否启动心肌细胞小窝中的信号传导。从未受刺激的心肌细胞制备的小窝组分中检测到非常低水平的佛波酯敏感性PKC亚型;佛波酯12-肉豆蔻酸酯13-乙酸酯（PMA）（但不是4 α-PMA，其不激活PKC）将钙敏感性PKC α和新的PKC δ和PKC β募集到该隔室。佛波酯不敏感的PKC λ亚型的亚细胞定位不受PMA的影响。内皮素还诱导PKC α和PKC β（但不诱导PKC δ或PKC λ）选择性易位到小窝。细胞外信号调节蛋白激酶（ERK）级联的多个组件，包括A-Raf，c-Raf-1，丝裂原活化蛋白激酶激酶，和ERK，在静息条件下在小窝中检测到。虽然这些蛋白质的水平没有改变PMA，佛波酯敏感的PKC亚型的小窝易位与当地的ERK级联的激活以及。作为该级分中约36-kDa底物蛋白的磷酸化。最后，一小部分被指定为活化蛋白激酶C受体的蛋白质位于小窝中，并且（沿着小窝蛋白-3）可能代表了将PKC亚型靶向心肌细胞小窝的机制。这些研究确定了心肌细胞小窝阿萨活化的PKC亚型及其下游靶底物的聚集地。
Protein kinase C (PKC) isoforms constitute an important component of the signal transduction pathway used by cardiomyocytes to respond to a variety of extracellular stimuli. Translocation to distinct intracellular sites represents an essential step in the activation of PKC isoforms, presumably as a prerequisite for stable access to substrate. Caveolae are specialized subdomains of the plasma membrane that are reported to concentrate key signaling proteins and may represent a locus for PKC action, given that PKC activators have been reported to dramatically alter caveolae morphology. Accordingly, this study examines whether PKC isoforms initiate signaling in cardiomyocyte caveolae. Phorbol ester-sensitive PKC isoforms were detected at very low levels in caveolae fractions prepared from unstimulated cardiomyocytes;, phorbol 12-myristate 13-acetate (PMA) (but not 4 alpha-PMA, which does not activate PKC) recruited calcium-sensitive PKC alpha and novel PKC delta and PKC epsilon to this compartment. The subcellular localization of the phorbol ester-insensitive PKC lambda isoform was not influenced by PMA. Endothelin also induced the selective translocation of PKC alpha and PKC epsilon (but not PKC delta or PKC lambda) to caveolae. Multiple components of the extracellular signal-regulated protein kinase (ERK) cascade; including A-Raf, c-Raf-1, mitogen-activated protein kinase kinase, and ERK, were detected in caveolae under resting conditions. Although levels of these proteins were not altered by PMA, translocation of phorbol ester-sensitive PKC isoforms to caveolae was associated with the activation of a local ERK cascade as well. as the phosphorylation of a approximate to 36-kDa substrate protein in this fraction. Finally, a minor fraction of a protein that has been designated as a receptor for activated protein kinase C resides in caveolae and (along with caveolin-3) could represent a mechanism to target PKC isoforms to cardiomyocyte caveolae. These studies identify cardiomyocyte caveolae asa meeting place for activated PKC isoforms and their downstream target substrates.