Degradation of HMG-CoA reductase-induced membranes in the fission yeast, Schizosaccharomyces pombe.
Degradation of HMG-CoA reductase-induced membranes in the fission yeast, Schizosaccharomyces pombe.
复制标题
裂殖酵母裂殖酵母中 HMG-CoA 还原酶诱导膜的降解。
DOI：
10.1083/jcb.131.1.81
复制
发表时间：
1995-10
期刊：
影响因子：
--
通讯作者：
Wright R
中科院分区：
文献类型：
--
作者：
Lum PY;Wright R
某些膜蛋白水平升高，包括固醇生物合成酶HMG-CoA还原酶，诱导内质网增殖。当这些蛋白质的量恢复到基础水平时，增殖的膜被降解，但这种降解的分子细节仍然未知。我们研究了裂殖酵母裂殖酵母中HMG-CoA还原酶诱导的膜的降解。在这种酵母中，由HMG 1编码的酿酒酵母HMG-CoA还原酶同工酶水平的增加诱导了几种类型的膜，包括karmament，其形成了部分包围细胞核的堆叠膜的帽。当HMG 1的表达受到抑制时，业力从细胞核中分离并形成同心的多层膜螺旋，然后被降解。在降解过程中，CDCFDA染色的车厢内形成的内部的螺纹从预先存在的空泡不同。除了这些隔间，含有中性脂质的颗粒也在螺旋内形成。随着螺纹厚度的减小，脂质颗粒变大。当降解完成时，仅剩下脂质颗粒。环己酰亚胺处理并不能阻止螺纹的形成。因此，业力退化的初始阶段不需要新的蛋白质合成。相反，放线菌酮促进了业力的分离，形成螺旋，这表明一个短寿命的蛋白质可能参与维持业力的完整性。总之，这些结果表明，业力膜分化成自我降解的细胞器。这一过程可能是ER膜在细胞中翻转的一个共同途径。
Elevated levels of certain membrane proteins, including the sterol biosynthetic enzyme HMG-CoA reductase, induce proliferation of the endoplasmic reticulum. When the amounts of these proteins return to basal levels, the proliferated membranes are degraded, but the molecular details of this degradation remain unknown. We have examined the degradation of HMG-CoA reductase-induced membranes in the fission yeast, Schizosaccharomyces pombe. In this yeast, increased levels of the Saccharomyces cerevisiae HMG-CoA reductase isozyme encoded by HMG1 induced several types of membranes, including karmellae, which formed a cap of stacked membranes that partially surrounded the nucleus. When expression of HMG1 was repressed, the karmellae detached from the nucleus and formed concentric, multilayered membrane whorls that were then degraded. During the degradation process, CDCFDA-stained compartments distinct from preexisting vacuoles formed within the interior of the whorls. In addition to these compartments, particles that contained neutral lipids also formed within the whorl. As the thickness of the whorl decreased, the lipid particle became larger. When degradation was complete, only the lipid particle remained. Cycloheximide treatment did not prevent the formation of whorls. Thus, new protein synthesis was not needed for the initial stages of karmellae degradation. On the contrary, cycloheximide promoted the detachment of karmellae to form whorls, suggesting that a short lived protein may be involved in maintaining karmellae integrity. Taken together, these results demonstrate that karmellae membranes differentiated into self-degradative organelles. This process may be a common pathway by which ER membranes are turned over in cells.