Lin Z X, Eshelman J R, Forry-Schaudies S, Duran S, Lessard J L, Holtzer H
Department of Anatomy, School of Medicine, University of Pennsylvania, Philadelphia 19104-6058.
J Cell Biol. 1987 Sep;105(3):1365-76. doi: 10.1083/jcb.105.3.1365.
The phorbol ester TPA induces the sequential disassembly of myofibrils. First the alpha-actin thin filaments are disrupted and then, hours later, the myosin heavy chain (MHC) thick filaments. TPA does not induce the disassembly of the beta- and gamma-actin thin filaments of stress fibers in presumptive myoblasts or fibroblasts, nor does it block the reemergence of stress fibers in 72-h myosacs that have been depleted of all myofibrillar molecules. There are differences in where, when, and how myofibrillar alpha-actin and MHC are degraded and eliminated from TPA-myosacs. Though the anisodiametric myotubes have begun to retract into isodiametric myosacs after 5 h in TPA, staining with anti-MHC reveals normal tandem A bands. In contrast, staining with mAb to muscle actin fails to reveal tandem I bands. Instead, both mAb to muscle actin and rhophalloidin brilliantly stain numerous disk-like bodies approximately 3.0 micron in diameter. These muscle actin bodies do not fuse with one another, nor do they costain with anti-MHC. All muscle actin bodies and/or molecules disappear in 36-h myosacs. The collapse of A bands is first initiated in 10-h myosacs. Their loss correlates with the appearance of immense, amorphous MHC patches. MHC patches range from a few micrometers to over 60 micron in size. They do not costain with antimuscle actin or rho-phalloidin. While diminishing in number and fluorescence intensity, MHC aggregates are present in 30% of the 72-h myosacs. Myosacs removed from TPA rapidly elongate, and after 48 h display normal newly assembled myofibrils. TPA reversibly blocks incorporation of [35S]methionine into myofibrillar alpha-actin, MHC, myosin light chains 1 and 2, the tropomyosins, and troponin C. It does not block the synthesis of beta- or gamma-actins, the nonmyofibrillar MHC or light chains, tubulin, vimentin, desmin, or most household molecules.
佛波酯TPA可诱导肌原纤维的顺序性解体。首先，α-肌动蛋白细肌丝被破坏，数小时后，肌球蛋白重链（MHC）粗肌丝也被破坏。TPA不会诱导成肌细胞或成纤维细胞中应力纤维的β-和γ-肌动蛋白细肌丝解体，也不会阻止在已耗尽所有肌原纤维分子的72小时肌囊中应力纤维的重新出现。肌原纤维α-肌动蛋白和MHC在TPA处理的肌囊中降解和消除的位置、时间和方式存在差异。尽管在TPA中处理5小时后，不等径的肌管已开始收缩成等径的肌囊，但用抗MHC染色显示正常的串联A带。相反，用抗肌肉肌动蛋白的单克隆抗体染色未能显示串联I带。取而代之的是，抗肌肉肌动蛋白的单克隆抗体和鬼笔环肽都能强烈地染色许多直径约3.0微米的盘状小体。这些肌肉肌动蛋白小体不会相互融合，也不会与抗MHC共染色。所有肌肉肌动蛋白小体和/或分子在36小时的肌囊中消失。A带的塌陷首先在10小时的肌囊中开始。它们的消失与巨大的、无定形的MHC斑块的出现相关。MHC斑块的大小从几微米到超过60微米不等。它们不会与抗肌肉肌动蛋白或鬼笔环肽共染色。虽然数量和荧光强度逐渐减少，但在72小时的肌囊中，30%存在MHC聚集体。从TPA中取出的肌囊迅速伸长，48小时后显示正常的新组装肌原纤维。TPA可逆地阻止[35S]甲硫氨酸掺入肌原纤维α-肌动蛋白、MHC、肌球蛋白轻链1和2、原肌球蛋白和肌钙蛋白C。它不会阻止β-或γ-肌动蛋白、非肌原纤维MHC或轻链、微管蛋白、波形蛋白、结蛋白或大多数常见分子的合成。
